Symposium Organizers
Kalpana Katti North Dakota State University
Christian Hellmich Vienna University of Technology (TU Wien)
Christopher Viney University of California-Merced
Ulrike Wegst Max-Planck-Institut for Metals Research
DD1:Cellular Mechanics
Session Chairs
Kalpana Katti
Christopher Viney
Monday PM, November 27, 2006
Back Bay D (Sheraton)
9:00 AM - DD1.1
AFM in Study of Mechanics of Cancer and Aging Human Cells.
Igor Sokolov 1 , Swaminathan Iyer 1 , Ravi Gaikwad 1 , Craig Woodworth 2 , Venkatesh Subba-Rao 1
1 Physics, Chemistry, Clarkson University, Potsdam, New York, United States, 2 Biology, Clarkson University, Potsdam, New York, United States
Show AbstractIn this presentation, I will discuss on AFM study of mechanics of human epithelial cell and their change with aging and with malignancy. Recently we have found a considerable increase in rigidity of human epithelial cells while their ageing in-vitro. This is important because the loss in elasticity of epithelial tissues with ageing is associated with many human diseases. It was also shown that the cells had three distinctive regions of different rigidity. Developing a novel high resolution method to study cytoskeleton, we found correlation between the cell rigidity and the density of microfilament cytoskeletal fibres. Furthermore, using drugs that inhibit polymerization of microfilament, we restored the cell rigidities of old cells back to the young level in all three areas of rigidity simultaneously while preserving cells vitality. Some preliminary data of such treatment applied to aging skin of mice will be presented.The second example is about new things that can be learned with AFM about cancer cells. Mechanics of such cells is still in controversy. Studying cervical cell, we found that physics of mechanical properties of these cells is more complicated than scientists thought before. I will demonstrate that the surface of cancer cells is covered by molecules that are mechanically rather different from those of normal cells. Based on these measurements we developed a method for easy identification of cancer cells using fluorescent silica particles. This is still ongoing research aiming at developing a method for fast screening of precancerous epithelial tissue without biopsy.
9:15 AM - **DD1.2
Multi-scale Mechanics of the Cytoskeleton of Human Red Blood Cell and Some Connections to Disease States.
Subra Suresh 1 , Ming Dao 2 , Ju Li 3
1 Division of Biological Engineering and Dept of Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 2 Dept. of Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 3 Dept. of Materials Science and Engineering, Ohio State University, Columbus, Ohio, United States
Show Abstract9:45 AM - DD1.3
Stress Heterogeneities in Biological Networks.
Alexandre Kabla 1 , David Vader 1 , David Weitz 1 , L. Mahadevan 1
1 DEAS, Harvard University, Cambridge, Massachusetts, United States
Show Abstract10:00 AM - DD1.4
Interaction Forces and Mechanics of Cellular Membranes using Novel Atomic Force Microscopy Probes.
Benjamin Almquist 1 , Nicholas Melosh 1
1 Materials Science & Engineering, Stanford University, Palo Alto, California, United States
Show AbstractTo date, the detailed interaction behavior between cellular membranes and various molecular species remains unclear. In particular, the ability to penetrate, fuse, seal to, and re-organize lipid membranes using functionalized inorganic architectures is essential for eventually coupling biological and electronic systems. In this report, we detail our activities relating to the development of a novel AFM based probe system for studying these interactions.In order to probe the nature of nanostructure-membrane interfaces, we have developed an AFM probe platform that can quantitatively measure the interaction forces between specifically functionalized layers and the cell membrane. This platform consists of a cantilever with a post-style tip that ends in a hetero-metallic layer. This metallic layer can be selectively functionalized with various molecules of interest. Once functionalized, the layer is inserted into the hydrophobic region of the cell membrane. By varying the molecular species and examining the associated penetration and extraction forces, we will be able to correlate the molecule-membrane interaction forces to the molecular structure. This, in turn, will allow us to determine the role of molecular size, hydrophobicity, and disorder. In addition, the effects of functional layer thickness and post geometry will be examined. Unlike previous studies, this new post geometry allows for a controllable interaction area and the ability to interact with discreet regions of the lipid bilayer.
10:15 AM - DD1.5
Adhesion Kinetics and Mechanics of a Biomimetic Cell on a Substrate Surface Mediated by Receptor-Ligand Binding.
Yong-Wei Zhang 1 2 , Ping Liu 2 , Qianhua Cheng 2 , Chun Lu 2
1 Materials Science and Engineering, National University of Singapore, Singapore Singapore, 2 , Institute of High Performance Computing, Singapore Singapore
Show AbstractA continuum model was introduced for the adhesion of biomimetic cells to substrate surfaces. In the model, the cell membrane was assumed to be a closed shell with hyperelasticity. The cell cavity is filled with a liquid of fixed volume. The receptors on the membrane are mobile and initially uniformly distributed while the ligands on the substrate surface are fixed and either uniformly distributed or patterned. The formation of localized regions of tight binding between receptors and ligands, results in cell adhesion to the substrate surface. An adhesive model was introduced to describe the adhesive interaction between the receptors and the ligands. The growth of the adhesion area occurs via recruiting receptors from the non-adhered region through diffusion. Finite element methods were used to solve the governing equations for the deformation of the cell and the receptor diffusion on the membrane surface. Effects of the membrane stiffness, the cohesive parameters and the receptor density on the adhesion kinetics of the cells were studied. In addition, the instability of the advancing front of the adhesion was analyzed. Furthermore, the effect of patterned substrate surface on the cell adhesion was also studied and compared favorably with experimental results
11:00 AM - **DD1.6
Understanding Smart Organic Materials (The Living Cell) with Inorganic Materials.
Philip LeDuc 1
1 , Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show AbstractMaterial research has provided amazing insight into a diversity of fields through advancing our abilities to probe scientific questions. The utilization of inorganic materials has been responsible for a multitude of these advances. The merger of these technologies with the biological world has already started to create a similar pattern of insights in multidisciplinary areas. Here, I will present the investigation of the cell as a smart material with a specific focus on linking mechanics to biochemistry through its structure. This link has been implicated in a myriad of scientific and medical problems, from orthopaedics and cardiovascular medicine, to cell motility and division, to signal transduction and gene expression. Most of these studies have been focused on organ-level issues, yet cellular and molecular research has become essential over the last decade in this field thanks to the revolutionary developments in material science, genetics, biotechnology, and microelectronics. I will discuss some of our work in this field including our development of subcellular stimulation using a controls approach with a closed-loop feedback system. Furthermore, I will show a novel computational system, which we use to understand structural behavior for organic and inorganic systems. By combining novel approaches through material science, biology, and medicine, these multidisciplinary ideas can make a huge impact to the studies on human health and diseases as well as have applications in entrepreneurial enterprises.
11:30 AM - DD1.7
Indentation to Probe Atelectasis in Mammalian Lung.
Maricris Silva 1 , Melissa Hoyos 1 , Andrew Gouldstone 1
1 Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States
Show AbstractOf all the internal organs, mechanical behavior of the lung is arguably most closely related to physiologic function. In inflation and deflation, lung parenchyma may be treated as an elastic material with some viscous damping. However, quasi-plasticity is observed, in the form of atelectasis, which is the localized collapse of alveoli under different conditions. General anesthesia in lung is known to increase tendency for pulmonary atelectasis, and this condition is typically removed by mechanical inflation to high pressures, which can be hazardous. The specific mechanisms of atelectasis are not fully known, one reason for this being the difficulty in developing a direct characterization method to perform causal investigations. In a previous abstract, we described the potential for controlled indentation tests to probe atelectatic tendency in lung. In this talk, we present the first results of ‘hardness testing’ on dog and rabbit lung, using different inflation schemes. Specifically, we indented excised lungs at physiologic pressures, inflated with air, pure oxygen, and 0.2% isoflorane in oxygen. Among these three conditions, we found marked differences in ‘hardness’ of the lung, when indented with tip radii comparable to that of ribs. That is to say, large contrasts in residual impressions, as well as re-inflation behavior, were observed, indicating different propensities for alveolar collapse. In addition, effects of different inflation gases occurred within a much shorter time than previously reported in other surgical experiments, indicating perhaps different, faster mechanisms controlling atelectasis than previously considered. In this talk we will comment on our results and implications for potential strategies during anesthesia.
11:45 AM - DD1.8
Direct Observation of the Mechanical Properties from Normal and Cancerous Keratinocytes.
Nadine Pernodet 1 , Kristin Hall 2 , Marcia Simon 1 , Michael Vaccariello 1 , Crystalee Forbes 2 , Miriam Rafailovich 1
1 Materials Science & Engineering, Stony Brook University, Stony Brook, New York, United States, 2 , Smithtown High School East, Smithtown, New York, United States
Show Abstract12:00 PM - DD1.9
Modeling of Large Deformation Behavior of Red Blood Cells.
Long Xiao 1 , H. Qi 1
1 Mechanical , University of Colorado, Boulder, Boulder, Colorado, United States
Show AbstractRed Blood Cells (RBCs) have a biconcave shape with an average diameter of 8um. During their 120-day life span, flowing through the human blood circulation system half a million times, RBCs experience large deformation in order to pass through capillaries as small as 3 um in diameter. This implies that RBCs have excellent deformation ability. If this high deformability is impaired, they either can not fulfill their biological function or will have a shorter life. The origin of this excellent deformability lies in the structure of the RBC membrane. The RBC membrane has a tri-layer structure, where a spectrin skeletal network is anchored to the lipid bilayer of the cell membrane via physical linkages, such as integral proteins band 3 and ankyrin. These components and proteins contribute to the deformation ability in different ways. For example, the bending stiffness mainly comes from the resistance to area change of lipid bilayer, but the shear deformation is dominated by the spectrin network. In this paper, a new micromechanical model is developed to simulate the structure-function relationship of RBC membranes. The model considers the detailed RBC membrane structure, such as the tri-layer structure, integral proteins and the connections between these component proteins. Simulations of some representative loading cases predict the area dilation modulus, shear modulus and bending stiffness on the same orders of literature values, confirming the accuracy and predictability of the model. The model provides a novel way to investigate the structure-function relationship of RBCs and how the structure proteins can influence the phenotype of RBCs.
12:30 PM - DD1.11
Effect of Cross-Linking on the Elastic Properties of Fiber Networks: A 3D Discrete Modeling Approach.
Florent Dalmas 1 , Camilla Mohrdieck 2
1 , Max Planck Institute for Metals Research, Stuttgart Germany, 2 Dept. of Metals Research, University of Stuttgart, Stuttgart Germany
Show Abstract12:45 PM - DD1.12
Mechanical Property Variation in Mouse Cortical Bone.
Sara Campbell 1 , Virginia Ferguson 1
1 Mechanical Engineering, University of Colorado, Boulder, Colorado, United States
Show AbstractThe use of mice for bone research has many distinct advantages: rapid development and ageing, transgenic capabilities, and economic factors. Increased use of mice as a tool for bone structural and material research necessitates proper characterization of tissue-level mechanical properties. These properties vary with porosity, variations in mineral composition, and bone type (e.g. lamellar versus woven bone). Mouse bones, in comparison to larger vertebrates, are non-Haversian and do not undergo coordinated remodeling. Consequently, regions of immature, highly porous woven bone persist in aged mice. Thus, tissue-level material characterization is non-trivial and requires a strategic approach to account for local material property variations. Instrumented microhardness testing was performed on 69 male C57BL/6J mice femora at the mid-diaphyseal surface (n=3 indents/sample). Indentations were placed in epoxy embedded dry bone (polished to a 6 μm finish) away from cracks, visible pores, and edges. Despite efforts to select similar, uniform regions of bone, indentation sites most likely sampled bone of varying composition, porosity, or ultrastructural organization, based on the large variability seen within many samples. Variability within each sample is well represented by the coefficient of variance (COV) of the Vickers Hardness number (VHN) data, which ranged from 1% to 15%. Values for COV followed a normal, Gaussian distribution. Indentations on bone samples with a low COV were likely collected from relatively uniform regions of bone. Conversely, a high COV indicated that indentations were located in regions of substantially differing properties within a single bone sample. Specifically, the largest variation of VHN within one sample was 24%. Microindentation has a spatial resolution (≈30 μm indent diagonal) that is significantly larger than the size of bone structural features. Microindents represent average tissue properties over multiple structural features (e.g. lamellae). Nanoindentation, on the other hand, has a significantly smaller resolution (≈1 μm) and is an ideal method for determining tissue level properties. This study seeks to use nanoindentation to explore bone tissue-level properties in mice with improved spatial resolution and selectivity of test location where large pores and other interfering structures are more readily avoided. Histological staining and polarized light microscopy will be used to determine bone type and collagen orientation. This investigation aims to characterize the complicated structure of mouse cortical bone tissue. In addition, this work will be one of the first to explore local mechanical property variations in mouse bone.
DD2:Tissue Mechanics I
Session Chairs
Christian Hellmich
Ulrike Wegst
Monday PM, November 27, 2006
Back Bay D (Sheraton)
2:30 PM - **DD2.1
Whole Tooth Structure-Function Relations: Mapping Nanoscale Displacements During Loading of Human Teeth.
Steve Weiner 1 , Paul Zaslansky 1 , Asher Friesem 2 , Ron Shahar 3
1 Structural Biology, Weizmann Institute of Science, Rehovot Israel, 2 Dept of Physics and complex Systems, Weizmann Institute, Rehovot Israel, 3 Koret School of Vetinary Medicine, Hebrew University, Rehovot Israel
Show AbstractTeeth have variable morphologies, sizes and perform different functions. Although they are composed of the same two materials, enamel and dentin, the properties of both these materials vary significantly within a tooth to produce a very complex hierarchically organized and graded structure. The details of how these materials function together under physiologic compressive loads in the human dentition are however unknown. Electronic speckle pattern interferometry (ESPI) [1} was used to directly map nanometer scale displacements on surfaces of human premolars mounted in water and loaded in ways analogous to chewing hard and soft foods [2]. The deformation patterns were compared with deformation patterns obtained from replicas of the same teeth made from an isotropic and homogeneous material. The enamel cap functions mainly as a stiff body causing the whole crown to deform more or less as a stiff entity. It thus distributes the applied stress over the whole tooth. Yet the enamel cap also undergoes some deformation and rotation. An area of minimal deformation is found near the contact point between adjacent teeth, which presumably minimizes damage to adjacent teeth. Deformation of tooth slices observed along a surface passing through the enamel and into the dentin shows that there is a relatively soft zone some 200-300 microns thick below the dentin-enamel junction (DEJ) that has an elastic modulus of around 5GPa [3], confirming earlier observations of Wang and Weiner [4]. This zone appears to have a more open reticulate composite structure when observed in a scanning electron microscope, and may well be the zone that absorbs much of the displacement of the stiff enamel cap when compressed during mastication. Measurements of the elastic modulus of root dentin using ESPI, shows that it too has anisotropic properties. Much still remains to be understood about the manner in which individual teeth function, and the differences in structure-function relations between teeth.This study was supported by grant DE006954 from the NIDCR to SW.References[1] Zaslansky P, Currey JD, Friesem AA and Weiner S: Phase shifting speckle interferometry for determination of strain and Young's modulus of mineralized biological materials: a study of tooth dentin compression in water. J Biomed Opt. 10(2):24020 (2005).[2] Zaslansky, P., Shahar, R. Friesem, A.A. and Weiner, S. Relations between shape, materials properties and function in biological materials using laser speckle interferometry: In-situ tooth deformation. Adv. Func. Mat. (2006) (in press).[3] Zaslansky, P., Friesem, A. and Weiner, S. Structure and mechanical properties of the soft zone separating bulk dentin and enamel in crowns of human teeth: insight into tooth function. J. Struct. Biol. 153, 188-189 (2006).[4] Wang RZ and Weiner S: Strain-structure relations in human teeth using Moire fringes. J Biomech. 31(2):135-41 (1998).
3:00 PM - DD2.2
Mechanical Response in Porcelain Veneered Prostheses in an Artificial Mouth.
Yu Zhang 1 , Bongok Kim 1 , Jae Won Kim 1 , Mitch Pines 1 , Van Thompson 1 , Dianne Rekow 1
1 Biomaterials, New York University College of Dentistry, New York, New York, United States
Show AbstractTeeth play a critically important role in our lives. Loss of function reduces our ability to eat a balanced diet which has negative consequences for systemic health. Loss of aesthetics can negatively impact social function. Both function and aesthetics can be restored with dental crowns and bridges. Dental ceramics that best mimic the optical properties of enamel and dentin are predominantly glassy materials which derive principally from feldspar. Dental porcelains contained high feldspathic glass content and are extremely brittle and weak. Various metal alloys and strong ceramics have been used to support the weak, but aesthetic porcelain. Despite the integration of strong substructures, fracture of the porcelain veneered prostheses still remains problematic, especially in all-ceramic systems. This in vitro study investigates contact fatigue response of a number of clinical systems, including porcelain/Au alloy, porcelain/Pd-Ag alloy, porcelain/zirconia, and porcelain/alumina. Veneered substructures (1mm thick porcelain and 0.5mm thick substructure) were cemented (Rely X, ARC, 3M/ESPE) to a dentin-like Z100 composite (3M/ESPE) and subjected to Hertzian indentation fatigue in water using a uniaxial mouth-motion simulator (Elf 3300, EnduraTEC, Minnetonka, MN). A maximum load of 200 N was utilized. Tests were conducted for prescribed number of contact cycles: 20,000, 50,000, 100,000, and 550,000. Three repeats were performed for each prescribed cycling numbers. All specimens were subjected to post-mortem damage examination using a sectioning technique. For the porcelain/zirconia system, fracture occurs exclusively in the veneer layer: the newly identified inner cone cracks initiate at the occlusal-surface and propagate downward, ultimately intersect the porcelain/zirconia interface. Although inner cones can reach the veneer/core interface as early as 50,000 cycles, they remain contained after 550,000 cycles - neither penetrate into the zirconia cores nor propagate along the veneer/core interface. Similar fracture characteristics are observed in the ceramic-metal systems. These results differ from the porcelain/alumina system where both contact induced occlusal-surface fracture and flexural induced cementation-surface fracture are evident. It can be concluded that for the veneer/substructure system, both strength and hardness of the substructure are crucial. Supported by New York University Research Challenge Fund and NIDCR P01 DE10976.
3:15 PM - DD2.3
Quasistatic and Dynamic Microscale Poroviscoelasticity of Cartilage.
Lin Han 1 , Jacqueline Greene 1 , Han-Hwa Hung 2 , Eliot Frank 2 , Alan Grodzinsky 3 4 5 , Christine Ortiz 1 5
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Center for Biomedical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 5 Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractCartilage (the loading bearing tissue in articulating joints) is a highly hydrated material consisting proteoglycans (PGs) enmeshed within a porous type II collagen fibril network. While cartilage is known to exhibit poroelastic behavior when tissue deformation causes fluid flow within the matrix, the solid matrix also exhibits intrinsic viscoelastic properties (due to macromolecular relaxation). In order to probe the underlying mechanisms of the time-dependent biomechanical properties of cartilage, we have compared the microscale poroviscoelasticity of native calf femoral cartilage disks (~0.5 mm thick, from both the surface and middle/deep zones) to that of tissue samples digested in 1mg/mL trypsin with and without 0.1U/mL chondroitinase-ABC, which results in depletion of > 95% of matrix PGs (assessed by dimethylmethylene blue dye binding assay), leaving a residual type II collagen network. Tapping mode atomic force microscopy (AFM) imaging of the surface of digested cartilage samples showed collagen fibers that were randomly oriented in the plane and had fibril diameters ~ 80 ± 8 nm with a distinct ~ 23 nm periodic banding, in addition to the well-known ~ 67 nm D-banding, which is the predominant structure observed for type I collagen fibers in other connective tissues (e.g., tendon and bone). Quasistatic AFM-based nanoindentation was carried out using a neutral colloidal probe tip functionalized with a hydroxyl-terminated self-assembled monolayer (11-mecaptoudecanol, HS(CH2)11OH, spring constant k ~ 0.58 N/m, end radius ~ 2.5 μm) at a constant ~ 1 μm/s indentation rate and a maximum total compressive strain ~ 0.5% in 0.1M phosphate buffered saline. Comparison of these data to the Hertz model for an isotropic, elastic sphere, yielded an equilibrium modulus E ~ 100 ± 16 kPa for the intact cartilage and ~ 85 ± 11 kPa for the residual type II collagen network after enzymatic removal of PGs. To study the time-dependent nanomechanical properties, a ramp-and-hold compressive strain (ε ~ 0.5 %) was applied to the tissue samples, and the relaxation in normal force recorded with time. The PG-depleted cartilage exhibited a faster relaxation process (with a characteristic relaxation time τ ~ 0.5 s and ~ 64 ± 2 % decrease in force after ~ 10 seconds) compared to that of intact cartilage (τ ~ 0.8 s, and force reduction ~ 43 ± 1 % by 10 seconds). Dynamic oscillatory experiments are ongoing in which a sinusoidal strain is applied to the tissue (via a function generator which controls the displacement of the AFM z-piezo) using an infinitesimal displacement amplitude (< 5 nm) and frequency ~ 1 – 100 Hz. By comparing the frequency-dependent stress-strain behavior to models for poro- versus viscoelastic dynamics, we hope to understand the relative contributions of fluid flow and molecular relaxation to the time dependent behavior of cartilage at the nanoscale.
3:30 PM - DD2: Tissue
break
4:30 PM - **DD2.4
Nature Designs Tough Collagen: Explaining the Nanostructure of Collagen Fibrils.
Markus Buehler 1
1 Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractCollagen is a protein material with superior mechanical properties. It consists of collagen fibrils composed of a staggered array of ultra-long tropocollagen molecules. Theoretical and molecular modeling suggests that this natural design of collagen fibrils maximizes the strength while providing large energy dissipation during deformation, thus creating a tough and robust material. We find that the mechanics of collagen fibrils can be understood quantitatively in terms of two critical molecular length scales χS and χR that characterize (i) when deformation changes from homogeneous intermolecular shear to propagation of slip pulses, and (ii) when covalent bonds within tropocollagen molecules begin to fracture leading to brittle-like failure. The ratio χS/χR indicates which mechanism dominates deformation. Our modeling rigorously links chemical properties of individual tropocollagen molecules to the macroscopic mechanical response of fibrils. The results help to explain why collagen fibers found in Nature consist of tropocollagen molecules with lengths in the proximity of 300 nm, and advance the understanding how collagen diseases that change the intermolecular adhesion properties influence the mechanical properties.
5:00 PM - DD2.5
Investigating the Interfacial Interactions Between Organic and Inorganic Phases and Their Influence on the Mechanics of Organic Phase in Natural Bone.
Rahul Bhowmik 1 , Kalpana Katti 1 , Dinesh Katti 1
1 Civil Engineering, North Dakota State University, Fargo, North Dakota, United States
Show Abstract5:15 PM - DD2.6
Multi-scale Modeling of Human Coritical Bone: Aging and Failure Studies.
Elisa Budyn 1 , Thierry Hoc 2
1 MIE, UIC, Chicago, Illinois, United States, 2 Department of Material Science, Ecole Centrale Paris, Chatenay Malabry France
Show Abstract5:30 PM - DD2.7
Biomolecular Origin of Rate-Dependent Deformation of Prismatic Enamel.
Jikou Zhou 1 , Luke Hsiung 1
1 Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show Abstract5:45 PM - DD2.8
The Temporal Evolution of the Poroviscoelastic Behavior of Individual Cartilage Chondrocytes and Their Pericellular Matrix Cultured in vitro.
Bo Bae Lee 1 , Lin Han 1 , Eliot Frank 2 , Alan Grodzinsky 3 4 5 , Christine Ortiz 1 5
1 Materials Science and Engineering, Massachussetts Instittute of Technology, Cambridge, Massachusetts, United States, 2 Center for Biomedical Engineering, Massachussetts Instittute of Technology, Cambridge, Massachusetts, United States, 3 Electrical Engineering and Computer Science , Massachussetts Instittute of Technology, Cambridge, Massachusetts, United States, 4 Mechanical Engineering , Massachussetts Instittute of Technology, Cambridge, Massachusetts, United States, 5 Biological Engineering, Massachussetts Instittute of Technology, Cambridge, Massachusetts, United States
Show AbstractWhile chondrocytes form a small percentage of cartilage tissue (<10 vol. %), they are solely responsible for the synthesis, assembly, and maintenance of the extracellular matrix (ECM). One promising approach to cartilage tissue engineering is embedding chondrocytes in synthetic scaffolds and exposing to various growth factors and mechanical loads to facilitate ECM synthesis and suppress catabolic degradation of ECM macromolecules. Chondrocytes (equilibrium modulus, E ~ 0.6 - 4 kPa) develop a micrometer-thick pericellular matrix (PCM) in vivo and in vitro which is softer (equilibrium modulus, E ~ 60 - 70 kPa) than the surrounding mature ECM (E ~ 0.5 MPa). Hence, the PCM is expected to play a key role in cellular mechanotransduction via amplification of strain signals and providing molecular connections between cell receptors and PCM/ECM. In this study, the time-dependent nanomechanical properties of individual chondrocytes were studied using atomic force microscope (AFM)-based nanoindentation with nanosized (end radius, Rtip ~ 50 nm) and micron-sized colloidal probe tips (Rtip ~ 2.5 μm) held at a constant normal displacement (~ 1 μm) for 60 seconds while recording the relaxation of the force. Chondrocytes isolated from bovine cartilage (2-3 week old) were cultured in alginate beads in 10% fetal bovine serum for periods up to 1 month and placed in microfabricated silicon wells for nanomechanical testing. For Day 0 chondrocytes (uncultured, no PCM) using the colloidal tip, relaxation data were compared to a modified viscoelastic Hertz standard linear model, yielding an equilibrium modulus, Et→∞ ~ 2.76 ± 0.45 kPa, an instantaneous modulus, Et=0 ~ 3.13 ± 0.34 kPa, and a characteristic time constant, τ ~ 2.43 ± 1.82 s. The equilibrium and instantaneous moduli were observed to increase with the culture time, reaching 3.12 ± 1.39 kPa and 4.25 ± 0.95 kPa, respectively, at Day 28 culture, presumably due to growth and assembly of the PCM. Meanwhile, τ remained ~ 2 - 3s for all culture times. The findings of the increase in both equilibrium and instantaneous moduli suggest that the PCM has attributed to stiffen the PCM associated chondrocytes. Also the observation that Et=0 > Et→∞ at all time points would be consistent with both poro- and viscoelastic behavior in that initially imposed loading to the system is relaxed to reach the equilibrium state as the time elapses. Further study to elucidate the relative contributions of poro- and viscoelastic behavior to the measured nanomechanical properties is ongoing.
DD3: Poster Session: Tissue Mechanics II
Session Chairs
Christopher Viney
Ulrike Wegst
Tuesday AM, November 28, 2006
Exhibition Hall D (Hynes)
9:00 PM - DD3.1
Determining Beta Sheet Crystallinity in Silks Films.
Xiao Hu 1 , David Kaplan 2 , Peggy Cebe 1
1 Physics Department, Tufts University, Medford, Massachusetts, United States, 2 Biomedical Engineering, Tufts University, Medford, Massachusetts, United States
Show AbstractSilk films behave as composite materials, comprising non-crystalline and crystalline regions. From the standpoint of mechanical behavior, it is crucial to be able to determine the fraction of crystals for proper modeling. In this work, we report on a new method for the quantitative evaluation of the crystal fraction in silk films.We investigated self-assembled beta pleated sheets in B. mori silk fibroin films using thermal analysis and infrared spectroscopy. Materials were prepared from concentrated solutions (2-5wt. % fibroin in water), and then dried to achieve a less ordered state without beta sheets. Crystallization of beta pleated sheets was effected either by heating the films above the glass transition temperature (Tg) and holding isothermally, or by exposure to methanol. The fractions of secondary structural components including random coils, alpha helices, beta pleated sheets, turns, and side chains, were evaluated using Fourier self-deconvolution (FSD) of the infrared absorbance spectra.The silk fibroin films were studied thermally using temperature-modulated differential scanning calorimetry (TMDSC) to obtain the reversing heat capacity. As crystalline beta sheets form, the heat capacity increment at Tg is systematically decreased. We find that the heat capacity increment from the TMDSC trace is linearly well correlated (negatively) with beta sheet content, determined from FSD. The correlation allows the beta sheet content to be determined from a direct measurement of the heat capacity increment at Tg. This type of analysis can serve as an alternative to X-ray methods and may have wide applicability to other crystalline beta sheet forming proteins.
9:00 PM - DD3.10
Micromechanical Measurements on Chemomechanical Protein Aggregates.
Andreas Heilmann 1 , Stefan Schwan 1 , Andreas Cismak 1 , Uwe Spohn 1
1 , Fraunhofer-Institute for Mechanics of Materials, Halle (Saale) Germany
Show Abstract9:00 PM - DD3.12
A Recombinant Fibroin Fused with a Mitogenic Protein: A Novel Biomaterial Prepared from Silk Fibers of Transgenic Silkworms Expressing a Recombinant Fusion Protein of Fibroin and Human Fibroblast Growth Factor.
Rika Hino 1 2 , Masahiro Tomita 1 , Katsutoshi Yoshizato 1 2
1 Yoshizato Project, Cooperative Link of Unique Science and Technology for Economy Revitalization, Hiroshima Prefectural Institute of Industrial Science and Technology, Higashihiroshima, Hiroshima, Japan, 2 Department of Biological Science, Graduate School of Science, Hiroshima University, Higashihiroshima , Hiroshima, Japan
Show Abstract Silk is a natural fiber produced by the silkworm Bombyx mori and its major components are fibroin and sericin. Fibroin is a fibrous protein constituting the core of silk fibers and is a candidate for a biomaterial because it is available in bulk, has no toxicity, and shows good biocompatibility with human tissues. Fibroin is processed into various forms such as film, sponge, gel, and powder, which will enable us to utilize with a variety of purposes as a biomaterial. In addition, we are able to chemically couple fibroins with bioactive proteins/peptides, which could further expand the utilization of fibroin as biomaterials for tissue engineering. We have established a method to yield germline transgenic silkworms that spin silk fibers containing recombinant fibroins. The present study aimed to produce a recombinant fibroin with bioactive proteins/peptides using the silkworm transgenesis technology. We generated germline transgenic silkworms bearing a fibroin light chain (FL) promoter-driven fusion gene of FL whose 3’-end was flanked with human basic fibroblast factor (bFGF). The silkworms spun the silk fibers containing the recombinant fusion protein [r(FL/bFGF)] comprising FL and bFGF. The silk fibers from transgenic silkworms were trypsinized to remove sericin layers, and treated with solution containing CaCl2, ethanol, and water at a molar ratio of 1:2:8 (CaCl2/ethanol/water) to solubilize fibroin layers. Western blot analysis showed that r(FL/bFGF) was solubilized with CaCl2/ethanol/water, but not with trypsin, indicating that r(FL/bFGF) was in fibroin layers. The r(FL/bFGF)-containing fibroin was solubilized with CaCl2/ethanol/water and then refolded using the glutathione redox system. Human umbilical vein endothelial cells (HUVECs) that grow bFGF-dependently were cultured in media supplemented with the refolded r(FL/bFGF)-containing fibroin. The cells grew in the media, which indicated that r(FL/bFGF) was biologically active. The cells were also cultured on culture dishes whose surface was coated with r(FL/bFGF)-containing fibroin. The cells grew well therein. Furthermore, we demonstrated the once immobilized to the surface of the dish, the recombinant fusion fibroin retained its mitogenic activity during culture periods. These results strongly support the idea that r(FL/bFGF)-containing fibroin is promising as a new biomaterial for tissue engineering. This study has shown that fibroin conjugated with various bioactive proteins/peptides could be prepared from silk fibers spun by germline transgenic silkworms. The presented technology utilizing transgenic silkworms will provide a new way for industrial applications of fibroin.
9:00 PM - DD3.13
Fracture Behavior and Shear Resistance of Lobster Cuticle.
Christoph Sachs 1 , Helge Fabritius 1 , Dierk Raabe 1
1 Microstructure Physics and Metal Forming, Max-Planck-Institut fuer Eisenforschung, Duesseldorf Germany
Show AbstractThe cuticle of the American lobster Homarus americanus represents a multilayer chitin-protein-based biological composite containing variable amounts of nanoscopic biominerals. The hierarchical structure and the pronounced texture of the material leads to an anisotropic deformation and fracture behavior. By performing compression tests and shear tests we examined the deformation and fracture behavior depending on the orientation of the sample.In the cuticle three structurally different layers can be distinguished: an outermost epicuticle and an inner procuticle consisting of the exocuticle and the endocuticle. The epicuticle is a thin waxy layer which provides a permeability barrier to the environment. Both exocuticle and endocuticle are made up of mineralized chitin-protein fibers forming lamellae. The endocuticle makes up around 90 vol.% of the cuticle. Local variations in composition and structure of the material provide a wide range of mechanical properties. Particularly, the grade of mineralization and the stacking density of the twisted plywood layers affect the mechanical properties of the cuticle. The test specimens originate from the claws of the lobster and are tested both in dry and in wet state to evaluate the effect of moisture on the deformation and fracture behavior. By probing the test specimens in different direction to the surface of the cuticle, anisotropic behavior of the endocuticle is detected. For estimating variations in the grade of mineralization, cross-sections of the cuticle were analyzed by the use of EDX mapping. The microstructure and the fracture surfaces of the test specimens were investigated using scanning electron microscopy.
9:00 PM - DD3.14
Structure and Formation of the Cuticle of Woodlice - Tough Biomineralized Structures in Animals.
Frank Neues 1 , Alexander Becker 1 , Andreas Ziegler 2 , Matthias Epple 1
1 Institute of Inorganic Chemistry, University of Duisburg-Essen, Essen Germany, 2 Department of Electron Microscopy, University of Ulm, Ulm Germany
Show AbstractWoodlice form an exoskeleton for protection against predators. This must be both tough and light in order to permit the animal moving and possibly running away from a predator. The cuticle consists of an organic polymer (chitin) and an inorganic phase (calcium carbonate). The first is responsible for its elasticity, the latter is its hardness. Both components are formed in a highly oriented way in order to fulfill these requirements. During the growth process, the animal regularly changes its cuticle by shedding off the old one and forming a new one. Due to the fact that calcium is very precious for land-living organisms, the cuticle is demineralized before it is shed off (so-called "moulding"). The calcium carbonate is stored as amorphous spheres at the belly of the animal, and remobilised when the new cuticle has been formed.Structure, composition and morphology of the different biomineralized species were studied and related to the biological behaviour of the different species when it comes to the attack of predators.
9:00 PM - DD3.16
Contact Mechanics of Biomechanical Dental Crown Layers.
Sanjit Bhowmick 1 , Juan José Meléndez-Martínez 2 , Ilja Hermann 1 , Brian Lawn 1
1 MSEL, NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY (NIST), Gaithersburg, Maryland, United States, 2 Departamento de Física, Facultad de Ciencias, Universidad de Extremadura, Badajoz Spain
Show Abstract9:00 PM - DD3.17
Nanoscale Imaging and Binding Kinetics of Receptors on Living and Chemically Fixed Cell Surfaces.
Sunyoung Lee 1 , Krystyn Van Vliet 1
1 Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - DD3.18
Indentation of an Elastic Half-Space Covered with a Tensed Membrane - Analysis and Experimental Implications.
Jae Kim 1 , Andrew Gouldstone 1
1 Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States
Show AbstractContact-based methods (e.g., indentation) are widely used in the biomechanics community for mechanical and structural characterization. One reason is the relative experimental simplicity compared to other methods. The other is the non-destructive nature of many contact approaches, a critical consideration for maintenance of physiological condition in in-vitro experiments, or avoidance of injury in in-vivo tests and diagnostics. Both attributes are particularly important when dealing with soft tissues or organs in the body. However, a number of these systems are not homogeneous, nor are they simple layered composites – they are best described as an elastic (or viscoelastic) bulk material, covered with a thin tensed membrane. Interpretation of indentation results on such structures is non-trivial, as the surface effect of the membrane is dependent upon material shear modulus, membrane tension, and contact dimensions. Past investigations have addressed this problem for an indenter of constant contact area (rigid flat punch, pressure column) but the perhaps more practical analog of a spherical indenter has not been discussed. Recently we have successfully developed closed-form analytical formulae to describe this problem. In this talk, we will describe our approach, and methods to use indentation force-depth curves to extract modulus and tension. In addition, we present further numerical approaches to calculate key values of stress and strain under the indenter tip, for the purpose of determining, e.g, the criterion for onset of inelastic events of physiological importance. Finally, we will describe our approach in the context of experiments on the mammalian lung, and applicability to other systems in the body.
9:00 PM - DD3.19
Mechanical Design of Scales from the Ancient Armored Fish Polypterus Senegalus.
Benjamin Bruet 1 , Jae Choi 1 , Emily Chen 1 , Jin Kim 1 , Joan Mao 1 , Mark Mascaro 1 , Emily Pfeiffer 1 , Christine Ortiz 1
1 Material Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - DD3.2
The Effect of Organic and Water Content on the Mechanical Properties of Murine Incisal Enamel.
Marta Baldassarri 1 2 , Henry Margolis 1 , Elia Beniash 1
1 Biomineralization, Forsyth Institute, Boston, Massachusetts, United States, 2 Mechanics, Polytechnique University of Marche, Ancona Italy
Show Abstract9:00 PM - DD3.20
Study on the Nanomechanical Properties of Hyaline and Repair Cartilage.
Karsten Durst 1 , Oliver Franke 1 , Kolja Gelse 2 , Mathias Göken 1
1 Materials Science, University Erlangen-Nürnberg, Erlangen Germany, 2 Experimental Medicine , University Erlangen-Nürnberg, Erlangen Germany
Show Abstract9:00 PM - DD3.21
Quantifying Cell Reorganizations During Morphogenesis.
Guy Blanchard 2 , Alexandre Kabla 1 , L. Mahadevan 1 , Richard Adams 2
2 Department of Physiology, University of Cambridge, Cambridge United Kingdom, 1 DEAS, Harvard University, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - DD3.22
Nanomechanical Characterization of Fiber Reinforced Type I Collagen.
Xiaodong Li 1 , Xinnan Wang 1 , Yongda Yan 1 3 , Michael Yost 2 , Shen Dong 3
1 Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States, 3 Department of Mechanical Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, China, 2 Department of Surgery, University of South Carolina, Columbia, South Carolina, United States
Show Abstract9:00 PM - DD3.23
Nanomechanics of Small Volume Tissue Samples: Murine Cartilage.
Lin Han 1 , Han-Hwa Hung 2 , Anna Plaas 3 , Wendy Anemaet 4 , Christine Ortiz 1 7 , Alan Grodzinsky 5 6 7
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Center for Biomedical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Internal Medicine, Division of Rheumatology, University of South Florida, Tampa, Florida, United States, 4 School of Aging Studies, University of South Florida, Tampa, Florida, United States, 7 Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 5 Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 6 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe intrinsic biomechanical properties of cartilage, and the effects of age, disease, diet and genetics on articular cartilage have been investigated using a variety of animal models. The mouse model has received increasing attention in the past several years because of the ability to modify specific tissue development and functional properties using gene knock-out and related gene-altering technologies. Murine cartilage have been investigated macroscopically to quantify the effects of certain gene knockouts on biomechanical properties (e.g., via osmotic swelling behavior). However, there are no published reports, to our knowledge, on quantification of micro- and nanoscale biomechanical properties of murine joint cartilage, which may provide important molecular level insights concerning the consequences of specific disease processes due to the relative small tissue dimension (~1 mm wide, ~100 μm thick). In this study, the nanomechanical properties of mouse cartilage were assessed using atomic force microscope (AFM)-based nanoindentation. Knee joint femoral condyles were dissected from fresh 13 weeks old male mouse hind legs. Constant displacement rate-nanoindentation was performed on the femoral condyle cartilage using a colloidal probe tip (spring constant k ~ 0.58 N/m, end radius ~ 2.5 μm, displacement rate ~ 1 μm/s) functionalized with a neutral self-assembled monolayer (11-mecaptoundecanol, HS(CH2)11OH). Tests were done in the fully wet state (0.1M phosphate buffered saline in the presence of protease inhibitors to prevent enzymatic degradation of cartilage matrix macromolecules). Force-indentation data were compared to the Hertz model assuming, initially, that the tissue could be approximated as a linear, homogenous, isotropic elastic material. The elastic modulus E was calculated to be ~ 2.5 ± 0.3 MPa which is higher than the equilibrium modulus of bovine cartilage (~ 0.5 MPa), but similar to that of guinea pig cartilage. The time-dependent behavior of the mouse cartilage was assessed by placing a ramp-and-hold compressive strain ε ~ 0.3% and measuring the relaxation of compressive force as a function of time. The mouse cartilage yielded a characteristic relaxation time constant τ ~ 1.4 s, which may be due to combined poro- and viscoelastic matrix behavior. The methodology presented in this study suggests a suitable way to quantify and compare the nanomechanical properties of normal and diseased or biologically (e.g., genetically) modified mouse cartilage. Ongoing studies are to compare normal murine cartilage to that from TGF-β-stimulated remodeling and inflammation, as well as matrix-specific knock-outs to explore specific molecular pathways associated with osteoarthritis-like disease.
9:00 PM - DD3.24
Polyelectrolyte Multilayers with Tunable Young’s Modulus: Influence of Film Stiffness on Cell Adhesion.
Catherine Picart 1 2 , Aurore Schneider 2
1 Department of Biology and Health, University of Montpellier 2, Montpellier France, 2 , University Louis Pasteur, Strasbourg France
Show Abstract9:00 PM - DD3.3
Time Dependent Nanomechanical Response of Nacre.
Bedabibhas Mohanty 1 , Devendra Verma 1 , Kalpana Katti 1 , Dinesh Katti 1
1 Civil Engineering, North Dakota State University, Fargo, North Dakota, United States
Show Abstract9:00 PM - DD3.4
Real-time Atomic Force Microscopy Imaging of Dibucaine-induced Conformational Changes in Model Membrane.
Gabriela Lorite 1 , Eneida Paula 2 , Mônica Cotta 1
1 Departamento de Física Aplicada, Instituto de Física Gleb Wataghin - UNICAMP, Campinas Brazil, 2 Departamento de Bioquímica, Instituto de Biologia - UNICAMP, Campinas Brazil
Show AbstractUnderstanding anesthetics-biomembrane interactions at high resolution is a key issue in current biophysical research. We show here real time atomic force microscopy (AFM) imaging to visualize the effects of the interaction between the local anesthetic (LA) dibucaine (DBC) and phospholipid domains in model membranes. Supported lipid bilayers are widely used as models to investigate the properties of biological membranes and associated processes such as molecular recognition, enzymatic catalysis, cell adhesion and membrane fusion. On the other hand, LA effects on structural and dynamic properties of the membrane lipid region could be the key to understand its mechanisms of action. Supported egg phosphatidylcholine (EPC) bilayers were formed on mica by the method of vesicle fusion. They were imaged in real time by AFM, in the absence or presence of LA. DBC was added to the liquid cell during topographic acquisition and successive AFM images were then recorded at the same location. Magnetic Acoustic Mode (MAC) images were obtained with a Pico Plus (Molecular Imaging) in liquid. The AFM images showed irregularly distributed and sized EPC domains on mica. From this morphology, bilayers of ~5nm height could be observed, in agreement with the literature. With the addition of small DBC amounts (up to 2 mM) the bilayer morphology was similar to that observed in the absence of DBC. Increasing DBC concentration in the liquid cell, a progressive decrease in the size of the original EPC domains, as well as the formation of small structures on the bilayer surface (height ~0.05 to 0.2nm), were observed. At higher concentrations (> 7 mM) DBC effect was more drastic, causing disruption of the bilayer. Our results suggest that mass transfer of lipids, both along the biomembrane surface and to the solution occurs, allowing the formation of the small surface structures. These may be also related to phase-separation effects – already described for DBC at high concentrations in phospholipid bilayers - which are currently under investigation.
9:00 PM - DD3.5
Correlating the Nanoscale Mechanical, Chemical and Structural Properties of Small Animal Bones.
N Beril Kavukcuoglu 1 , Shiva Kotha 3 , Adrian Mann 1 2
1 Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States, 3 School of Dentistry, University of Missouri, Kansas City, Missouri, United States, 2 Biomedical Engineering, Rutgers University , Piscataway, New Jersey, United States
Show AbstractBone is a living tissue that undergoes matrix formation and resorption throughout its life span. Aging, disease and genetic variations can all lead to changes in the ratio of bone resorption to bone formation. Uncoupling of the two processes (for instance in osteoporosis) causes a deterioration in bone quality and, consequently, an increase in fracture risk. This is becoming a significant health concern for today’s aging society. A better understanding of how aging, disease and genetic variations affect the properties of bone is essential to the treatment of many debilitating bone conditions. Previously there have been many investigations of the mechanical, chemical and structural properties of bone. However, the correlation between these different properties at the nanoscale is not clear. In this study we report the results of an investigation that has used nanoindentation testing combined with raman microspectroscopy to correlate the hardness, elastic modulus and mineral-to-organic matrix ratio (phosphate-to-collagen amide I ratio) of cortical bones from the femora of mice and rats. The effects of aging, mechanical loading and genetic abnormalities have been studied. The results show that in general there is a strong correlation on the nanoscale between the degree of mineralization relative to the organic matrix and the mechanical properties. However, there may be some instances where the relationship between hardness and mineralization is not the same as the relationship between elastic modulus and mineralization. These results will be highlighted and explained in terms of current models for bone mechanics.
9:00 PM - DD3.7
The Skeleton and Pharyngeal Teeth of Zebrafish (Danio rerio) as a Model of Biomineralization in Vertebrates.
Frank Neues 1 , Peter Gaengler 2 , Wolfgang Arnold 2 , Jens Fischer 3 , Felix Beckmann 4 , Matthias Epple 1
1 Institute of Inorganic Chemistry, University of Duisburg-Essen, Essen Germany, 2 University of Witten/Herdecke, Faculty of Dental Medicine, Witten Germany, 3 Department of Orthopaedic Surgery, Hannover Medical School, Hannover Germany, 4 Institute for Materials Research, GKSS Research Center Geesthacht, Geesthacht Germany
Show AbstractZebrafish (Danio rerio) has become one of the most common models for genetics, and developmental research in the biosciences. Synchrotron radiation micro computer tomography (SRµCT), scanning electron microscopy, polarized light microscopy, and energy-dispersive X-ray analysis were applied to visualize the biomineralization in teeth and bones in high spatial resolution.
9:00 PM - DD3.8
Shape and Function of Gecko Foot-hair for Wall Mobility.
Jose Berengueres 1 , Shigeki Saito 2
1 International Development Engineering, Tokyo Institute of Technology, Tokyo, Tokyo-to, Japan, 2 Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology, Tokyo, Tokyo-to, Japan
Show Abstract9:00 PM - DD3.9
Ultrastructural Mechanical and Material Characterization of Fossilized Bone.
Sara Campbell 1 , Virginia Ferguson 1 , Michelle Oyen 2 3
1 Mechanical Engineering, University of Colorado, Boulder, Colorado, United States, 2 Department of Materials, Queen Mary, University of London, London, E1 4NS, United Kingdom, 3 Engineering, Cambridge University, Cambridge United Kingdom
Show Abstract
Symposium Organizers
Kalpana Katti North Dakota State University
Christian Hellmich Vienna University of Technology (TU Wien)
Christopher Viney University of California-Merced
Ulrike Wegst Max-Planck-Institut for Metals Research
DD4: Tissue Mechanics III
Session Chairs
Christian Hellmich
Christopher Viney
Tuesday AM, November 28, 2006
Back Bay D (Sheraton)
9:30 AM - **DD4.1
Nanoscale Deformation and Toughening Mechanisms of Nacre.
Xiaodong Li 1
1 Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show Abstract10:00 AM - DD4.2
Mechanical Properties of the Lobster Cuticle Investigated by Bending Tests and Digital Image Correlation.
Christoph Sachs 1 , Helge Fabritius 1 , Dierk Raabe 1
1 Microstructure Physics and Metal Forming, Max-Planck-Institut fuer Eisenforschung, Duesseldorf Germany
Show AbstractIn our study we present a novel experimental approach to the characterization of the deformation of a mineralized biological composite using arthropod cuticle as a model material. By performing bending tests combined with a detailed strain analysis via digital image correlation, the elastic-plastic deformation behavior of the endocuticle and the exocuticle of the American lobster Homarus americanus is examined. The combination of a miniaturized bending test with the digital image correlation method allows to measure at a global scale with high precision the stress-strain behavior of the bulk cuticle and to reveal strain heterogeneity and strain localization phenomena at a microscopic scale. In the cuticle three structurally different layers can be distinguished: an outermost epicuticle and an inner procuticle consisting of the exocuticle and the endocuticle. The epicuticle is a thin waxy layer which provides a permeability barrier to the environment. Both exocuticle and endocuticle are made up of mineralized chitin-protein fibers forming lamellae. The endocuticle makes up around 90 vol.% of the cuticle. Local variations in composition and structure of the material provide a wide range of mechanical properties. Particularly, the grade of mineralization and the stacking density of the twisted plywood layers affect the mechanical properties of the cuticle. The test specimens originate from the claws of the lobster and are tested both in dry and in wet state to evaluate the effect of moisture on the deformation behavior. By probing the test specimens in different direction to the surface of the cuticle, anisotropic behavior of the procuticle as well as differences in the deformation behavior between the exocuticle and the endocuticle are detected. For estimating variations in the grade of mineralization, cross-sections of the cuticle were analyzed by the use of EDX mapping. The microstructure and the fracture surfaces of the test specimens were investigated using scanning electron microscopy.
10:15 AM - DD4.3
Texture of Alpha-chitin and Calcite as a Microscopic Composite Design and Macroscopic Biological Construction Principle of the Exoskeleton of the Lobster Homarus americanus.
Dierk Raabe 1 , Ali Al-Sawalmih 1 , Lars Raue 1 2 , Helmut Klein 2 , Helge Fabritius 1
1 , Max-Planck-Institut, Duesseldorf Germany, 2 , Goettingen University, Goettingen Germany
Show AbstractThe crystallographic texture of the alpha-chitin matrix and the calcite nanoparticles in the biological nano-composite material forming the exoskeleton of the lobster Homarus americanus have been determined using synchrotron and lab-scale x-ray pole figure measurements and the subsequent calculation of orientation distribution functions. The study has three objectives: The first one is to elucidate possible crystallographic building principles of such biological materials via the preferred synthesis of certain orientations in mineralized tissue using the cuticle material of lobster as a model material. The second one is to identify whether a characteristic orientation relationship exists between the crystalline chitin and calcite. The third one is to study whether a general global construction principle exists for the exoskeleton which exploits preferred crystallographic textures relative to the local coordinate system.
10:30 AM - DD4.4
Macroscopic Crystallographic Structure of Strongylocentrotus Purpuratus and Spisula Solidissima by Polefigure Analysis.
Simone Herth 1 2 3 , Jeremy Bigness 1 2 , Anne Hynes 1 2 , Robert Doremus 1 2
1 Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Materials Science and Engineering Department, Rensselaer Polytechnic Institute, Troy, New York, United States, 3 Faculty of Physics, University Bielefeld, Bielefeld Germany
Show AbstractThe shells of sea animals, such as the sea urchin Strongylocentrotus purpuratus and the clam Spisula solidissima, provide a strong protection against enemies while retaining a low weight. In Strongylocentrotus purpuratus the high toughness of the skeleton is achieved by the combination of a strong, but 50% porous backbone made of the mineral calcite and proteins, which distribute stress concentrations. In contrast, the shell of Spisula solidissima consists of the mineral aragonite and has a very low porosity of 5%. However, little is known about the macroscopic texture of these surprisingly strong composites, which was studied by a pole figure analysis of an oral and an aboral piece of a sea urchin skeleton and a small part of a clam shell. The sea urchin exhibits a strong texture in only a few crystallographic directions indicating a preferred macroscopic orientation of the calcite planes. The orientation of the planes in the aboral part is slightly more symmetric with about the same degree of texture. In contrast, the texture of the clam shell is very weak. Polefigures of other seashells, such as the tiger cowrie Cypraea tigris and pink murex Hexaplex erythrostoma, exhibit textures in two and four preferred orientations, respectively.
10:45 AM - DD4.5
Nanoscale Anisotropic Plastic Deformation in Single Crystal Aragonite.
Cathal Kearney 1 , Z. Zhao 2 , B. Bruet 3 , R. Radovitzky 2 , M. Boyce 1 , C. Ortiz 3
1 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract11:30 AM - **DD4.6
Multiscale Mechanics of Nacre: From Micro Scale to Molecular.
Dinesh Katti 1 , Kalpana Katti 1 , Pijush Ghosh 1
1 Civil Engineering, North Dakota State University, Fargo, North Dakota, United States
Show Abstract12:00 PM - DD4.7
Nanomechanical Heterogeneity within Individual Nacre Tablets from Trochus Niloticus.
Benjamin Bruet 1 , Julian Villarreal 1 , Christine Ortiz 1
1 Material Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show Abstract12:15 PM - DD4.8
Microstructures and Mechanical Behavior of Biological Composite Materials for Armor Design Applications.
Hongjoo Rhee 1 , Youngkeun Hwang 1 , Steven Elder 2 , Mark Horstemeyer 1 3 , Randall German 1 3
1 , Center for Advanced Vehicular Systems (CAVS) at Mississippi State University, Starkville, Mississippi, United States, 2 Department of Agricultural and Biological Engineering, Mississippi State University, Mississippi State, Mississippi, United States, 3 Department of Mechanical Engineering, Mississippi State University, Mississippi State, Mississippi, United States
Show AbstractThe principal aim of this study is to investigate the microstructures of various biological structural-materials such as shells of turtle and abalone. The roles of microstructures and structural layer arrangements on the mechanical behavior of such biological composite materials are also evaluated for armor applications. Microstructural observation and nano-, micro-, and macro-mechanical experiments on these biological structural-materials were carried out to characterize the structure-property relations. Such biological materials are the multiphase composite materials which consist of the successive stacking of a hard crystalline structure and a ductile organic material. The experimental results reveled that the mechanical properties of these biological materials were strongly affected by microstructures and layer arrangements, and such structural-materials exhibited a superior crack penetration blocking performance. Based on this investigation, a novel design approach of bio-inspired armor system (BIAS) is developed and is comprised of multiple layers of strategically placed materials in a bio-mimetic methodology. The results from present study may provide a better understanding of various modeling parameters contributing to establish successful BIAS design.Acknowledgement: Work supported by the CAVS Initiative grant 190000-060803-021000.
12:30 PM - DD4.9
The Effect of Stain-removal Agents on the Morphology and Nano-mechanical Properties of the Acquired Salivary Pellicle Layer.
Michelle Dickinson 1
1 , Hysitron Inc., Eden Prairie, Minnesota, United States
Show Abstract12:45 PM - DD4.10
Effect of Surfactant and Enzyme Treatments on the Delamination Behavior of Human Stratum Corneum.
Kemal Levi 1 , Kenneth Wu 2 , Joy Baxter 3 , Helen Meldrum 3 , Manoj Misra 3 , Eugene Pashkovski 3 , Reinhold Dauskardt 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Mechanical Engineering, Stanford University, Stanford, California, United States, 3 , Unilever Research and Development, Trumbull, Connecticut, United States
Show Abstract The stratum corneum (SC), the outermost layer of the skin, is the first level of mechanical protection for the body and the initial layer through which mechanical stimuli must pass to reach underlying tissue. The SC is subjected to variable conditions including changes in local temperature and humidity as well as potentially damaging acute and chronic chemical exposure. This exposure can be induced by surfactants (e.g. soaps) or use of skin-adherent technologies (e.g. transdermal drug patches) and influences the structure and mechanical behavior of human SC. We present mechanics-based techniques to study the effect of surfactant treatments on the graded and sub-critical delamination behavior of human SC tissue. To probe the debonding of SC as a function of treatment, a fracture-mechanics-based approach was used to characterize the SC cohesion energy, Gc, as a function of temperature, hydration, chemical treatment and tissue depth. In addition to these critical delamination measurements, sub-critical time dependent delamination measurements were performed to better understand kinetic mechanisms associated with debonding of SC such as the role of lipid separation and relaxation or environmental interactions. The delamination behavior of SC was further investigated by treating SC with an exogenous enzyme in the presence and absence of a protease inhibitor. SC cohesion energy, Gc, was observed to decrease from ~ 6 J/m2 to ~ 2 J/m2 after being subjected to recombinant stratum corneum chymotryptic enzyme (rSCCE). Transmission electron microscopy studies on enzyme treated SC demonstrated a strong link between the cohesion energy of SC and its corneodesmosome density. The methods employed help quantify mechanical properties of SC, which can be utilized to better understand the relation between tissue structure and properties.
DD5/FF6: Joint Session: Biomaterials and Biocomposites
Session Chairs
Joanna Aizenberg
Kalpana Katti
Tuesday PM, November 28, 2006
Back Bay C (Sheraton)
2:30 PM - **DD5.1/FF6.1
Structural Hierarchy and Mechanics of the Skeleton in a Glass Sponge.
Joanna Aizenberg 1 , Peter Fratzl 3 , James Weaver 2 , Daniel Morse 2
1 , Lucent Technologies/Bell Laboratories, Murray Hill, New Jersey, United States, 3 , Max-Planck-Institute of Colloids and Interfaces, Potsdam Germany, 2 , University of California, Santa Barbara, California, United States
Show Abstract3:00 PM - DD5.2/FF6.2
Self-Assembled Peptide Fibrils-based Nanocomposite: Using Peptides as both the Matrix and Reinforcement.
Rohan Hule 1 , Darrin Pochan 1
1 Materials Science and Engineering and Delaware Biotechnology Institute, University of Delaware, Newark, Delaware, United States
Show AbstractNanocomposites were formed using self-assembled, peptidic β-sheet fibrils as the reinforcement phase and polypeptide as the matrix. The fibrils, self-assembled from short (16-30 amino acids) peptide sequences were characterized using TEM and exhibit either a non-twisting, laminated or a highly twisted fibril morphology. Each of the fibrils, both non-twisting and twisting, exhibits lengths exceeding several microns. The secondary conformation of the peptides, investigated using Circular Dichroism (CD) spectroscopy and FTIR, is predominantly β-sheet. SANS studies globally quantify the local morphology of these fibrils as rod-like structures, as indicated by a good agreement between experimental data and cylinder form fits. Atomic Force Microscopy (AFM) reveals the height of each fibril to be consistent with an interdigitated peptide assembly. Modeling a single fibril using an interdigitated peptide assembly as a constitutive unit was carried out to determine the elastic modulus. The modulus values from modeling agree well with those from Indentation Force Microscopy, a technique for nanoscale mechanical characterization. The nanocomposites so formed are biodegradable and exhibit mechanical properties comparable to traditional engineering polymers.
3:15 PM - DD5.3/FF6.3
Physical Properties and Shear Sensing Potential of a SWNT/Copolypeptide Bionanocomposite.
Conrad Lovell 1 , Kristopher Wise 2 , Cheol Park 2 , Joycelyn Harrison 3
1 Materials Science and Engineering, University of Virginia, Charlottesville, Virginia, United States, 2 , National Institute of Aerospace, Hampton, Virginia, United States, 3 Advanced Materials and Processing Branch, NASA Langley Research Center, Hampton, Virginia, United States
Show AbstractWith the existence of twenty natural amino acids, numerous combinations of copolypeptides may be developed, each with their own unique properties. In addition, polypeptides have been shown to exhibit shear piezoelectricity. One of these combinations, a high molecular weight copolypeptide of the amino acids Leucine and Phenylalanine, was combined with single wall carbon nanotubes (SWNTs) in an attempt to create a stronger and more conductive bionanocomposite for potential shear sensing applications. The dispersion state of the carbon nanotubes will be shown through scanning electron micrographs, and the mechanical and dielectric property enhancement of the nanocomposites will be discussed. Our investigation into the shear sensing capabilities of this copolypeptide will also be detailed.
3:30 PM - DD5.4/FF6.4
Effect of Crystallinity on the Protein Adsorption and Friction Behavior of Ultra-high-molecular-weight-polyethylene.
Kanaga Karuppiah Kanaga Subramanian 1 , Angela Bruck 1 , Sriram Sundararajan 1 , Zhiqun Lin 2 , Zhi-Hui Xu 3 , Xiaodong Li 3
1 Mechanical Engineering, Iowa State University, Ames, Iowa, United States, 2 Materials Science and Engineering, Iowa State University, Ames, Iowa, United States, 3 Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show Abstract3:45 PM - DD5.5/FF6.5
Novel, High Strength Nanostructured Composites Prepared with Layer-by-Layer Assembly Technique.
Paul Podsiadlo 1 , Bong Sup Shim 1 , Zhongqiang Liu 2 , Zhiyong Tang 1 , Messersmith Phillip 2 , Nicholas Kotov 1
1 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Biomedical Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractNature has evolved highly complex and elegant mechanisms for materials design and synthesis with physical properties that still surpass those of analogous synthetic materials with similar phase compositions, e.g. nacre, or bones. Finding a synthetic pathway to artificial analogs of such materials represents a fundamental milestone in the development of composites. Recently we have reported preparation of a thin film nanostructured composite from montmorillonite clay nanosheets and (poly(diallylmethyl ammonium chloride (PDDA) (Nature Materials, 2003, 2, 413) using the layer-by-layer assembly technique (LBL). The structure, deformation mechanism, and mechanical properties (tensile strength ~100 MPa and Young’s modulus ~11 GPa) of the material are very similar to those of natural nacre and lamellar bones. These results are encouraging for generation of new class of biomimmetic materials.We present here our results from exploration of different routes towards further improvement of the mechanical properties of the material. New composites were prepared from different polyelectrolytes: chitosan, a custom-designed 4-armed poly(ethylene glycol) with L-3,4-dihydroxyphenylalanine (DOPA), an amino acid that is responsible for both unusual adhesion and crosslinking characteristics of mussel adhesive proteins, and poly-L-lysine molecules grafted at the four ends, and poly(vinyl alcohol). LBL assembly of chitosan and clay resulted in a completely natural composite with high uniformity and stability under aqueous environment. High rigidity of the polymer chains, despite high macroscopic properties (tensile strength ~60-67 MPa), resulted in lower overall mechanical properties when compared to PDDA-clay system, tensile strength ~66 MPa and Young’s modulus ~7 GPa. LBL assembly of the (DOPA-Lys-PEG)4 system (22% of overall DOPA content) resulted in a composite with tensile strength approaching that of our previously reported values, σ ≈ 78 MPa and Y ≈ 4 GPa. Further cross-linking with Fe3+, implicated to be the natural cross-linking agent, resulted in dramatic increase in the tensile strength to σ ≈ 220 MPa and Y ≈ 6 GPa. Finally, LBL assembly with poly(vinyl alcohol) and further chemical cross-linking with glutaraldehyde or Al3+ ions, resulted in an increase of the tensile strength, from ~80 MPa to ~330 MPa (as high as 430 MPa) and to ~250 MPa (as high as 330 MPa), respectively. Young’s modulus for plain and cross-linked PVA composites was ~10 GPa. Results from dynamic nanoindentation studies showed Young’s modulus ranging from 10-20 GPa for the PVA composites and hardness of ~0.7 GPa.
4:30 PM - **DD5.6/FF6.6
Flaw Tolerant Hierarchical Structures in Biocomposites.
Huajian Gao 1
1 Engineering, Brown University, Providence, Rhode Island, United States
Show AbstractThis talk is focused on making use of the principle of flaw tolerance to explain the hierarchical structures of biological systems including bone and gecko. Bone-like biological materials have achieved superior mechanical properties through hierarchical composite structures of mineral and protein. Gecko and many insects have evolved hierarchical surface structures to achieve robust and releasable adhesion on random rough surfaces. We show that the hierarchical structures of these biological systems from nanoscale and up may have played a key role in allowing these materials to achieve their superior properties. We suggest that the principle of flaw tolerance may have had an overarching influence on the evolution of biological materials. We discuss that the bottom-up hierarchical designs allow mechanical properties of biological nanostructures to be optimized from nanometer to macroscopic length scales.
5:00 PM - DD5.7/FF6.7
Formation of Porous Hydroxyapatite
Deepa Khushalani 1
1 Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai India
Show Abstract5:15 PM - DD5.8/FF6.8
Characterization of Electrospun Polymer Biocomposite
Smita Gadre 1 , Perena Gouma 1
1 Materials Science and Engineering, SUNY at Stony Brook, Stony Brook, New York, United States
Show AbstractPolymer biocomposite fibers find applications in biosensing, tissue engineering, and as smart fibers in textile industry. Polymer biocomposites fibers consisting of one or more polymers such as hydroxypropyl cellulose, chitosan, cellulose acetate and a biological component such as enzymes, cell growth factor were synthesized using the electrospinning process. The processing parameters such as applied voltage, needle tip to collector distance, flow rate of polymer solution affect the microstructure of biocomposite fibers. The diameter of polymer biocomposite fibers was found to vary with these parameters. Concentration of polymer solution also affects the diameter of electrospun biocomposite fibers. Results will include mechanical properties of such biocomposite fibers and their dependence on processing and microstructure
5:30 PM - DD5.9/FF6.9
The Influence of Sterilization Pprocesses on the Micromechanical Properties of Carbon Fiber Reinforced PEEK Composites for Bone-implant Applications.
Ajay Godara 1 , Dierk Raabe 1 , Stuart Green 2
1 Department of Microstructure Physics and Metal Forming, Max-Planck Institute for Iron Research, Duesseldorf Germany, 2 Research and Development, Invibio Ltd, Cleveleys Lancashire United Kingdom
Show AbstractThe effect of sterilization on the structural integrity of the thermoplastic matrix composite PEEK (polyetheretherketone) reinforced with carbon fibers (CF) is investigated by nanoindentation and nanoscratch tests. The use of the material as a medical grade implant requires extensive understanding of its micromechanical properties which primarily define the in-vitro performance. Sterilization is a mandatory process for materials that are used in medical applications such as bone-implants. The steam and gamma radiation sterilization processes employed in this study are at sufficient levels to affect the micromechanical properties of some polymer materials, particularly in the interphase region between the polymer matrix and the reinforcing fibers.Nanoindentation and nanoscratch tests are a powerful method to reveal local gradients in the hardness and the elastic properties of such interphase regions. In this work both techniques are used to explore microscopic changes in the hardness, reduced stiffness and scratch resistance properties of the interphase region and bulk polymer matrix due to the different sterilization processes employed. The results reveal that sterilization by steam and gamma induces no significant change in the reduced elastic modulus, hardness or coefficient of friction in the bulk polymer matrix, and only a minimal modification of the PEEK matrix at almost negligible levels in the micron-scale interphase region. Of the two sterilization methods used, steam sterilization is shown to have the greatest influence on the small changes in properties in this region and it appears to slightly increase the thickness of the interphase zone.
5:45 PM - DD5.10/FF6.10
Mechanical Properties of an in-vivo Modified Biological Nano-composite Material.
Christoph Sachs 1 , Helge Fabritius 1 , Dierk Raabe 1
1 Microstructure Physics and Metal Forming, Max-Planck-Institut fuer Eisenforschung, Duesseldorf Germany
Show AbstractThe cuticle of the American lobster Homarus americanus has to meet a wide range of mechanical properties according to its various biological functions. In our study we examined the deformation behavior and the microstructure of cuticle as a function of the grade of mineralization. Two distinct locations of the exoskeleton were selected, namely, the flexible articular membranes and the rigid parts of the claws. By performing tensile tests the elastic-plastic deformation behavior was examined. The combination of tensile tests with a detailed strain analysis via digital image correlation allows to measure at a global scale with high precision the stress-strain behavior of the bulk cuticle and to reveal strain heterogeneity and strain localization phenomena at a microscopic scale. In the cuticle three structurally different layers can be distinguished: an outermost epicuticle and an inner procuticle consisting of the exocuticle and the endocuticle. The epicuticle is a thin waxy layer which provides a permeability barrier to the environment. Both exocuticle and endocuticle are made up of mineralized chitin-protein fibers forming lamellae. The endocuticle makes up around 90 vol.% of the cuticle. Local variations in composition and structure of the material provide a wide range of mechanical properties. Particularly, the grade of mineralization and the stacking density of the twisted plywood layers affect the mechanical properties of the cuticle. The test specimens originate from the claws of the lobster and are tested both in dry and in wet state to evaluate the effect of moisture on the deformation behavior. For estimating variations in the grade of mineralization, cross-sections of the cuticle were analyzed by the use of EDX mapping. The microstructure and the fracture surfaces of the test specimens were investigated using scanning electron microscopy.
DD6: Poster Session: Mechanics of Biomaterials
Session Chairs
Kalpana Katti
Ulrike Wegst
Wednesday AM, November 29, 2006
Exhibition Hall D (Hynes)
9:00 PM - DD6.1
Microbially Produced Levan – Safe for Users and the Environment.
Joan Combie 1
1 , Montana Polysaccharides Corp, Rock Hill, South Carolina, United States
Show AbstractLevan is a polymer of fructose. Unlike many nanomaterials, the spheres formed by this polysaccharide are not hollow, but rather are densely packed with sugar molecules. Branches with available hydroxyl groups stick out from the sphere surface, providing room for attachment of moieties without causing problems with steric hindrance. For example, large substituents can transform levan into a surfactant. These closely packed spheres block UV light, particularly in the region below 300 nm.First identified over 100 years ago, the literature holds numerous reports on studies of the beneficial health effects of levan. Despite the lengthy study, as far as we know, there is not a single report of adverse effects on laboratory animals. Levan has not previously been available in large quantities, but we have developed a method suitable for production in tonne lots. Some of the properties of this material are listed in the following table.
9:00 PM - DD6.12
Bioinspired Enhancement of Artificial Haircell Flow Sensor using Hydrogel.
Sergiy Peleshanko 1 2 , Michael Julian 1 , Melburne Lemieux 1 , Nannan Chen 3 , Craig Tucker 3 , Jonathan Engel 3 , Chang Liu 3 , Vladimir Tsukruk 1 2
1 Department of Materials Science and Engineering, Iowa State University, Ames, Iowa, United States, 2 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Micro Actuators, Sensors, and Systems Group, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show Abstract9:00 PM - DD6.13
Fracture and Energy Partitioning in Uncooked and Cooked Noodles.
Zhongquan Sui 1 , Harold Corke 1 , Peter Lucas 2 , Michelle Oyen 3
1 Botany, University of Hong Kong, Hong Kong Hong Kong, 2 Anthropology, George Washington University, Washington, District of Columbia, United States, 3 Engineering, Cambridge University, Cambridge United Kingdom
Show Abstract9:00 PM - DD6.14
Nanomechanical Characterization and Piercing of Biological Structures Using Carbon Nanotube AFM Probes.
Minhua Zhao 1 , Haoyan Wei 1 , Harris Marcus 1 , Fotios Papadimitrakopoulos 1 , Bryan Huey 1
1 Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States
Show Abstract9:00 PM - DD6.15
Mechanical Properties and Microarchitecture of Nanoporous Hydroxyapatite Bioceramic Nanoparticle Coatings on Ti and TiN.
Andrei Stanishevsky 1 , Shafiul Chowdhury 1 , Nathaniel Greenstein 2 , Helene Yockell-Lelièvre 3 , Jari Koskinen 4
1 , University of Alabama at Birmingham, Birmingham, Alabama, United States, 2 , Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 3 , Université Laval, Québec, Quebec, Canada, 4 , VTT Technical Research Centre of Finland, Espoo Finland
Show Abstract9:00 PM - DD6.2
An Easy Preparation of ``Monolithic Type" Hydrophilic Solid Phase Capability for Affinity Resin to Isolate Target Proteins.
Tomoko Mori 1 , Teruki Takahashi 2 , Akito Tanaka 2 , Ken Hosoya 1
1 Biommolecular Engineering, Kyoto Insititute of Technology, Kyoto, Kyoto, Japan, 2 Chemistry Department, Reverse Proteomics Research Institute Co., Ltd., Kisarazu, Chiba, Japan
Show AbstractMany physiologically active substances such as medicines, natural products, and toxins have been known. However, majority of their target proteins, which immediately bind the substances and dominate their physiological action involving unexpected toxicity and side effects, have not been elucidated. Affinity chromatographic matrices immobilizing such physiologically active substances as ligands play an important role for the identification of their target proteins. The successful isolation of target proteins by affinity chromatography depends on the properties of polymeric resins that can bind to the cellular target proteins with maximum selectivity and efficiency. Nonspecific binding of other cellular proteins onto the affinity matrices is a tragically significant limitation to this approach. Therefore, development of novel polymeric resins that are chemically stable as poly-methacrylate based matrices and are hydrophilic enough to eliminate the nonspecific binding as agarose-based ones, is an important goal. We have studied preparation of brilliant monolithic type affinity resins to overcome above mentioned defects of existing affinity resins using a newly developed PEG type functional monomer and hydrophilic cross-linker. These poly-methacrylate based monolithic matrices for affinity resins were prepared using rather simple radically initiated copolymerization. Then, we succeeded preparation of affinity resins having monolithic non-particulate continuous bed using relatively low molecular weight porogen in place of usually utilized high molecular weight polymer solution. This was a very simple method. In order to assess capability of the novel monolithic affinity resins we immobilized an immune-suppressing drug, FK506 through the PEG type functional monomer. These resins were mixed with protein mixture (lysate) obtained from rat brain, and proteins bound on the monolithic resins were comparatively analyzed. The novel monolithic resins bearing FK506 successfully captured the specific binding protein, FKBP12, with greatly reduced amount of nonspecific binding proteins. Unexpectedly, the novel monolithic affinity resins also isolated another specific binding proteins, FKBP, calcineurin A and B, and calmodulin, although commercially available Affigel and Toyopearl affinity resins could not capture those using the same strategy. The development of novel monolithic type affinity resins that are chemically stable as poly-methacrylate based derivatives and are hydrophilic enough to eliminate the nonspecific absorption. It is one of the most brilliant resins because monolith has excellent property for mobility of substance, so it can be also applied for an easy experimental work using a tool of chip. At this moment, we think it is useful as the novel affinity resins for isolation of target proteins by affinity chromatographic method.
9:00 PM - DD6.3
Directed Mineralization on Polyelectrolyte Multilayer Films.
Maria Advincula 1 , Pritesh Patel 2 , Patrick Mather 2 , Daniel Underhill 3 , Bryan Huey 3 , Jon Goldberg 1 3
1 Oral Rehabilitation, Biomaterials and Skeletal Development, University of Connecticut Health Center, Farmington, Connecticut, United States, 2 Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 3 Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States
Show AbstractSilica formation aided by polypeptides has been actively investigated recently for a wide range of applications including biomaterials synthesis, ceramics, and controlled release systems. Simple polypeptides like polylysine (PLL) and small molecules with amine functionality have been shown to mediate silica formation from the precursor solutions. Hence, in order to understand silicification in the presence of polypeptide catalysts like PLL, we investigated the formation of silica on multilayered thin films formed by layer-by-layer (LbL) assembly of polyelectrolytes. To examine the effect of catalyst (PLL), its location within a polymer host, the number of deposited layers and other process parameters on silicification, PLL was adsorbed layer-by-layer up to 10 bilayers on silicon wafers in combination with a negatively charged polyelectrolyte, polystyrene sulfonate (PSS). Poly (ethyleneimine) (PEI) was also used as the alternating polycation for LbL growth or in combination with PLL to prepare (PEI/PSS/PLL/PSS)10 multilayer films. To induce silicification, prehydrolyzed silica precursor in citrate-phosphate buffer or ethanol was added dropwise on the films. The samples were incubated in a water chamber for 24 hours then dried at room temperature, 60oC and 150oC under vacuum. The morphology, roughness and contact mechanical stiffness of the films were characterized using optical microscopy, SEM and AFM. The resulting morphology of silica in and on the films was plate-like or spherical, and porous with the average particle size depending on the catalyst location, composition of the LbL assembly and number of layers. Without catalyst, the formed silica was fine and gel-like. The morphology of silica produced as films was different from that formed in solution using the same combination of polyelectrolytes. Topographically, the (PLL/PSS)10 films consisted of spherical domains, 0.1 µm to 1 µm in size, suggesting mesoporosity. The homogeneity of (PLL/PSS)10 films increased with increased temperature and silica precursor concentration and in the presence of ethanol which was attributed to a decrease in porosity and densification of the films. Roughness measurements further revealed that these films became smoother with increased temperature and in the presence of ethanol. The contact mechanical stiffness of individual silica particles was lower (~ 40.50 N/m) than the surrounding areas (~47.09 N/m) suggesting that the formed silica was amorphous and hydrated. These results shows that the catalyst, its location within a polymer host, the number of deposited layers and the other process parameters (precursor concentration, temperature and solvent) provide additional control over the silicification. The difference in surface properties among polypeptides indicates that the silica formation was mediated by these macromolecules and that the process may be catalyst-specific or even synergistic as in the case of the (PEI/PSS/PLL/PSS)10 film.
9:00 PM - DD6.4
Development of Novel Separation Media having Selective Recognition Ability for Thyroid Hormone Activate OH-PCBs.
Takuya Kubo 1 , Kunimitsu Kaya 1
1 Graduate School of Environmental Studies, Tohoku University, Sendai Japan
Show Abstract Polychlorinated biphenyls (PCBs) are industrial chemicals that have had a variety of uses but have been banned in most countries for some years. They are metabolized in vivo to hydroxyl and sulfur compounds and hydroxylated metabolites have been found in human serum, blood and plasma. Additionally, hydroxylated PCBs (OH-PCBs) have been shown to inhibit mitochondrial oxidative phosphorylation, thyroid hormone sulfation, estrogen sulfotranferase and the sulfation and glucuronidation of 3-hydroxybenzo[a]pyrene, to affect thyroxine (T4) levels and to exhibit estrogenic or antiestrogenic activity. Mono-OH-PCBs are attracting increasing attention as potentially endocrinologically active metabolites of PCBs. Recently, Arulmozhiraja et al. reported the structural requirements for the interaction of 91 OH-PCBs with estrogen and thyroid hormone receptors and authors showed the correlations between chemical structure and activations. In analyses and/or remove for these activate homologues in environment; the selective separation is strongly required.On the other hand, to achieve effective analysis of environmental organic as well as inorganic substances, adsorbents having specific molecular recognition ability are quite useful. The specific molecular recognition ability can be easily realized with a specially prepared polymer adsorbent, namely a molecularly imprinted polymer (MIP). Molecular imprinting technique (MIT) is attractive to obtain selective molecular recognition ability for a certain compound according to selective recognition site constructed into nano-scale structure with template molecule, functional monomers and excessive amount of cross-linking agent, and have been applied for some adsorption media. However, in the traditional MIT, the real molecule should be required as the template molecule so that rare naturally occurring compounds and/or highly toxic compounds can be hardly utilized as the templates. In fact, some of compounds having relatively high molecular weight cannot be easily molecularly imprinted. By contrast, the fragment imprinting effect can be obtained through a molecular imprinting mechanism where a part of the target molecule is utilized as a pseudo-template molecule. Therefore, the concept of fragment imprinting technique will expand the applicable range of molecular imprinting.In this study, we developed novel separation media by the fragment imprinted polymers having selective recognition ability for certain OH-PCBs. The results of the liquid chromatography (LC) showed that the selective structural recognition was worked for OH-PCBs on some MIPs. The recognition mechanism for OH-PCBs was related the pKa value dependent on chemical structure of OH-PCBs. Additionally, we achieved the direct selective separation of some OH-PCB analogues which have prospects of thyroid hormone activity from mixture sample by LC with MIPs.
9:00 PM - DD6.5
Nano-Hydroxyapatite Coated Hip Stem Implant by Electrophoretic Deposition.
Heng Zhang 1 , Jay Krajewski 1 , Zhongtao Zhang 1 , Danny Xiao 1
1 , Inframatm Corporation , Farmington, Connecticut, United States
Show Abstract9:00 PM - DD6.6
Designing Hydrogel-Colloid Composites as Cellular Substrates with Tunable Mechanical Properties.
Bryan Baker 1 , Valeria Milam 1
1 MSE, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractPolyacrylamide hydrogels are a popular choice as cellular substrates; however, the mechanical properties of these hydrogels are much weaker than that of tissue. Our aim is to develop stiffer polyacrylamide-based hydrogels using colloidal particles as macroscopic cross-linking agents and controlling the nature of the interactions between the colloidal particles and the hydrogel matrix. Using oscillatory rheology, we have examined several distinct types of particle-matrix interactions: hydrogels reinforced by relatively “inert” particles, particles with long-range attractions for the matrix, and particles with short-range attractions for the matrix. Rheological tests include strain amplitude sweeps, frequency sweeps, and time dependent gelation studies.
9:00 PM - DD6.7
Mechanical Properties Evolution Of Polydimethylsiloxane During Crosslinking Process.
Yi Zhao 1 , Xin Zhang 2
1 Biomedical Engineering Department, The Ohio State University, Columbus, Ohio, United States, 2 , Boston University, Boston, Massachusetts, United States
Show AbstractPDMS is one of the most widely used engineering polymers in biomedical microsystems due to its good biocompatibility, easy handling and low cost. It can be cultured with various cellular objects without incurring notable damage. The application of this polymer is recently moving towards mechanical biosensors, where the microfabricated PDMS structures are used to in situ monitor force/stress information of living cellular objects at small scale, derived from the deflections. In such applications, the mechanical properties (e.g. Young's modulus) of PDMS are crucial for a precise measurement. However, in commonly used thermal crosslinking process, these properties vary dramatically with operational conditions. The relationship between these properties and the crosslinking parameters remains obscure. Therefore, we investigate, in this paper, the evolution of elastic modulus and the coefficient of thermal expansion (CTE) of PDMS during a typical crosslinking process. The properties changes are continuously monitored, for the first time, throughout the whole crosslinking process with the help of a curvature measurement system.PDMS prepolymer (Dow Sylgard 184) was mixed 1:10 and spin coated on a 4-inch single-crystal silicon wafer at a low spin rate. The wafer was then put into a vacuum chamber for 5-minute degassing, forming a bilayered substrate with the top layer of PDMS prepolymer and the bottom layer of single crystal silicon. The bottom silicon layer is to provide support and to allow optical curvature measurement. A wafer curvature measurement system was used to conduct thermal cycling. The predetermined curing curve is described as follows: temperature was rapidly brought up to 65°C within 2 minutes, followed by a 240-minute temperature holding duration, and then slowly cooled down (cooling rate: ~3 °C/minute). The curvature change was in situ measured during the thermal cycles, reflecting the mechanical properties evolution of the PDMS polymer.The curvature change shows the PDMS solidification was primarily completed in the first 15 minutes, while the mechanical properties of the polymer kept changing afterwards. Since the elastic modulus of PDMS polymer is much smaller than that of the silicon substrate (> 100,000 times), the curvature can be regarded as a function linearly relates to Young's modulus of PDMS and varies upon temperature change. The Young’s modulus change with the curing duration was thus achieved from the curvature evolution in temperature holding region, which indicates that longer curing helps a full crosslinking and results in rougher polymer. Moreover, CTE of PDMS was in situ obtained from the curvature change during the cooling region, which is due to the thermal mismatch between polymer and underlying silicon substrate. This work provides a feasible way to investigate the mechanical properties of thin film transparent polymer materials, which may shed some light on their application in mechanical biosensors.
9:00 PM - DD6.8
Magnetron Sputtering Deposition of Calcium Phosphate Films with Nanoscale Grain Morphology in their Surface.
Wilfredo Otano 1 , Víctor Pantojas 1
1 Physics, University of Puerto Rico at Cayey, Cayey, Puerto Rico, United States
Show Abstract9:00 PM - DD6.9
Failure Investigation of Polymer Mechanical Components.
Yi Zhao 1 , Xin Zhang 2
1 Biomedical Engineering Department, The Ohio State University, Columbus, Ohio, United States, 2 , Boston University, Boston, Massachusetts, United States
Show Abstract
Symposium Organizers
Kalpana Katti North Dakota State University
Christian Hellmich Vienna University of Technology (TU Wien)
Christopher Viney University of California-Merced
Ulrike Wegst Max-Planck-Institut for Metals Research
DD7: Molecular Mechanics of Biological Systems
Session Chairs
Kalpana Katti
Christopher Viney
Wednesday AM, November 29, 2006
Back Bay D (Sheraton)
9:30 AM - **DD7.1
Spider Silk Proteins as Biomaterials.
Randolph Lewis 1 , Florence Teule 1 , Amanda Brooks 1 , Shane Nelson 1
1 Molecular Biology, University of Wyoming, Laramie, Wyoming, United States
Show Abstract10:00 AM - DD7.2
Influence of Mineral on the Deformation Mechanism of Protein in Natural Biocomposite, Nacre.
Pijush Ghosh 1 , Dinesh Katti 1 , Kalpana Katti 1
1 Civil Engineering, North Dakota State University, Fargo, North Dakota, United States
Show Abstract10:15 AM - DD7.3
Numerical Analysis Technique to Simulate Detachment of Cells from Adhering to Substrates.
Chun Lu 1 , Qian Hua Cheng 1 , Yong Wei Zhang 2 , Ping Liu 1
1 , Institute of High Performance Computing, Singapore Singapore, 2 Department of Materials Science and Engineering, National University of Singapore, Singapore Singapore
Show Abstract10:30 AM - DD7.4
Microstructure, Nanostructure and Properties of the Wasp Petiole.
Emily Reed 1 , Michael Dunlap 1 , Christopher Viney 1
1 , University of California at Merced, Merced, California, United States
Show AbstractThe petiole (waist) of a wasp is a narrow constriction occurring between the first and second abdominal segments. In the case of mud dauber wasps [Sceliphron caementarium (Hymenoptera: Sphecidae)] the petiole is approximately cylindrical; in mature adults it can attain lengths approaching 10 mm, while the external width is only ca. 0.5 mm. It is hollow, accommodating and protecting the alimentary canal, nerve tissue and open circulatory functions that communicate between the thorax and remaining abdominal segments. The legs and wings are attached to the thorax, so that, whether the insect is crawling or flying, almost all of the weight of the abdomen must be supported by the petiole – without the petiole undergoing deformations that would damage its contents. The load on the petiole increases when a wasp uses its stinger to immobilize prey.There are two intriguing materials-related lessons to be learned from studying the structure of the wasp petiole. First, there is a structural lesson, concerned with the relationship between efficient use of material, molecular organization, and mechanical property optimization. The petiole wall thickness in relation to the length and internal diameter of the petiole requires a molecular arrangement that guarantees sufficient stiffness to avoid bending and/or buckling. A second lesson concerns the factors that limit molecular and energy transport in self-assembling materials systems. In the absence of a closed circulatory system, the wasp must rely significantly on diffusion and the control of chemical potential to deliver metabolites to where they are needed. The length of the petiole may represent an upper limit to the distances over which simple diffusion-limited chemistry in the wasp is able to sustain its life functions. Alternatively, the petiole may contain structures that promote fluid flow through its interior. Given our ability to obtain information about its microstructure and nanostructure, the petiole represents an interesting model system for studying biomolecular transport phenomena in a relatively accessible context.We will present the results of studies performed by light microscopy, environmental scanning electron microscopy and transmission electron microscopy – complemented by mechanical property data – to address these two lessons.
10:45 AM - DD7.5
Poroelastic Indentation Analysis for Hydrated Biological Tissues.
Michelle Oyen 2 3 , Sakya Tripathy 1 , Edward Berger 1 , Amanpreet Bembey 2 , Andrew Bushby 2
2 , Queen Mary, University of London, London United Kingdom, 3 Engineering, Cambridge University, Cambridge United Kingdom, 1 , University of Virginia, Charlottesville, Virginia, United States
Show Abstract11:30 AM - DD7.6
Characterization of Ultra-Sensitive Air Flow Receptors of live Wandering Spiders.
Michael McConney 1 2 , Clemens Schaber 3 , Michael Julian 1 , Friedrich Barth 3 , Vladimir Tsukruk 1 2
1 Department of Materials Science and Engineering, Iowa State University, Ames, Iowa, United States, 2 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Department of Neurobiology and Behavioral Sciences, University of Vienna, Vienna, Vienna, Austria
Show Abstract11:45 AM - DD7.7
A Study of the Passive and Active Responses of the Pulmonary Arterial Wall.
Katherine Zhang 1 , Kendall Hunter 2 , Craig Lanning 2 , D. Ivy 2 , Robin Shandas 2 3
1 Department of Aerospace and Mechanical Eng, Boston University, Boston, Massachusetts, United States, 2 Department of Pediatric Cardiology, The Children's Hospital, Denver, Colorado, United States, 3 Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado, United States
Show Abstract12:15 PM - DD7.9
Universal Morphological Patterns in Wood:Micromechanics-based Prediction of Anisotropic Strength from Composition and Microstructure.
Karin Hofstetter 1 , Christian Hellmich 1 , Josef Eberhardsteiner 1
1 Institute for Mechanics of Materials and Structures, Vienna University of Technology (TU Wien), Vienna (Wien) Austria
Show Abstract12:30 PM - DD7.10
Single Molecule Manipulation of β-Carotene on Au(111) at 4.6 K with a Scanning Tunneling Microscope Tip.
Timur Skeini 1 , Violeta Iancu 1 , Saw-Wai Hla 1
1 Quantitative Biology Institute, and Physics & Astronomy, Ohio University, Athens, Ohio, United States
Show AbstractThe single molecules of an all-trans β-carotene adsorbed on the Au(111) surface were investigated using a low temperature scanning tunneling microscope (STM) at 4.6 K in a ultra-high-vacuum condition. On the Au(111), the β-carotene molecules can be found as a form of a cluster, as well as, isolated single molecules. Furthermore, the β-carotene molecules can transform from the trans to cis conformation on this surface. The STM manipulation experiments on β-carotene often result in lateral displacement of entire clusters indicating strong interactions between the neighboring molecules within the cluster, but weak between the molecules and the Au(111) surface. By injecting the tunneling electrons, we can excite and induce the rotation of a cis β-carotene on the surface. This work is financially supported by the US-DOE DE-FG02-02ER46012 grant.
12:45 PM - DD7.11
An Improved Analysis for Damping of Viscoelastic Materials in Nanoindentation.
Wendelin Wright 1 , Aileen Maloney 2 , William Nix 2
1 Mechanical Engineering, Santa Clara University, Santa Clara, California, United States, 2 Materials Science and Engineering, Stanford University, Stanford, California, United States
Show AbstractDD8: Tissue Mechanics IV
Session Chairs
Christian Hellmich
Christopher Viney
Wednesday PM, November 29, 2006
Back Bay D (Sheraton)
2:30 PM - **DD8.1
Some Thermodynamics Aspects of Biological Remodeling.
Krishna Garikipati 1 , Joseph Olberding 2 , Karl Grosh 3 , Ellen Arruda 4 , Harish Narayanan 5
1 Mechanical Engr, and Applied Physics, University of Michigan, Ann Arbor, Michigan, United States, 2 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Mechanical Engineering, and Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Mechanical Engineering, and Macromolecular Science & Engineering, University of Michigan, Ann Arbor, Michigan, United States, 5 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractWe examine some conclusions that follow from the premise that biological remodelling processes are driven by an overall tendency toward thermodynamic equilibrium. While true equilibrium is attained only at cell or tissue death, it appears that some insight can be gained by considering the stationarity of a limited free energy in certain "quasi-equilibrium" states. At first, a formal variational derivation will be sketched out in the context of configurational changes, and an easily-accessed example of this treatment will be presented. Next, the talk will proceed to a simpler description of remodelling in the setting of internal variables. This latter treatment is especially applicable to remodelling of the extra-cellular matrix (ECM), and the cytoskeleton. Some experiements on remodelling of the ECM will be discussed. To conclude, the remodelling of the ECM and cytoskeleton will be used to point out an apparent thermodynamic inconsistency of stiffening biomaterials, and its resolution by the inclusion of coupled biophysics.
3:00 PM - DD8.2
Modeling the Mechanics of Unbinding Between Extracellular Ligands and Cell Surface Receptors.
Emily Walton 1 , Krystyn Van Vliet 1
1 Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show Abstract3:15 PM - DD8.3
Effect of Resting Length and Viscoelasticity on Stiffness and Contractile Force in the Intact Muscle.
Virginia Ferguson 1 2 , Louis Stodieck 2
1 Department of Mechanical Engineering, University of Colorado, Boulder, Colorado, United States, 2 BioServe Space Technologies, University of Colorado, Boulder, Colorado, United States
Show Abstract3:30 PM - DD8.4
Indentation Mechanics of Soft Materials using a Secondary Sensing Device.
Asha Balakrishnan 1 , Simona Socrate 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractIndentation techniques are very often used to measure mechanical properties of materials when a specimen must remain in specific form and location. Typically, the motion of the main indenter is driven to a specified depth by an actuator, and the in-line force response is measured accordingly. The procedure to obtain unique material properties that correspond to the observed force-displacement response from the indenter tip is not straightforward. This inverse problem is often solved numerically using finite element simulations. A simple force-displacement curve for the indenter does not contain enough information to characterize complex material responses. Even for the simplest case of isotropic linear elasticity, material behavior is characterized by two independent material properties such as the elastic modulus and Poisson’s ratio, or shear modulus and bulk modulus. These properties are traditionally obtained from compression or tension experiments where lateral stretch can be measured. Materials with different combinations of elastic moduli and Poisson’s ratio can give rise to a force-displacement response which differs only in minor details. To date, there are no additional measurements performed to attempt to capture the second material property.We believe there is opportunity to gain more behavioral data by measuring the response of the material in the near field of a semi-infinite body to the indentation. By placing a captive spring-guided linear variable differential transducer (LVDT) at a critical offset distance away from the main indenter, near field behavior of the tissue can be measured. Preliminary finite element simulations have been performed to include the response of the passive LVDT. A flat 10mm diameter indenter and a passive spring with a 10mm diameter ball at the end are placed 20mm away from the main indenter. The indenter and spring are put into contact with the tissue, and the indenter is displaced 3.5mm into the material while the passive spring remains in the same location. The simulation is performed for two materials with similar elastic moduli and very different Poisson’s ratios where nu1 is 0.1, and nu2 is 0.49. In the low Poisson’s ratio case, the force on the LVDT decreased as the indenter traveled into the material. In the opposing case, where Poisson’s ration is high, the force increase as the nearly incompressible material prescribed more material flow. The results clearly show that the main indenter response is exactly the same for both cases, but the LVDT response is completely different. This result indicates that useful information can be gained by placing a secondary sensor at a critical distance to the indenter. In the case of simple linear elasticity, uniqueness can be preserved. The behavior of more complex materials, such as viscoelastic materials, has also been simulated and the ball response indicates the secondary sensor is capable of determining differences in material response.
3:45 PM - DD8.5
Seeing The Invisible: Scanning Near-Field Ultrasound Holography (SNFUH) For High Resolution Sub-Surface Imaging.
Gajendra Shekhawat 1 , Vinayak Dravid 1
1 Material Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show Abstract4:30 PM - **DD8.6
A Novel Shear Assay Technique of the Measurement of Single Cell Viscoelastic Properties and Cell Adhesion.
Zong Zong 1 2 , Yifang Cao 1 2 , Guoguang Fu 1 2 , Alberto Cuitino 3 , Dajun Zhang 3 , Wole Soboyejo 1 2
1 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States, 2 Princeton Institute of Science and Technology of Materials, Princeton University, Princeton, New Jersey, United States, 3 Mechanical and Aerospace Engineering, Rutgers University, New Brunswick, New Jersey, United States
Show AbstractTransferWednesday 11/29DD8.8 to *DD8.64:15 pm to 3:30 pmA Novel Shear Assay Technique of the Measurement of Single Cell Viscoelastic Properties and Cell Adhesion. Wole Soboyejo
5:00 PM - DD8.7
How Baby Plants Avoid Getting Hurt And Blossom Into Adulthood: The Story Of A Tropical Seed.
Peter Lucas 1 , Timothy Lowrey 2 , Robert Cook 3
1 Anthropology, George Washington University, Washington, District of Columbia, United States, 2 Biology, University of New Mexico, Albuquerque, New Mexico, United States, 3 Ceramics, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractSeeds, the embryo-containing units dispersed by plants, vary in construction greatly. However, few seeds have been analyzed mechanically, certainly not in their ecological context. This is a great pity because they are faced with an awkward dilemma, needing to open for germination, but avoid being opened by predators. With an eye on this problem, the ecology, and related materials science and engineering, of a seed (Mezzettia parviflora, Annonaceae) have been studied. The plant lives in the understory of Southeast Asian tropical forests, attacked by predators big (orangutans, the largest living arboreal mammals) and small (two species of scolytid beetles). To combat this multi-scaled onslaught, the seed (outer dimensions 35 x 25 x 15 mm) has a 3-4 mm thick woody shell of complex design: The outer millimeter of the shell has parallel sclerenchyma fibres while most of the rest has fibers coursing in bundles in apparently random orientations. However, there is also a prominent band running around the seed containing roughly spherical, equally thick-walled, cells called brachysclereids. Within the band at one end of the seed is a diamond-shaped woody plug, also made of brachyslereids, but ringed by thinner-walled cells that form a potential fracture zone. To germinate, the embryo—a thin sheet in the center of the seed—imbibes water. The turgor creates hydrostatic pressure inside the shell sufficient to generate a germination crack that starts from either side of the woody plug. The crack propagates within the band of brachysclereids, causing the seed to open up. Clearly, the seed seems engineered in a sophisticated manner, with the stress in the shell produced by turgor acting on a pre-crack (half the width of the woody plug) that is just large enough to extend in a quasi-equilibrium fashion. To confirm this Griffith energy balance, we used tensile, three-point bending and double cantilever beam tests to establish values for elastic moduli and fracture resistance. However, given the size of some of the seed’s anatomy, we also resorted to indentation techniques to track the properties of each of the shell’s parts. The results predict the turgor pressure that the embryo must produce. The shell’s hardness is probably the major deterrent to the beetles (these bore holes randomly in the shell): despite its structural complexity, shell hardness is pretty similar everywhere. In contrast, orangutans crack the shell open, but can’t use the germination crack, because the seed is too large to allow this.
5:15 PM - DD8.8
Universal Microstructural Patterns in Bone:Micromechanics-based Prediction of Anisotropic Material Behavior.
Christian Hellmich 1 , Andreas Fritsch 1
1 Institute for Mechanics of Materials and Structures, Vienna University of Technology (TU Wien), Vienna (Wien) Austria
Show AbstractTransferWednesday 11/29DD8.10 to DD8.84:45 to 4:15 pmUniversal Microstructural Patterns in Bone:Micromechanics-based Prediction of Anisotropic Material Behavior. Christian Hellmich
5:30 PM - DD8.9
FIB Applied to Biological Materials.
Ulrike Wegst 1 , Steffen Orso 1 , Birgit Heiland 1 , Eduard Arzt 1
1 , Max-Planck-Institute for Metals Research, Stuttgart Germany
Show Abstract
Symposium Organizers
Kalpana Katti North Dakota State University
Christian Hellmich Vienna University of Technology (TU Wien)
Christopher Viney University of California-Merced
Ulrike Wegst Max-Planck-Institut for Metals Research
DD9: Tissue Mechanics X
Session Chairs
Kalpana Katti
Ulrike Wegst
Thursday AM, November 30, 2006
Back Bay D (Sheraton)
10:00 AM - DD9.2
Cohesive-Frictional Plasticity of Bone.
Kuangshin Tai 1 , Franz-Josef Ulm 2 , Christine Ortiz 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThere is an increasing amount of interest in the ultrastructural origins of plasticity in bone and its nontrivial relationship to fracture. At this length scale, apatite mineralites exist (10s of nanometers (nm) in length and width, 1-5 nm in thickness) which permeate in and around type I collagen fibrils in an overlapping manner. We have reported previously the direct visualization of bone plasticity at the ultrastructural level by tapping mode atomic force microscopy imaging of residual nanoindentation impressions which showed the nanogranular structure of contacting mineralites flattened, but still visible, within the deformation zone. These data suggest the possibility of interparticle frictional interactions as a potential contributing energy dissipating mechanism. Hence, we hypothesize that the ultrastructure of bone behaves as a cohesive-frictional material and assume a Mohr-Coulomb pressure dependent strength criterion (arising from the pressure dependence of the density of interparticle contacts). To explore this hypothesis, dual nanoindentation experiments (maximum load ~ 1 mN, maximum depth ~ 200 nm) were carried out on adult bovine cortical bone perpendicular to the long bone axis (~ 65 weight % mineral content as measured by back-scattered electron microscopy) for two independent triaxial stress states that were achieved with two different indenter geometries, Berkovich (included angle 142.3°, half angle 65.3°) and Cube Corner (included angle 90°, half angle 54.6°). The mechanical response was modeled using an elastic-plastic three-dimensional finite element analysis model which incorporated the probe tip geometry and the Mohr-Coloumb pressure dependent strength criterion. A modulus of 18 GPa and a Poisson's ratio of 0.25 were approximated from the unloading slope of the force-depth curves using an isotropic, elastic continuum mechanical half-space formulation and fixed in the simulations. The two fitting parameters were the interparticle cohesion, c, and the internal friction angle, φ. The best fit φ and c values were found to be 13-17° and 80-120 MPa, respectively, for both indenter geometries. These values for φ estimated from the FEA simulations were consistent with angle of repose measurements in vacuum on thermally treated and sonicated deorganified bone particles (18.2 ± 2.5°, independent of particle size). Our results indicate that mineral interparticle frictional interactions are an important energy dissipating mechanism at the nanoscale in compressive modes of deformation and that the organic component has minimal contribution or effect on the frictional behavior (for the range of loads and depths probed here experimentally), suggesting that other mechanisms such as mechanical interlocking of interparticle surface nanoasperities may play a role.
10:15 AM - DD9.3
Lattice Deformations in Biogenic Crystals.
Boaz Pokroy 1 , Andy Fitch 2 , Emil Zolotoyabko 1
1 Materials Engineering, Technion Israel Institute of Technology, Haifa Israel, 2 ID31, European Synchrotron Radiation Facility, Grenoble France
Show AbstractOrganisms produce a variety of minerals (biogenic crystals), which often demonstrate superior characteristics as compared to their counterparts of non-biogenic origin. It is commonly believed that this is mainly achieved through crystal growth confined within the organic matrix. However, very recently we found evidences that the crystal properties are seemingly controlled at a deeper level, i.e. a nm or even molecular level. In particular, by using high-resolution x-ray powder diffraction measurements at synchrotron beam lines we observed clear differences between structural parameters of biogenic and geological CaCO3, which were attributed to the organic macromolecules entering the crystallites during biomineralization [1-3]. We demonstrated that the crystal lattices in the mollusk-made aragonite and calcite are anisotropically deformed as compared to their geological counterparts. The highest deformation (tensile strain of about 0.1-0.2 %) is always along the c-axis, i.e. perpendicular to the planes of carbonate groups to which the organic macromolecules exhibit a stereo-chemical recognition.In this paper we present the results of systematic structural measurements in biogenic CaCO3 crystals subjected to heat treatments at elevated temperatures. High-resolution x-ray powder diffraction measurements were carried out at the dedicated beam line ID-31 of the ESRF equipped with a crystal-monochromator and crystal-analyzer optical elements. The use of advanced x-ray optics resulted in the powder diffraction patterns of superior quality which allowed us to extract lattice parameters with an accuracy of 10 ppm.Mild heat treatments for 30 min at temperatures of 150-200 0C (aragonite) and of 250-300 0C (calcite) have led to the pronounced lattice relaxation that indicates thermal degradation of organic molecules. This is accompanied by substantial broadening of diffraction peaks which is rather unusual for ceramic materials subjected to annealing and resembles the x-ray diffraction profile modifications due to strain relief in epitaxial heterostructures by threading dislocations.Our findings indicate that organisms can, to some extent, control the atomic structure of grown crystals and thus, their mechanical properties. Deeper understanding of this phenomenon will aid in the development of new approaches towards growing nature-inspired composites and tailoring their properties at the molecular level.[1] B. Pokroy, J. P. Quintana, E.N. Caspi, A. Berner, and E. Zolotoyabko. Nature Materials 3, 900 (2004). [2] B. Pokroy, A. Fitch, P. Lee, J. P. Quintana, E. N. Caspi, and E. Zolotoyabko. J. Struct. Biology 153, 145 (2006).[3] B. Pokroy, A. Fitch, F. Marin, M. Kapon, N. Adir, and E. Zolotoyabko. J. Struct. Biology 155, 96 (2006).
10:30 AM - DD9.4
Effect of Water on Mechanical Properties of Mineralized Tissue Composites.
Amanpreet Bembey 1 , Michelle Oyen 1 3 , Virginia Ferguson 2 , Andrew Bushby 1
1 Department of Materials, Queen Mary, University of London, London United Kingdom, 3 Engineering, Cambridge University, Cambridge United Kingdom, 2 Department of Mechanical Engineering, University of Colorado, Boulder, Colorado, United States
Show Abstract10:45 AM - DD9.5
Elastic Properties of Flow Sensing Structures in Blind Cavefish.
Michael McConney 1 2 , Maryna Ornatska 1 2 , Melburne LeMieux 1 , Sheryl Coombs 3 , Vladimir Tsukruk 1 2
1 Department of Materials Science and Engineering, Iowa State University, Ames, Iowa, United States, 2 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Department of Biological Sciences, Bowling Green State University, Bowling Green, Ohio, United States
Show Abstract11:30 AM - DD9.6
Nanomechanical Heterogeneity as a Toughening Mechanism in Bone.
Kuangshin Tai 1 , Ming Dao 1 , Subra Suresh 1 , Ahmet Palazoglu 2 , Christine Ortiz 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Chemical Engineering and Materials Science, University of California at Davis, Davis, California, United States
Show AbstractThe ultrastructure of bone, like most natural materials, is highly heterogeneous due to distributions in shape, chemical structure, and composition of nanosized building blocks. At this length scale, type I collagen fibrils are mineralized with apatite crystals (tens of nanometers (nm) in length and width, and 1-5 nm in thickness), as well as a small concentration of noncollageneous proteins (<5%). The resulting local mechanical heterogeneity is expected to critically influence macroscopic mechanical function, in particular inelastic deformation and fracture. We investigate this topic by quantifying the two-dimensional spatial distribution of nanomechanical properties of adult bovine cortical bone parallel to and perpendicular to the long bone axis at the length scale of individual collagen fibrils. A series of nanoindentation experiments were carried out on a 2 μm × 2 μm square grid with a 100 nm inter-indent spacing using a 3-axis closed-loop atomic force microscope (AFM) and a nanosized AFM silicon cantilever probe tip (end-radius < 15 nm). Moduli were estimated at each position within the grid from the unloading slope using an isotropic, elastic half-space contact mechanical analysis. Contour maps produced from these data show elaborate spatial patterns of stiffness (~2-35 GPa) which do not correlate directly with corresponding topographical images and hence, are attributed to underlying local structural variations. These data were analyzed using discrete wavelet transform with three levels of decomposition where each level is associated with a "pseudo frequency" that identifies the relevant periodic patterns. The spatial patterns isolated at the first two levels possess length scales on the order of 136-166 nm and 274-334 nm, respectively. In order to investigate the effects of nanomechanical heterogeneity biomechanical properties at larger length scales, an elastic-plastic two-dimensional (plane strain) notched four-point bend finite element analysis model was built implementing the heterogeneous nanomechanical properties measured experimentally. A strain-based yield criterion was used to estimate the flow stress at each position within the heterogeneous region based on a 2D axisymmetric analysis of individual nanoindentation force-depth curves. Plasticity (damage) accumulation was tracked via the plastic equivalent strain of the elements. The effect of notch location, size, and orientation of heterogeneous maps were also studied. It is likely that these general concepts are applicable to a broad class of biological materials and may serve as a design parameter for biologically-inspired materials technologies.
11:45 AM - DD9.7
Nanotomography of Bone.
Stephanie Röper 1 , Anke Bernstein 2 , Christian Dietz 1 , Robert Magerle 1 , Nicolaus Rehse 1
1 Chemische Physik, TU Chemnitz, Chemnitz Germany, 2 Experimentelle Orthopaedie, Martin-Luther-Universitaet Halle/Wittenberg, Halle Germany
Show AbstractNatural materials such as bone and teeth are nanocomposites of proteins and minerals, which exhibit many levels of complex structure from macroscopic to microscopic length scale. Nanotomography is a novel approach to image such complex structures. We focus on human and ovine bones, which are first embedded in a methacrylate resin and then microtomed. For nanotomography the specimen is ablated layer-by-layer by wet chemical etching and imaged with scanning force microscopy after each etching step. From the resulting series of images the three-dimensional structure is reconstructed. Finding a proper etching method for both components, the mineral platelets and the collagen matrix is the first requirement for successful nanotomography imaging. On our poster we will present our results on etching experiments with different etching solutions. We will also show first nanotomography images of bone.
12:00 PM - DD9.8
Four-step Single Molecule Switch Made of Chlorophyll-a from Spinach.
Violeta Iancu 1 , Saw Hla 1
1 Physics and Astronomy, Ohio University, Athens, Ohio, United States
Show Abstract12:15 PM - DD9.9
Bioinspired Design of Functionally Graded Dental Multilayers.
Nima Rahbar 3 2 , Min Huang 1 2 , Stephen Farias 1 2 , Onobu Akogwu 1 2 , Jianbo Chen 1 2 , Wole Soboyejo 1 2
3 Civil and Environmental Engineering, Princeton University, Prineton, New Jersey, United States, 2 Prineton Institute of Science and Technology of Materials, Prinecton University, Princeton, New Jersey, United States, 1 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States
Show Abstract12:30 PM - DD9.10
Nanomechanics of Knockout Mouse Bones.
N Beril Kavukcuoglu 1 , Adrian Mann 1 2
1 Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States, 2 Biomedical Engineering, Rutgers University , Piscataway, New Jersey, United States
Show Abstract12:45 PM - DD9.11
Modeling Adhesion Forces in the Indentation of Cells Using Atomic Force Microscopy.
Zhang Chunyu 1 , Zhang Yongwei 1
1 Department of materials science and engineering, National university of singapore, Singapore Singapore
Show AbstractThe specific adhesion force in the indentation of cells using atomic force microscopy was modeled by combing the dynamics of the formation and rupture of ligand-receptor pairs with the finite element method. The multiple-steps rupture during the retracting procedure was quantitatively reproduced. Parametric studies were conducted to investigate the influence of the indentation rate and contact duration on the adhesion forces. The deformation induced by the adhesion force during the unloading phase was also studied. The numerical results were compared with several recently reported experimental findings.
DD10: Molecular Mechanics of Biological Systems
Session Chairs
Kalpana Katti
Christopher Viney
Thursday PM, November 30, 2006
Back Bay D (Sheraton)
2:30 PM - DD10.1
Force-Controlled Crystallization Microstamping.
Chao-Min Cheng 1 , Philip LeDuc 1
1 Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show AbstractThe bottom-up approach of growing and assembling inorganic crystals of biological relevance has received much attention recently. While this assembly is important, the ability to position these materials at defined locations would introduce additional control for a diversity of applications. The use of stamping methods has enabled to the ability to create spatially positioned patterns on surfaces in areas such as liquid actuation. Combining assembly and stamping of crystals to create gradient patterns though simple and reproducible methods would provide a new degree of freedom in studying many processes. Here, we propose a novel stamping method that applies pressure (mechanical force) on the upper surface of a stamp to regulate the dewetting process of a biocompatible inorganic buffer. This occurs while also controlling the evaporation rate of the solvent between the substrate and surface of the stamp. We implement this approach to define inorganic microstructures in specific patterns with the crystallization of associated inorganic salts. The mass transport during the dewetting process along with the evaporation rate of the inorganic solvent increases the concentration gradient in front of the solidification boundary. This allows us to have a greater growth velocity of the crystallizing structures when mechanical force is applied to the stamp. Furthermore, we also can control the size and distribution of the inorganic material using a single stamp with analogue patterning and force-contact control; this could alleviate issues with mask-based systems. This work has potential applications in a variety of fields including small scale fabrication and crystallization technology.
2:45 PM - DD10.2
Structural Evolution and Mechanical Behavior of Bio-inspired Oxide Films on Self-Assembled Organic Layers.
Guangneng Zhang 1 , Junghyun Cho 1
1 Mechanical Engineering, SUNY Binghamton, Binghamton, New York, United States
Show AbstractA bio-inspired approach is employed to deposit the ceramic films on the substrates coated with self-assembled organic layers. Several oxide films (e.g., titania, zirconia, silica) are grown in aqueous precursor solutions at near room temperatures (~70°C). This process, directed by the nanoscale organic template, mimics the controlled nucleation and growth of the biominerals such as bones and teeth. Multiscale structural evolution involving initial bulk nucleation, nanoparticle aggregation, and film formation are systematically studied by adjusting the precursor solutions and the organic template surface conditions. Dynamic light scattering (DLS) is utilized to characterize the nucleation and growth of the nanoparticles and associated aggregates formed in situ in solution. Corresponding microstructure developments of the ceramic films are investigated through high-resolution and analytical transmission electron microscope (TEM). In addition, mechanical performance is evaluated with the aid of dynamic nanoindentation testing to establish the structure-property relationships of the bio-inspired ceramic films, as well as to investigate the effect of the organic template. Further, scratch tests using the nanoindenter are employ to examine the adhesion between the ceramic films and substrates. One goal of this study is to identify controlling mechanisms responsible for nucleation and growth of such oxide films. It will ultimately provide a means of tailoring microstructures and mechanical behaviors of the oxide films through bio-inspired synthetic mechanisms.
3:00 PM - DD10.3
Biopolymer Polyelectrolyte Complex-hydroxyapatite Composites for Bone Tissue Engineering.
Devendra Verma 1 , Kalpana Katti 1 , Dinesh Katti 1
1 Civil Engineering, North Dakota State University, Fargo, North Dakota, United States
Show Abstract3:15 PM - DD10.4
Strength Calcium Phosphate Cements.
Alexander Veresov 1 , Alexander Kuznetsov 1 , Valery Putlayev 1 , Alexander Stepuk 1 , Kamilla Agahi 2 , Vladimir Kuznetsov 2
1 Materials Science, Moscow State University, Moscow Russian Federation, 2 Institute of Mechanics, Moscow State University, Moscow Russian Federation
Show Abstract4:15 PM - DD10.6
Nanobiomechanics of Stem-Cell Based Tissue Engineered Bone Generated in a Non-Union Defect Model.
Kuangshin Tai 1 , Gadi Pelled 2 , Dima Sheyn 2 , Yoram Zilberman 2 , Christine Ortiz 1 , Dan Gazit 2
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Skeletal Biotechnology Laboratory, Hebrew University-Hadassah Medical Campus, Jerusalem Israel
Show Abstract4:30 PM - DD10.7
Mechanical Properties and Permeability of Collagen-GAG Scaffolds: Experimental Results and Cellular Solids Modeling.
Brendan Harley 1 , Fergal O'Brien 2 , Lorna Gibson 3
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 2 , Trinity College and Royal College of Surgeons in Ireland, Dublin Ireland, 3 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States
Show Abstract4:45 PM - DD10.8
Characterization of Microvascular Autonomic Composites for Self-Healing.
Nancy Sottos 2 1 , Kathleen Toohey 2 , Andrew Hamilton 2 , Scott White 3 1 , Jennifer Lewis 4 1
2 Theoretical and Applied Mechanics, University of Illinois, Urbana, Illinois, United States, 1 Beckman Institute, University of Illinois, Urbana, Illinois, United States, 3 Aerospace Engineering, University of Illinois, Urbana, Illinois, United States, 4 Materials Science and Engineering, University of Illinois, Urbana, Illinois, United States
Show Abstract5:00 PM - DD10.9
Multiscale Modeling of Carbon Nanotube Adhesion for Dry Adhesives.
Zhenhai Xia 1 , Jianyu Liang 2
1 Department of Mechanical Engineering, University of Akron, Akron, Ohio, United States, 2 Department of Mechanical Engineering, WPI, Worcester, Massachusetts, United States
Show AbstractGeckos have extraordinary ability to move on vertical surfaces and ceilings. The secret of the climbing ability stems from their foot pads, a special hierarchical hairy structure. Mimicking such structure would lead to dry adhesives for many applications. Recent experiments showed that the adhesion of multiwalled carbon nanotubes is larger than that of a gecko foot-hair. To explore the adhesive mechanisms of the nanotubes, we have developed a multiscale approach to simulate the adhesion process of carbon nanotubes. A molecular dynamics is used to simulate the deformation and damage of the nanotubes when contacting with a rough surface at atomic scale. A coarse graining method is developed to predict the interactions and adhesion of larger scale nanotube array. The parameters used in the coarse graining method are determined by the detailed molecular dynamics. The preliminary results show that the nanotube bending under pre-applied pressure increases the contact area and therefore enhances the adhesion. The nanotube breakage during pre-loading will reduce the adhesion in post cycles. These results are consistent with the experiments found in literature.
5:15 PM - DD10.10
Friction between Polymer Brushes.
Jeffrey Sokoloff 1
1 Physics, Northeastern University, Boston, Massachusetts, United States
Show AbstractA polymer brush consists of a surface with a fairly concentrated coating of polymer chains, each one of which has one of its ends tightly bound to the surface. They serve as extremely effective lubricant, producing friction coefficients as low as 0.001 or less! Polymer brushes are a promising way to reduce friction to extremely low values. They must be immersed in a liquid solvent in order to function as a lubricant. The presence of a solvent is believed to result in osmotic pressure which partially supports the load. The fact that the joints in the human body are known to be immersed in a fluid known as the synovial fluid and polymers, known as hyaloronan and lubricin, are attached to the cartilage which coats the bones making up the joints strongly suggests that they are lubricated by the polymer brush mechanism. The force of static friction between two polymer brush coated surfaces is calculated using the mean field theory of their monomer density profile. The results agree with recent friction measurements for polymer brush lubricated surfaces. At sufficiently light loads polymer brush coated surfaces can slide, with the load supported entirely by osmotic pressure, and thus exhibit no static friction and only extremely weak viscous kinetic friction.