Symposium Organizers
Zhiqun Lin Iowa State University
Philip Moriarty University of Nottingham
Orlin Velev North Carolina State University
Xiao-Min Lin Argonne National Laboratory
MM1: Far-from-Equilibrium Assembly of Materials by Evaporation I
Session Chairs
Tuesday PM, April 06, 2010
Room 3018 (Moscone West)
9:30 AM - **MM1.1
Drying-mediated Self-assembly of Nanocrystals and Nanorods.
Eran Rabani 1
1 , Tel Aviv University, Tel Aviv Israel
Show AbstractA coarse-grained lattice gas model is presented to study the drying-mediated self-assembly of nanocrystals and nanorods. The model describes the nanocrystals/nanorods, the solvent and the substrate on length scales that are typical to the solvent bulk correlation length. Monte Carlo simulation techniques are used to delineate the various mechanisms of this out-of-equilibrium self-assembly processes. Several different assembly scenario corresponding to different evaporation conditions are discussed. The role of surface tension, evaporation rate, diffusion rate, coverage, aspect ratio is explored.
10:00 AM - **MM1.2
Evaporative Dewetting of Suspensions - Approaches From Dynamical Density Functional Theory to Thin Film Hydrodynamics.
Uwe Thiele 1 , Lubor Frastia 1 , Robbins Mark 1 , Andrew Archer 1
1 Department of Mathematical Sciences, Loughborough University, Loughborough United Kingdom
Show AbstractAfter reviewing recent experiments on evaporating anddewetting thin films of suspensions and solutions we focus on their description employing approaches ranging from microscopic discrete stochastic to mesoscopic continuous deterministic theories [1]. In particular, we first review a recently employed microscopic kinetic Monte Carlo model [2,3]. We then develop and apply a dynamical density functional theory (DDFT) [4] and a continuous thin film model [5] that are each able to capture certain aspects of the process.The DDFT is employed to discuss the formation of polygonal networks, spinodal structures and branched structures. Detailed results are given for the dependency of the observed transverse front instability on material constants and transport coefficients [4]. Finally, we discuss the simple thin film model consisting of coupled evolution equations for the film thickness profile and mean particle concentration [5]. It is used to discuss the self-pinnning of a contact line related to the 'coffee-stain' effect [6] and the emergence of periodic deposit structures.[1] for a small review see: U. Thiele et al., J. Phys.-Cond. Mat. 21, 264016 (2009).[2] E. Rabani, D.R. Reichman, P.L. Geissler, L.E. Brus, Nature 426, 271-274 (2003). [3] I. Vancea, U. Thiele, E. Pauliac-Vaujour, A. Stannard, C. P. Martin, M.O. Blunt and P. Moriarty, Phys. Rev. E 78, 041601 (2008). [4] A.J. Archer, M.J. Robbins and U. Thiele, submitted (2009).[5] L. Frastia, A.J. Archer and U. Thiele, in preparation (2009).[6] R.D. Deegan, Phys. Rev. E 61, 475-485 (2000).
10:30 AM - MM1.3
Electric Field Assisted Convective Assembly of Colloidal Crystal Coatings.
Jairus Kleinert 1 , Sejong Kim 1 , Orlin Velev 1
1 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractWe will present and discuss a new method of convective assembly of colloidal crystal coatings enhanced by application of an electric field. Convective assembly is a simple and controllable technique for depositing colloidal crystal coatings from a microparticle suspension evaporating at a withdrawing meniscus. However, the process can be slow, and the resulting coatings contain many small crystal domains. By applying an AC field across the particle suspension and substrate, the length of the liquid film in which the crystal assembles was extended by the electrowetting-on-dielectric effect. Film extension increased the evaporation-driven flux of particles to the growing crystal, resulting in a six-fold increase in the crystal assembly rate. The longer film provided more space for particle rearrangement before the coating dried, resulting in crystal structures with fewer defects. The crystal domains in coatings deposited with this new method were an order of magnitude larger than the domains in coatings deposited by convective assembly without an electric field. This work demonstrates how electric fields can be used to control liquid shape in order to fine tune evaporation-driven colloidal assembly processes and also provides an improved technique for large-scale colloidal crystal coating deposition.
10:45 AM - MM1.4
High Throughput Surface Nanopatterning of Organosilanes Using Masks of Latex Mesospheres.
Jing-jiang Yu 1 , Jie-Ren Li 2 , Jayne Garno 2
1 Nanotechnology Measurements Division, Agilent Technologies, Inc., Chandler, Arizona, United States, 2 Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana, United States
Show AbstractMillions of nanopatterns of organosilanes can be prepared with high throughput using particle lithography to define the size, arrangement and surface coverage of nanopatterns. Different strategies for particle lithography can be applied to prepare nanostructures using simple bench chemistry steps of centrifuging, mixing, drying, heating (evaporation) and rinsing. The sites for silane attachment are defined by the locations of water at the base of latex spheres. The area of contact between latex mesospheres and the surface determines the geometry of the nanostructures, as well as the placement of nanoscopic residues of water for silane binding. The surface coverage and periodicity of nanostructures can be exquisitely defined by the diameter of monodisperse mesospheres. Patterns were prepared on surfaces of mica, silicon, gold, glass or ITO films. The molecular head groups can be selected to spatially define the surface selectivity for further chemical steps to accomplish bottom-up assembly of nanostructures.
11:00 AM - MM1: Far-from-eq
BREAK
11:15 AM - **MM1.5
Mechanical Properties of Large-scale, Freestanding Nanoparticle Membranes Formed by Evaporative Self-assembly.
Heinrich Jaeger 1 , Jinbo He 1 , Pongsakorn Kanjanaboos 1 , Xiao-Min Lin 2
1 James Franck Institute, University of Chicago, Chicago, Illinois, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractThe ultimate limit of a thin film membrane is a single layer of atoms. In the form of graphene, the remarkable mechanical properties of such atomically thin, freestanding sheets recently have attracted considerable interest. Here I discuss their mesoscopic analogue, freestanding monolayers of close-packed nanocrystals or “artificial atoms”. These nanocrystal membranes combine several desirable properties. They are formed by evaporative self-assembly from a solution of ligand-coated nanocrystals, and they are exceedingly flexible yet strong under indentation, exhibiting Young’s moduli of several GigaPascals. In contrast to what currently is possible for their atomic counterparts, freestanding nanoparticle membranes can be assembled from a range of particle types, sizes and shapes and their mechanical properties can be tuned by the organic ligands. I will describe recent experiments designed to test the effect of different core materials (Au, Fe/Fe3O4 and CoO), different core sizes (mean diameter 5 nm, 13.8 nm and 8.5 nm, respectively), and different capping ligands (dodecanethiol, oleylamine and oleic acid, respectively). Our results demonstrate that from all of these materials close-packed monolayer membranes can be fabricated that span holes 1,000 or more particles wide by drying-mediated self-assembly. In fact, for CoO we were able to self-assemble membranes over 70 micron wide square openings, thereby freely suspending ~10^7 particles. Comparison of the three different core-ligand combinations suggests that the membrane strength is set by how tightly the ligands are bound to the particle core, rather than by the ligand-ligand interactions. Finally, I show how the monolayers’ mechanical response is modified by adding second and third layers.
11:45 AM - **MM1.6
Orientation and Assembly of Anisotropic Particles by Capillary Interactions.
Kathleen Stebe 1
1 Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractThe assembly of particles into ordered structures via capillary interactions is studied. These interactions arise when deformation fields from neighboring particles overlap. The excess area created by the particles decreases as the particles approach each other. Particles with shape anisotropy create undulations with excess area that is locally elevated, creating sites for preferred assembly. Particles orient and aggregate in preferred orientations. Furthermore, deformation fields created by the particles can interact with background curvature of the interface to orient and align the particles along principle axes of the interface. Thus, we have developed means to dictate object orientation, alignment, and the sites for preferred assembly, including means of promoting registry of features on particles. These ideas are developed for the example of a right circular cylinder using analysis, experiment and numerics. A series of other shapes are then studied to illustrate the generality of the concepts developed.
12:15 PM - MM1.7
The Relationship between Growth Speed and Ambient Humidity in Convective Self-assembly.
Hans Robinson 1 , Kai Chen 1 , Stefan Stoianov 1
1 Physics, Virginia Tech, Blacksburg, Virginia, United States
Show AbstractWe have investigated the effect of ambient humidity on the growth of colloidal crystals made with convective self-assembly. We find that the growth speed is strongly dependent on the humidity and we provide a simple scaling argument to explain our result. Our data is consistent with the length of the drying zone being of constant length, independent of flow rates and the pressure gradient in the drying colloidal crystal. This notion is also supported by the fact that additives such as surfactants and salt have little or no effect on the growth speed, even though they strongly affect both the capillary and disjoining components of the pressure in the water film. In fact, conditions can be created such that the latex spheres are deformed by the pressure during assembly, even while the growth speed remains unchanged. We also note that the geometry of the space surrounding the drying zone has as a strong influence on the speed of the self-assembly process.
12:30 PM - MM1.8
Reversible Evaporation to Measure and Control the Phase Behavior of Nanorod and Nanosphere Mixtures.
Seth Fraden 1 , Rafael Cabanas 1
1 Physics, Brandeis University, Waltham, Massachusetts, United States
Show AbstractTo study the phase behavior of mixtures of liquid crystals of filamentous virus fd and spherical colloids we employ a microfluidic device, the PhaseChip, which precisely meters, mixes, and stores sub-nanoliter amounts of sample, solvent, and other reagents. Thousands of individual mixtures are stored on a chip in individual wells. Furthermore, each well is in contact with a reservoir through a membrane through which only water can pass, but not salt, polymer, or amphiphile. This enables the precise and reversible dehydration and rehydration of all the nanoparticles in the mixture.Movies of the PhaseChip in action: http://www.elsie.brandeis.edu/
12:45 PM - MM1.9
Three-dimensional Patterning of Micro, Nano-Particle Assembly With Single Droplet.
Sun Choi 1 2 , Albert Pisano 1 2 , Tarek Zohdi 2
1 Berkeley Sensor and Actuator Center, UC Berkeley, Berkeley, California, United States, 2 Department of Mechanical Engineering, UC Berkeley, Berkeley, California, United States
Show AbstractCreating regular, repetitive and well-defined three-dimensional patterns of particle assembly in targeted area is a major bottleneck in various applications such as the fabrication of three-dimensional photonic crystals, printed electronics on flexible substrates, colloidal quantum-dot based devices for display, plasmonics and etc. Previous approaches to pattern particle assembly, however, are required to use entire substrates without selective positioning of particle assembly, chemically pre-patterned substrates or use soft-lithographic methods of which applicable particles are largely constrained by molds and substrate. Moreover, most of the previous techniques are grounded on the two-dimensional interaction between the substrate and particle assembly, thus, structuring three-dimensional particle assembly has been a huge challenge with those approaches. Evaporative self-assembly of meso, micro and nano-scale particles is well-known, interesting physical phenomenon at three-phase boundary (particle-medium-air), however, its applications have been mainly confined to fabricate planar structures since technical difficulty lies in controlling interaction between medium and particles in three-dimension. We propose unique and counter-intuitive idea that the coffee-ring effect of evaporating suspension can offer a governing method to create three-dimensional patterns of micro, nano-particle assembly via evaporative self-assembly. The patterns of the three-dimensional assembly of various sizes of micro-particles (Silica), metal oxide nano-particles (TiO2, ZnO) and metallic nano-particles (Ag) have been successfully generated by evaporating, low-concentrated particle suspension on photo-patterned substrate. The geometry of patterns was finely controlled by adjusting parameters of process and brief theoretical validation of this process has been also included. We demonstrate that photo-patterns with proper surface treatment can be used as an effective scaffold to structure particle assembly. Thanks to great simplicity, wide applicability to various materials and compatibility with existing IC processes, we anticipate that this simple technique will be widely used in the fabrication of three-dimensional photonic crystal, key-components in low-cost electronics / MEMS and will also provide an effective platform to study interesting electrical, optical properties of particle assembly with micro-size apparatus on-chip.
MM2: Structuring of Anisotropic Particle Systems
Session Chairs
Tuesday PM, April 06, 2010
Room 3018 (Moscone West)
2:30 PM - **MM2.1
Complexity in Nanocrystal Self-assembly: Size Mixing, Rods, Disks, Triangles, and Multiple Length Scales.
Brian Korgel 1
1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractAdvances in nanomaterials synthesis now provide a variety of size and shape monodisperse nanocrystals with characteristic dimension of ~10 nm and less. These nanocrystals are excellent models for studying self-assembly since they readily disperse in a variety of solvents, rapidly diffuse relative to the rate of solvent evaporation and are too small to be affected to gravitational settling. Nanocrystals have been observed to self-assemble into a wide range of different ordered structures, depending on their size, shape, and assembly process. Many of the fundamental forces that drive these self-assembly processes are known, however, experimental studies continue to surprise with many observations of unexpected complexity. This presentation will detail a range of examples of self-assembly, including breath-figure templated inverse opals of nanocrystals, aligned nanorod "stripes", mixed monolayers of spherical and rod-shaped nanocrystals, and ordered arrays of triangular nanocrystals along with an overview of the fundamental underpinnings of what forces direct nanocrystal self-assembly. The example of the formation of a simple hexagonal AB2 binary superlattice of nanocrystals of two different sizes will also be used to illustrate the intricacy of some of these assembly processes.
3:00 PM - MM2.2
Convective Assembly of Three-dimensional Dimer- and Spherocylinder-based Colloidal Crystals.
Ian Hosein 1 , Chekesha Liddell 1
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States
Show AbstractCalculations suggest that photonic bandgap structures with nonspherical bases promote defect resilient properties and wide bandgaps at low refractive index contrasts. However, the realization of complex ordered structures in three-dimensions has remained challenging and it is not clear that phases which form spontaneously using common methods will exhibit the desired optical properties. In the present work, we explore the self-assembly of polystyrene dimer- and spherocylinder shaped colloids via controlled drying on glass and silicon substrates. 3D monoclinic colloidal crystal structures are determined from scanning electron microscopy images of sections prepared using focused ion-beam (FIB) milling. Full photonic band gaps between the eighth and ninth bands are found for a systematic range of colloidal dimer shapes explored with respect to the degree of constituent lobe fusion and radius ratio. The pseudogap between bands 2 and 3 for spherocylinder-based monoclinic crystals is also probed using normal incidence reflection spectroscopy.
3:15 PM - MM2: Structuring
BREAK
MM3: Evaporation-driven Assembly in Biological Systems
Session Chairs
Tuesday PM, April 06, 2010
Room 3018 (Moscone West)
4:15 PM - **MM3.1
Protein Depositions from Drying Droplets.
Ronald Larson 1 , Marc Lopez 1 , Dong Lim 1 , Joerg Lahann 1
1 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractWe use a drying water droplet to deposit nanoparticles and proteins, such as BSA and rhodamine, onto substrates, including the affect of buffer salts, such as sodium bicarbonate, on the deposition patterns. We use fluorescently stained proteins to image the patterns in a fluorescence microscope, and video microscopy to follow the dynamics of the pattern formation. We find a wide range of phenomena, including Marangoni instabilities, wave-like crystallization fronts, and jerky contact line motion. We also find a wide variety of patterns, including concentric circles, dendritic patterns, bizarre squares, and partially filled patterns. These patterns are sensitive to protein content and concentration, buffer content and concentration, drying conditions, and substrate treatments. These phenomena are largely still mysterious, although they can be partially explained by contact line self-pinning, and supersaturation of salts for which nucleation is suddenly initiated. Possibly applications are discussed.
4:45 PM - MM3.2
Ultrathin Biocomposite Coatings from Particle and Live Cell Blends by Convective-Sedimentation Assembly.
Jessica Jenkins 1 , Lindsey Jerrim 1 , Michael Flickinger 1 2 , Orlin Velev 1
1 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Golden LEAF Biomanufacturing Training and Education Center (BTEC), North Carolina State University, Raleigh, North Carolina, United States
Show AbstractMonolayer (one cell height) coatings of bimodal blends of living cells surrounded by nanoporous polymer particles (for coating adhesion) offer several advantages over thicker film-forming composites, including: enhanced cell stability and adhesion, curtailed mechanical degradation, and increased reactivity via minimization of diffusion resistance and mutual shading of the embedded cells. Studies of convective-sedimentation assembly of bimodal blends of ~5 to 10 μm diameter yeast and 1 to 10 μm diameter non-film forming polystyrene particles on various substrates allowed us to develop such composite monolayer coatings of latex particles and live yeast cells. The results suggest that the coating apparatus incline, relative sizes of the suspension components (cells or particles), and the surface properties of the coating substrate influence the assembly process and subsequent coating homogeneity by affecting component movement during coating formation. Variations in the apparatus incline compensate for cell sedimentation by changing the direction of the sedimentation pathway. Similarly, the relative size ratio creates size-selective segregation, leading to either cell-particle segregation or dispersion. Finally, the substrate’s hydrophobicity influences the suspended component settling time by affecting the fluid evaporation rate. We have constructed and tested a novel prototype of a coating deposition apparatus that uses a continuously-fed coating suspension of polymer particles and/or live cells to yield longer, larger surface area uniform coatings than those previously deposited. These biological composite coatings are promising as multifunctional living paints with diverse environmental and energy applications, such as self-cleaning surfaces and photobiological hydrogen generators. They can also significantly expand the use of microbes in biosensors and anticorrosive coatings.
5:00 PM - MM3.3
Evaporative Deposition of Bacteria and Microspheres on Mica from a Sessile Drop: The Use of Surface Conditioning in a Laboratory Atmosphere to Control Drop Spreading and Particle Deposition Patterns.
Joan Curry 1 , Raina Maier 1 , Theresa Norris 1 , Kyle Baughman 2
1 Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona, United States, 2 Material Science and Engineering, University of Arizona, Tucson, Arizona, United States
Show AbstractEvaporative deposition from a sessile drop is an appealing way to deposit materials on a surface due to the simplicity of the technique. In this work we deposit aqueous solutions of two types of colloidal particles, namely bacteria and microspheres, on mica. We show that by controlling the extent of initial drop spreading through subtle changes in surface conditioning caused by exposure to the laboratory atmosphere in a laminar flow hood it is possible to systematically vary the particle deposition patterns. On freshly cleaved mica the contact angle of water is < 5°. Drops of bacterial and microsphere solutions deposited on freshly cleaved mica spread to cover a large surface area. Drying occurs through pinning and depinning events leaving a series of colloidal particle rings. We found in our laboratory that the contact angle of water on mica exposed to a constant flow of filtered laboratory air in a laminar flow hood gradually increases with time. For drops of both bacterial and microsphere solutions there is a corresponding decrease in the extent of drop spreading with increasing exposure of the mica surface to laboratory air. This results in a profound change in the colloidal particle deposition pattern. Short exposures of minutes to hours are enough to decrease spreading and affect the resulting deposition pattern. For our longest mica surface exposure times (months to 1 year) the contact angle of water reaches values near 20°. Spreading of the bacterial and microsphere drops is substantially decreased. A portion of the colloidal particles are deposited in an outer deposition ring which marks the extent of drop spreading and the remainder of the particles are deposited in the drop interior as a honeycomb or cellular film. The fraction of the drop residue covered with the cellular film increases with particle concentration as well as the length of time the mica is exposed to the laboratory atmosphere. This work shows that evaporative deposition on mica is very sensitive to surface conditioning through atmospheric exposure and also suggests that particle deposition patterns can be tuned by small changes in drop spreading.
5:15 PM - MM3.4
Evaporative Deposition of Bacteria from a Sessile Drop: Effects of Suspension Aging.
Kyle Baughman 1 , Raina Maier 2 , Joan Curry 2
1 Materials Science and Engineering, The University of Arizona, Tucson, Arizona, United States, 2 Soil Water and Environmental Science, The University of Arizona, Tucson, Arizona, United States
Show AbstractThis talk focuses on the behavior of sessile drops of a bacterial suspension with an emphasis the response of the drop behavior to the age of the bacterial suspension under carbon starved conditions. The bacterium studied was Pseudomonas aeruginosa (PAO1), and the surface used was mica. Aging effects of the mica will also be discussed. When a bacterial suspension which had been aged for 4 days or more was dropped on a mica surface, the contact angle was found to decrease as a function of the time between mica cleavage and the formation of the sessile drop, when the mica age was between 5 seconds and approximately 3 minutes. At longer mica ages, the contact angle was found to increase as a function mica age. The suspension aging process was found to be sensitive to the exposure of the bacteria to air.
5:30 PM - MM3.5
Evaporative Assembly of Two Dimensional Virus Nanoparticle Arrays.
Chin Li Cheung 1 , Alexander Rubinstein 2 , Erik Peterson 3 , Anju Chatterji 4 , Renat Sabirianov 2 , Wai-Ning Mei 2 , Tianwei Lin 4 , John Johnson 4 , James DeYoreo 3
1 Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 2 Physics, University of Nebraska-Omaha, Omaha, Nebraska, United States, 3 , Lawrence Livermore National Laboratory, Livermore, California, United States, 4 Molecular Biology, The Scripps Research Institute, La Jolla, California, United States
Show AbstractAssembly principles determining the organization of ordered nanosized objects are often revealed in the ordered assembly of biological molecules. We report our study of evaporative assembly of two dimensional cowpea mosaic virus (CPMV) arrays on mica substrates using osmotic depletion effects and a drop-and-dry method. Virus solutions of different polyethylene glycol surfactant concentrations are prepared to examine the effect of osmotic depletion forces in the virus assembly. Steric and electrostatic complementarity principles were demonstrated to explain the rhombic and hexagonal virus array morphology observed in our atomic force microscopy data. The charge patterns on each viral capsid protein coating and the geometry of the viral capsids were found to strongly influence different possible pair-wise inter-viral interaction configurations. These possible pair-wise configurations were extended to construct other two dimensional configurations for the explanation of different assembly array morphologies under the influence of surfactant.
MM4: Poster Session
Session Chairs
Tuesday PM, April 06, 2010
Exhibition Hall (Moscone West)
6:00 PM - MM4.10
Self-assembled Structures from Nonspherical C-60 Hexagonal Discs and Rods.
Ian Hosein 1 , Remington Fischer 1 , Chekesha Liddell 1
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States
Show AbstractSelf-assembly of submicron particles into colloidal crystal structures offers a rapid, tunable and scalable process for creating spatially periodic templates for nano-fabrication, micro-lens arrays and photonic crystals. Theoretical calculations have shown that colloidal crystals from non-spherical particles may allow robust and complete photonic bandgaps to open at lower refractive index contrasts, enabling a wider range of materials to be accessible for fabrication. Reprecipitation of fullerene (C-60) in ‘good’ and poor solvent mixtures produces uniform anisotropic particles in quantities amenable to particulate thin film formation. In the present work, 2D structures from C-60 discs and rods with hexagonal cross-section were fabricated via convective and confinement assembly methods. The structures were examined using scanning electron and optical microscopy. Photonic band calculations of corresponding model packing arrangements show that stable gaps open between several optical bands, for both transverse electric (TE) and transverse magnetic (TM) polarizations of light. The gaps were optimized by adjusting the particle shape and filling fraction of high refractive index material.
6:00 PM - MM4.2
Robust Self-assembly of Highly Ordered Complex Structures by Controlled Evaporation of Confined Microfluids.
Zhiqun Lin 1 , Suck Won Hong 1 , Myunghwan Byun 1
1 Materials Science and Engineering, Iowa State University, Ames, Iowa, United States
Show AbstractWe describe a robust, inexpensive, and one-step method that capitalizes on imposed axially symmetrical geometries (i.e., a curved surface placed upon a flat substrate) to control solvent evaporation and the associated capillary flow of an evaporating microfluid. By simply tailoring the shape of the upper surface, the imposed geometry directs the formation of a variety of complex, highly regular structures in a precisely controllable manner. As such, this method represents a significant advance in creating regularly organized, complex structures with potential applications in microelectronics, optoelectronics, and biotechnology, among other areas. By rationally designing the upper surface to accommodate different shapes, we envision the possibility of creating an even richer family of surface patterns. Furthermore, there should be no limitation on the solutes that can be applied to form such highly ordered structures. For example, by employing nanocrystals and/or block copolymers, complex multifunctional materials and highly regular devices demonstrating hierarchical order over two or multi-length scales may be created.
6:00 PM - MM4.3
Hierarchically Ordered Structures Enabled by Evaporative Self-assembly of Confined Comb Block Copolymer.
Myunghwan Byun 1 , Ned Bowden 2 , Zhiqun Lin 1
1 Materials Science & Engineering, Iowa State University, Ames, Iowa, United States, 2 Chemistry, University of Iowa, Ames, Iowa, United States
Show AbstractWe demonstrate the controlled evaporative self-assembly of an asymmetric comb block copolymer toluene solution in a wedge-on-flat geometry for generating the microscopic gradient surface patterns of comb block copolymer. These periodic hierarchically ordered structures (i.e., straight lines and punch-hole like mesh) are dictated by the height of the upper wedge lens that determines the height of capillary bridge. Upon subsequent solvent vapor treatment, morphological changes via the interplay of surface tension-driven destabilization at the micrometer scale and solvent vapor-induced microphase separation of comb block copolymer at nanometer scale are observed. As such, this facile approach offers a new platform for patterning the block copolymer thin film with various domain structures in a simple, robust, and cost-effective manner.
6:00 PM - MM4.4
Controlled Evaporative Self-assembly of Hierarchically Structured Regioregular Conjugated Polymers.
Myunghwan Byun 1 , Robyn Laskowski 2 , Ming He 3 1 , Feng Qiu 3 , Malika Jeffries-El 2 , Zhiqun Lin 1
1 Materials Science & Engineering, Iowa State University, Ames, Iowa, United States, 2 Chemistry, Iowa State University, Ames, Iowa, United States, 3 Macromolecular Science & Enineering, Fudan University, Shanghai China
Show AbstractA toluene solution of the semiconducting conjugated polymer regioregular poly (3-hexylthiophene) (rr-P3HT) was confined in a sphere-on-flat geometry, forming an axially symmetric, capillary-held microfluid, from which the consecutive ‘‘stick–slip’’ motion of the contact line of the solution via solvent evaporation was effectively regulated. As a result, hierarchical ‘‘snake-skin’’ like structures of high regularity were obtained where each microscopic ellipsoid within the ‘‘snake-skin’’ was composed of bundles of rr-P3HT nanofibers. This facile, one-step deposition technique based on controlled evaporative self-assembly opens up a new avenue for organizing semicrystalline conjugated polymers into two-dimensional ordered patterns in a simple, cost-effective, and controllable manner.
6:00 PM - MM4.5
Functional Polymers for Advanced Lithography.
Kyung Choi 1
1 , University of California, Irvine, California, United States
Show AbstractNanotechnology has been seeking for novel functional polymers at low cost to improve performance of plastic electronics. New polymers and novel fabrication techniques are desperately required in this area. Soft lithography has been widely used in the replication and fabrication of small features as a low cost alternative to conventional photolithography. However, commercial materials used in current soft lithography are limited in their applications to nano-resolution lithography. These limitations have motivated us to develop functional polymers to overcome the limitations and thus to extend this technology to the advanced level. Since the resolution of soft lithography significantly relies on the performance of stamp materials, we present here an enhanced performance from advanced stamp materials for the case of nano-striated features, which is one of the most challenging nano-patterning tasks in soft lithography. We also demonstrated elastomeric photopatterns by developing photocurable PDMS prepolymer. We will also present novel microfluidic reactors specifically designed for microfluidic synthesis by taking advantage of micro-scale mixing of multiple reagents and of the use of quenching sequences for greater reaction selectivity. The use of microfluidics offers a number of potential advantages over existing technology. Chemical mixings and reactions run in microfluidic devices have high thermal and mass transfer rates with an opportunity to use more aggressive reaction conditions allowing for improved product yield. Moreover, high chemical homogeneity can be achieved by complex mixing.
6:00 PM - MM4.6
Fabrication of Core-shell Structured Nanofibers by Using One-step Electrospinning Technique and 3-D Nanofibers Meshed Form in Hydrogel Cube for Programmable Delivery.
Eunmin Jo 1 , Unyong Jeong 1
1 Materials and Science Engineering, Yonse University, Seoul Korea (the Republic of)
Show AbstractPolymeric nanofibers have been attracting significant attention lately for topical drug delivery system applications. The ever growing interest on nanofibers are based on their ability to incorporate a wide range of drugs, the high surface area of the 3-dimensional mats for efficient drug release and the ease of fabricating the delivery vehicle in the required architecture. The nanofibers are considered to be useful for wound dressing, artificial organs and multifunctional membranes. Electrospinning system is a useful way to fabricate nanofibers in a continuous process. The dimension of the nanofibers can be controlled from tens of nanometers to a few micrometers. We fabricated core-sheath nanofibers consisting of polymer shell and hydrogel core by using electrospinning method & core-shell structured (polymeric shell and several threads in the core) nanofibers by using one-step technique. And then nanofibers covered hydrogel which are observed that dye & protein of nanofibers released during experimental period. The hydrogel system block off dye & protein released.
6:00 PM - MM4.7
A Phase Diagram to Determine the Deposit Left by an Evaporating Colloidal Droplet.
Rajneesh Bhardwaj 1 , Xiaohua Fang 2 , Ponisseril Somasundaran 2 , Daniel Attinger 1
1 mechanical engineering, columbia university, New York, New York, United States, 2 Department of Earth and Environmental science, Columbia University, New York, New York, United States
Show AbstractThe shape of deposits obtained from drying colloidal drops matters for technologies such as inkjet printing and bioassay manufacturing. In this work, we propose a phase diagram that explains how the shape of a colloidal deposit results from the competition between three flow patterns: a radial flow driven by evaporation at the wetting line, a Marangoni recirculating flow driven by surface tension gradients, and the transport of particles towards the substrate driven by DLVO interactions. This phase diagram explains three types of deposits observed experimentally, such as a peripheral ring, a small central bump, or a uniform layer. Simulations with an in-house numerical code [1] and experiments using solutions of Titania particles with varying pH values are found in good agreement. References[1] Bhardwaj, R., X. Fang, and D. Attinger, Pattern formation during the evaporation of a colloidal nanoliter drop: a numerical and experimental study. New Journal of Physics, 2009. 11: p. 075020.
6:00 PM - MM4.8
Formation of Nanoscale Structures by Evaporative Patterning Using Ion-beam-modified Masks of Silica Particles.
Juan-Carlos Cheang-Wong 1 , Eder Resendiz 1 , Ulises Morales 1
1 , Instituto de Física, Universidad Nacional Autónoma de México, México, D.F. Mexico
Show AbstractColloidal silica particles are being intensively studied due to their potential applications in catalysis, intelligent materials, optoelectronic devices and coating technology. The properties of these SiO2 particles depend on their size, size distribution and shape, which in turn determine the different roles they can play as electronic substrates, electrical and thermal insulators, photonic bandgap crystals, masks for lithographic nanopatterning, etc, in technologically expected nanodevices. Ion irradiation induces damage and structural changes in solids due to energy losses of multi-MeV heavy ions via ionization events and atomic collisions occurring in the near-surface region of the irradiated sample. Indeed, it has been observed that amorphous glassy materials like silicon dioxide can undergo extreme deformations under exposure to high-energy beams. This ion-beam induced anisotropic deformation of amorphous materials such as silica has been observed in the case of SiO2 films on Si substrates as well as in colloidal silica particles. Spherical submicrometer-sized silica particles were prepared by the Stöber method and deposited as a monolayer onto silicon wafers, in order to use them as a mask to create regular arrays of nanoscale surface features, such as Ag deposits. Also, ion beam modified masks were used to tailor the size and arrangement of these Ag deposits on Si substrates as a function of the ion fluence. Some of the samples were irradiated at room temperature with Si ions at 4 and 6 MeV and fluences up to 0.3×1015 Si/cm2, under an angle of 90° with respect to the sample surface. After the irradiation the silica particles turned into oblate particles, as a result of the increase of the particle dimension perpendicular to the ion beam and the decrease in the parallel direction. By this way, the mask openings of the silica particle monolayer were modified and a subsequent evaporative lithographic patterning of metallic Ag allowed the formation of 1-D ordered arrays of Ag features, after the silica removal with a HF solution. The size, size distribution and shape of both the silica particles and the Ag deposits were determined by scanning electron microscopy.
6:00 PM - MM4.9
Effects of Two Different Oxidants on the Growth of Conductive Poly(3,4-ethylenedioxythiophene) Thin Films in Vapor Phase Polymerization (VPP) Process.
Mohammad Ali 1 , Hyunho Kim 1 , Kyunghoon Jeong 1 , Heosup Soh 1 , Jaegab Lee 1
1 Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of)
Show AbstractPoly (3,4-ethylenedioxythiophene) (PEDOT) is particularly interesting conducting polymer due to its excellent environmental stability, high optical transparency in a visible wavelength and moderately high conductivity. Field emission scanning electron microscopy (FESEM) cross section images and Rutherford backscattering spectrometry (RBS) depth profiles revealed that in vapor phase polymerization (VPP), Fe3+ outdiffused to the Fe 3+ spin-coated surface and catalyzed the absorbed EDOT monomer to grow a PEDOT film, leaving the unreacted species underneath it. Two oxidants (FeCl3 and Iron(III) p-toluenesulfonate hexahydrate (Fe(PTS)3)) were employed for producing PEDOT films and then compared in terms of formation mechanism, surface roughness, conductivity of the conducting films. In case of the FeCl3 oxidant, thin layer of PEDOT film rapidly formed at the initial stage of growth followed by the formation of PEDOT islands. This resulted in the rough surface (RMS value ~10 nm for 55 nm thick PEDOT film) of PEDOT film. FeCl3 provided relatively higher growth rate (60 nm/min) and the conductivity of the PEDOT film was reached up to 400 S/cm. In contrast, Fe(PTS)3 oxidant with pyridine was forming a thin organic-rich layer on top of the Fe(PTS)3 spin-coated surfaces which controlled the incoming flux of EDOT monomer to the interface, where the polymerization occurred. It yielded the low growth rate (20 nm/min) of PEDOT films, leading to homogeneous PEDOT film having smooth surfaces (RMS value ~1 nm for 80 nm thick film) and high conductivity ~700 S/cm. As a result, the striking difference in the mechanism of PEDOT formation on between the two different oxidants, and its effects on morphology, crystalline structure, and conductivity of the PEDOT film will be presented.
Symposium Organizers
Zhiqun Lin Iowa State University
Philip Moriarty University of Nottingham
Orlin Velev North Carolina State University
Xiao-Min Lin Argonne National Laboratory
MM5: Assembling Nanomaterials by Surface Patterning
Session Chairs
Wednesday AM, April 07, 2010
Room 3018 (Moscone West)
9:30 AM - **MM5.1
Self-assembled Colloidal Building Blocks for Plasmonic Metamaterials.
Peidong Yang 1 , Joel Henzie 1
1 , Department of Chemistry, Berkeley, California, United States
Show AbstractColloidal nanocrystals are building blocks for an important class ofcomposite materials that can be completely assembled from the bottom up.This is because materials properties can be defined by finite-size effectsin inhomogeneous solids---often called metamaterials. Generation of large(>1 mm), ordered supercrystals depends on the monodispersity of thecomponent nanocrystals, and careful alignment of attractive and repulsiveinterparticle forces. We describe the synthesis and self-assembly ofsilver nanocrystals into different 1D, 2D and 3D lattices. Because thesestructures support collective excitations of free electrons called surfaceplasmon polaritons, they have interesting optical properties that dependon the resonance of the geometrical lattice.
10:00 AM - **MM5.2
Surface Nanopatterning from Bottom-up: Concepts and Perspectives.
Lifeng Chi 1
1 , Physikalisches Institut, Muenster Germany
Show AbstractSurface nanostructuring or nanopatterning is of great importance in modern science and technology. Patterning is usually achieved by top-down strategies, such as optical and e-beam lithography, soft-lithography, scanning probe lithography, and nanoimprint lithography. On the other side, concepts of self-assembly and self-organization provide alternative routes toward the formation of patterned structures via bottom-up approaches. In this talk, different methods for creating nanostructured surfaces by means of bottom-up concepts as well as the combination of top-down and bottom-up methods will be introduced, together with their potential applications.
10:30 AM - MM5.3
A Simple and Versatile Approach to Generate Superhydrophobic Surfaces via Dual-scale Roughness.
Raghuraman Karunakaran 1 , Cheng-Hsin Lu 1 , Zanhe Zhang 1 , Shu Yang 1
1 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractA superhydrophobic surface with extremely high water-repellency and very low flow resistance is of interest to numerous applications ranging from self-cleaning coating, microfluidics to biotechnology. Generally, wetting behavior is dependent on both surface chemistry (i.e. surface energy) and surface topography (i.e. physical roughness). The dual roughness observed in aquatic plants and insets has been suggested critical to the observed superhydrophobicity. While various groups have attempted to mimic the dual roughness in synthetic materials, their fabrication often involves complicated procedures and in some cases, long reaction time (e.g. > 10 hrs) to hydrophobilize the surface. Here, we present a simple and versatile approach to create dual-scaled rough surface to achieve superhydrophobicity. The dual-scaled nanoroughness was obtained by evaporation-induced assembly of APTES functionalized silica nanoparticles of two different sizes, 100 nm and 20 nm, on silicon wafers via dip-coating process. The co-assembly of dual scale nanoparticles resulted in superhydrophilic surface (water contact angle less than 5 o). After deposited with heptadecafluoro-1,1,2,2,-tetrahydrodecyl)trichlorosilane for only 1 h, the nanoparticle films became superhydrophobic with the advancing water contact angle greater than 160 o and the water droplet roll-off angle less than 5 o. In comparison, the assembly from the corresponding single nanoparticles did show enhanced hydrophobicity, advancing CA value = 143o, with large hysteresis after deposition of fluorosilane for a prolonged time, however, not superhydrophobicity. Further, we found that the sequence of dip coating of different sized nanoparticles and the nanoparticle concentration, thus nanoparticle coverage and distribution, were important to warrant the surperhydrophobicity. Finally we demonstrated self-cleaning behaviors on the dual-scale nanoparticle assembly.
10:45 AM - MM5: Surface pat
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MM6: Evaporation Induced Assembly in Polymeric Nanostructures I
Session Chairs
Wednesday PM, April 07, 2010
Room 3018 (Moscone West)
11:15 AM - **MM6.1
Phase Transition through Immiscible Solvent Vapors in Thin Films of Block Copolymers.
Bokyung Kim 1 , Sung Woo Hong 1 , Thomas McCarthy 1 , Thomas Russell 1 , Soojin Park 1 , Sung-Kwon Hong 1
1 Polymer Science & Engineering, University of Massachusetts, Amherst, Massachusetts, United States
Show AbstractThe phase transitions of a cylinder-forming block copolymer, BCP, thin film exposed to immiscible solvent vapors at two different temperatures was investigated. Preswelling with non-volatile solvent was used to prevent dewetting prior to the addition of a volatile solvent used to affect the annealing. The temperature and, therefore, the vapor pressure of the solvent was varied, which led to remarkably different kinetics of lateral ordering of the BCP microdomains. At 22 oC, a rapid annihilation of defects occurred with exchange of BCP chains between adjacent domains. At 17 oC a slow coalescence of two adjacent domains led to enhanced lateral ordering of the swollen BCP microdomains occurred leading to domains twice as large as those observed at 22 oC .These studies demonstrated that the large interfacial energy arising from the immiscibility of the components, coupled with an incommensurabilty of the swollen film thickness with the period of the BCP morphology, gave rise to the obeserved differences and subsequent lateral ordering of he BCP microdomains.
11:45 AM - **MM6.2
Evaporative Ordering of Block Copolymer Thin Films.
Ho-Cheol Kim 1 , Bokyung Yoon 1 , Pil Sung Jo 1 , Sang-Min Park 1 , Oun-Ho Park 1 , Cheolmin Park 2
1 , IBM Almaden Research Center, San Jose, California, United States, 2 Materials Science and Engineering, Yonsei University, Seoul Korea (the Republic of)
Show AbstractThin films of block copolymers have attracted much attention due to their potential lithographic applications. Indeed the length scales of microdomains, which typically range from 10 nm to 50 nm, are very attractive for extending the scaling roadmap of optical lithography for future technology generations. With the simplest molecular architecture of block copolymers, i.e. diblock copolymers, one could easily create periodic line/space patterns or arrays of dots on substrates. Extensive studies have been performed for controlling the orientation and lateral placement of microdomains on substrates, which is prerequisite for practical use of the block copolymer thin films as an alternative patterning method. Common process for block copolymer lithography involves thermal annealing to obtain ordered structures in thin films of block copolymers, which often limits the throughput. In this presentation we will discuss the ordering of block copolymers under controlled solvent environment and evaporation. We focus on ordering behavior during film deposition step (rather than post-annealing under solvent vapor) using three model material systems, poly(styrene-b-methyl methacrylate), poly(styrene-b-hydroxy styrene), and poly(styrene-b-ethylene oxide)/Organosilicate hybrid. Key experimental parameters governing the ordering behavior will be addressed based on both real space images and reciprocal space data.
12:15 PM - MM6.3
Study of Structural Anisotropy of P3HT Films During Solvent Evaporation Using in-situ Polarized Raman Spectroscopy.
Min Sang Park 1 , Avishek Aiyar 2 , Jung Ok Park 1 , Elas Reichmanis 2 , Mohan Srinivasarao 1 3
1 School of Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractThe charge transport properties of self-organized conjugated polymer films are strongly dependent on the molecular ordering during the solution casting process. We studied how the chain orientation of poly(3-hexylthiophene) (P3HT) is altered as function of evaporation time during the process of solvent evaporation, using polarized Raman spectroscopy and polarized optical microscopy. We observed the time evolution of anisotropy of P3HT films prepared by drop-casting with 1,2,4-trichlorobenzene as a solvent and found that directional preference of P3HT chain alignment changes only during the specific time duration. No anisotropy was detected either before or after this duration. These results were compared with the in-situ current measurements of P3HT solution during evaporation, and interpreted in terms of the solute-solvent-substrate interfacial interactions. The information of chain ordering in this study addresses the question of whether conjugated polymer films by solution casting can have nematic ordering with non-separable anisotropic interactions where mean field theory predicts ordering.
12:30 PM - MM6.4
Fine Tuning of Pattern Formation in Evaporation-induced Self-assembly of Polymer Bristles.
Sung Kang 1 , Ning Wu 1 , L. Mahadevan 1 , Joanna Aizenberg 1
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractEvaporation-induced self-assembly has been exploited as a new way of forming ordered and complex structures at different length scales. Recently, we have shown that unique hierarchical helical patterns of polymer bristles could be formed using capillary-induced evaporative self-assembly. During this process, careful tuning of the evaporation process, nucleation and propagation of the assembled clusters is crucial for controlling the size and pattern of the uniform domains. In this study, we have utilized a variety of approaches to manipulate the formation and movement of the meniscus line and studied its effect on the assembly of polymeric nano/microbristle. These included the use of confined geometries, changes in the direction and rate of evaporation, different liquids and temperatures. We have achieved a significant (~50 fold) improvement in the uniformity of the assembled features over a large area, as well as intriguingly complex patterns that were not observed by conventional evaporation methods. We will also report our work on real-time imaging of the assembly process that provides detailed information on the correlation between the meniscus movement, nucleation, and propagation of the assembled front and can be thus used to model the evaporation-induced assembly process. This study will significantly enhance our understanding of the evaporative assembly of the surface-attached arrays of polymer fibers and can provide a simple approach and new opportunities for fabricating complex, functional structures.
12:45 PM - MM6.5
Controlling Interdigitation in Self-assembled Nanoparticles Structures by Solvent Vapor Annealing.
Jin Young Kim 1 , Francesco Stellacci 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe successful application of nanoparticles-based devices will need reliable fabrication methods for well-defined, defect-free self-assembled structures of nanoparticles (NPs) through novel and innovative approaches, we believe that self-assembly of particles supracrystals will necessarily be one of them. NPs self-assembly is a process governed by an interplay between inter-particles interactions of various nature, such are core-core van derWaals and dipolar interactions as well as ligand shell interdigitation. The result of this delicate balance between strong interactions is often kinetically trapped self-assembled NPs structures . We will present an approach to improve the order of two-dimensional NPs supracrystals (NPSCs) after their assembly. This approach is based on a solvent vapor annealing (SVA) process that aims at providing enough ‘fluidity’ and energy to NPSCs so to foster particles movement out of kinetics traps and to achieve a structure closer to a true thermodynamic equilibrium structure. SVA operates only on interdigitation forces and has little or no effect on core-core interactions. Recently, in many soft materials containing self-assembled alkyl chains, SVA treatments have been reported to have a desirable effect on reorganizing the interchain overlap and improving crystallinity.1 The mechanism of SVA requires that solvent vapors interact with the interdigitated alkyl chains, so without re-dissolving the NPs the vapor promotes mobility and rearrangement at the nanoscale. Therefore it is expected that SVA treatment can supply activation energies to kinetically-trapped states of the assembled structures. We find that the choice of solvent determines the strength of interactions in the self-assembly, e.g. molecule-molecule vs molecule-solvent, and thus provides control over the self-assembly process. The key materials advancement that enables this work is that we have recently been able to make 2D NPSCs in the large areas onto many different substrates, which exhibits an extraordinary degree of monolayer perfection with a hexagonal array. We will show the effect of the particle size as well as ligand length on the NPSCs formation and SVA treatement. Results will be presented by quantification of the particles’ interdigitation by an accurate analysis of their images, using an in-house developed software program that enable the direct visualization of the degree of interdigitation. A general framework of understanding of interdigitation as a function of ligand used, ligand shell morphology, and SVA treatment will be presented.1)Lu, G.H.; Li, L.G.; Yang, X.N., Achieving perpendicular alignment of rigid polythiophene backbones to the substrate by using solvent-vapor treatment. Adv. Mater. 2007, 19, 3594-3598.
MM7: Controlled Evaporative Assembly of Polymers and Nanocrystals in Confined Geometries
Session Chairs
Wednesday PM, April 07, 2010
Room 3018 (Moscone West)
2:30 PM - **MM7.1
Evaporative Lithographic Patterning of Colloidal Films.
Jennifer Lewis 1
1 Materials Science and Engineering, University of Illinois, Urbana, Illinois, United States
Show AbstractWe have developed a promising new route for patterning a broad array of soft materials, known as evaporative lithography. In this approach, films are dried beneath a mask that induces periodic variations between regions of free and hindered evaporation. In aqueous systems, direct imaging reveals that colloidal particles segregate laterally within the film, as fluid and entrained particles migrate towards regions of higher evaporative flux. The films exhibit remarkable pattern formation that can be regulated by tuning the colloid volume fraction and size, separation distance between the mask and underlying film, and mask geometry. Additionally, more complex patterns arise in binary microsphere-nanoparticle suspensions or in non-aqueous systems subject to Marangoni stresses, in which recirculating flows are induced by temperature and surface tension gradients that arise during drying.
3:00 PM - MM7.2
Hierarchically Ordered Structures Enabled by Controlled Evaporative Self-assembly.
Zhiqun Lin 1 , Suck Won Hong 1 , Jun Wang 1
1 Materials Science and Engineering, Iowa State University, Ames, Iowa, United States
Show AbstractWe describe a simple and robust method for producing intriguing hierarchically ordered nanomaterials in a precisely controllable manner that dispenses with the need for lithographic techniques. Cylinder-forming diblock copolymer solutions are confined in a restricted geometry comprised of a spherical lens placed upon a flat substrate. At the micrometer scale, the synergy of the controlled evaporative self-assembly of a polymer solution and controlled fingering instabilities mediated by the interaction between the polymer and substrate yields intriguing concentric serpentine microstructures of diblock copolymer over large areas. Selective solvent vapor annealing then transforms these microstructures into a macroscopic web-like pattern composed of regularly arranged microporous mesh arrays, at the same time forming domains of closely packed, nanoscopic hexagonal cylinders of diblock copolymer that are vertically oriented to the surface of the web at the nanoscale. This approach thus utilizes two consecutive self-assembly processes to precisely organize unique nanomaterials into spatially ordered structures that can serve as functional materials for potential applications in optical, electronic, and photonic devices, biosensor arrays, templates for complex structures and pattern transfer, scaffolds for inorganic hierarchical structures, among other areas. By the judicious choice of shapes other than spheres for the upper surface, we anticipate the creation of a rich family of complex, hierarchically assembled surface patterns of varying architectures formed, on the one hand, via the synergy of the "stick-slip" motion and controlled fingering instabilities at the microscopic scale, and, on the other hand, the self-assembly of block copolymers with different morphologies (i.e., spheres, cylinders, or lamellae) and chemical structures (i.e., glassy, semicrystalline, or rubbery blocks) at the nanoscale.
3:15 PM - MM7.3
Fingers of Colloidal Particles Formed by Evaporative Self-assembly in Curve-on-flat Geometry.
Nathan Black 1 , Douglas Bousfield 2 , William Unertl 1
1 Department of Physics and Astronomy, University of Maine, Orono, Maine, United States, 2 Department of Chemical and Biological Engineering, University of Maine, Orono, Maine, United States
Show AbstractWe demonstrate that fingers of colloidal particles, oriented perpendicular to the solid-liquid contact line, can be formed by spontaneous evaporative self-assembly from confined colloidal suspensions. The aqueous suspensions consist of various polymeric latexes (100-1000 nm diameter) at concentrations in the range 0.05 – 5.0 weight parts/thousand. Confinement is between clean and modified glass surfaces in both cylinder- and sphere-on-flat geometries. Transportation of particles to the contact line during evaporation is observed optically in real time. After evaporation, atomic force microscopy is used to characterize the structure of the deposited particles. For contact angles less than 90°, particles are carried to the contact line by convective flow due to enhanced evaporation at the drop edge. Finger-like deposits, oriented perpendicular to the contact line, are left behind as the contact line retreats. The fingers typically consist of a monolayer of particles, are 10-50 particles wide, and are 500-1500 microns in length. Finger formation occurs in the following sequence: 1) particles accumulate just inside the drop edge; 2) finger growth initiates at the drop edge; 3) growth continues as the meniscus retreats; 4) growth stops when the suspension is depleted of particles. During the growth phase, fingers remain in contact with the liquid phase. This contact allows for evaporation from the surface of the fingers, supplied by capillary flow. This capillary flow leads to localized changes in the fluid flow within the drop, providing a self-sustaining mechanism for finger growth by preferentially bringing more particles to the growing fingers. Finger formation ceases as contact angles are increased to above 90° because enhanced evaporation at the three-phase contact line stops. Small amounts of glycerin are found to influence finger formation. For some conditions, glycerin eliminates finger formation, possibly due to accumulation of glycerin in the finger deposits which restricts capillary flow into the finger.
3:30 PM - MM7.4
Macroscopic Alignment of Self-assembled Gold Nanorods.
Jake Fontana 1 , Ashish Agarwal 2 , Nicholas Kotov 2 , Peter Palffy-Muhoray 1
1 Liquid Crystal Institute, Kent State University, Kent, Ohio, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractA critical component bringing optical metamaterials to fruition is the ability to produce self-assembled, highly-ordered, macroscopic assemblies of nanoparticles. We present a technique to produce self-assembled films with a high loading of orientationally ordered nanorods in macroscopic domains. Short aspect ratio gold nanorods were encased in silica to prevent aggregation while preserving both plasmon resonances in the visible spectrum at high loading. A suspension of silica encased gold nanorods in a solvent was placed between two glass substrates in a controlled atmosphere. A voltage was applied across the glass plates as the solvent evaporated from the suspension. Due to the complex interaction between the substrate, electric field and the fluid-vapor interface, films with macroscopic (~mm2) domains of radially aligned nanorods are produced on the substrate. We examine these films using various characterization methods to determine their physical and optical properties. Such radial structures may have useful applications in transformation optics. This work was supported by the AFOSR under MURI grant FA9550-06-1-0337.
3:45 PM - MM7: Controlled
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MM8: Far-from-Equilibrium Assembly of Materials by Evaporation II
Session Chairs
Wednesday PM, April 07, 2010
Room 3018 (Moscone West)
4:00 PM - **MM8.1
Capillary Force-induced Self-assembly of Colloidal Building Blocks.
Peng Jiang 1 , Wei-Lun Min 1 , Chih-Hung Sun 1 , In-Kook Jun 2 , Tzung-Hua Lin 1 , Wei-Han Huang 1
1 Department of Chemical Engineering, University of Florida, Gainesville, Florida, United States, 2 Department of Materials Science and Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractBottom-up self-assembly of spherical and nonspherical colloidal building blocks is of great interest for the development of new materials with potential applications in optoelectronics, photonics, magnetics, catalysis, and mechanics. For instance, spontaneously organized colloidal crystals provide a much simpler and faster alternative to complex nanolithography in creating 3-D ordered photonic crystals for next-generation nanophotonics. Inspired by the ordered assemblies of aragonite platelets in the nacreous layer of mollusk shells, oriented assembly of colloidal nanoplatelets is also interesting as it enables the production of nanocomposites with unique combination of stiffness, strength, and toughness. In this talk, we will discuss the spontaneous assembly of both spherical and nonspherical colloidal building block, including silica nanoparticles, silicon nanowires, gibbsite and graphene nanoplatelets, and ferromagnetic nanorods induced by capillary force at evaporating menisci. The resulting assemblies exhibit unique optical, antireflection, dewetting, mechanical, and magnetic properties.
4:30 PM - MM8.2
In situ GISAXS Characterization of 2D Virus-like Particle (VLP) Arrays Deposited via Convective Assembly.
Carlee Ashley 1 , Darren Dunphy 1 , Dimiter Petsev 1 , Plamen Atanassov 1 , Jin Wang 2 , David Peabody 3 , C. Jeffrey Brinker 1 3 4
1 Chemical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Advanced Photon Source, Argonne National Laboratories, Albuquerque, New Mexico, United States, 3 Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico, United States, 4 Self-Assembled Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractThe use of viral particles as building-blocks for the self-assembly of 2D materials presents a unique set of features relative to inorganic or polymeric nanoparticles, including (for icosahedral viruses) perfect monodispersity, ease of synthesis from laboratory cultures, the potential for genetic or chemical modification of surface functionality to direct the growth and/or binding of inorganic materials around the viral particle, and the ability of viral capsids to serve as encapsidation vessels for foreign materials. Integration of viral particles into long-range, hierarchical assemblies will require a continuous coating method applicable to large-scale solid substrates, however. One such deposition method is that of convective assembly (CA); in CA, evaporation of solvent drives the self-assembly of particles deposited from a meniscus trapped between the substrate and a plate moving across the substrate at a fixed angle. Here, we investigate the CA of 2D arrays of virus-like particles (VLPs) formed from the bacteriophages MS2 and Q-beta by following the self-assembly process in real-time using Grazing-Incidence Small-angle X-Ray Scattering (GISAXS) at a synchrotron source. We find that assembly of 2D VLP lattices from aqueous solutions is driven by convective flow induced by evaporation. When water is replaced in part by a non-volatile medium, however, our scattering data suggests that in-plane particle diffusion controls lattice formation, with increased long-range ordering relative to assembly under convective flow. Comparison of lattice assembly between VLPs for MS2 and Q-beta shows that modulation of interparticle forces is critical for maximizing the degree of long-range lattice ordering.
4:45 PM - MM8.3
Engineering Mass Transport in an Evaporating Sessile Droplet Using Silica Nanoparticles.
Sanjeevi Sivasankar 1 2 , Nathan Fowler 1 2
1 Physics and Astronomy, Iowa State University, Ames, Iowa, United States, 2 , Ames Laboratory, Ames, Iowa, United States
Show AbstractControlled mass transport during droplet drying is vital in many industrial and scientific applications. Here we show that the presence of non-volatile nanoparticles in an evaporating sessile drop gives rise to a complex pattern of fluid flow during desiccation. Using bright-field microscopy with multiple, triggered, high-speed cameras, we show that mass transport within a drying droplet correlates with the evolution of droplet shape. By varying the concentration of silica nanoparticles in the evaporating droplet, we can control fluid flow within the droplet. Droplets with engineered fluid flow can be used as 'micro-reactors' for controlled solute mixing during evaporation.
5:00 PM - MM8.4
Convective Steering in Growth of Colloidal Crystals.
Damien Brewer 1 , Joshua Allen 1 , Michael Miller 1 , Juan de Santos 1 , L.E. "Skip" Scriven 1 , David Norris 1 , Satish Kumar 1 , Tsapatsis Michael 1
1 , University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractColloidal self-assembly techniques are being actively investigated as routes to monolayer and multilayer crystals. Among the most promising applications for self-assembly processes are membrane separations and photonic crystals. Since early observations of phase behavior in colloidal suspensions, experiments and simulations have showed that face centered-cubic (fcc) packings are favored over random and hexagonally close-packed (hcp) structures. Because the free energy difference between hcp and fcc packings is a miniscule quantity (on the order 0.005 kBT per particle), hydrodynamic and colloidal interactions must direct crystal assembly in all but the most extraordinary phase-transition processes.There can be no uncertainty about the role of hydrodynamic and colloidal forces in ordered crystal assembly, for spheres as they take their places at the boundaries of a crystal must displace liquid, and this displacement of liquid constitutes flow. Liquid flow induces or follows in all aspects of the self-assembly process: expulsion of liquid from between latex or silica spheres as they are brought into actual contact by van der Waals forces; the motion of liquid that bears suspended particles towards the sphere pack boundary, or growth front, and continues into and through the packed particles.Among the predominant descriptions of fluid flow in both ordered and disordered porous media, the network model has provided insight into the link between microscopic structure and macroscopic transport properties. In this approach, an equivalent electrical network describes fluid motion through a connected graph of nodes. The network approach is particularly useful in elucidating the relationships between pore structure and fluid transport in the pore space. By distilling the constitutive equations for creeping flow through complex geometries, the network model enables one to describe key features of the colloidal assembly: packing selectivity, particle convection and growth rates, boundary facets, and capillary pressure distributions.In this discussion, we highlight microscopic features of the colloidal assembly process and their relationships with the macroscopic particulate coating. Selectivity for face-centered cubic packing through the {111} growth facet is discussed, as is solvent flow through {100} and {311} planes. Differences amongst these boundary arrangements are shown to dictate the distribution of liquid amongst the available pore throats, while not influencing the total convective flux. Network simulations of the entire wetted domain provide a self-consistent approximation for the capillary pressure and flow rate distributions in the assembling crystal as key processing parameters vary; convective flux and crystal growth rates can also be estimated.
5:15 PM - MM8.5
Numerical Simulations of Pattern Formation During the Evaporation of Colloidal Drops.
Rajneesh Bhardwaj 1 , Xiaohua Fang 2 , Ponisseril Somasundaran 2 , Daniel Attinger 1
1 mechanical engineering, columbia university, New York, New York, United States, 2 Department of Earth and Environmental Engineering, Columbia University, New York, New York, United States
Show AbstractAn efficient way to precisely pattern particles on solid surfaces is to dispense and evaporate colloidal drops, as for bioassays. The dried deposits often exhibit complex structures exemplified by the coffee ring [1] pattern, where most particles have accumulated at the periphery of the deposit. In this work, the formation of deposits during the drying of nanoliter colloidal drops on a flat substrate is investigated numerically. A finite-element numerical model is developed that solves the Navier-Stokes, heat and mass transport equations in a Lagrangian framework. The diffusion of vapor in the atmosphere is solved numerically, providing an exact boundary condition for the evaporative flux at the droplet-air interface. Laplace stresses and thermal Marangoni stresses are accounted for. The particle concentration is tracked by solving a continuum advection-diffusion equation. Wetting line motion and the interaction of the free surface of the drop with the growing deposit are modeled based on criteria on wetting angles. In this talk, our modeling, described in [2], is extended to account for the transport of particles towards the substrate driven by DLVO interactions. Numerical results for evaporation times, flow field and deposit shapes are in very good agreement with experimental and theoretical results. [1] Deegan, R.D., O. Bakajin, T.F. Dupont, G. Huber, S.R. Nagel, and T.A. Witten, Capillary flow as the cause of ring stains from dried liquid drops. Nature, 1997. 389: p. 827.[2] Bhardwaj, R., X. Fang, and D. Attinger, Pattern formation during the evaporation of a colloidal nanoliter drop: a numerical and experimental study. New Journal of Physics, 2009. 11: p. 075020.
5:30 PM - MM8.6
Concentrated Crystallization on Closely Packed Colloidal Crystal Films from Aqueous Suspension Under Silicone Oil.
Hiroshi Fudouzi 1 , Tsutomu Sawada 1 , Lucien Brush 2
1 Optronic Materials Center, National Institute for Materials Science, Tsukuba Japan, 2 Material Science Engineering, University of Washington, Seattle, Washington, United States
Show AbstractColloidal crystals have been attracting much attention due to their novel use as 3D-photonic crystals and to their structural color. Typically colloidal crystals are processed via convective self-assembly by vertical dip-coat deposition in which colloidal particles are directly packed by capillary flow within a suspension. A key issue for industry is the scaling-up of the processing of high-quality colloidal crystal films for larger area applications. We present recent results of a unique self-assembly process for large-area colloidal crystal films using the controlled manipulation of phase transitions within a colloidal suspension immersed in a silicone oil layer. (H. Fudouzi, J. Colloid Inter. Sci. 2004; H.Fudouzi, Colloids Surf. A 2007). We have developed a manufacturing technology based on this immersed-oil method for meter-scale coatings, patent application WO/2009/119677. In this process oxygen plasma cleaning is used to make a solid substrate surface hydrophilic. The surface of the substrate is then covered with a film of the colloidal suspension, and then the film is immersed in a layer of silicone oil. The liquid of the suspension diffuses through the silicon oil layer and evaporates at the silicone oil-air interface leaving the particles in the solution to crystallize. Optical microscope observations made in a suspension containing 202 nm polystyrene spheres show the suspension changes color from milky white in the bulk liquid, characteristic of random Brownian motion, to green near the contact line where the suspension meets the substrate. The green color is due to Bragg diffraction from the (111) planes of the close-packed colloidal crystal. In addition, the Bragg diffraction peak near the contact line of the opal film is measured with a miniature fiber optic spectrometer. The microscope image shows that between the ordered close-packed and the disordered states of the colloidal suspension the color gradually changes from red to yellow to green in a direction towards the contact-line. This corresponds to a Bragg diffraction peak shift from 603.5 nm for the red colored area to 565.7 nm for the green colored area suggesting a decrease in the distance between (111) planes of approximately 10-15 nm.This crystallization process is different from that of conventional convective self-assembly processes. Here, the colloidal crystal grows from the contact line at the outer edge of the suspension due to the loss of the liquid from the suspension through the oil. The role of the silicone oil is to slow down the self-assembly process. In front of the advancing colloidal crystal a non-close-packed colloidal crystal first forms followed by the formation of the close-packed colloidal crystal film after all the water among the colloidal particles has evaporated. Understanding the mechanism and kinetics of the crystallization process is important in scaling-up the coating of high-quality colloidal crystal films and we present our findings to date.
5:45 PM - MM8.7
Guided Organization of λ-DNAs into Microring-arrays from Liquid Capillary Microbridges.
Myunghwan Byun 1 , Suck Won Hong 1 , Jin-Woo Cho 2 , Zhiqun Lin 1
1 Materials Science & Engineering, Iowa State University, Ames, Iowa, United States, 2 Green Energy Research Center, Korea Electronics Technology Institute, Seongnam, Gyeonggi, Korea (the Republic of)
Show AbstractWell-ordered, mesoscale λ-DNA ring-arrays have been successfully produced via controlled evaporative self-assembly with capillary actions in liquid capillary microbridges. The dimension of the λ-DNA microrings can be readily tuned by the choice of the PDMS molds. This approach opens a new avenue to utilize evaporative self-assembly as an alternative to conventional lithographic techniques for generating biomolecular patterned arrays in a simple, precise, and cost-effective manner. Using this facile and robust route, a great variety of biomaterials can easily and precisely organized into well-ordered ring arrays, which may have potential applications in functional scaffolds for cell and tissue growth, biosensors, etc.
Symposium Organizers
Zhiqun Lin Iowa State University
Philip Moriarty University of Nottingham
Orlin Velev North Carolina State University
Xiao-Min Lin Argonne National Laboratory
MM9: Evaporation Induced Assembly in Polymeric Nanostructures II
Session Chairs
Thursday AM, April 08, 2010
Room 3018 (Moscone West)
9:30 AM - **MM9.1
Breath Figure Templated Assembly of Ordered and Disordered Array of Holes in Polymer Films.
Mohan Srinivasarao 1 2 3 , Jung Ok Park 1 3 , Vivek Sharma 4
1 School of Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Center for Advanced Research on Optical Microscopy (CAROM), Georgia Institute of Technology, Atlanta, Georgia, United States, 4 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractBreath figures are patterns are formed when water vapor from our breath condenses over a cold substrate. These patterns, which mimic the behavior of dew or chemical vapor deposition, comprise of drops with range of self-similar sizes, and form through coalescence assisted growth. Water drops that condense over evaporating polymer solutions can organize into close packed arrays, and template nicely ordered arrays of holes in polymer films. Using experiments and theory, we examine the role of various parameters that contribute to the formation of ordered assembly. We will present our findings about how the choice of polymer and polymer concentrations and air flow conditions influences the extent of order and the pore size.
10:00 AM - **MM9.2
Controlled Pattern Formation During Nanobristle Assembly in an Evaporating Liquid.
Joanna Aizenberg 1 , Sung Hoon Kang 1 , L. Mahadevan 1 , Philseok Kim 1
1 SEAS, Harvard University, Cambridge, Massachusetts, United States
Show AbstractSelf-assembly of fibrous materials is a common phenomenon in nature. We show how bio-inspired principles can be used to control self-organization of a synthetic polymeric nanobristle assembling in an evaporating liquid. We use a simple theoretical model to characterize the geometry, stiffness, and surface properties of the pillars that favor the adhesive self-organization of bundles with pillars wound around each other. The process can be controlled to yield highly ordered helical clusters with a unique structural hierarchy that arises from the sequential assembly of self-similar coiled building blocks over multiple length scales. We demonstrate their function in the context of self-assembly into previously unseen structures with uniform, periodic patterns and controlled handedness and as an efficient particle-trapping and adhesive system.
10:30 AM - MM9.3
Superhydrophobic Materials from Fumed Silica.
Brian Prevo 1 , Angelica Sanchez 1 , Joseph Carroll 1
1 , Cabot Corporation, Billerica, Massachusetts, United States
Show AbstractScientific research and understanding of superhydrophobic materials has grown and expanded tremendously in the past several decades. Mimicry of naturally occurring microstructures (e.g. lotus leaf) and periodic arrays by lithographic techniques have demonstrated specific wetting and non-wetting properties with the potential to be of immense value for the coatings and surfaces industries. However, many of these materials are costly to prepare and / or too fragile to withstand real world use. Colloidal scale materials deposition offers a ‘bottom up’ approach to this class of materials. Cabot has expanded on this approach by preparing coatings containing fumed silica, which offer cost effective access to such nano and microscale surface structures. The coating topographies are comprised of re-entrant microstructures that enable superhydrophobic surface properties such as high water contact angles with low contact angle historesis.
10:45 AM - MM9.4
Assembly Behavior of pH-responsive Heteroarm Star Block Terpolymers.
Ikjun Choi 1 2 , Ray Gunawidjaja 2 , Constantinos Tsitsilianis 3 4 , Vladimir Tsukruk 2 1
1 School of Polymer, Textile & Fiber Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Department of Chemical Engineering, University of Patras , Patras Greece, 4 , Institute of Chemical Engineering and High Temperature Processes (FORTH/ ICE-HT), Patras Greece
Show AbstractWe report the surface behavior and morphologies of two series of pH-responsive amphiphilic heteroarm star copolymers and star block terpolymers. These symmetric, amphiphilic star-shaped block copolymers differ by architecture, chain length (molecular weight from about 16 000 up to 30 000), and number of arms (n = 9, 22, and 28). We studied polystyrene/poly(2-vinylpyridine), PSnP2VPn heteroarm star copolymers, and polystyrene/poly(2-vinylpyridine)/polybutylacrylate, PSn(P2VP-PtBA)n , heteroarm star block terpolymers. Stable Langmuir monolayers of heteroarm star block copolymers were formed at the air-water interface. The π-A isotherms and compression-expansion cycles at different subphase pH (pH = 5.8 and 2.0) exhibit the strong pH dependency leading to the different limiting molecular area and surface micelle stability. Due to the pH-sensitive ionization of P2VP block, the morphology of star copolymers bearing the P2VP block as free arms was strongly dependent on the pH of the subphase, while the star terpolymer containing the protonated hydrophilic P2VP block at the midblock, maintained the same spherical surface micelle structure at low pH. Both the Langmuir isotherms and the surface morphologies suggest that the high number of arm star terpolymers maintained stable unimolecular micelles at the transitions from the gaseous to liquid monolayer state, and eventually to solid state.
11:00 AM - MM9: Polymer II
BREAK
11:30 AM - **MM9.5
Hybrid Nanomaterials Based on Layer-by-layer Self-assembly.
Veronika Kozlovskaya 1 , Eugenia Kharlampieva 1 , Vladimir Tsukruk 1
1 MSE, Georgia Tech, Atlanta, Georgia, United States
Show AbstractWe review our recent efforts in layer-by-layer (LbL) assembly of various functional nanomaterials on planar, patterned, or particulate substrates. One example involves pH-responsive plasmonic membranes of poly(methacrylic acid) (PMAA-Au NRs)20 with gold nanorods embedded into the swollen ultrathin hydrogel. In contrast to most known pH responsive materials based on pH-triggered change in the intensity of bands, the reported responsive structures exhibit a significant pH-triggered shift in easily detectable plasmon resonance band. We will also demonstrate that hydrogel PMAA microcapsules, produced from cross-linked hydrogen-bonded multilayers can facilitate in-situ growth of gold nanoparticles inside the capsule wall at ambient conditions. Gold nanoparticles possess good biocompatibility and easily monitored optical plasmon resonances. We show that size of gold nanoparticle can be controlled by reduction pH. We explored responsive properties of hollow multilayer shells of tannic acid (TA) assembled via hydrogen-bonding LbL. Gold nanoparticles can be grown within TA-based shells under mild conditions for further modification of the shell via thiol-based surface chemistry. The reported methods can be useful for fabrication of robust containers with ultrathin yet responsive walls for biochemical sensing or laser-induced cargo release for biotechnology applications. We will highlight how neutron reflectivity can be applied to probe the internal structure of spin-assisted layer-by-layer (SA-LbL) films which are shown to be either highly stratified or intermixed. Finally, we demonstrate of highly oriented one-dimensional nanostructures such as carbon nanotubes and metal nanowires on LbL modified patterned substrates.
12:00 PM - MM9.6
New Block Copolymer Micelles for Gene Therapy: In Vitro and In Vivo Applications.
Diana Velluto 1 , Jeffrey Hubbell 1
1 LMRP, EPFL, Lausanne Switzerland
Show AbstractThe common method to deliver DNA is the use of viral vectors, but numerous problems exist that prevent gene therapy using viral vectors, such as: trouble preventing undesired effects, ensuring the virus will infect the correct target cell in the body, and ensuring that the inserted gene doesn't disrupt any vital genes already in the genome.Recent advances in vector technology have yielded molecules and techniques with transfection efficiencies similar to those of viruses.Based on this, we prepared new polymeric micelles as non-viral vectors for DNA/RNA which showed to be much less toxic in vitro and in vivo respect to many of the commercial vectors and highly efficient in complexing, stabilizing and delivering the DNA.The AB block-copolymer made of poly(ethylene glycol) (PEG), as hydrophilic domain, and poly(propylene sulfide) (PPS), as hydrophobic domain, has been conjugated with a linear poly(ethylene amine) (L-PEI) block, which is able to complex DNA and RNA providing a good system for gene delivery. The asymmetric ABC triblock has been synthesized by a thiol-disulfide exchange reaction between the PPS sulfidryl and PEI pyridyl disulfide terminal groups.This ABC block copolymers can easily aggregate in water forming micelles which average size is 165 nm.The same ABC tri-block copolymer can be mixed with an AB diblock-copolymer made of PEG-b-PPS, the latter in excess respect the former. The mixture is re-suspended in water to get much smaller micelles which average size is around 30nm and 40 nm after addition of DNA.We demonstrated the ability of both of the systems to complex DNA plasmids, transfect them into different cell lines mediating the expression of the reporter gene with efficiency in the range of 50 to 100%.The DNA delivery mediated by ABC and AB/ABC block copolymers has been also observed in vivo, being different mouse’s organs and tissues targeted by different ways of administration. Among those, interesting results have been obtained in melanoma tissues in which GFP expressing plasmid has been transfected as reporter gene by mean of both ABC and AB/ABC micelles, showing the higher efficiency of the smaller micelles.
12:15 PM - MM9.7
Networked Oxide Nanocomposites From Evaporative Co-assembly With ABC Polymers.
Morgan Stefik 1 , Hiroaki Sai 1 , Sol Gruner 2 , Francis DiSalvo 3 , Ulrich Wiesner 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Physics, Cornell University, Ithaca, New York, United States, 3 Chemistry and Chemical Biology, Cornell University, Ithaca, New York, United States
Show AbstractThe evaporative co-assembly of amphiphilic block copolymers with oxide nanoparticles has been extensively applied towards the synthesis of ordered nanocomposites. While many different compositions have been explored – including oxides, metals, and carbon materials – published examples have generally been limited to morphologies containing a component with only one- or two-dimensional continuity. Key technologies under development such as photovoltaics, batteries, fuel cells, and supercapacitors could be greatly enhanced by structuring the active components in an interwoven three-dimensional network on the nanometer length scale. The use of ABC triblock terpolymers was found to enable facile synthesis of such ordered networked oxide nanocomposites. The highly hydrophobic nature of the A and B blocks combined with the presence of hydrophilic oxide nanoparticles made it necessary to carefully tune the processing conditions during evaporation to ensure control over the final structure.
12:30 PM - MM9.8
Controlled Growth of Autophobic Brush Layers in Hierarchically Ordered Block Copolymer Micropatterns by Solvent Annealing.
Tae Hee Kim 1 , June Huh 1 , Cheolmin Park 1
1 Department of Materials Science and Engineering, Yonsei University , Seoul Korea (the Republic of)
Show AbstractThe spreading of liquid droplets on a hard substrate has been a long standing issue attracting a lot of interest due to its implications for understanding lubrication, molecular scale friction, and coating, and thus, for controlling hard surfaces. In particular, the spreading frequently accompanies the formation of unique molecular and/or nanometer scale terraces characterized by distinct monomolecular layers in the direction of z normal to the surface.The regularly spaced wetting and/or dewetting of a structured fluid in the z-direction is useful for understanding the origin and dynamics of the structural formation; however, there are several issues which require consideration not only for better understanding of the structural formation, but also for utilizing it in further applications. First of all, the droplets that have been investigated so far are all varied in size, and in fact, their size is in the range of several millimeters. In addition, registry of the micron-sized droplets is important. It would be very desirable, therefore, to developing a way to control all x, y, and z-directions whereby, one could imagine nearly monodispersed micro-droplets terraced in a z-direction and at the same time arrayed on the xy plane in a periodic order. Such a system would also offer a more convenient route for investigating the growth of monolayered first layers in a controlled manner. In the present study, we have achieved the 3D positional control of the terraced block copolymer micro-droplets based on transfer printing the micro-droplets, dewet and arrayed on a topographic poly(dimethylsiloxane) (PDMS) pre-pattern and the subsequent solvent annealing onto a hard substrate. Solvent vapor treatment gives rise to the wetting of the patterned droplets, initiated with the concentric spreading of the characteristic brush monolayer, allowing for precise monitoring of the growth of the brush layer over time. The method presented here enables the fabrication of patterned arrays of the multi-terraced micro-droplets, consisting of both monolayered brush and hierarchically ordered block copolymer microdomains over a large area.