Sonia Grego RTI International
Orlin Velev North Carolina State University
J. Michael Ramsey University of North Carolina-Chapel Hill
Sabeth Verpoorte University of Groningen
P1: Device Surface Modification
Tuesday PM, April 10, 2007
Room 2005 (Moscone West)
9:30 AM - **P1.1
Preventing Nonspecific Adsorption in Plastic Microfluidic Devices Using Photoinitiated Grafting
Frantisek Svec 1 , Timothy Stachowiak 2 Show Abstract
1 The Molecular Foundry, LBNL, Berkeley, California, United States, 2 Chemical Engineering, University of California, Berkeley, California, United States
Microanalytical systems require that chemical functionality be accurately patterned and positioned within a microfluidic device. Numerous techniques exist for introducing or attaching chemical functionality into such devices, but preventing unwanted nonspecific adsorption of chemical or biological species often poses a difficult challenge. We fabricate microfluidic chips from cyclic olefin copolymer. Since this plastic is highly hydrophobic, it tends to adsorb a variety of compounds including proteins and peptides. Therefore, we first modify all surfaces that can come in contact with these compounds using UV initiated photografting of neutral, hydrophilic poly(ethylene glycol) methacrylate (PEGMA). This modification significantly decreased contact angle for water and minimizes the adsorption of proteins within the chip. We also prepared porous polymer monoliths inside the channel. These materials are useful for creating a variety of analytical components needed in an integrated system such as preconcentrators, chromatographic stationary phases, and immobilized enzymatic microreactors. Since the monoliths can also exhibit nonspecific adsorption in regions where surface interactions should be avoided, such as valves, filters, or supports for immobilized enzymatic reactors, we control the surface polarity of the monoliths via a patternable photografting process in order to prepare again hydrophilic surfaces that prevent protein adsorption. Photografting is a powerful technique for in situ surface modification of polymers and allows multiple different chemistries to be introduced into a single device with the use of appropriate photomasks. Here we utilize both single-step and sequential photografting techniques to graft patterns of neutral, hydrophilic monomers such as PEGMA, acrylamide, 2-hydroxyethyl methacrylate, and vinyl pyrrolidinone. Using these photografting processes, adsorption of model proteins, such as bovine serum albumin, can be reduced by two orders of magnitude compared with ungrafted regions. The ability to prepare patterned hydrophilic regions on polymer monoliths is useful for creating multifunctional devices for many chemical and biological applications.
10:00 AM - **P1.2
Tailoring Topography and Chemistry of Surfaces for Detection and Separation.
Jan Genzer 1 Show Abstract
1 Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
10:30 AM - P1.3
Surface Engineering in Microfluidic Devices for the Isolation of Smooth Muscle Cells and Endothelial Cells.
Shashi Murthy 1 , Brian Plouffe 1 , Milica Radisic 2 3 Show Abstract
1 Dept of Chemical Engineering, Northeastern University, Boston, Massachusetts, United States, 2 Institute of Biomaterials & Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada, 3 Dept of Chemical Engineering & Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
Microfluidic cell separation systems have emerged as attractive alternatives to traditional techniques in recent years. These systems offer the advantages of being able to handle small sample volumes and at the same time achieve highly selective separation. Conventional separation techniques, including both fluorescence-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS), typically require a pre-processing incubation step to attach ligated tags (such as fluorescent dyes or magnetic beads) to cell surfaces prior to separation. These techniques are also constrained by infrastructure and high cost. Microfluidic devices with surface-immobilized adhesion molecules eliminate the need for pre-processing incubation and are a low cost alternative.
We describe the selective adhesion of smooth muscle cells and endothelial cells in microfluidic devices coated with adhesion peptides. The device geometry is such that the shear stress varies linearly as a function of flow channel length, allowing simultaneous evaluation of the effects of surface chemistry and fluid shear on cell adhesion. The adhesion peptides, val-ala-pro-gly (VAPG) and arg-glu-asp-val (REDV), are known to bind selectively to smooth muscle cells and endothelial cells, respectively. These peptides were tethered to the device surface using silane chemistry and NHS-ester coupling. Cell adhesion was examined in a shear stress range of 1.3-4.0 dyn/cm2.
Under these conditions, endothelial cells show significantly higher adhesion to REDV-coated devices compared to smooth muscle cells and fibroblasts. Correspondingly, smooth muscle cell adhesion in VAPG-coated devices is much greater than that of endothelial cells and fibroblasts. This selective binding behavior is also observed when mixed suspensions of the three cell types are flowed into both types of peptide-coated microfluidic devices. These results suggest that microfluidic devices coated with REDV and VAPG can be used as effective separation tools in various applications, such as tissue engineering. Specific examples of applications in cardiac and skin tissue engineering will be discussed.
10:45 AM - P1.4
Electrochemical Biolithography for Micropatterning Proteins and Cells within Three-Dimensional Microstructures.
Matsuhiko Nishizawa 1 , Hirokazu Kaji 1 , Masahiko Hashimoto 1 , Takeaki Kawashima 1 , Soichiro Sekine 1 , Takashi Abe 1 Show Abstract
1 , Tohoku Univ., Sendai Japan
Microfluidic systems have been widely investigated for biological applications and hold great promise in the development of diagnostic assays and bioreactors. The combination of the surface patterning techniques with the microfluidic systems paves the way to multi-functional, high-throughput, and cost-effective analysis, in which the “real-time” and “on-demand” micropatterning of delicate bioelements is strongly required. However, most of the photolithography-based techniques are unable to be applied within the sealed microchannels.We would like to report a novel technique “electrochemical bio-lithography”, which enables the localized immobilization of proteins and cells within 3D microstructures such as microfluidic channels. The principle of the technique is based on our finding that the albumin- or heparin-coated surfaces, initially anti-biofouling, rapidly becomes protein- and cell-adhesive upon exposure to the reactive oxidizing agent such as hypobromous acid, which can be produced by the electrochemical oxidation of bromide ion in a biological buffer solution. Since this lithography can be conducted under typical physiological conditions, it enables the spatiotemporal control of cell adhesion and growth on substrates; it facilities the stepwise immobilization of multitype protein arrays and multiphenotype cell arrays. And importantly, this technique is simple enough to be integrated into the miniaturized and semi-closed systems such as microfluidic devices, indicating the possible “on-demand” immobilization of proteins and living cells just prior to use of the microfluidic biodevices.
11:30 AM - **P1.5
Curable Perfluoropolyethers for Microfluidic Devices and as Enabling Materials for Molding and Harvesting Complex Nano-objects
Joseph DeSimone 1 , Junhoe Cha 1 , Jason Rolland 1 , Zhaokang Hu 1 , Michael Ramsey 1 Show Abstract
1 , University of North Carolina, Chapel Hill, Chapel Hill, North Carolina, United States
Photocurable perfluoropolyethers (PFPEs) have been developed for use as novel elastomeric, chemically resistant microfluidic devices and as high performance molding materials for us in imprint lithographic applications. The PFPE-based materials employed herein have Young's modulus values that range from 1.5 to 90 MPa and are tunable throughout that range based on changes in the molecular weight between crosslinks. With photochemically and thermally curable PFPE materials in hand, PFPE-based microfluidic devices could easily be fabricated by soft lithography using an SU-8 master. Since the absorption or partitioning of analytes into bulk PDMS have been reported, small molecule partitioning behavior for PFPE- and PDMS-based devices was investigated. PDMS chips showed a strong fluorescence signal due to Nile Red and Rhodamine B base partitioning into it, while no partitioning was observed in PFPE-based devices as indicated by the lack of fluorescence. An electrokinetic property of PFPE was investigated by measuring electroosmotic mobility (EOM). To demonstrate electrokinetic control of solutions in these microchips, pinch flow and injection of Lissamine Rhodamine B sulfonyl chloride and Oregon green 488 carboxylic acid was successfully performed in PFPE chips. Due to the excellent resistance of small molecule partition and chemical and electrokinetic properties, the PFPE material has the potential to expand the field of microfluidics to many novel applications such as chemically-intensive lab-on-a-chip devices.The PFPE-based materials make for excellent imprint lithography molding materials. We are adapting and merging the precision, uniformity and mass production concepts associated with imprint lithography to generate and solution harvest extremely versatile organic carriers having specific chemical functionality and tailored mechanical properties for application in nano-medicine. We have been able to fabricate and harvest using PFPE-based molding materials monodisperse, shape-specific nano-particles that can be made from any organic matrix material (e.g. PEG, polylactide, cationic hydrogels, degradable di-sulfide linked materials), containing any cargo (e.g. therapeutics, contrast agents, linker groups), and conjugated with any ligand (e.g. integrin receptor peptide, melanocyte stimulating hormone, vasoactive intestinal peptide, anti-Her2 mouse antibodies, cell-penetrating peptides, and a variety of vitamins). This paper will also discuss our recently initiated in vitro and in vivo studies with these harvested particles for the detection, imaging and treatment of various diseases.
12:00 PM - P1.6
Biofunctionalizing Nitride Surfaces without Silanes.
Rory Stine 1 , Kendra McCoy 1 , Shawn Mulvaney 1 , Lloyd Whitman 1 Show Abstract
1 , U. S. Naval Research Lab, Washington, District of Columbia, United States
Silicon nitride is widely used as a coating in the microelectronics industry because of its ability to resist penetration by contaminants such as water, oxygen, and ionic species. This property also makes silicon nitride a common terminal passivation layer for chip-based biosensors and bioMEMS devices, all of which come into contact with aqueous saline solutions. Current methods for biofunctionalizing silicon nitride rely almost exclusively on silane-based films, both for direct functionalization and as bifunctional linkers. However, even under stringent controls, the chemistry of silane films on silicon nitride surfaces is notoriously inconsistent and suffers from degradation over time when used in aqueous environments. We have developed an alternate, silane-free, method for functionalizing silicon nitride surfaces. The native oxide is first stripped via HF solution, and then treated with a plasma that makes the surface reactive to aldehydes. Using a bifunctional aldehyde coupler, we then adsorb a robust NeutrAvidin layer that can be used to immobilize any biotinylated biomolecule and has excellent nonfouling properties. We will describe the surface chemistry and compare our approach with silane-based methods as analyzed by XPS and radiolabeling experiments. We will also show that this chemistry can be successfully applied to GaN surfaces, and used for immunoassays and DNA hybridization assays in a range of sample matrices on both surfaces.
12:15 PM - P1.7
Micro-channel Patterning for Preparing a Self-referencing Surface for the Detection of Cancer Antigens using Surface Plasmon Resonance Biosensor.
Fengyu Su 1 , Chunye Xu 1 , Minoru Taya 1 Show Abstract
1 Mechanical Engineering, University of Washington, Seattle, Washington, United States
12:30 PM - P1.8
Merging Photoresist Lithography and Protein Microarraying to Design Depatocellular Microenvironment.
Ji Youn Lee 1 , Sunny Shah 1 , Gang-Yu Liu 2 , Alexander Revzin 1 Show Abstract
1 Department of Biomedical Engineering, University of California, Davis, California, United States, 2 Deparatment of Chemistry, University of California, Davis, California, United States
12:45 PM - P1.9
Chemical Modifications of Inert Self-Assembled Monolayers with Oxygen Plasma for Biosensor Applications
Kun-Lin Yang 1 , Changying Xue 1 Show Abstract
1 Chemical and Biomolecular Engineering, National University of Singapore, Singapore Singapore
We report a new approach to chemically modify inert self-assembled monolayers (SAMs) with oxygen plasma and generated functional groups which permit the immobilization of protein human IgG on the surface. The covalent attachment of IgG to the surface is possibly through the formation of Schiff base between the aldehyde functional groups generated in situ from the oxygen plasma treatment and the amine functional groups of proteins. However, only 1 to 2 s of treatment time is required to modify the surface of the SAMs. Longer treatment time will result in the etching of the SAMs and no protein can be immobilized on the surface. This approach may provide a new means of introducing functional groups to the inert SAMs and avoid the use of bifunctional linkers for protein immobilization.
P2: Device Fabrication Strategies
Tuesday PM, April 10, 2007
Room 2005 (Moscone West)
2:30 PM - **P2.1
Electrohydrodynamic Jet Printing for Digital Microfabrication
John Rogers 1 Show Abstract
1 , University of Illinois, Urbana, Illinois, United States
Electrically driven formation of droplets in conducting fluids combined with electrostatic control of droplet trajectory forms the basis of a method that can be used to print fluids with sub-micron resolution. This talk describes basic aspects of this approach, together with its use in printing a variety of fluids, including suspensions of single walled carbon nanotubes, solutions of conducting polymers, and range of dielectric materials. Simple devices, such as organic transistors and light emitting diodes demonstrate some of the patterning capabilities. Advantages and disadvantages compared to conventional thermal or piezeoelectric ink jet printing for these classes of applications will be described.
3:00 PM - P2.2
Carbon Nanofiber Forests as the Volume Exclusion Feature in a Cell Mimic Device.
Jason Fowlkes 1 2 , Scott Retterer 2 , Ben Fletcher 1 2 , Mike Simpson 1 2 , Kate Klein 1 2 , Anatoli Melechko 2 , Mitch Doktycz 2 Show Abstract
1 , The University of Tennessee, Knoxville, Tennessee, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
3:15 PM - P2.3
Use of Poly(ethylene glycol) (PEG) Photolithography for Integration of Cells and Microdevices
He Zhu 1 , Jun Yan 1 , Alexander Revzin 1 Show Abstract
1 Biomedical Engineering, University of California, Davis, Davis, California, United States
Seamless integration of biological and electrical/mechanical components is critical for successful development of BioMEMS. In this presentation, we will describe the use of photopatternable biomaterial, poly (ethylene glycol) (PEG), that can be utilized in a fashion similar to photoresist. In this process, PEG prepolymer solution is spin-coated onto a surface and exposed to UV light through a photomask, resulting in formation of cross-linked PEG hydrogel micro-domains. Because the patterning process is similar to traditional “top-down” photoresist lithography, PEG gel microstructures can be registered with pre-existing microfabricated layers. Two applications utilizing PEG photolithography for biological packaging of microdevices will be highlighted. In one application, gold electrodes, packaged in PEG gel, were selectively modified with avidin followed by the attachment of biotynilated antibodies specific to T-lymphocytes. Presence of the avidin and antibodies on the electrodes was verified by immunofluorescent staining. T-lymphocytes were shown to selectively attach onto the antibody-modified electrodes. In the future, this device may be employed for capture, interrogation and electrochemical release of cells. In the second application, we will demonstrate ability to deposit PEG hydrogel microstructures containing active enzymes onto microfabricated gold electrodes. This application will be valuable for constructing miniature enzyme-based electrochemical biosensors for multi-analyte detection.
3:30 PM - P2.4
Tools for Manipulation of a Two-Dimensional Fluid Membrane.
Bryan Jackson 1 , Jay Groves 1 2 Show Abstract
1 Chemistry, University of California - Berkeley, Berkeley, California, United States, 2 Physical Bioscience and Materials Science Divisions, Lawrence Berkeley National Laboratory, Berkeley, California, United States
3:45 PM - P2.5
Improved Neuronal Adhesion to the Surface of Electronic Device by Engulfment of Protruding Micronails Fabricated on the Chip Surface.
Micha Spira 1 , Dotan Kamber 1 , Ada Dormann 1 , Carmen Bartic 4 , Gustaaf Borghs 4 , Shlomo Yitzchaik 3 , Keren Shabtai 3 ,
Joseph Shappir 2 Show Abstract
1 Neurobiology, The Hebrew University of Jerusalem, Jerusalem Israel, 4 MCP/ART, Cell Based Sensors & Circuits, IMEC vzw , Leuven Netherlands, 3 Chemistry, The Hebrew University of Jerusalem, Jerusalem Israel, 2 Engeneering, The Hebrew University of Jerusalem, Jerusalem Israel
4:30 PM - **P2.6
Sacrificial Layer and Rapid Prototyping Methods for Creating Microfluidic Devices in Various Materials.
Adam Woolley 1 Show Abstract
1 Chemistry and Biochemistry, Brigham Young University, Provo, Utah, United States
Lab-on-a-chip systems are seeing increased application in biomolecular analysis. However, materials constraints in the fabrication of high-performance microchips still hinder the broader use of microdevices in bioanalysis. Indeed, microfabrication of materials such as poly(dimethylsiloxane) (PDMS) is fairly easy, but separation performance is often less than ideal; in contrast, glass microchips provide quality separations, but device construction is much more involved and expensive. Our efforts have been directed toward the development of novel approaches for creating microfluidic systems to improve biomolecular analysis. Specifically, we have focused on using hard polymeric materials to form multilayer microchips and to rapidly prototype microfluidic devices; in addition, we have applied thin-film sacrificial layers in constructing microfluidic arrays on inorganic substrates. We have devised a phase-changing sacrificial layer fabrication approach that enables straightforward solvent bonding of polymer microfluidic systems. We are now applying this same method in making multilayer microfluidic structures for simplifying multiplex analyses and facilitating on-chip sample labeling. Recently, we developed a solvent imprinting and bonding approach for the rapid prototyping of microfluidic systems in hard polymer substrates. Total device fabrication times are just several minutes, and quality electrophoretic separations can be achieved in these microchips. Our new methods are as easy to carry out as PDMS molding, but offer better device material characteristics and separation performance. Moreover, we have studied thin-film sacrificial layer techniques for constructing microcapillaries. Our thin-film microfluidic devices offer excellent performance in rapid separations of amino acids and peptides, and provide opportunities for the direct integration of optical and electrical capabilities on-chip. These advances in the fabrication of lab-on-a-chip systems broaden the range of materials available for microchip construction and should enable continued improvements in biomolecular analysis.
Kelly, R.T.; Pan, T.; Woolley, A.T. Phase-Changing Sacrificial Materials for Solvent Bonding of High-Performance Polymeric Capillary Electrophoresis Microchips. Anal. Chem. 77, 3536-3541 (2005).
Peeni, B.A.; Lee, M.L.; Hawkins, A.R.; Woolley, A.T. Sacrificial Layer Microfluidic Device Fabrication Methods. Electrophoresis in press (2006).
5:00 PM - P2.7
Fluorescence Spectroscopy on a Moving Particle
Oliver Schmidt 1 , Michael Bassler 1 , Peter Kiesel 1 , Noble Johnson 1 Show Abstract
1 , Palo Alto Research Center Inc. (PARC), Palo Alto, California, United States
An optical lab-on-a-chip system is presented that enables fluorescence spectroscopy to be performed on moving analytes. The analytes are continuously excited within a novel optical waveguide structure. Fluorescence spectra are recorded as the analyte traverses the detection area of a chip-size spectrometer that is integrated onto a microfluidic platform. To achieve a strong interaction between the excitation light and analyte we use an anti-resonant waveguide: the light is guided within the target-containing medium, thereby enabling a continuous excitation of a large volume. Guiding the excitation light within the lower-refractive-index fluid is achieved by coupling the light into the waveguide at a specific angle of incidence. A compact spectrometer is integrated along the fluidic channel. The spectrometer consists of a detector array that is coated with a linear variable band-pass filter. The filter converts the spectral fluorescence information into a spatially dependent signal that is analyzed by the detector array. Such chip-size spectrometers are especially applicable for characterizing moving analytes.The operational system will be demonstrated by characterizing polystyrene beads coated with a fluorescent dye. The fluorescence was excited with a 533 nm green laser at a flow speed of 2 mm/s and recorded during flow with a spectral resolution of 5 nm. Experiments are in progress to measure native fluorescence spectra of bacteria in solution with UV excitation light.
5:15 PM - P2.8
3D Microhorns for Capillary Driven Microdroplet Transport.
Chunguang Xia 1 , Andrew Cox 1 , Nicholas Fang 1 Show Abstract
1 MechSE, UIUC, Urbana, Illinois, United States
The rapid advancement of two-dimensional microfluidic systems in recent years now enables a multitude of micro total analysis systems to perform complex sorting and processing at the microscale on disposable lab-on-a-chip devices. It is becoming an inevitable thrust of research and development of the micro and nano total analysis systems in both the consumer and military applications to drive to ever higher levels of integration, requiring the exponential growth of material transport and information processing functions such as sensing and manipulation at the shrinking dimensions. However, current planar manufacturing technologies face the challenge of attaining a high degree of integrated functionalities on the same device, as they offer very limited layers in the device architecture and constrain the interconnect density for heterogeneous integration.In this work, we will pursue the design and microfabrication of 3D microchannels using an innovative parallel micro-freeform technology, the projection microstereolithography. Using a data projector as the dynamic mask, our technology defines high resolution micro-objects by solidifying a light curable solution. By playing a movie that incorporates the cross-sectional patterns and stacking the defined patterns on a small and precise elevator, 3D microstructure are fabricated in a layer-by-layer fashion. In our preliminary works, a set of molecularly imprinted methacrylic acid and poly(ethylene glycol) microstructures are demonstrated with resolution better than 1 micron, sufficient to reproduce the intricacy of the smallest capillaries in the microfluidic networks. This technology provides a unique prototyping method of highly complex 3D microstructures at the table top. In addition, this process offers a variety of functional and biocompatible polymers and hydrogels with tunable surface properties and compliance that can be patterned for the heterogeneous integration of the lab-on-a-chip devices and microfactories. To demonstrate the technology, an array of 3D branching microhorns are designed and fabricated. The conical shape of the capillaries functions as a hydraulic machine: by Pascal’s law, the pressure difference at the smaller and larger meniscus generates a force that drives the wetting droplet towards the narrower end. This phenomenon resembles the movement of fluid in the stems of plant to the leaves. The flow rates of various fluids driven by the capillary force gradient in the conical capillaries will be analyzed. Variations of the horn geometry and their effects on fluid flow rates through the microhorns will be reported. Theoretical analysis of the surface forces involved will be also presented. These branching microhorns show great promise as vital components of fully three dimensional microfluidic systems. Sun C., Fang N., Wu D.M., Zhang X., “Projection micro-stereolithography using digital micro-mirror dynamic mask”, Sensors and Actuators A, 121(2005)113-120.
5:30 PM - P2.9
Patterned Conducting Polymers for All-Polymer Cell Electroporation Microsystems.
Niels Larsen 1 , Thomas Hansen 2 1 , Keld West 1 , Ole Hassager 2 Show Abstract
1 Danish Polymer Centre, Risoe National Laboratory, Roskilde Denmark, 2 Department of Chemical Engineering, Technical University of Denmark, Kgs. Lyngby Denmark
Cancer immunotherapy shows increasing potential for assisting in fighting cancer, based on reinjection of dendritic cells “trained” in the laboratory to recognize a patient’s cancer cells. The training proceeds via transient formation of nanopores in the cell membranes induced by a pulsed high electrical field. Highly defined electroporation of single cells has been demonstrated by a number of methodologies during the past decade. However, none of these techniques may be easily up-scaled in a cost-effective manner to handle the large number of cells required for immunotherapy (10-100 million trained dendritic cells). Furthermore, the initial generation of high numbers of dendritic cells, by chemically induced differentiation of the patient’s blood monocytes in the laboratory, is a labor intensive and costly procedure. The differentiation process and subsequent electroporation procedure are therefore well suited as targets for direct integration in a lab-on-a-chip configuration.We have set out to produce such an integrated microsystem based exclusively on commodity polymers for microchannel structures combined with micropatterned conductive polymers (CP) as active field generators and active components of the microfluidic pumping system. Our technology platform is based on new methodologies, to be presented here, for integrating and patterning CP layers into the surface of bulk polymers: Integration occurs via solvent-induced blending of a nanoscale thickness CP layer into a thermoplastic polymer surface . This results in mechanically highly stable surfaces retaining the conductivity of the CP layer. Surprisingly, the procedure works equally well for thermoplastic elastomers which may be strained by more than 50% without irreversible change in conductivity . Patterning of the free-standing or integrated CP occurs in a fast parallel micropatterning (<2 micrometer resolution in seconds to minutes) procedure based on spatially selective transfer of an oxidant from a stamp surface relief to CP areas to be deactivated . We have demonstrated the application of these combined methodologies for the fabrication of an all-polymer electroosmotic microfluidic pumping system, suitable for the slow controlled release of agents inducing monocyte differentiation . Furthermore, we have manufactured interdigitated microelectrode arrays for controlled electroporation of large cell numbers and shown their ability to electroporate and transfect live dendritic cells by messenger-RNA coding for enhanced Green Fluorescent Protein. Results of both demonstrations will be presented. T.S. Hansen, K. West, O. Hassager, N.B. Larsen. Synthetic Metals. In press. T.S. Hansen, K. West, O. Hassager, N.B. Larsen. Advanced Materials. Submitted. .S. Hansen, K. West, O. Hassager, N.B. Larsen. Advanced Functional Materials. Submitted.
P3: Poster Session
Wednesday AM, April 11, 2007
Salon Level (Marriott)
9:00 PM - P3.1
Nanoporous Silicon Sensor for Biological Applications
Gagik Ayvazyan 1 , Vahe Buniatyan 1 Show Abstract
1 Semiconductor R&D Center, EAA, Yerevan Armenia
Nanoporous silicon is a unique and versatile material that has several features that make it especially attractive for biological sensors, including a very high surface area to volume ratio, simple and inexpensive fabrication techniques, and suitability for integration with silicon electronics. Offered patented architecture and method of making biosensors provide a sensitive way to measure small changes in the in electrical properties (capacitance and conductance) of nanoporous silicon that occur when exposed to organic solvents or when biological molecules attach to the internal surfaces. In particular, use of unilateral electrical contact allows a complete exposure of the surface to the sensing species and reduces the generation of ionic currents through the porous matrix. Pore selective distribution (gradient in pore sizes) in matrix increases sensitivity of biosensors.Based on offered sensor engineering prototype of portable, hand-held diagnostic device is developed. Such sensitive label-free devices can be used by consumers worldwide, for example to detect the presence of specific biological agents (viral DNA, proteins, and potentially bacteria) or organic solvents (ethanol, acetone, benzene).Preliminary testing demonstrated the main advantages of the proposed sensors, including miniaturization, portability, high throughput, high signal to noise ratio, and production of on-site and real-time results.
9:00 PM - P3.10
Cell Behaviour on Nanoscale Hierarchical Patterned Surfaces
Bimalraj Rajalingam 1 , Myoung-Woon Moon 2 , Ashkan Vaziri 2 , Ali Khademhosseini 1 3 Show Abstract
1 Center for Biomedical Engineering, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States, 2 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 3 Harvard-MIT Division of Health Science and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
We report a novel technique for fabricating hierarchical wrinkling patterns on the surface of PDMS in micron and submicron level. Initially stretched PDMS slabs were exposed to plasma treatment and then allowed to relax. The wavelength of the wrinkling patterns can be effectively selected by controlling the oxidation time, while the initial stretch controls the amplitude of wrinkles. Using this technique, wrinkling patterns with wavelength in the range of 50 nm to 5 microns and amplitude in the range of 20 nm to 400 nm were fabricated. We also show that wrinkles in the submicron level can be nested within larger wrinkles using multi step plasma treatment, resulting in hierarchical wrinkling patterns. We used this technique to manufacture wrinkling patterns with wavelength in the range of 50 nm to 5 microns and amplitude in the range of 20 nm to 400 nm, as well as patterns comprising hierarchical wrinkles. We characterized the surface using atomic force microscopy and scanning electron microscopy. These patterns were employed to study the role of surface topology on the behavior of NIH-3T3 cells. Cells aligned and elongated on these patterns depending on the surface topology. Moreover, the cells proliferated on these nanopatterned substrates and gave rise to progeny that was also aligned on these nanopatterned substrates. We systematically studied the role of surface topology on the orientation and the morphology of NIH-3T3 cells as well as their cytoskeletal structure. The double scale wavelength effect on the cell behavior was also explored. We varied the duration of the multi step plasma treatment and the strain of the PDMS samples to arrive at the optimal wavelength and amplitude for controlling the cell orientation. The alignment of the cellular focal adhesions and actin fibres in relation to the variations in the amplitude of the waves was analyzed. The cell orientation and elongation is a function of the wavelength,with wavelengths around 1 to 2 microns showing maximal orientation and elongation. Moreover the cells dynamically changed their orientation over time, with cells after three days of incubation showing better orientation compared with those after 12 hours of incubation. Our results indicate the potential of the developed technique for controlling the cell orientation and morphology in tissue engineering templates and in the fabrication of biomimetic surfaces.
9:00 PM - P3.11
A Controlled Release Approach to Generate Microengineered Hydrogels of Controllable Shapes and Sizes made from Fast Gelling Polymeric Precursors
Giovanni Franzesi 1 , Yibo Ling 1 2 , Bin Ni 3 , Ali Khademhosseini 1 4 Show Abstract
1 Harvard-MIT Division of Health Science and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Center for Biomedical Engineering, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, United States
Microscale hydrogels are useful for a variety of applications such as drug delivery, tissue engineering and food sciences. However, some of the most useful and better studied fast gelling ionically and pH-crosslinked hydrogels are not amenable to standard micromolding and micropatterning techniques that are commonly used to generate microscale hydrogels. Here, we present an approach that uses controlled release of the gelling agent to generate molded structures of this class of hydrogels. As model hydrogels we used alginate representing an ionically crosslinked hydrogel and chitosan, a pH dependent hydrogel. To micromold the hydrogels calcium alginate was molded between a plasma-cleaned PDMS mold and a calcium-containing agarose slab and subsequently gelled by the controlled release of calcium ions from the agarose. The slab provides a physical barrier while simultaneously inducing the gelation of the hydrogel precursor, resulting in the formation of both membranes and microparticles of controlled morphology. A similar approach was used to obtain chitosan micropatterns, by using an agarose at high pH. Using this approach, features with lateral dimensions between 5 µm and 2000 µm, and vertical dimensions between 10 µm and 200 µm could be obtained. In addition cells could be embedded in microgels in a range of densities (10E3 - 10E8 cells/ml) and remained >80% viable. Different cell types could be co-cultivated, either in two separate hydrogel phases micromolded on top of each other or one cell type could be encapsulated in a micromolded hydrogel, while the other is seeded on top of the structure. Furthermore, by varying the precursor concentration and gelling conditions the mechanical properties of the micropatterned hydrogels were controlled. These microgels (often as small as 10 µm) remained stable for >2 weeks incubation in cell culture media at 37°C. Thus, we demonstrate that controlled release of the gelling agent can be used to micromold hydrogels not amenable to traditional molding approaches.
9:00 PM - P3.12
Fabrication of Superhydrophobic Micro/Nanostructures
Donghyun Kim 1 , Joonwon Kim 1 , Woonbong Hwang 1 , Hyun Park 1 , Kun-Hong Lee 2 Show Abstract
1 Mechanical Engineering, POSTECH, Pohang Korea (the Republic of), 2 Chemical Engineering, POSTECH, Pohang Korea (the Republic of)
A surface was created with the same superhydrophobic property as the lotus leaf (Lotus Effect) by dipping of sandblasted porous alumina into polytetrafluoroethylene (PTFT, Teflon®: DuPont™) solution. The fabricated artificial lotus leaf had PTFT micro/nanostructures. This fabrication process has several advantages, including low fabrication cost, simplicity and easy coverage of a large area. The sandblasted porous alumina template was fabricated by sand blasting of aluminum sheet and anodization in oxalic acid. To obtain PTFT micro/nanostructures, PTFT replication based on the dipping method was used, with a 0.3 w% PTFT solution. To remove the aluminum and alumina layers, wet etching by chromic and phosphoric acid mixed solution and liquid HgCl2 solution was used. The fabricated surface has a superhydrophobic property whose apparent contact angle of the PTFT micro/nanostructures was approximately 165 degrees and sliding angle is less than one degree.
9:00 PM - P3.14
Dynamic Properties and Flow rates of Novel Piezoelectric Micropump
Sang-Jong Kim 1 2 , Dae-Yong Jeong 1 , Chong-Yun Kang 1 , Ji-Won Choi 1 , Hyun-Jai Kim 1 , Man-Youmg Sung 2 , Seok-Jin Yoon 1 Show Abstract
1 Thin Film Material Research Center, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 Department of Electrical Engineering, Korea University, Seoul Korea (the Republic of)
In recent years, much attention has been given to developing the microfluidic systems based on MEMS(Micro Electro Mechanical System) technologies. Among them, micropump have a large potential for an application to micromechanical analysis system such as LOC(Lab On a Chip) as well as embedded medical devices. Micropumps have been developed using several actuation methods such as a electrostatic, thermopneumatic, electroosmotic, piezoelectric, etc. Most of them require complex structure. But, the piezoelectric actuation has advantages of the relatively simple structure, low power consumption and high pumping performances. In this paper, the characteristics of the novel piezoelectric micropump were studied. We have designed and fabricated 3 types of micropump. The first type consists of single piezoelectric element and single top electrode. The second is the separate two piezoelectric elements which include top electrode, respectively, Final third type is made of single piezoelectric element including two separate top electrodes. The diffuser has been optimized as 1 mm length and 1 to 2 ratio width from the fluidal analysis. The micro diffuser and the chamber were fabricated using bulk micromachining method. The parts of actuator, bottom electrode Ag and piezoelectric thick films were fabricated using screen printing method, respectively. Piezoelectric thick films were sintered by RTA(Rapid Thermal Annealing). Top electrodes Pt were deposited by DC sputtering system and lift-off. We investigated dynamic properties by vibrometer and measured the flow rates.
9:00 PM - P3.15
Chitosan for Selective Biofunctionalization of Microsystems.
Stephan Koev 1 4 , Vlad Badilita 1 4 , Hyunmin Yi 7 , William Bentley 3 5 6 , Gregory Payne 5 6 , Gary Rubloff 2 4 6 , Reza Ghodssi 1 4 6 Show Abstract
1 Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland, United States, 4 Institute for Systems Research, University of Maryland, College Park, Maryland, United States, 7 Department of Chemical and Biological Engineering, Tufts University, Medford, Massachusetts, United States, 3 Fischell Department of Bioengineering, University of Maryland, College Park, Maryland, United States, 5 , University of Maryland Biotechnology Institute, College Park, Maryland, United States, 6 Bioengineering Graduate Program, University of Maryland , College Park, Maryland, United States, 2 Department of Materials Science and Engineering, University of Maryland, College Park, Maryland, United States
We present chitosan-mediated electrochemical assembly of biomolecules on MEMS biosensors. Chitosan is an amino-polysaccharide with unique properties: (i) pH-dependent solubility transition that allows electric signal-guided assembly onto conductive surfaces and (ii) chemical reactivity that allows covalent conjugation of biomolecules for biosensing surface construction. This biofunctionalization method has significant advantages over printing-based techniques such as soft lithography because non-planar device surfaces can be patterned (e.g. sidewalls) and the deposition is electrically controllable. In this presentation we report two BioMEMS platforms that employ chitosan as the biomolecule assembly scaffold for DNA hybridization sensing: a micromechanical sensor and an in-plane waveguide biophotonic sensor.Our micromechanical sensor is a cantilever that detects the binding of biomolecules by the change in deflection due to surface stress (static mode) or by the change of resonant frequency due to added mass (dynamic mode). The cantilever is fabricated of thin films of Si3N4 (500nm) and Au/Cr (100nm) on a silicon substrate by standard lithographic and etching techniques. Chitosan is electrodeposited on the device and probe DNA is covalently coupled to the chitosan film. The device is exposed to target DNA for hybridization, and then to urea solution for denaturation. At each step, the bending of the cantilever in solution and the resonant frequency in air are measured by an optical interferometer. Both static and dynamic responses demonstrate that sequence-specific biological recognition occurs and is transduced to a large mechanical signal.The biophotonic sensor consists of SU-8 polymer optical waveguides and microfluidic channels defined on a pyrex substrate. The facets of the waveguides have transparent indium tin oxide (ITO) electrodes, on which chitosan is electrodeposited and biomolecules are subsequently assembled. The waveguides deliver excitation light to and collect emitted light from the biomolecules for fluorescence or absorption analysis. The waveguides in turn are coupled to optical fibers, which are connected to an external light source and a spectrum analyzer. The key advantage of this device is that the analyte is immobilized on the waveguide facet, which leads to large collection efficiency of the emitted light compared to more common evanescent coupling techniques. The optical biosensor was tested in response to fluorescent DNA hybridization. The measured sequence-specific response demonstrates the feasibility of optical detection by sidewall biofunctionalization with chitosan. This work shows that chitosan facilitates both optical and mechanical biosensing. It is electrodeposited as a stable film at specific electrode addresses, and it is transparent and mechanically responsive. Our future goal is to combine the chitosan-based optical and mechanical sensors in a single multimodal detection platform.
9:00 PM - P3.16
Assessment of Fluidic Channels Produced via Femtosecond Laser Iinduced Delamination of Thermal Oxide Films from Silicon Substrates.
Vanita Mistry 1 , Joel McDonald 2 , Steven Yalisove 3 Show Abstract
1 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Applied Physics, University of Michigan, Ann Arbor, Michigan, United States, 3 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
9:00 PM - P3.17
Microfluidic Love Wave Sensor for Highly Viscous Environments.
Vincent Raimbault 1 , Dominique Rebiere 1 , Corinne Dejous 1 , Matthieu Guirardel 2 , Jean-Luc Lachaud 1 Show Abstract
1 , Laboratoire IXL, Talence France, 2 , Rhodia - Laboratoire du Futur, Pessac France
9:00 PM - P3.18
Multiplexed Transport and Detection of Cytokines Using Kinesin-Driven Molecular Shuttles.
Lynnette Rios 1 , George Bachand 1 Show Abstract
1 Biomolecular Interfaces & Systems Department, Sandia National Laboratories, Albuquerque, New Mexico, United States
Multiple analyte immunoassays are a simple way to achieve simultaneous analysis of various analytes in a sample without the need to run separate tests. To date, most multiple analyte assays have focused on array-based systems. Such arrays, however, become problematic when analyzing cocktail samples, or samples that contain multiple analytes, due to a dependence on the signal from a single label and the immobilization of only one type of antibody per analyte. The intrinsic limitations of this approach also prevent miniaturization of such array-based devices. As an alternative, we are currently exploring the use of biomolecular active transport systems as a means of downscaling multiple analyte assays for lab-on-a-chip applications. Recently, the ability to capture and transport a wide range of target analytes including proteins, virus particles, and bacterial spore was demonstrated using kinesin-driven molecular shuttles. The molecular shuttles consisted of microtubule filaments that were functionalized with analyte-specific antibodies, thus facilitating selective target capture and transport. In the present work, we have applied this nanofluidic platform for the simultaneous detection of multiple target analytes. Multiplexing of molecular shuttles was achieved by immobilizing biotinylated antibodies against interleukin-2 (IL-2) and tumor necrosis factor-α (TNF-α) on biotin microtubules using a streptavidin bridge. ELISA results show detection of TNF-α across a broad range of concentrations using the antibody-functionalized microtubules. To facilitate multiplexed detection in nanofluidic architectures, we have functionalized nanocrystal quantum dots (nQDs) of different sizes and spectral emissions with IL-2 and TNF-α antibodies. Current work is focused on applying both the functionalized microtubules and nQDs for simultaneous detection of IL-2 and TNF-α in kinesin-based motility assays. The results of both the multiplexed microplate and motility assays will be presented and discussed.Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
9:00 PM - P3.19
A Planar Electroosmotic Micropump for Lab-on-Microchip Applications.
Konstantin Seibel 1 , Lars Schoeler 1 , Heiko Schaefer 1 , Marcus Walder 1 , Markus Boehm 1 Show Abstract
1 Institute of Microsystem Technologies, University of Siegen, Siegen Germany
9:00 PM - P3.2
Using Tubular Millifluidics as a Versatile Tool Box for The Generation of New Complex Architectures: Some Integrative Chemistry Synthetic Pathways
Wilfrid Engl 2 , Cindy Hany 2 , Pascal Panizza 2 , Renal Backov 1 Show Abstract
2 GMCM, UMR CNRS 6626, CNRS-Université de Rennes, Rennes France, 1 , CNRS-Universite Bordeaux-I, Pessac France
There is today a crucial need for new complex hierarchical materials possessing diverse functionalities at different length scales. To design such multiscale architectures accompagned with either organic, inorganic or hybrid compounds in nature are assembled within the new concept of Integrative Chemistry. Herein, beyond the first use of Millifluidic toward shaping complex integrated materials, we demonstrate that "Modular Tubular Millifluidic Synthesis" (MTMS) overcomes the limitations of microfluidics synthesis while maintaining its high potentialities. By assembling together elementary modules and integrating their corresponding functions, modular set-ups can be designed “on demand” to engineer newly advanced materials in characteristic sizes ranging from 50 microns up to a few mm. The great versatility of this method is limited only by the number of combinations possible using the modular tool box and one’s imagination. This is illustrated through the formation of double and triple macro-emulsions, non-spherical particles containing several liquid compartments and the encapsulation of solid objects of various shapes in drops. Beyond, and again for the first time we have combined sol-gel chemistry and milli-fluidic to generate silica ceramic engineering their sizes and aspect ratios. The particle sizes are controlled by varying the flow rates of the continuous and disperse phases within the home-made milli-fluidic reactor. Also, the silica particles aspect ratio can be tune by adjusting the constrained geometry of the milli-fluidic devices, leading to the production of rod-like silica ceramics. Both SAXS and Nitrogen physisorption Its potential use as a production tool for industry is also addressed. This new process combined either with polymeric networks or sol-gel chemistry is appearing thus as new Integrative Chemistry pathways.1- R. Backov, Soft Matter, 2006, 2, 452.2- W. Engl, C. Hany, P. Panizza, R. Backov, Adv. Mater., Submitted3- M. Tochibana, W. Engl, P. Panizza, R. backov, Chemical Engineering and Processing, Submitted.
9:00 PM - P3.20
Characterisation of Lab-on-chip Electrophoresis Systems with Integrated Amorphous Silicon based Optical Detectors.
Lars Scholer 1 , Marcus Walder 1 , Lars Storsberg 1 , Konstantin Seibel 1 , Heiko Schaefer 1 , Markus Boehm 1 Show Abstract
1 Institute of microsystem technologies, University of Siegen, Siegen Germany
9:00 PM - P3.21
Simulation and Experimental Characterization of Plug Distortion in On-chip Capillary Electrophoresis Systems with Hybrid Micro Channels.
Lars Storsberg 1 , Markus Walder 1 , Konstantin Seibel 1 , Lars Schoeler 1 , Heiko Schaefer 1 , Markus Boehm 1 Show Abstract
1 Institute of microsystem technologies, University of Siegen, Siegen Germany
9:00 PM - P3.22
Configurational Model for the Elctronic Coupling of Neurons to MOS Transistors.
Joseph Shappir 1 , Ariel Cohen 2 , Carmen Bartic 4 , Gustaaf Borghs 4 , Shlomo Yitzchaik 3 , Micha Spira 2 Show Abstract
1 Engineering, The Hebrew University of Jerusalem, Jerusalem Israel, 2 Neurobiology, The Hebrew University of Jerusalem, Jerusalem Israel, 4 MCP/ART, Cell Based Sensors & Circuits, IMEC vzw, Leuven Belgium, 3 Chemistry, The Hebrew University of Jerusalem, Jerusalem Israel
9:00 PM - P3.23
Tunability of Dielectrophoretic Mobility of Semiconductor Nanowires and Its Implications in Device Design.
Grace Xing 1 , Gabor Galantai 3 , Vladimir Protasenko 3 , Masaru Kuno 3 , Amol Singh 1 , Debdeep Jena 1 , Ronghui Zhou 2 , Hsueh-Chia Chang 2 Show Abstract
1 Electrical Engineering Department, University of Notre Dame, Notre Dame, Indiana, United States, 3 Chemistry and Biochemistry Department, University of Notre Dame, Notre Dame, Indiana, United States, 2 Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana, United States
Both nanocrystals and nanowires have attracted a lot of attentions as building blocks for nano-opto-electronics or hybrid electronics and systems. Furthermore, nanocrystals and nanowires both offer unique properties stemming from quantum confinement, especially in terms of optical properties. However, to interface with the outer world via electronic connections, nanowires are more advantageous since they allow carrier band transport while nanocrystal-based devices suffer from low carrier mobilities due to variable range hopping conduction. We have investigated semiconductor nanowire assembly using dielectrophoresis (DEP) in solution and discovered strong dependence of nanowire DEP mobility on super bandgap illumination. In this talk, we will present the origin of this phenomenon; as device examples, we will report 1) the polarization sensitivity of optical emission and absorption as well as photocurrent of the assembled semiconductor (CdSe and CdTe) nanowires and 2) carbon nanotube enhanced bacteria trapping. We will also discuss the implications of this tunability of semiconductor nanowire DEP mobility and several novel device designs.
9:00 PM - P3.24
Nanofluidic Size Focusing of Functionalized CdSe Quantum Dots
Louis Tribby 1 , Youn-Jin Oh 1 , Timothy Boyle 2 , Timothy Lambert 2 , Cornelius Ivory 3 , Sang Han 1 Show Abstract
1 Chemical & Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Inorganic Chemistry and Nanomaterials, Sandia National Laboratories, Albuquerque, New Mexico, United States, 3 Chemical Engineering, Washington State University, Pullman, Washington, United States
We have conducted size-separation of surface-functionalized fluorescent quantum dots (QDs) based upon their electrokinetic mobility in “gate” biased nanochannels and field flow fractionation. We are utilizing lithographically fabricated nanochannels (approximately 104 to 105 parallel channels), where each channel is on the order of 100 nm wide, 500 nm deep, and 16 mm long. In order to acquire extreme size focusing, we systematically manipulate and detect the influence of size, pH, and net surface charge on the electrokinetic mobility and resulting size distribution. We place different charges on the surface of the QDs to tailor the particles’ response to various induced field gradients in the nanochannels. We have synthesized functionalized CdSe QDs that can be easily modified with different charge carriers in aqueous as well as organic solutions. The resulting size distribution is evaluated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and high-efficiency dynamic light scattering sampling. The advancing speed of NCs in the channels is measured by laser scanning confocal fluorescence microscopy (LS-CFM) and multiple internal reflection Fourier transform infrared spectroscopy (MIR-FTIRS). Experimental measurements will be presented in further detail within the context of size-separation. The authors acknowledge generous support from NSF-NIRT (CTS-0404124) and Keck Foundation. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
9:00 PM - P3.25
Integration of Immobilized Polymeric pH, O2 and Glucose Sensors into a Novel Microbioreactor Array for Use in High Throughput Cell Culture Optimization.
Denis Leroux 1 , Scott Miller 1 , Brett Bernier 1 , Xin Yu Li 1 , George Vella 1 , Michelle Muscatello 2 , Stunja Lee 2 , Sanford Asher 2 Show Abstract
1 , BioProcessors , Woburn, Massachusetts, United States, 2 , University of Pittsburgh, Pittsburgh, Pennsylvania, United States
9:00 PM - P3.26
Development of A First-Responder Fluorescence Reader for Microplate Cytokine Assay of Human Immune Response to Disease.
David Fenner 1 , D. Rosen 1 , A. Ferrante 1 , A. Stevens 1 , C. Bigelow 1 , S. Davis 1 Show Abstract
1 , Physical Sciences Inc, Andover, Massachusetts, United States
The practical utility of technologies for early detection of disease has been limited in many cases by the absence of instruments suitable for first responders and in scenarios such as the field hospital. Bioanalysis with sandwich microarray is a technique whereby fluorescent labels on antibody-antigen pairs at microarray spots are imaged in a laboratory setting for quantitative assay. New methods and instruments are needed for point-of-care use. Microplate-based schemes provide multiplexed assay of a large number of human cytokines including those that are known to indicate imbalances in the immune system. Analysis of blood is the common method but saliva is more readily available and also able to provide quick indication of immunological challenge. We report development of a highly portable system configuration with microarray cytokine capture set, dye selection, excitation by filtered LED and fluorescence imaging by 16-bit CCD camera. At present, plates have 16 microarray wells, with 12 cytokines per well and quadruplicate spots. Excitation with multiple one-watt amber (~590 nm) LEDs provides efficient, uniform illumination directly over each full microarray well. The fluorescence from an array of spots (100-200 micron diameter) in a well is imaged through a long working-distance objective, long-pass filter and onto a cooled CCD chip. Image data is immediately transferred into a laptop PC for data reduction. Assay with this small, portable battery-powered reader provides cytokine concentrations over about three orders of magnitude and measured to as little as ~5 pg/ml, the same limit as for laboratory instruments. Profiles of selected cytokines in whole, unprocessed saliva are known to be clinically significant as fingerprint indicators of human disease state. Such indications of a generalized disease state can precede the development of clinical symptoms and hence take on extra significance. The cytokine profiles of a small clinical study of healthy and flu-vaccine challenged individuals, assayed in this manner, will be reported. Opportunities to extend this field-use technology for human health assay to include other biomarkers is discussed. Work supported by Wright-Patterson AFRL-HE through SBIR contract FA8650-06-C-6647.
9:00 PM - P3.27
Real-Time Detection of Micron-Sized Magnetic Beads using a Highly Sensitive Spin-Valve Sensor for a Chip-cytometer.
Jong Wook Roh 1 , Sun Gu Yi 1 , Kyoung Il Lee 1 , Oh-Taek Son 2 , Hyo-Il Jung 2 , Wooyoung Lee 1 Show Abstract
1 Department of Materials Science and Engineering, Yonsei Univ., Seoul Korea (the Republic of), 2 School of Mechanical Engineering, Yonsei Univ., Seoul Korea (the Republic of)
9:00 PM - P3.28
Nanolithography Studies of Chemical and Topographical Signaling on Osteoblast Cells.
Somjai Sangyuenyongpipat 1 , Ananda Arcot 1 , Sergey Gorelick 1 , Mikko Laitinen 1 , Timo Sajavaara 1 , Paavo Rahkila 2 , Sulin Cheng 2 , Matti Putkonen 3 , Harry Whitlow 1 Show Abstract
1 Physics, University of Jyvaskyla, Jyvaskyla Finland, 2 Sport and Health Sciences, University of Jyvaskyla, Jyvaskyla Finland, 3 , Beneq Oy, Ensimmäinen savu, Vantaa Finland
Reinstate Poster P3.28Tuesday, April 10Nanolithography Studies of Chemical and Topographical Signaling on Osteoblast Cells. Somjai SangyuenyongpipatUnderstanding the dynamical processes in bone development at the cellular and sub-cellular level will be an important key for understanding and developing effective treatments for bone formation disorders. In order to study living bone cell function, a method using nanometer-scale materials process technology to create an artificial environment to study bone cells under the microscope is being developed. In this study murine pre-osteoblast cells have been grown on lithographically produced substrates. The Si and glass substrates were first coated with a thin layer of hydroxyapatite-like material by sputtering or atomic layer deposition. Subsequently, 2D patterns were written using electron beam lithography while 3D patterns were produced using the high aspect ratio writing capability of MeV proton beam writing. After culturing the cells they were fixed and stained with a fluorescent stain to image the cytoskeleton under the confocal fluorescence microscope. Cell-growth substrates where a hydroxyapatite-like surface is exposed or covered in nanometer-scale geometric patterns are used to investigate how this signal effects pre-osteoblast cell proliferation and function. In a related investigation focused MeV ion beam lithography has been used to fabricate cell growth substrates with 3D patterns and controlled feature size to investigate how topography on a nanometer and micrometer scale influence cytoskeleton organization in pre-osteoblast cells.
9:00 PM - P3.3
Functionalized Microfluidic Channels And Resistive-Pulse Sensing For Cell-Surface Antigen Detection.
Andrea Carbonaro 1 , Lydia Sohn 1 , Lucy Godley 2 Show Abstract
1 Mechanical Engineering, University of California Berkeley, Berkeley, California, United States, 2 Section of Hematology/Oncology, Department of Medicine, University of Chicago, Chicago, Illinois, United States
The expression of a particular antigen on the cell surface can indicate a pathological condition of the cell. For this reason, the detection of antigens bound to the cell membrane plays a crucial role in disease detection and monitoring. Here, we describe our ability to use resistive-pulse sensing integrated with microfluidics and surface chemistry to sense and separate cells based on their surface antigens. The sensing is done without labeling of the cells, which can subsequently be isolated for further study.In resistive-pulse sensing, a non-conductive particle flowing through a channel blocks the flow of current, thereby leading to a transient increase, or pulse, in the channel’s electrical resistance. Electronic pulses can be characterized in terms of their magnitude and width: the first is strictly related to the size of the particle, and the latter indicates the transit time of the particle as it travels through the channel. In addition, for aspherical particles, such as cells, the shape of a resistive pulse can provide useful information about the shape, orientation, and motion of cells through the channel.Our integrated microfluidic device consists of a 15 μm-wide × 15 μm-high × 800 μm-long channel, which connects two reservoirs, and is embedded in a polydimethylsiloxane (PDMS) slab that is permanently bonded to a glass slide having two sets of lithographically defined Ti/Pt electrodes. The area between the electrodes on the glass substrate is functionalized with antibodies using surface silanization and then derivatization with N-5-Azido-2-nitrobenzoyloxysuccinimide (ANB-NOS), a heterobifunctional cross-linker, which is covalently coupled to the antibodies. We generate a flow by applying a pressure (0.5-2.0 psi) to one of the two reservoirs, and we measure the transit time of cells as the width of the resistive pulses generated by cells as they flow one by one through the channel.When cells flow near a channel wall functionalized with antibodies, the antigen-mediated interaction of the cells to the antibodies functionalized on the wall results in a force, which is function of the antigen-antibody affinity, the antibody and antigen density, and the shear rate of the flow. When there is high affinity between the antigens on the cell surface and the antibodies functionalized on the channel walls, the force of the interaction slows down the cells, leading to longer transit times and correspondingly wider resistive pulses. When the antigen-antibody affinity is low, our data show that the interaction effect is negligible. In addition, the analysis of pulse shape shows a change of cell motion when the channel is functionalized as opposed to the case in which the channel is unfunctionalized.We have used our resistive-pulse technique to develop a number of important assays (e.g. immunophenotyping of leukemia), which we will describe in this talk.
9:00 PM - P3.4
Microbioassays Based on Nanoparticle Agglutination and Evaporation Driven Separations inside Droplets on a Chip.
Vinayak Rastogi 1 , Suk Tai Chang 1 , Orlin Velev 1 Show Abstract
1 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
We present a new on-chip bioassay technique based on nanoparticle agglutination inside microdroplets floating on the surface of dense fluorinated oil. The floating droplets are captured and transported by alternating electric fields created through addressable arrays of electrodes below the oil. Evaporation on top surface of droplet leads to rapid collection of the particles suspended in the droplets in their top region. Experimental results and theoretical simulations show that this microseparation is a result of series of processes driven by mass and heat transfer during the evaporation. The assays based on agglutination of antibody-conjugated particles in the presence of analyte are read out by the pattern of particle collection on the droplet using the evaporation-driven microseparation. These droplet-based microbioassays require samples of nanoliter volume, which are confined within the droplet and cannot contaminate the walls of the vessel. The experimental results for different assay formats are interpreted by theoretical analysis of the kinetics of particle agglutination and mass transfer processes inside the droplets. The performance of the droplet-based microbioassays will be compared to the one of conventional hand held assays.
9:00 PM - P3.6
Electroseparation in Microfluidic Channels Using Inverse Opal Structure
Jau-Ye Shiu 1 , Peilin Chen 1 Show Abstract
1 Research Center for Applied Sciences, Academia Sinica, Taipei Taiwan
Gel electrophoresis and capillary gel electrophoresis are widely used for the separation of biomolecules molecules. With increasing demand in the miniaturized devices such as lab-on-a-chip, it is necessary to integrate such separation component into a chip format. Here we describe a simple approach to fabricate robust three-dimensional periodic porous nanostructures in the microchannels for the separation of DNA molecules. In our fabrication procedure, the colloidal crystals were first grown at the desired area inside the PDMS microchannel using evaporation assisted self-assembly process. Then the void space inside the colloidal crystals can be filled with sol-gel or SU-8 photoresist. After solidification, the inverse opal structure in the microchannel can be obtained by removing the nanoparticles with proper solvent. Our results indicated both sol-gel and SU-8 photoresist can be used to construct inverse opal structure inside a 5 mm long microfluidic channel with pore size around 25-30 nm.To demonstrate the capability of separating different size of biomolecules in our device, DNA markers labeled with fluorescence dye was first loaded into reservoir by electrokinetic injection. After applying proper voltage, DNA molecules with different size can be separated within one minute and visualized in a microscope.
9:00 PM - P3.7
Surface Enhanced Raman Scattering using Built-in Noble Metal Nanoarrays in Integrated Optofluidic Devices
Chul-Joon Heo 1 2 , Se Gyu Jang 1 2 , Seung-Kon Lee 1 2 , Seung-Man Yang 1 2 Show Abstract
1 Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Chungnam, Korea (the Republic of), 2 National Creative Research Initiative Center for Integrated Optofluidic Systems, KAIST, Daejeon Korea (the Republic of)
Molecular specific detection using surface enhanced Raman scattering (SERS) has been widely investigated after its initial discovery. The high-density metal nanoarrays have been used as a SERS substrate because gaps between adjacent metallic nanostructures induce extremely intense local electromagnetic fields, known as “hot spots,” upon optical excitation. Colloidal lithography is a robust method for fabricating regularly ordered nanostructures in a controlled and reproducible way using spontaneous assembly of colloidal particles. SERS enhancement characteristics could be tuned by changing the materials or conditions for fabrication. In this study, embossed nanostructures of polymer thin film with different shapes and spacings were fabricated via colloidal lithography. Then, metallic embossed structures with high density hot spots were created by sputtering noble metals such as gold (Au) and silver (Ag). The enhancement on Raman signal and tunability of afore-mentioned structures were confirmed by the SERS spectra of Rhodamine 6G and other molecules on metal nanoarrays. Finally, SERS active substrates which were fabricated by colloidal lithography were integrated in optofluidic chips to achieve in-situ molecular and multi-channel detection of Rhodamine 6G and other molecules.
9:00 PM - P3.8
Modeling of Nanoscale Inorganic-organic Hybrid System for in-situ Molecular Recognition.
Sehoon Jeon 1 , Ui Seong Kim 1 , Chee Burm Shin 1 , Jongheop Yi 2 Show Abstract
1 Division of Energy Systems Research, Ajou University, Suwon Korea (the Republic of), 2 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of)
9:00 PM - P3.9
Continuous-flow PCR Chip with PDMS / ITO Heater Patterned Glass for DNA Amplification.
Seung-Ryong Joung 1 , Yung-Jin Choi 1 , Chi-jung Kang 1 , Jaewan Kim 1 , Yong-Sang Kim 1 2 Show Abstract
1 Nano Science and Engineering, Myongji university, Yong-in, Gyeonggi, Korea (the Republic of), 2 Electrical Engineering, Myongji university, Yong-in, Gyeonggi, Korea (the Republic of)
Sonia Grego RTI International
Orlin Velev North Carolina State University
J. Michael Ramsey University of North Carolina-Chapel Hill
Sabeth Verpoorte University of Groningen
P4: Biochemical analysis and Biosensors I
Wednesday AM, April 11, 2007
Room 2005 (Moscone West)
10:00 AM - P4.2
Dielectrophoresis based On-chip Particle Concentrator Using Carbon Nanofiber Electrode Arrays.
Prabhu Arumugam 1 2 , Hua Chen 1 , Jessica Koehne 1 , Alan Cassell 1 2 , Jun Li 1 Show Abstract
1 , NASA Ames Research Center, Moffett Field, California, United States, 2 , UARC/UCSC, Moffett Field, California, United States
We report the use of carbon nanofiber nanoelectrode arrays (CNF-NEA) based dielectrophoresis (DEP) to develop an on-chip sample concentrator with E.coli as a model species. Sample preparation is one of the key functions in detection of biologically important organisms. Traditionally, it is performed through separate, standalone centrifugation and filtration systems and then transferred to a detector. The main disadvantages are cross-contamination, slow processing times, high cost and the need for skilled personnel. Recent efforts are geared towards the development of lab-on-a-chip systems (LOAC) with integrated sample processors and detection capabilities, which is yet to be fully realized. The reason for the slow progress is due to lack of design methodologies, tools and standards owing to application-specific requirements, complexity in integration of multifunctional components, and the difficulty in processing large sample volumes. We need new technologies to seamlessly integrate sample processors and develop a compact, rapid, fully automated, real-time bio-monitoring system for health care, environmental and homeland security applications.DEP is defined as the translational motion of neutral matter in an electric field gradient. The particles are separated based on their electrical properties such as permittivity and conductivity. The gradient is generated by applying an AC potential between the nanoelectrode array located on the bottom of the microchannel and a conducting electrode on the top. The advantage of using a NEA compared to existing interdigitated microelectrode arrays (MEA) is that it can concentrate particles more efficiently from high speed microflows (10-100’s of mm/s) due to high electric field gradients. This is a precondition for applications where the entire analysis needs to be performed in few minutes. We discuss in detail (i) design guidelines for on-chip concentrator through multi-physics modeling and simulations, (ii) the merits of using NEA vs. MEA in terms of collection efficiency and stopping distance, (iii) systematic study of various parameters such as microchannel dimensions, NEA array size, density and spacing, fluid velocity, particle size, electrical properties of the particle and medium, amplitude and frequency of AC voltage, and (iv) microfabrication and packaging issues.
10:15 AM - P4.3
On-chip Collection and Concentration of Live Cells and DNA Based on a Combination of Dielectrophoresis and AC ElectroHydrodynamics
Sonia Grego 1 , Ketan Bhatt 2 , Clifford Tse 2 , Jonathan Black 1 , Orlin Velev 2 Show Abstract
1 , RTI International, Research Triangle Park, North Carolina, United States, 2 Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
We show how the use of alternating electric fields can be exploited for on-chip collection and manipulation of particles, small organisms and large biomolecules by a combination of dielectrophoresis (DEP) and AC electrohydrodynamics (AC-EHD). First, we will present a microfluidic chip that collects and concentrates colloidal particles from bulk liquid medium to a specific region of the surface. Alternating fields are applied to dilute suspensions of microspheres enclosed between a patterned silicon wafer and an ITO-coated glass slide. The latex particles entrained by the liquid flow are collected in the center of conductive "corral" patterns. The leading effect in the particle collection process is AC-EHD. We discuss how the electrohydrodynamic flows emerge from the spatially non-uniform field and interpret the experimental results by means of electrostatic and hydrodynamic simulations. On-chip collection of latex particles, yeast cells and microbes will be demonstrated. Second, we will discuss how AC-EHD methods can be combined with DEP above interdigitated electrode patterns. DEP capture of lambda-phage DNA fragments at a typical field intensity of 100 V/cm as a function of different gap sizes is investigated. The frequency is the most sensitive parameter affecting the performance of these devices as it allows “tuning” of the interactions from AC-EHD to DEP. Positive DEP (pDEP) combined with AC-EHD is observed at low frequencies, so particles are moved and captured in the areas of the highest field intensity, which are the edges of the bottom electrodes. Negative DEP (nDEP) is observed at higher frequencies, where the particles are pushed to the area of minimum electric field, tenths of microns above the electrode surface, where they can be transported by AC-EHD. The potential of these electrode designs in devices for biological analysis will be discussed.
10:30 AM - P4.4
Label-Free Investigation of Enzymatic Catalysis on Surface-Bound Substrates: How Secondary Structure and Accessibility Affect Enzymatic Proteolysis of a Surface-Bound Polypeptide.
Jasper Hardesty 1 Show Abstract
1 Chemical Engineering, Stanford University, Stanford, California, United States
In this work, I study the interactions of enzymes with model substrate surfaces under varied environments and label-free conditions. My model system is based on serine proteases – a class of enzymes that digest proteins – and surface-bound polypeptide substrates. Previous studies have shown that single point mutations made at the surface of the enzyme, but distant from the active site, have little effect on solution activity but can have profound effects on activity with surface-bound substrates. So how do single point mutations affect the interplay between the surface processes of adsorption, reaction, and surface diffusion? With regard to substrate, how might secondary structure and film density influence surface reactivity? Furthermore, other studies have shown that labels can alter biological interactions, and given the sensitivity of our enzyme-substrate systems, it is desirable to avoid labels. Ultimately, it is hoped that elucidating the primary factors that drive overall surface reactivity will lead to rational engineering of enzymes to meet specific needs. In addition, development of label-free techniques to interrogate surface biocatalysis can lead to improved tools to researchers in many science disciplines.
10:45 AM - P4.5
Electroosmotic Flow and Electromigration of DNA Molecules in a Microfluidic Device Investigated by Surface Vibration Spectroscopy.
Tomoyuki Miyoshi 1 , Ayumi Hirano 1 , Ryotaro Yamaguchi 1 , Ko-ichiro Miyamoto 1 , Yasuo Kimura 1 , Michio Niwano 1 Show Abstract
1 , Tohoku University, Sendai Japan
11:30 AM - **P4.6
Materials Processing Methods and Issues in the Development of Nanofluidic Systems for Biomolecular Analysis.
Gabriel Lopez 1 , S. Brueck 1 , Sang Han 1 , Cornelius Ivory 1 , Dimiter Petsev 2 , Scott Sibbett 1 Show Abstract
1 , University of New Mexico, Albuquerque, New Mexico, United States, 2 Chemical Engineering, Washington State University, Pullman, Washington, United States
This talk will present an overview of materials processing methods developed at the University of New Mexico in the development of integrated micro- and nanofluidic systems for biomolecular analysis. Methods for rapid prototyping, high resolution lithography and facile fabrication of enclosed and porous nanofluidic channel arrays will be presented. These methods allow the creation of fluidic systems that allow dynamic control of electrokinetic molecular transport through specific localized regions of micro and nanofluidic channels. Methods for achieving molecular focusing and separations include field gradient focusing, isoelectric focusing, nanoelectrosmosis and electrokinetic analogues of field effect transistors. In addition, the molecular-scale cross-sectional dimensions of these channels may permit entirely new separations that are difficult or impossible to perform in larger-scale channels. Materials-dependent system properties, materials processing, and materials related performance issues will be emphasized.
12:00 PM - P4.7
Automated Formation of Lipid bilayer Membranes within a Microfluidic Device for Channel Protein-based Sensing.
Noah Malmstadt 1 , Jason Poulos 1 , Jacob Schmidt 1 Show Abstract
1 Department of Bioengineering, UCLA, Los Angeles, California, United States
12:15 PM - P4.8
Parallel Gene Synthesis in a Microfluidic Device.
David Kong 1 , Peter Carr 1 , Lu Chen 2 , Joseph Jacobson 1 Show Abstract
1 MIT Media Lab, Center for Bits and Atoms, MIT, Cambridge, Massachusetts, United States, 2 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
It has long been recognized that the capacity to design and synthesize genes and longer DNA constructs can be enabling to a broad cross section of applications within molecular biology including the design of genetic circuitry, the engineering of entire metabolic pathways for target molecule manufacture, and even the construction and re-engineering of viral and bacterial genomes. The core technology for custom DNA synthesis centers on the assembly of pools of oligonucleotides (oligos), typically less than 50 nucleotides in length, into increasingly larger DNA molecules. The most widely reported methods for building long DNA molecules involve variations of the polymerase-mediated assembly technique collectively termed Polymerase Construction and Amplification (PCA). Here, much like in the more conventional Polymerase Chain Reaction (PCR), three temperature steps are employed to denature, anneal, and elongate the various overlapping oligos until, after multiple rounds of thermocycling, the desired full length DNA construct is obtained. Using such polymerase-mediated techniques, researchers have successfully synthesized DNA constructs as large as tens of kb. Despite these promising results significant challenges remain, most significantly the cost and time of synthesizing long constructs. Currently, the cost for custom gene synthesis services is significant, on the order of $1.00-$1.60 dollars per base pair, with the major expenditure components for such long syntheses being attributable to reagent and sample handling. Microfluidic technology provides an elegant means to overcome these limitations. By scaling reactions down to volumes of less than a microliter, reagent costs can be substantially reduced. Furthermore, microfluidic technology enables highly parallelized synthesis along with the potential for automated sample handling and process integration. In this paper we report the synthesis and amplification of various genes in a poly(dimethylsiloxane)-based microfluidic device. Genes such as GFP (933 bp), dsRed (733 bp), a Holliday junction cleavase (hjc) gene from the bacteriophage SIRV-1 (390 bp), and a variant alba gene from S. solfataricus (327 bp) were synthesized. In other reports oligos for gene synthesis were synthesized in situ in a microarray, cleaved from a glass substrate and subsequently assembled in macroscopic (≥ 5 μl) reactions. In contrast, we have synthesized these DNA constructs in parallel within four 500 nanoliter reactors of a microfluidic device. Furthermore, the minute oligo concentrations utilized (10-25 nM each oligo) are significantly lower than concentrations expected to be attainable (without amplification) from high density oligonucleotide microarrays. Thus, such a microfluidic approach should be compatible with DNA microarray-derived oligonucleotides, further reducing the cost of this crucial reagent.
12:30 PM - P4.9
Chitosan-mediated Enzyme Assembly toward Rebuilding a Metabolic Pathway in the Microfluidic Environment.
Xiaolong Luo 1 5 , Jung Park 8 , Hyunmin Yi 7 , Angela Lewandowski 3 6 , William Bentley 1 6 , Gregory Payne 6 , Reza Ghodssi 4 5 , Gary Rubloff 2 5 Show Abstract
1 Fischell Department of Bioengineering, University of Maryland, College Park, Maryland, United States, 5 Institute for Systems Research (ISR), University of Maryland, College Park, Maryland, United States, 8 Polymers Division, Materials Science and Engineering Laboratory, NIST , Gaithersburg, Maryland, United States, 7 Department of Chemical and Biological Engineering, Tufts University, Medford, Massachusetts, United States, 3 Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland, United States, 6 University of Maryland Biotechnology Institute (UMBI), University of Maryland, College Park, Maryland, United States, 4 Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland, United States, 2 Department of Materials Science and Engineering, University of Maryland, College Park, Maryland, United States
We demonstrate enzyme assembly at readily addressable sites in the microfluidic environment by utilizing two unique properties of the amino-polysaccharide chitosan. The pH responsive solubility of chitosan enables site-selective electrodeposition onto conductive inorganic surfaces within microfluidic channels. Secondly, the abundant primary amine groups on chitosan allow covalent assembly of biomolecules while preserving biological activity. We have utilized chitosan as the biointerface for facile in situ biomolecule assembly in microfluidic environment. The site-selective assembly of proteins enables multiple-step, multiple-site bioreactions in metabolic engineering and many applications. For example, we can harvest an important cell signal molecule Autoinducer 2 (AI-2) if the precursor SAH is introduced over immobilized enzymes Pfs and LuxS. Here we present the unique features of our microfluidic device for biomolecule assembly, the enzyme assembly procedures and the first enzymatic reaction toward rebuilding a metabolic pathway of producing AI-2 in the microfluidic environment.The microfluidic wafer is fabricated of Au/Cr as electrodes and SU-8 polymer as microfluidic channels on a Pyrex wafer with standard lithographic and etching technique. Then the wafer is leak-tightly sealed by a top sealing PDMS layer, and the SU-8/PDMS junction is compressed with two packaging Plexiglas plates by pressure-adjustable compression bolts. Fluidic connectors are assembled and connected to external pressure-driven aqueous transport, and electric Pogo pins are assembled and connected to electrical signal to guide the biomolecule assembly onto selective sites.To assemble Pfs enzyme within microfluidic channel, a tyrosine tagged enzyme Pfs is first conjugated to chitosan. Then the Pfs-chitosan conjugate is introduced into a microfluidic channel, which is already treated with buffer to minimize nonspecific binding. Current signal is applied to the cathode to electrodeposit the Pfs-chitosan conjugate onto the readily addressable assembly site, and the electrodeposited film is then neutralized by buffer. After the enzyme is immobilized, the substrate SAH solution is continuously introduced into microchannel. The reaction product is collected and analyzed using high performance liquid chromatography (HPLC) to determine the efficiency of the enzymatic reaction. The HPLC analysis results show that the assembled Pfs efficiently convert 100% of SAH into intermediate product SRH and by-product adenine, while the negative control (no electric signal when Pfs-chitosan solution is in) shows only 20% conversion rate. Currently we are working on assembling the second enzyme LuxS to convert SRH into AI-2. Our end goal is to achieve a complete bio-microfactory by integrating a cell-based sensor to identify the final product AI-2.
12:45 PM - P4.10
On-chip Detection of Chemiluminescent Biomolecules Using an Integrated Thin Film Silicon Photodiode.
Ana Pereira 1 2 , A. Pimentel 1 , V. Chu 1 , D. Prazeres 2 , J. Conde 1 3 Show Abstract
1 , INESC Microsistemas e Nanotecnologias, Lisbon Portugal, 2 Centro de Engenharia Biológica e Química, Instituto Superior Técnico, Lisbon Portugal, 3 Dept. of Chemical and Biological Engineering, Instituto Superior Técnico, Lisbon Portugal
Current biochip data acquisition is based primarily on the use of fluorescence microscope image capture of the emission from a fluorescent marker. Although these optical systems have high sensitivity, they require the use of complex image acquisition and processing systems. On-chip electronic data acquisition could improve both the speed and the reliability of the biochip pattern analysis. Previous work has demonstrated integrated photodetectors for fluorescently-tagged biomolecule detection. However, these systems require an integrated filter system to cut the excitation light. The use of chemiluminescence instead of fluorescence for on-chip detection has the advantage of not requiring either these filters or the use of an external light source. This would allow a simple integrated platform for on-chip electronic data acquisition. In a chemiluminescence analysis system, an enzymatic label such as horseradish peroxidase (HRP) or alkaline phosphatase (AP) is used to tag the biomolecule. In the presence of the appropriate reactants, these enzymes can catalyze a light emitting reaction that can be detected by a photodiode. Two different device configurations have been developed for the successful detection of HRP in solution by capturing the light emitted by a chemiluminescent reaction using an integrated thin film amorphous silicon p-i-n photodiode. Amorphous silicon photodiodes show high photosensitivity, low dark current, and can be deposited on glass, plastic and steel substrates.In the first configuration (A), the bottom electrode of the photodiode is a transparent conductive oxide (ITO) deposited on a glass substrate. By means of a flip-chip technique the glass substrate faces the reaction chamber. In the second configuration (B), the top electrode is transparent and is passivated by silicon dioxide. In configuration B, the solution is in direct contact with the passivation layer of the photodiode. A set of a-Si:H n-i-p photodiodes with lateral dimensions of 200 x 200 microns were fabricated on a glass substrate and tested. In both device configurations it is possible to detect in real time the presence of HRP in solution. The sensitivities so far obtained are in the range of nanomole of HRP per liter of solution. Efforts are under way to increase the sensitivity of the devices. In addition, device B is being tested for detection of surface immobilized antibodies labelled with HRP, which simulations suggest should be possible. If these tests are successful, multiple parallel immunoassays could be performed using on-chip detection with integrated photodetectors.
P5: Biochemical Analysis and Biosensors II
Wednesday PM, April 11, 2007
Room 2005 (Moscone West)
2:30 PM - **P5.1
Encapsulation of Yeast Cells in Alginate Hydrogels Generated from Monodisperse Double Emulsion Drops.
Carlos Martinez 1 2 , Jin Woong Kim 1 , Manuel Marquez 1 2 3 , David Weitz 1 Show Abstract
1 DEAS, Harvard, Cambridge, Massachusetts, United States, 2 INEST, PMUSA, Richmond, Virginia, United States, 3 Center for Computational Nanoscience, NIST, Gaithersburg, Maryland, United States
We have developed a technique to encapsulate yeast cells in alginate hydrogels from monodispersed water/oil/water double emulsion drops made using a capillary microfluidic device. The capillary microfluidic device consists of two tapered cylindrical glass capillaries with different tip diameters (dsmall = 20 μm to 40 μm and dlarge = 40 μm to 120 μm), that are aligned facing each other and nested within a square capillary tube. In this device the innermost fluid is pumped through the smaller tapered capillary tube, while the middle and outer fluids are pumped in opposite directions through the outer coaxial region. The three fluids are forced through the larger tapered round capillary resulting in the hydrodynamic focusing of the coaxial flow. The inner and middle fluids then break into drops, forming the double emulsions. The inner drop contains an aqueous 2% alginate solution plus yeast cells (Ncells ~ 106/mL), while the outer drop consists of mineral oil with 0.4% by wt. SPAN 80. Such a low percentage of surfactant provides just enough stability for these drops to be collected in a 500 mM CaCl2 solution. Hydrogels are formed when the aqueous alginate inner drop breaks from the mineral oil shell and comes in contact with the Ca2+ ions in solution. The hydrogels were left in the CaCl2 solution for 15 minutes to ensure full crosslinking and to minimize cell damage by the Ca2+ ions. Excess CaCl2 and mineral oil were then removed via several short centrifuging steps. Hydrogels with diameters ranging from 30 µm to 200 µm were obtained by varying the capillaries tip diameters and the flow rates of the inner and middle fluids. There were on average 0.2 cells per hydrogels and their occurrence followed a Poisson distribution. Cells were found to be viable for several days after encapsulation (using a live/dead stain). This technique provides an effective and biocompatible way to encapsulate cells in alginate hydrogels.
3:00 PM - P5.2
Templated Self-assembly of Magnetic Particles for Microfluidic Cell Sorting.
Antoine-Emmanuel Saliba 1 , Eleni Psychari 1 , Laure Saias 1 , Vincent Studer 2 , Jean-Louis Viovy 1 Show Abstract
1 , Curie Institute, Paris France, 2 , ESPCI, Paris France
3:15 PM - P5.3
A Controllable Microfluidic Gradient Device for Studying Neuronal Polarization.
Ning Ma 1 , Mu-Ming Poo 2 , Lydia Sohn 1 Show Abstract
1 Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California, United States, 2 Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California, United States
We have developed a microfluidics-based device that generates a stable soluble guidance cue concentration gradient for investigating axonal chemotaxis. The device, consisting of a series of alternating cell-culture chambers and reagent reservoirs that are interconnected via microchannels, establishes and maintains steady concentration gradients within static cell-culture chambers. Concentrations of both small molecules (pharmaceutical agents and second messengers) and macromolecules (neurotrophins and other proteins) are easily achieved and quantified in this device. Thus, this device is ideally suited for quantitative studies of neuronal polarization and axon pathfinding of shear-sensitive primary neurons in response to micro-environmental cues. The device is designed to have three cell-culture chambers of size 20,000 μm × 1000 μm × 100 μm, and four reagent reservoirs. The volume of the reagent reservoirs was designed per the different diffusivities of the guidance cues used, and ranges from 2 ml for the guidance cues with lower diffusivities (e.g. BDNF, D ~ 5x10-7 cm2/s) to 6 ml for those with higher diffusivities (e.g. membrane permeable cAMP, D ~ 3x10-6 cm2/s). We use standard photolithography and soft-lithography techniques to fabricate the device. In more detail, we lithographically create a negative master on a silicon wafer, which is subsequently cast into a poly(dimethylsiloxane) (PDMS) slab, a well-known biocompatible material that has been used for a variety of cell-culture applications. The PDMS slab is then cleaned and reversibly sealed to a Poly-L-Lysine coated microscope slide. Specific guidance cues with different concentrations, e.g. 100 μg/mL, 10 µg/mL, etc., are loaded into different reagent reservoirs. They then diffuse through the interconnecting microchannels and establish specific concentration gradients in each cell-culture chamber. We have successfully cultured embryonic rat hippocampal neurons in our devices and have observed good cell viability over seven days of culture, a critical time period during which neurons mature and polarize. The rat hippocampal neurons in our devices undergo normal polarization and develop an axonal process that sprouts from the cell body. In this presentation, we will show these results and preliminary data that demonstrate our ability to measure the minimum concentration gradient required to guide the path-finding of the axon growth-cone in response to known guidance cues. Overall, our device is truly a platform technology, as it is also capable of identifying novel guidance cues that regulate neuronal development and guide axonal movement. As well, it enables the simultaneous testing of multiple environmental cues to discern potential signaling crosstalk. Our future studies include evaluating opposing and reinforcing gradients of guidance cues to identify combinations that optimize the distance over which the axon can be guided.
3:30 PM - P5.4
A Microfluidic Array with Micro Cell Sieves for Cell Cytotoxicity Screening
Zhanhui Wang 1 , Min-Cheol Kim 1 , Manuel Marquez 2 , Todd Thorsen 1 Show Abstract
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , Research Center, Philip Morris USA, Richmond, Virginia, United States
There is currently great interest in cell arrays for cell-based studies to improve experimental throughput. Microfluidics is an inherently scalable technology, offering an exciting new alternative to fabricate cell arrays for cell studies in a parallel fashion. In recent years, this method has been applied to several cell-based biological studies including mammalian cell patterning in an enclosed array, cellular responses to chemical gradients, investigation of celluar differentiation, and observation of dynamic gene expression. However, current microfluidic cell arrays are unable to screen multiple cytotoxins with multiple living mammalian cells. In addition, there are some difficulties to fabricate microfluidic live cell array for toxin screening. Uniform cell loading and distribution are main challenges in a large array format, because cells are suspended in medium and very small perturbations to fluid flow will significantly disturb cell positions in culture chamber with nanoliter volume. Inhomogeneous cell loading and distribution can affect cell viability evaluation after toxins exposure, leading to false toxins screening result.In this report, we developed a microfluidic array platform with lithography molding technology for high-throughput cell cytotoxicity screening. The channels in this platform were individually addressable in both directions (column and row), enabling parallel loading of various cell lines in one direction and introducing of different toxins in the other direction. The channels for cells seeding were orthogonal to channels for toxins exposure, and each region at channel intersection was a circular chamber which was compartmentalized by array valves. Several micro cell sieves were built in each culture chamber to form several low flow velocity regions, and cells can be trapped and immobilized within cell sieves. Cell number and distribution in chambers can be conveniently controlled by the adjustment of cell sieve number, distribution and size.
3:45 PM - P5.5
Development of a Lab-on-a-Chip for the Characterization of Human Cells.
Peter Ertl 1 , Lukas Richter 1 , Christoph Stepper 1 , Hubert Brueckl 1 , Rudolf Heer 1 , Michael Kast 1 Show Abstract
1 ARC-Seibersdorf research, Nano-Systems-Technologies, Vienn Austria
4:30 PM - **P5.6
Strategy and Method for Construction of Micro-Nano Chemical Process on Microchip.
Takehiko Kitamori 1 Show Abstract
1 Department of Applied Chemistry, The University of Tokyo, Tokyo Japan
5:00 PM - **P5.7
Lab-On-A-Chip Devices for Protein Analysis & Clinical Diagnostics.
Anup Singh 1 Show Abstract
1 , Sandia National Labs, Livermore, California, United States
Lab-on-a-chip or microfluidic devices are attracting significant attention in the area of biochemical analysis because of their portability, speed of analysis, potential for multiplexing and high-throughput, and ability to analyze minute sample volumes. In this talk, I would present a few examples of application of microfluidic chips for protein separation and clinical diagnostics. The two most commonly used techniques for protein separation are chromatography (e.g., HPLC) and gel electrophoresis. Their miniaturization holds substantial promise for analysis of complex biological samples as microchip-based separation offers faster analysis (minutes), better sensitivity, and ability to analyze minute amounts of sample. Microchip-based chromatography and gel electrophoresis were developed using a photopolymerization technique to controllably and reproducibly place porous polymer matrices in the channels of a chip. The polymer matrices can be cast in situ in less than 10 minutes and are robust and reproducible with respect to separation characteristics. Microchips containing photopatterned acrylate were used for chromatography of peptides and amino acids and yielded separations that were fast (6 peptides in 45 sec), efficient (up to 600,000 plates/m) and reproducible (run-to-run variability <3%). SDS-PAGE-in-a-chip was developed by using photopolymerized crosslinked polyacrylamide and led to separation of 6 proteins of molecular weight from 20 to 200 kD in less than 30 seconds using a 1 mm-long channel. An integrated on-chip concentrator enabled detection of proteins at concentration as low as 100fM.Taking advantage of the small size of the chips and the rapid analysis they offer, we have also developed a point-of-care device for detection of disease biomarkers in saliva. Saliva offers many advantages over other bodily fluids because it is easy to collect using noninvasive methods in both clinical and non-clinical settings. The device performs rapid microfluidic chip-based immunoassays (< 3-10 minutes) with low sample volume requirements (10 µL) and appreciable sensitivity (nM-pM). Our microfluidic method facilitates hands-free saliva analysis by integrating sample pretreatment (filtering, enrichment, mixing) with electrophoretic immunoassays to quickly measure analyte concentrations in minimally pretreated saliva samples. The chip has been integrated with miniaturized electronics, optical elements, fluid-handling components, and data acquisition software to develop a portable, self-contained device. The device is being tested by detecting biomarkers in saliva samples from patients diagnosed with periodontal disease.
5:30 PM - P5.8
Biosensing using Thin Film Microresonators.
Joao Pedro Conde 1 2 , Teresa Adrega 1 , Guandong Zhang 1 , Ana Teresa Pereira 1 3 , Samadhan Patil 1 , Duarte Prazeres 2 3 , Virginia Chu 1 Show Abstract
1 , INESC MN, Lisbon Portugal, 2 Deptartment of Chemical and Biological Engineering, Instituto Superior Tecnico, Lisbon Portugal, 3 Center for Biological and Chemical Engineering, Instituto Superior Tecnico, Lisbon Portugal
There has been growing interest in using microelectromechanical systems (MEMS) as biological sensors. Microresonators, in particular, have been proposed as sensors to detect and quantify the presence of specific biological compounds. Thin-film silicon and polymer-based MEMS have recently been developed to benefit from the advantages of thin-film technology. Thin film materials are of great interest for electronic devices and MEMS applications due to their relative low cost and simple processing. Thin-film silicon and all-polymer suspended microbridges incorporating a conductive polymer are fabricated on glass substrates using surface micromachining. The use of low temperature processing (< 110°C) allows the use of substrates such as glass, plastic and stainless steel. In addition, thin-film MEMS are CMOS compatible enabling the monolithic integration of MEMS with its control electronics.This work presents DNA and protein sensors based on thin-film microresonators. The sensor works by the measurement of the resonance frequency shift induced by a specific biological reaction on a resonating microbridge. Hybridization of DNA oligonucleotides and antibody-antigen interactions are the biological models used.The thin-film silicon sensor is fabricated using surface micromachining and consists of a n+-a-Si:H/ aluminum bilayer microbridge with SiO2 patterned on the top. An aluminum gate underneath the bridge allows the electrostatic excitation of the microbridge. The resonance frequency of the microbridges is in the 1-10 MHz range. Quality factors in vacuum are of the order of 1000. For the polymer-based microbridges, a blended conductive polymer material of polymethyl methacrylate (PMMA) and Baytron P (a waterborne dispersion of the polymer complex PEDOT and PSS) is used as the structural layer. In the fabrication process, a Cr gate is first deposited and patterned on a glass substrate. Then, an Al film is deposited and patterned on the Cr gate to function as the sacrificial layer. The resonance frequency of the polymer bridge is in the MHz range and the quality factor in vacuum is of the order of 100.Covalent and electrostatic immobilization of DNA oligonucleotide probes, and subsequent hybridization of target DNA, as well as covalent immobilization and adsorption of probe proteins, and their subsequent interaction with target proteins, will be described for thin-film silicon microresonators. In these devices, resonance frequency shifts are below 1% in vacuum and are controlled by the mass loading of the microstructure. These results will be compared to the adsorption of proteins and DNA on polymer microresonators. Larger frequency shifts (above 1% in vacuum) are observed in the polymer MEMS biosensors, and these shifts are attributed to a higher sensitivity of the polymer microresonator to the stress induced by the immobilization of the biomolecules, because of the significantly lower rigidity of the polymeric microbridges.
5:45 PM - P5.9
Chip-Scale Affinity Microcolumn Biosensors for Toxic Agents
Mangesh Bore 1 , Aurelio Evangelista 1 , Linnea Ista 1 , Steven Brueck 2 , Gabriel Lopez 1 Show Abstract
1 Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 2 Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico, United States
This presentation will describe a microscale, multi-threat agent detection system (including unknown agents) using toxin receptor binding and electrokinetic separations in microchannel. Most current threat detection systems rely on precise identification of the biological or chemical toxin. While this approach has its uses, it is ineffective against either newly developed or modified threats that, by novelty or design, can evade precise recognition elements. In our strategy, the potential physiological effect is key, and the exact identity of the threat agent is secondary. Because the detector is the target of the threat, or one of the targets of the threat, either novel threats, or those deliberately designed to thwart current detection schemes, will be quickly detected. The technology is based on two essential components: binding of potential toxins to receptors, enzymes and other biomolecules known to be affected by toxic agents (including chemical, biochemical and biological agents) followed by detection of binding events by altered electrokinetic mobility. We have developed a rapid prototyping method for forming packed microcolumns at the intersection of a cross microfluidic design containing sample, separation and waste streams. This simple cross design forms the prototype component for all of the chip designs envisioned. We have conducted proof-of-concept experiments that demonstrate that the microfluidic design for achieving the new biosensing approach envisions works. Specifically methods for microcolumn packing, sample introduction, pumping, analyte capture, analyte release, separation of receptor and receptor/ analyte complex, and finally detection of receptor and receptor analyte complex (receptor/toxin pair is Ganglioside GM1/Cholera Toxin).
Sonia Grego RTI International
Orlin Velev North Carolina State University
J. Michael Ramsey University of North Carolina-Chapel Hill
Sabeth Verpoorte University of Groningen
P6: Assembly and Synthesis of Micro/Nanostructures
Thursday AM, April 12, 2007
Room 2005 (Moscone West)
9:30 AM - **P6.1
Magnetic Nanocrystals as Building Blocks for Biotags and Sensors.
Christopher Murray 1 2 Show Abstract
1 Chemistry & Materials Science, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Nanoscale Materials & Devices, IBM T. J. Watson Research Center, Yorktown Heights, New York, United States
10:00 AM - **P6.2
Continuous Microfluidic Reactors for Polymer Colloids.
Eugenia Kumacheva 1 , Zhihong Nie 1 , Minseok Seo 1 , Shengqing Xu 1 , Ethan Tumarkin 1 , Hong Zhang 1 , Patrick Lewis 1 Show Abstract
1 Chemistry, University of Toronto, Toronto, Ontario, Canada
10:30 AM - P6.3
Controllable Fluidic Assembly of Nanostructures by Chaotic Advection.
David Zumbrunnen 1 Show Abstract
1 Mechanical Engineering, Clemson University, Clemson, South Carolina, United States
Research in the author’s laboratory has demonstrated that nano-scale materials can be controllably assembled in the melt by instilling chaotic advection . Smart blending devices have resulted that are currently being adopted. Chaotic advection refers to chaotic motions in fluid markers that can arise even in response to simple flow fields [2,3]. Chaotic advection has two defining and related characteristics of significance to in situ structure development. In one characteristic, the region of space enclosing an initial minor component body becomes stretched and folded. Stretching and folding can occur recursively until nano-scale dimensions are attained. In another characteristic, the positions of individual nano-particles diverge exponentially fast over time. Networks of particles can emerge with features such as alignment or interconnections that can be tailored. Unlike mixing, material components become organized on progressively smaller length scales and nano-structured materials with hierarchical features can arise. In addition to the nano-scale dimensions in materials produced, property enhancements are derived from the structural arrangement of nano-solid additives or nano-scale shapes formed in melt-processable materials. Moreover, it has been found that a multi-layer morphology is a parent to other morphologies. Multi-layers, can for example, transform to dual phase continuous, sponge-like structures. Nano-sponges can thereby be produced . Processing can be done continuously and in either small or large capacities. Miniature devices operate much as do larger devices for large-volume production. Examples of nanocomposites that have been produced include extruded polymeric multi-layer films having thousands of discrete layers and where individual layers have thicknesses of only a few nanometers, multi-layer polymeric films having alternate layers with aligned nano-platelets, composites with aligned nanotubes, and composites with conducting networks. Where molecules are synthesized to self-assemble, results suggest that methods may yield expansive functional supramolecular structures. ReferencesZumbrunnen, D. A., Nano Letters, 2: 1143( 2002). Aref, H., J. Fluid Mech., 143: 1 (1984).Aref, H., Phys. Fluids, 14, 1315 (2002).Joshi, A.S. and Zumbrunnen, D. A., Chem. Eng. Comm., 193: 765 (2006).
10:45 AM - P6.4
Microfluidic Electrospinning of Hollow and Core/Sheath Nanofibers.
Yasmin Srivastava 1 2 , Manuel Marquez 2 3 4 , Todd Thorsen 1 Show Abstract
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 2 INEST Group Postgraduate Program, Philip Morris USA, Richmond, Virginia, United States, 3 NIST Center for Theoretical and Computational Nanosciences, NIST, Gaithersburg, Maryland, United States, 4 Harrington Department Bioengineering, Arizona State University, Tempe, Arizona, United States
The versatile technology of electrospinning for the preparation of polymer nanofibers has been recognized as an efficient technique to generate sub-micron scale nanofibers [1,2]. In the conventional electrospinning method, a syringe with a fixed inner diameter of 0.3-1 mm is used as an electrospinning source which, in many cases, limits the process by single jet and single component spinning. Recently, co-axial electrospinning has been extensively exploited as a simple technique to generate hollow and core/sheath nanofibers [3,4,5,6,7]. However, the process of making coaxial-spinnerets is labor-intensive and, to date, has utilized a single spinneret source for generating hollow nanofibers.In this communication, we describe the development of a multichannel microfluidic device for the parallel electrospinning of single, composite, hollow and core/sheath nanofibers. Advantages of this technology over conventional syringe-based methods include the ability to dynamically combine multiple components into a single nanofiber, rapid prototyping and the ability to spin multiple fibers in parallel through arrays of individual microchannels. Nanofibers of poly (vinylpyrrolidone) (PVP) and a conducting composite (PVP+Polypyrrole (PPy)) were successfully fabricated using this microfluidic integration with electrospinning. Fourier transform infrared spectroscopy and conductivity measurements reveal the polymerization of pyrrole in the matrix of PVP.Also, this microfluidic methodology was successfully used to fabricate hollow PVP + titania (TiO2) and core/sheath PPy/PVP nanofibers of the order of 100 nm and 250 nm respectively. The design utilized two layers of microchannels to flow PVP solution as sheath material and heavy mineral oil or pyrrole as the core phase through an array of spinners. Two layers of non-intersecting, stacked 100µm (w) × 100µm (h) microchannels are arranged in a branching tree pattern to provide constant pressure to each of eight outlet spinnerets. Hollow composite nanofibers of PVP + TiO2 were synthesized from the PVP + TiO2 / heavy mineral oil nanofibers by extracting the mineral oil core with octane. Fiber characterization was subsequently carried out using a combination of Scanning electron microscopy, Transmission electron microscopy and Fourier transform infrared spectroscopy.References1.Formhals, A. US 1,975, 504, 1934.2.Reneker, D. H.; Chun, I. Nanotechnology, 1996, 7, 216-223.3.Loscertales, I.G.; Barrero, A.; Marquez, M.; et al. J. Am. Chem. Soc. 2004, 126, 5376-5377. 4.Li, D.; Xia, Y.N. Nano letters 2004, 4, 933-938. 5.Li, D.; McCann, J.T.; Xia Y.N. Small 2005, 1, 83-86. 6.McCann, J.T.; Li, D.; Xia, Y.N. J. Mater Chem. 2005, 15, 735-738. 7.Sun, Z. C.; Zussman, E.; Yarin, A. L.; Wendorff, J. H.; Greiner, A. Adv Mater. 2003, 15, 1929-1932.
11:30 AM - **P6.5
Droplet-Based Microfluidics for High Throughput BioAssays.
David Weitz 1 Show Abstract
1 Department of Physics and Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
This talk will describe the use of microfluidic devices to precisely control independent droplets of water in an inert carrier oil. Each droplet contains several picoliters to femtoliters of fluid, and each can be controlled and manipulated with a high degree of precision. This allows these droplets to be used as minute microreactors for high throughput screening purposes. This talk will describe the microfluidic devices and some potential uses.
12:00 PM - P6.6
Programmable Manufacturing of Anisotropic Particle Assemblies by Fluidic Processing.
Kyung Eun Sung 1 , Deshpremy Mukhija 1 , Siva Vanapalli 1 , Hugh McKay 2 , Joanna Mirecki-Millunchick 2 , Michael Solomon 1 , Mark Burns 1 3 Show Abstract
1 Chemical Engnieering, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
12:15 PM - P6.7
Microfluidic Assembly of Granular Shells and Janus Colloidal Granules
Robert Shepherd 1 , Jacinta Conrad 1 3 , Summer Rhodes 1 , Darren Link 2 , Manuel Marquez 3 , David Weitz 4 , Jennifer Lewis 1 Show Abstract
1 Materials Science, University of Illinois, U-C, Urbana, Illinois, United States, 3 , Phillip Morris USA, Richmond, Virginia, United States, 2 , RainDance Technologies, Inc., Guilford, Connecticut, United States, 4 Physics, Harvard University, Cambridge, Massachusetts, United States
The microfluidic assembly of colloid-filled hydrogel drops and dried granules of varying shape and composition is investigated. Drops are formed by shearing a concentrated colloidal microsphere-acrylamide suspension in a continuous oil phase using a sheath-flow or a double emulsion capillary device. Silica microspheres are synthesized with different fluorescent cores to allow direct visualization of the process. Homogenous and Janus (hemispherically distinct) spheres and disks are produced by confining the assembled drops in microchannels of desired geometry while granular shells of micron size colloids are produced in a double emulsion micro-capillary device. To preserve their drop structure, photopolymerization of an acrylamide-based hydrogel solution is carried out immediately after drop-breakup. Representative drops and dried granules are imaged using fluorescence and scanning electron microscopy to probe their structural evolution during assembly and drying while micro-CT is used to probe packing of the disk and sphere geometries. Our approach offers a facile route for assembling colloid-filled hydrogel drops and dried granules with controlled morphology and composition.
12:30 PM - P6.8
Materials Strategies for Advanced NanoTechnology.
Kyung Choi 1 Show Abstract
1 , Bell Labs, Lucent Technologies, Murray Hill, New Jersey, United States
Since we have sought new advances in nanotechnology, developments of new materials and new synthesis techniques have been pursued to meet our growing demands in miniaturization. In this talk, we will present design of new materials by fabricating microfluidic reactors specifically designed for microfluidic synthesis, taking advantage of micro-scale mixing 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. The microreactors may also be coupled to additional processing steps (i.e. multistep synthesis) and in some cases the product is transported directly for integration into an application device or as part of an assay. The overall goal is to carry out all operations normally performed in a chemical laboratory including synthesis, processing, mixing, purification and analysis on one microfluidic reactors efficiently and economically using minute amounts of solvents and reagents.
12:45 PM - P6.9
Selective Enrichment of Phosphorylated Peptides by Magnetic Nanoparticles and Mesoporous Magnetic Sub-micron Particles.
Yi Huang 1 , Chia-Kuang Tsung 2 , Qihui Shi 2 , Pengyuan Yang 1 , Galen Stucky 2 , Xian Chen 1 3 Show Abstract
1 Institutes of Biomedical Sciences, Fudan University , Shanghai China, 2 Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California, United States, 3 Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, United States
Protein phosphorylation is a one of most critical posttranslational modifications (PTMs) that regulate various biological processes including signal transduction, cellular regulations, etc. Mass spectrometry (MS) has been emerging as the most precise tool for identifying phosphorylated proteins and mapping out those biologically relevant phosphorylation sites. However, due to the low ionization efficiency of phosphopeptides the signals from phosphopeptides can always be suppressed by their nonphosphorylated counterparts. Pre-enrichment and isolation of phosphorylated peptides from proteolytic peptide mixtures resulting from enzymatic digestions of proteins becomes a critical step for tandem MS/MS-based site determination. This procedure eliminates nonphosphopeptide interferences and specifically enhances the signal from phosphopeptides. The common enrichment strategy is the immobilized metal ion affinity chromatography (IMAC), which uses Fe3+, Ga3+, or other metal ions to capture phosphopeptides. Recently, metal-containing nanoparticles have shown a high efficiency as well as a high extraction capacity for phosphopeptide enrichments because of their large surface area-to-volume ratio. Here we demonstrate a series of our newly developed magnetic nanoparticles (Fe3O4) and submicron mesoporous magnetic particles (TiO2) that can selectively enrich phosphorylated peptides from peptide mixtures in solution. Beta-casein and casein conatining the phosphorylated sites were analyzed by our new nanoparicle enrichers, meanwhile, other four nonphosphorylated proteins (bovine serum albumin, hemoglobin, myoglobin and cytochrome c) were used as the controls of non-phosphorylated peptides. The enrichment efficiency was evaluated by matrix assisted laser desorption and ionization time-of flight mass spectrometry.
P7: Fluid Transport and Modeling
Thursday PM, April 12, 2007
Room 2005 (Moscone West)
2:30 PM - **P7.1
Multiphase Flow in Small Devices: From Colloidal Shells to Numerical Simulations for Drop Breakup and Gas-liquid Microreactors.
Howard Stone 1 Show Abstract
1 Engineering & Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
3:00 PM - P7.2
Diffusion Effects on Fractionation by Deterministic Lateral Displacement in a Microfluidic Device.
John Davis 1 , David Inglis 1 , Suberr Chi 1 , Robert Austin 2 , James Sturm 1 Show Abstract
1 Electrical Engineering, Princeton University, Princeton, New Jersey, United States, 2 Physics, Princeton University, Princeton, New Jersey, United States
3:15 PM - P7.3
Tuning Surface Dynamics for Transport in Microchanels.
Lyderic Bocquet 1 Show Abstract
1 LPMCN, université de Lyon and CNRS, Lyon France
3:30 PM - P7.4
General Continuum Boundary Conditions for Miscible Binary Fluids from Molecular Dynamics Simulations.
Colin Denniston 1 , Mark Robbins 2 Show Abstract
1 Applied Mathematics, University of Western Ontario, London, Ontario, Canada, 2 Physics and Astronomy, Johns Hopkins Univ., Baltimore, Maryland, United States
3:45 PM - P7.5
Study of FET Flow Control of Proteins and pH Changes in Nanochannels Using Scanning Laser Confocal Fluorescence Microscopy and Multiple Internal Reflection Fourier Transform Infrared Spectroscopy
Youn-Jin Oh 1 , Danny Bottenus 3 , Dimiter Petsev 1 , Steven Brueck 2 , Lopez Gabriel 1 , Cornelius Ivory 3 , Sang Han 1 2 Show Abstract
1 Chemical & Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 3 Chemical Engineering, Washington State University, Pullman, Washington, United States, 2 Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico, United States
We have studied the field-effect-transistor (FET) flow control and separation of proteins in a parallel array of nanochannels (100 nm W ×500 nm D), using scanning laser confocal fluorescence microscopy (SL-CFM) and multiple internal reflection Fourier transform infrared spectroscopy (MIR-FTIRS). For fluidic FET, a DC potential is applied to the gate surrounding an isolated mid-section of the channels. The gate potential controls the surface charge on SiO2 channel walls and therefore the zeta-potential. Depending the polarity and magnitude, the gate potential can accelerate, decelerate, or reverse the flow. From our experiments, we observe that the electroosmotic flow of protein molecules is successfully controlled by the gate potential. We also detect a pH shift in the nanochannels according to the surface charge modulation, using SNARF-1 and Fluorescein as pH indicators. For instance, using MIR infrared waveguide, into which nanochannels are integrated, we observe that Fluorescein dye molecules are hydrogenated and dehydrogenated in response to the gate bias and subsequent pH shift. We demonstrate that the pH shift affects the FET flow control with SL-CFM analysis. A nanochannel device containing multiple gates is used to improve the controllability of protein flow and to introduce a pH gradient along the channels for isoelectric focusing. A different potential is applied to each gate to differentially control the surface charge on the SiO2 channel walls and to create a pH gradient along the channels. The control and separation of proteins, the pH gradient in the nanochannels as a function of gate bias, and the molecular orientation will be further discussed in this presentation.
4:30 PM - **P7.6
Microevaporators for Phase Behaviour Studies and Materials Formulation.
Jacques Leng 1 2 , Mathieu Joanicot 2 , Armand Ajdari 1 Show Abstract
1 UMR Gulliver 7083, CNRS-ESPCI, Paris France, 2 Lab Of the Future , Rhodia/CNRS/Université Bordeaux 1, Pessac France
5:00 PM - P7.7
Distributed Microfluidic Pumping, Mixing and Separations Using Remotely Powered Miniature Diodes.
Suk Tai Chang 1 , Vesselin Paunov 2 , Dimiter Petsev 3 , Orlin Velev 1 Show Abstract
1 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Surfactant and Colloid Group, Department of Chemistry, University of Hull, Hull United Kingdom, 3 Department of Chemical and Nuclear Engineering and Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico, United States
We demonstrate how miniature diodes embedded into microfluidic channel walls can provide locally distributed pumping or mixing functions powered by a global external field. The millimeter-sized diodes attached to the walls rectify the voltage induced between their electrodes from external alternating electric field. The resulting electroosmotic flux localized on the surface of diodes pumps fluids in the microfluidic channel in the direction of either the cathode or the anode depending on their surface charge. The flow velocity linearly increases with applied voltage, but does not depend on the frequency of the applied field. This could eliminate intrinsic problem with vortices in areas of non-uniform field that occur in conventional AC electrohydrodynamic pumps. The localized electroosmotic flow between diodes could also be used to construct microfluidic mixers. Theoretical analysis and numerical simulations of the microfluidic pumping and mixing provided by the diodes on a chip were in excellent agreement with the experimental data. The combined application of AC and DC fields in our microfluidic chips allows decoupling the velocity of the particles and the liquid. By precisely and independently adjusting the magnitude of the AC and DC fields particles with small differences in their charges or sizes could be efficiently separated. The technique can be used in "smart", dynamically reconfigurable, microfluidic chips.
5:15 PM - P7.8
Microfluidic Devices to Investigate Kinetics and Thermodynamics of Crystallization Processes.
Philippe Laval 1 , Jean-Baptiste Salmon 1 , Galder Cristobal 1 , Jacques Leng 1 , Mathieu Joanicot 1 Show Abstract
1 , LOF, CNRS-Rhodia-Bordeaux 1, Pessac France
5:30 PM - P7.9
Design & Optimisation of a Micromixer by FLIM and CFD
David Mendels 1 , Francois Mendels 3 , Steven Magennis 2 , Emmelyn Graham 2 , Anita Jones 2 Show Abstract
1 Division of Engineering and Process Control, National Physical Laboratory, Teddington, Surrey, United Kingdom, 3 , Cognoscens, Lyon France, 2 Collaborative Optical Spectroscopy, Micromanipulation and Imaging Centre, University of Edinburgh, Edinburgh, Scotland, United Kingdom
Over the past ten years, the application of micro-manufacturing technologies to producing fluidic devices has led the rapid development of now widely accepted lab-on-a-chip and point-of-care devices. One of the bottlenecks in micro-fluidics remains mixing, because of the practical impossibility to create turbulence in smallchannels, emphasised by the low Reynolds numbers of the flows at play - generally smaller than 10. Several alternatives to turbulent mixing have been developed. Two types of mixers are commonly used: passive mixers, which involve the exclusive use of non-actuated elements, and active mixers, which include moving elements such as micro-pumps or dynamically changing the surface interactions. The former have the obvious advantage of being made of one single material, hence being much cheaper and easier to manufacture and operate than their counterpart, and will be the subject of this presentation.In this work, a refined fluorescence lifetime imaging microscopy (FLIM) technique was introduced, where a specific image treatment enhances the contrast of an ANS fluorescent dye, and allows direct comparison to numerical results obtained using ANSYS CFX. Having validated the model of mixing water and methanol in a T-joint, we embarked on the optimisation of the channel geometry. To do so, a number of topological grooves and herringbone structures were simulated and the best compromise in terms of mixing efficiency for this couple of fluids and one inlet flow rate was determined.The micro-channels were further manufactured in glass and quartz, and tested by the same FLIM technique. The mixing efficiency, higher than 90%, demonstrated the usefulness of the approach, while the mixing time was decreased by a factor 3.
5:45 PM - P7.10
Electrorheologically-controlled Microfluidic Chips.
Weijia Wen 1 Show Abstract
1 Dept. of Physics, The Hong Kong University of Science and Technology, Hong Kong Hong Kong