High Performance Tunable Materials FAR0017947 (HPTM)
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High Performance Tunable Materials FAR0017947 (HPTM) Dr. Konstantin Pokhodnya (PI), Fikadu Alema Center for Nanoscale Science and Engineering, North Dakota State University NNIN Facility utilized: Nanofabrication Center DESCRIPTION OF WORK: MAJOR OBSERVATIONS: Fabrication of top Pt electrodes in MIM (I= BaxSr1-xTiO3 or BST) capacitor structure on a 4” alumina wafer using NNIN Ar ion mill. A total of 2432 pairs of capacitors have been fabricated on a 4” wafer A significant enhancement of BST dielectric properties was achieved without sacrificing of capacitor tunability. Publications: Figure1. Capacitor test structures Pt/BST/Pt/Al2O3 on a 4” alumina wafer. Fikadu Alema, Aaron Reinholz, and Konstantin Pokhodnya, “Tunable dielectric properties of Barium Magnesium Niobate (BMN) doped Barium Strontium Titanate (BST) thin film by magnetron sputtering”, presented at the American Physical Society March Meeting, 2013, Baltimore, MD. Fikadu Alema, Michael Reich , Aaron Reinholz, and Konstantin Pokhodnya, “Effect of Concurrent Mg/Nb-doping on Dielectric Properties of Ba0.45Sr0.55TiO3 Thin Films”, manuscript in preparation NNIN University of Minnesota – 2012 MINNESOTA Quantitative In Situ Tensile Testing of Suspended Graphene Jun Lou (PI), Peng Zhang, Cheng Peng Mechanical Engineering and Materials Science, Rice University NNIN Facility utilized: Nanofabrication Center MAJOR OBSERVATIONS DESCRIPTION OF WORK The research goal of this project is to seek for an experimental method, which is named ‘Quantitative In Situ Tensile Testing’ to probe fracture mechanics of graphene. Based on the micro-electromechanical system (MEMS) fabricated in UM and a nanoindenter inside the SEM chamber, data on mechanical behaviors of graphene were obtained directly. Fig.1 Dry transfer of graphene onto MEMS Through a dry transfer method (shown in Fig. 1), graphene was transferred on the MEMS successfully for follow-up mechanical testing; Stress-strain curves of graphene show its brittle behavior under uniaxial tensile stress; The big variations in breaking stress are accounted for by the size difference of cracks in samples and Griffith theory is a decent explaination of this phenomenon. Fig.2 In situ tensile testing by the MEMS and a nanoindenter inside SEM chamber NNIN University of Minnesota – 2012 MINNESOTA Flexible Sensor Deboa Zhou (PI), Lucas Giesen Mechanical Engineering, University of Minnesota Duluth NNIN Facility utilized: Nanofabrication Center DESCRIPTION OF WORK Apply layers of chromium and gold to a PDMS material Use AJA Sputter deposition along with masks to evenly apply layers MAJOR OBSERVATIONS Good conductivity when stretched to a degree Gold thickness was not sufficient enough to connect top and bottom of sensor Masks need to be refined NNIN University of Minnesota – 2012 MINNESOTA Self-Assembled Silicon Microstructures for Photovoltaic Applications U.R. Kortshagen (PI), Nicolaas Kramer Mechanical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center and Characterization Facility’s JEOL6500 DESCRIPTION OF WORK Silicon nanoparticles are formed in a nonthermal plasma. Self-Assembled silicon microstructures are formed by impacting the nanoparticles on a substrate. Adding dopants to the particles allows for the formation of doped structures. High aspect ratio structures are promising for photovoltaic applications. NNIN University of Minnesota – 2012 MINNESOTA Surface and Interface Effects in Nanoscale Lateral Spin Valves D. Spivak, L. O’Brien, M. Erickson, C. Leighton (PI), P. A. Crowell (PI) School of Physics and Astronomy, University of Minnesota Department of Chemical Engineer and Materials Science, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’sJEOL 6500 DESCRIPTION OF WORK Spin relaxation processes in metallic lateral spin valves were investigated. Devices were fabricated using multiple-angle metal deposition through an electron-beampatterned shadow mask. Various combinations of ferromagnets (Fe, NiFe, Co, Ni) and non-magnetic metals (Cu, Al) were investigated. Use of the NFC’s Vistec EBPG5000 system permitted sub-100 nm mask feature sizes. X-ray reflectivity, scanning probe microscopy, and scanning electron microscopy facilities at CharFac were instrumental in determining sample dimensions and characterizing the quality of deposited films. Transport measurements probed the spindependent resistance in devices between 5 K and 300 K under vacuum. MAJOR OBSERVATIONS The temperature dependence of the observed spin signal is well-described by an Elliot-Yafet mechanism in conjunction with enhanced spin relaxation at device surfaces. Low-temperature behavior cannot be reproduced through modeling of known spin-scattering processes. NNIN University of Minnesota – 2012 MINNESOTA Surface Roughness and Vortex Pinning Paul Crowell (PI), Chris Leighton (PI), Andrew Galkiewicz, Te-yu Chen, Michael Erickson Physics and Chemical Engineering and Materials Science, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL6500 Observations: Magnetic Vortices Micron-sized disks are patterned in Ni80Fe20 thin films at the NFC Ground state magnetization is a vortex with core ~20nm Excitation with fast magnetic fields induces core oscillations Localized pinning of the core leads to higher oscillation frequencies Pinning site energy scales linearly with surface roughness on the length scale of the vortex core Publications T.Y. Chen, M.J Erickson, P.A. Crowell, C. Leighton, PRL 109, 097202 (2012) T.Y. Chen, A.T. Galkiewicz, P.A. Crowell, PRB 85, 180406(R) (2012) NNIN University of Minnesota – 2012 MINNESOTA Electrostatic Tuning of High-Tc Superconductors Allen M. Goldman and Javier Garcia Barriocanal Physics, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL6500 MAJOR OBSERVATIONS DESCRIPTION OF WORK Four atomic layer thick La2CuO4+d films were grown by ozone-assisted MBE Films were carefully characterized using CharFac facilities Electrical properties were measured as a function of temperature and magnetic field using a van der Pauw arrangement. Properties were controlled using a field effect transistor employing an ionic liquid in an electric double layer configuration. The ionic liquid employed was DEME-TFSI When holes were depleted a clear evolution to an insulator from a superconductor was observed. The resultant superconductor0insulator transition is anisotropic. Hall number data suggest that this transition is due to a change in the electronic structure of the film. compound. Sheet resistance as a function of the scaling variable for the two orthogonal directions in the plane. Scaling is shown for six different hole concentrations (p) ranging from 0.046 - 0.034. pcis the critical concentration and nz = 1.2 ± 0.2. Publication Javier Garcia Barriocanal et al, “Electronically driven superconductor insulator transition in electrostatically doped La2CuO4+d films,” Phys. Rev. B 87, 024519 (2013). NNIN University of Minnesota – 2012 MINNESOTA Naowire-based Energy Harvester Rusen Yang (PI), Ren Zhu, Vu Nguyen, Mechanical Engineering, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL6500) DESCRIPTION OF WORK Controlled growth of nanowire Energy harvester fabrication MAJOR OBSERVATIONS Nanowire can be grown on patters defined in NFC Electrodes can be deposited on top of the nanowire 100 µm NNIN University of Minnesota – 2012 MINNESOTA Localized Programmable Electrodynamic Precipitation and SERS-based Detection Heiko O. Jacobs (PI), En-Chiang Lin, Jun Fang Electrical Engineering, University of Minnesota NNIN Facilities utilized: Nanofabrication Center, Characterization Facility’s JEOL6500 Electrodynamica precipitation of airborne species on a nanostructured SERS gas sensor substrate Collection is driven by electrostatic precipitation through a bias voltage Electrostatic precipitation is enhanced using an electrodynamic nanolens approach Comparison of the recorded SERS signals using the floating, biased plate, and biased nanolens collection approach. The SERS signal is enhanced by a factor of 615 En-Chiang Lin et al. “Effective Collection, Spotting, and Identification of Airborne Species and Hybrid Molecular Arrays through Localized Programmable Electrodynamic Precipitation and SERS-based Detection”, Nature Communications (2012). (Accepted) NNIN University of Minnesota – 2012 MINNESOTA Multichannel Optomechanics for All-Optical Amplification of RF Signals Mo Li (PI), Huan Li, Yu Chen, Jong Noh, Semere Tadesse Electrical and Computer Engineering, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL6500 MAJOR OBSERVATIONS DESCRIPTION OF WORK A mechanical switch is actuated by the optical force of one low power laser and subsequently controls the optical path of another high power laser. Analogous to the principles of electromechanical relays or electronic transistors. All-optical amplification of RF signals. Rich and completely controllable optomechanical nonlinearity in cavity optomechanics. Publications Li, H., Chen, Y., Noh, J., Tadesse, S. & Li, M. Multichannel cavity optomechanics for all-optical amplification of radio frequency signals. Nature communications 3, 1091 (2012). NNIN University of Minnesota – 2012 MINNESOTA Fabrication of Vertical Metal – Insulator - Metal (MIM) Nanogap Sang-Hyun Oh (PI), Xiaoshu Chen Electrical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center and Characterization Facility’s JEOL6500 DESCRIPTION OF WORK MAJOR OBSERVATIONS Photolithography, focus ion beam (FIB), atomic layer deposition (ALD), and electron beam evaporation were used to make MIM nanogap structures. Scanning electron microscope was used to characterize the width and uniformity of nanogap. Visible and infrared light transmission has been observed through 2 nm MIM nanogap in optical thick metal film. Optical trapping of nano spheres by the MIM nanogap structures has been tested. Publications are expected soon. 5 nm gap MIM nanogaps were designed to have different resonances by tuning metal thickness, gap width, for applications in surface enhanced Raman, optical force trapping etc., and in terahertz region. Ag Ag 300 nm A 5 nm annular nanogap made by FIB and ALD. NNIN University of Minnesota – 2012 MINNESOTA Passive flow induced concentration and particle assembly on suspended nanohole array biosensors Sang-Hyun Oh (PI), Shailabh Kumar Biomedical Engineering, University of Minnesota Facilities used: Nanofabrication Center and Characterization Facility’s JEOL 6500 MAJOR OBSERVATIONS DESCRIPTION OF WORK LPCVD, Photolithography and KOH wet etching were used to prepare biosensor chips with suspended nitride membranes. The CHA system was used to deposit gold on nitride surface and focused ion beam (FIB) was used to make nanohole arrays on these suspended membranes. These nanohole arrays were utilized for passive flow driven concentration of analytes, formation of nanoparticle arrays and membrane based analysis of liposome nanoarrays. The suspended nanohole array platform utilized evaporation and capillary effect to promote protein concentration and binding at the sensor surface Nanopore arrays were also utilized for creating ordered nanoscale arrays of nanoparticles and liposomes for subsequent assays. Publications Kumar, S., Wittenberg, N. J., and Oh, S. H. (2013). Nanoporeinduced spontaneous concentration for optofluidic sensing and particle assembly. Analytical chemistry, 85(2), 971-977. NNIN University of Minnesota – 2012 MINNESOTA Mechanical Properties of Biological Nanocomposites using In Situ SEM Indentations In collaboration with Hysitron Yuping Li, Conrado Aparicio (PI) Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL 6500 NANOINDENTATION (E// and H//) Longitudinal nanoindentation by PI85 Transversal indentation by PI 950 RESULTS biomimetic mineralized collagen fibrils mimic the natural ultrastructure of bone and dentin. In-situ SEM indentations help identify individual nanofibrils and observe deformation during indentation. (E, H)// > (E, H)┴ suggests the effect of orientation and interwoven structure. MINNESOTA Doped SiGe nanocrystals for thermoelectrics David Rowe1, Tyson Baldridge2, Mool Gupta2, Uwe Kortshagen1 1 Dept. of Mechanical Engineering, UMN 2 Dept. of Electrical Engineering, University of Virginia NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL6500 MAJOR OBSERVATIONS DESCRIPTION OF WORK • • • • Si0.8Ge0.2 alloys of interest for high temperature thermoelectric (TE) materials Nanostructured TE materials show lower thermal conductivity Small grain size and layered films desirable for phonon management Produce doped Si0.8Ge0.2 nanocrystal films • • • Grains of ~ 10 nm possible for B and P doped SiGe NCs consist of a true SiGe alloy, not separate Si and Ge phases Using an impaction deposition, layered films of Si and Ge NCs are also possible NNIN University of Minnesota – 2012 MINNESOTA Complex Oxides for Spintronics Chris Leighton (PI), Palak Ambwani Chemical Engineering and Materials Science, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL6500 MAJOR OBSERVATIONS DESCRIPTION OF WORK Complex oxides offer the possibility of growing epixatially matched materials for spintronic applications Doped Strontium Titanate is a possible choice for semiconducting spacer layer between two layers of ferromagnetic complex oxides However, the properties of ptype doped strontium titanate are not well understood. We used NFC facilities to sputter metallic contacts on p-type doped strontium titanate singlecrystals to determine their electronic properties So far, we have determined that Pt and Au do not make Ohmic contacts to ptype Strontium Titanate Annealing the contacts in RTA does not make a difference either. Further work needs to be done to establish a suitable contact material for these crystals NNIN University of Minnesota – 2012 MINNESOTA Growth of Zinc Oxide Nano/Microwire Array Ren Zhu, Wengui Zhang and Rusen Yang (PI) Mechanical Engineering, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL6500 Growth Result Growth Method • • • Vapor deposition Wet chemical • Vapor deposition Vapor deposition • Wet chemical (CH2)6N4 • Wet chemical Zn(NO3) NNIN University of Minnesota – 2012 MINNESOTA Heavily P-doped Si NCs for plasmonics David Rowe1, Jong Seok Jeong2, K. Andre Mkhoyan2, Uwe Kortshagen1 1 Dept. of Mechanical Engineering, 2 Dept. of Chemical Engineering, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL6500 MAJOR OBSERVATIONS DESCRIPTION OF WORK • • • • Nanoparticles with high free carrier concentrations exhibit localized surface plasmon resonance (LSPR) Metals exhibit LSPR in visible region Semiconductors should show LSPR in IR Produce NCs with varying amounts of dopant and measure absorbance • • • Mid-IR LSPR (broad peak in FTIR) observed for SiNCs doped with P Large amounts of P reside at NC surface NC structure dictates free carrier density Nano Letters (2012) in review NNIN University of Minnesota – 2012 MINNESOTA Ion Gel Gating of Complex Electronic Materials Chris Leighton (PI), Dan Frisbie (PI), Shun Wang, Mingjing Ha, Mike Manno, Jeff Walter, Sri Polisetty Chemical Engineering and Materials Science, University of Minneosta NNIN Facility utilized: Nanofabrication Center Transistors based on ionic gels, formed by combining ionic liquids with block polymers, are a recently developed means to study charge transport in novel materials at extremely high charge density We are employing such methods in the study of electronic transport of a number of complex conductors including polymer and smallmolecule semiconductors, complex oxides, and novel sulfide materials 2012 Publications Wang, Ha, Manno, Frisbie and Leighton, “Hopping, Hall effect, As an example, we have studied the and the approach to the insulator-metal transition in electrochemically-gated poly(3-hexylthiophene) transistors”, polymer semiconductor P3HT at Nature Communications 3, 1210 (2012). electrostatically-induced hole densities up to 1021 cm-3, observing the Hall effect for the first time, and deducing proximity to a regime of truly diffusive band-like transport. NNIN University of Minnesota – 2012 MINNESOTA Microfluidic Device For Spatial Control of Cell Seeding in Engineered Tissues Patrick W. Alford, Zaw Win, Geoffrey D. Vrla Department of Biomedical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center DESCRIPTION OF WORK MAJOR OBSERVATIONS Use of photolithography to create patterns for PDMS stamps and molds for microfluidic device Individual cells were precisely placed using the mCPD The efficiency of cell capture in the traps is over 90% Stamps used to pattern extracellular matrix (ECM) proteins onto a substrate Development of a microfluidic cell placement device (mCPD) for cell capture Figure 1. (A) The mCPD with red dye in the channels. Inset: cell traps. Scale bar: 5mm. (B) Diagram of cells flowing through the mCPD (i) Cell flows around the support pillar. (ii) Cell flows into the trap. (iii) Cell flows around a trap occupied by a cell. (C) 3T3 fibroblasts are captured in the cell traps. Scale bar: 100 µm. Figure 2. (A) Overview of the mCPD (i) Microcontact printing is used to pattern the substrate with fibronectin (FN). (ii) The device is aligned and placed on top of the patterned substrate. Cells are flowed through the device and allowed to adhere to the ECM. (iii) The device is removed. (B) Cells seeded without the mCPD onto uniform FN. Scale bar: 100 µm. (C) Cells seeded using the mCPD. Scale bar: 100 µm. (D) DAPI stained cell nuclei. Scale bar: 100 µm. NNIN University of Minnesota – 2012 MINNESOTA High-Throughput Microscale Assays for Vascular Contractility and Remodeling Eric S. Hald, Patrick W. Alford (PI) Biomedical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center MAJOR OBSERVATIONS DESCRIPTION OF WORK Use of photolithography to create patterns for PDMS stamps Stamps used to pattern extra cellular matrix proteins or fluorescent microspheres onto substrate Microcontact printing Transfer of a patterned fluorescent microsphere grid onto soft substrates Development of a highly-aligned monolayer of vascular smooth muscle cells to mimic arterial lamellae 5 x 20 μm grids of fluorescent microspheres can be patterned onto soft PDMS substrates for displacement tracking Arrays of 500 x 500 μm microtissues can mimic the high alignment and confluence of native arterial lamellae and allow for high-throughput experimentation Microtissue Array and Microsphere Grid Printing Procedure Microcontact Printing Procedure NNIN University of Minnesota – 2012 MINNESOTA Microfluidic Devices for Tissue Imaging E. Arriaga (PI), M.A. Donoghue, A. Sawhney, L. Ulmer Chemistry, University of Minnesota NNIN Facility utilized: Nanofabrication Center Preliminary Observations DESCRIPTION OF WORK Fabrication of SU8 masters and PDMS channels Capture and align tissue at taper Improve imaging and characterization Throughput Orientation Inspired by devices used to capture C. elegans1 Test devices fabricated successfully 2, 4, or 8 tapered channels Pieces of muscle tissue trapped and imaged 1 µM NAO labeling 20x objective, 100 ms exposure 1. Hulme, S.E. Lab Chip, 2007, 7, 1515–1523 NNIN University of Minnesota – 2012 MINNESOTA Optical Micromachined Ultrasound Transducer (OMUT) - A New Approach for High Frequency Transducers Shai Ashkenazi (PI), Mohammad Amin Tadayon Biomedical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center l l DESCRIPTION OF WORK MAJOR OBSERVATIONS Using optical cavity as an ultrasound detector The device is polymer based and biocompatible which make it a good candidate for intravascular ultrasound imaging Fabricated Device l Characteristic Curve Detected Ultrasound Signal Publications: Ultrasound Cavity Detector Principal A new technology for ultrasound detection (OMUT) developed Making tiny detectors which are able to be used for dual modality intravascular imaging A new bonding method developed which is useful for fabrication of highly flat surface Tadayon, M.A., Ashkenazi, S., “Optical Micromachined Ultrasound Transducer (OMUT)- a New Approach for High Frequency Transducers ,” Submitted to IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. Tadayon, M.A., Ashkenazi, S., “Optical micromachined ultrasound transducers (OMUT) - a new approach for high resolution imaging,” Proc. of SPIE Vol. 8581, 858115, 2013. NNIN University of Minnesota – 2012 MINNESOTA Microfluidic Chemostat for Measurement of Single-cell Dynamics in Bacteria Kevin D. Dorfman (PI) and Zhicheng Long Chemical Engineering and Materials Science, University of Minnesota NNIN Facility used: Nanofabrication Center DESCRIPTION OF WORK We developed a microfluidic chemostat that allows us to trap E. coli cells and force them to grow in lines for days. We could measure the growth dynamics and gene expressing at single cell level for many generations. We tracked the movements of fluorescently tagged loci in more than one thousand cells on a single microdevice. High throughput loci tracking. a) Fluorescently tagged loci; b) The trajectory (in red) of the centroid of a locus; c) Mean square displacements (MSD) of all loci; d) Ensemble-averaged MSD. Publications: 1. The microfluidic chemostat a) GFP expressing E.coli cells growing in the microchannels, the scale bar represents 5μm; b) Mean GFP intensity of cells over time in two different media. NNIN University of Minnesota – 2012 2. Z. Long, et al., Lab Chip, 2013, DOI: 10.1039/c2lc41196b. A. Javer, et al., Nat. Commun., In revision. MINNESOTA Observing cell migration through confined microchannels David Odde (PI), Thomas Hoelkinger, Rebecca Klank Biomedical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center We use soft lithography to generate PDMS microchannels for observing glioma cell migration under controlled confinement. Channel design has varying lengths and widths Dimensions are relevant to pore sizes in the brain, where our cells originate. Observations So far we have been able culture cells within our microfluidic devices. We are working to solve issues with complete surface wetting to allow cells to interact with the channels. NNIN University of Minnesota – 2012 MINNESOTA Multi-Intracellular Recordings with NanoWires David Redish (PI), Brandy Schmidt, John Ferguson, Chris Boldt Department of Neuroscience, University of Minnesota NNIN Facility utilized: Nanofabrication Center Intracellular Recordings with Nanowires CURRENT FOCUS: In Vivo Recordings Nanoelectrodes offer a novel method of intracellular recordings. Current methods are not conducive for long term in vitro or in vivo recordings. A scanning electron microscope permits the growth of nanowires at the tips of electrodes (Fig.1). The Atomic Layer Deposition insulates the nanowires. The Focused Ion Beam removes the tips of the nanowires to permit recordings. We have successfully recorded intracellular activity in a hippocampal slice preparation and isolated leech ganglia (Fig.2) Will soon implant a drive with12 moveable nanowires in an awake behaving animal for potential multi-intracellular recordings. Publications Figure 1 Figure 2 Ferguson JE, Boldt C, Puhl JG, Stigen TW, Jackson JC, Crisp KM, Mesce KA, Netoff TI, Redish AD (2012) Nanowires precisely grown on the ends of microwire electrodes permit the recoridng of intracellular action potentials within deeper neural structures. Nanomedicine, 7(6): 847-53. NNIN University of Minnesota – 2012 MINNESOTA Spatioelectrochemistry of Geobacter sulfurreducens Daniel Bond (PI), Rachel Snider Biotechnology Institute, University of Minnesota NNIN Facility utilized: Nanofabrication Center Fabrication of gold interdigiated array microelectrodes 2 bands of 50 15µm each Biofilm grown across the electrodes spanning the gaps Measure current conducted through the biofilm MAJOR OBSERVATIONS Allow separation of catalytic current from conducted current Determine the redox gradient with in a biofilm NNIN University of Minnesota – 2012 MINNESOTA Further Development of Micro Free-Flow Electrophoresis Applications Michael Bowser (PI), Sarah Anciaux, Nic Frost, Matt Geiger Department of Chemistry, University of Minnesota NNIN Facility utilized: Nanofabrication Center MAJOR OBSERVATIONS DESCRIPTION OF WORK Microfluidic free-flow electrophoresis (µFFE) 2D-Separations • CE-µFFE • nLC-µFFE Open edge µFFE-MS Analyte streams efficiently separated Couplings possible Figure 1 Figure 3. nLC-µFFE Buffer Flow Electric Field Cathode (-) FFE is a continuous electrophoretic separation technique performed in a planar channel. By applying an electric field perpendicular to the separation channel, analyte streams deflect laterally (Figure 2). It’s miniaturization has led to analytical and preparative scale separations of small volumes. More recently developments in 2D separation (Figure 3) and mass spectrometry coupling (Figure 1) have been investigated by modifications of the original µFFE design. Anode (+) Figure 2. Analyte streams (purple, green and yellow) deflect laterally in electric field. INNESOTA NNIN University of Minnesota – 2012 M MEMS Proportional Pneumatic Valve Prof. Tom Chase (PI) and Nebiyu Fikru Mechanical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center Targets High flow rate (40 slpm at 6 → 5 bar) Compact (< 4 cm3) Low power usage (< 1 mW) Actuator Active piezoelectric (PZT) layer Passive oxide layer Main parts are port plate and actuator Port plate Silicon substrate Orifice diameter ranges from 29-86 µm PZT based actuator Sol-gel PZT deposition and patterning done at Penn State All other works (both port plate and actuator) done at NFC Port plate with through holes NNIN University of Minnesota – 2012 MINNESOTA Understanding Spin Transport in Metallic Nanostructures Chris Leighton (PI), Paul Crowell (PI), Liam O’Brien, Dima Spivak, Mike Erickson Departments of Chemical Engineering and Materials Science, and Physics University of Minnesota NNIN Facility Utilized: Nanofabrication Center Transport of spins in metals is utilized in nanoscale metallic spintronic devices such as current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) sensors, and non-local read head sensors for disk drives. Nevertheless, there are large gaps in our understanding of spin transport in metals. We are studying these issues using a device known as a lateral non-local spin valve, where pure spin currents can be injected into non-magnetic metals, and separated from charge currents The work has revealed a number of surprising conclusions, including high spin scattering rates at surfaces, an anomalous temperature dependence of the spin accumulation, and complex effects at the magnet/non magnet interface NNIN University of Minnesota – 2012 MINNESOTA Measurements of the Inverse Spin Hall Effect in n-GaAs C. C. Geppert1, K. D. Christie1, M. K. Chan1, Q. O. Hu2 , C. J. Palmstrøm2, P. A. Crowell1(PI) 1Physics 2Electrical & Astronomy, University of Minnesota, and Computer Engineering, University of California Santa Barbara NNIN Facility utilized: Nanofabrication Center • Electrons traveling down a semiconducting channel experience spin-dependent scattering off localized impurity sites. The nature of this scattering is not fully understood. This gives rise to the inverse spin Hall effect, whereby a spin polarized current is preferentially deflected toward one side of the device. This deflection is observed as a voltage by a pair of nonmagnetic Hall arms placed in the vicinity of the central ferromagnetic electrode. An extreme sensitivity to applied field is observed due to the presence of polarized nuclei. • • • Au lead V+ 125 -1944 A/cm2 300 T = 60 K I- 200 75 V (V) I+ V (V) 100 I- 50 25 0 VFe spin injector = 0° M M 100 = 5° 0 M 2 0 A/cm -100 -25 -500 M -250 0 250 500 Field, H (Oe) NNIN University of Minnesota – 2012 -500 -250 0 250 500 Field, H (Oe) MINNESOTA Spin Transport in FM/GaAs Heterostructures K. D. Christie1, C. C. Geppert1, S. J. Patel2, C. J. Palmstrøm2, P. A. Crowell1 1School 2Department of Physics & Astronomy, University of Minnesota of Electrical and Computer Engineering, University of California Santa Barbara NNIN Facility utilized: Nanofabrication Center detector Vdet (V) Ferromagnetic contacts are typically used to electrically inject and detect non-equilibrium spin accumulation in III-V semiconductors. Devices are fabricated in a top-down approach into lateral spin-valves as shown below. Spins are injected when a forward bias is applied across the injection contact. The presence of spin accumulation in the semiconductor is verified by the spin-valve effect. 20 10 0 -300 0 100 device 1 device 2 device 3 50 0 -0.5 field Vdet 0.0 Vinj (V) injector 300 Field (Oe) Vdet (V) 30 Recent measurements on devices using the Huesler Co2MnSi as the ferromagnet contacts have demonstrated the largest spin signal observed in III-V lateral spin-valves.. NNIN University of Minnesota – 2012 MINNESOTA Density of states effects in Ni tunnel junctions E. Dan Dahlberg (PI), Bern Youngblood Department of Physics, University of Minnesota NNIN Facility utilized: Nanofabrication Center Theory: Features from the DOS of the electrodes in a tunnel junctions should be present in the differential tunneling conductance. This effect is well documented in superconductor tunnel junctions, but has never been observed in magnetic tunnel junctions. Electrodes MAJOR OBSERVATIONS Junction Junctions with a crystalline Ni electrode were patterned in an attempt to observe the prominent peak in the minority-spin DOS of Ni. No peak was observed, despite well characterized junctions. This is consistent with a theory by M.B. Stearns that asserts that d-band electrons do not participate in tunneling NNIN University of Minnesota – 2012 MINNESOTA Magnetic Noise Studies of Sub-Micron Square Py Dots Daniel Endean, E. Dan Dahlberg Physics Department, University of Minnesota NNIN Facility utilized: Nanofabrication Center Project goal: determine the conditions necessary to observe magnetic noise and characterizes its properties Transport Measurements of Magnetic Dots Magnetic dots and non-magnetic contacts fabricated using Electron Beam Lithography 4 terminal resistance measurements can extract the dot magnetization Observations and Results Transport measurements extract of hysteresis loops and reveal nature of magnetic reversal in the dots (a). Electronic noise (b) associated with two level switching (c,d) is observed in the transport signal and is determined to originate from thermal fluctuations of the magnetization. Publications and Presentations IPRIME Annual Meeting, Poster, 2012 Endean, D., C. Weigelt, R. Victora, E. D. Dahlberg, “Magnetic Noise in Sub-Micron Square Py Dots.” Phys. Rev. Lett. (in preparation). NNIN University of Minnesota – 2012 MINNESOTA DNA Electrophoresis in Colloidal Crystals Kevin D. Dorfman (PI) and Scott B. King Chemical Engineering and Materials Science, University of Minnesota NNIN Facility used: Nanofabrication Center DESCRIPTION OF WORK Glass microchannels are filled with silica colloids and packed to form crystals Short DNA is separated by Ogston sieving of DNA through crystal matrix Crystals have varying grain sizes Optical image of a typical channel exhibiting both short- and long-range order, on the left and right sides respectively. MAJOR OBSERVATIONS Inverse brightness laser diffraction measurements showing (left) a single crystal orientation in the laser spot, and (right) multiple orientations. Laser spot is approximately four channel widths. Grain size can be measured using laser diffraction DNA electrophoretic separation of short DNA is not affected by grain size Local order yields good separations NNIN University of Minnesota – 2012 MINNESOTA DNA Transport in Ordered and Disordered Micropost Arrays Kevin D. Dorfman (PI) and Daniel W. Olson Chemical Engineering and Materials Science, University of Minnesota NNIN Facility used: Nanofabrication Center DESCRIPTION OF WORK Long DNA are separated by size in micropost arrays DNA are driven through the array by an applied electric field DNA collide with the posts of the array, causing a delay in motion Top: Disordered post array of 1 micron diameter posts. Bottom: Ordered hexagonal post array of 1 micron diameter posts. Fluorescent microscopy image of DNA molecules moving through the ordered post array under an applied electric field of 10 V/cm. MAJOR OBSERVATIONS Both ordered and disordered post arrays can be used to separate DNA by size The delay in DNA motion is the same in both types of post arrays There is lower dispersion of the DNA molecules in the ordered post array Ordered post arrays provide superior separation performance Reference: D.W. Olson and K.D. Dorfman, Phys. Rev. E 86, 041909 (2012). NNIN University of Minnesota – 2011 MINNESOTA DNA Stretching in Nanochannel Confinement Kevin D. Dorfman (PI), Julian Sheats, Damini Gupta Chemical Engineering and Material Science, University of Minnesota NNIN facility used: Nanofabrication Center DESCRIPTION OF WORK DNA molecules are injected into channels smaller than the radius of gyration to induce elongation Extension and diffusion measured as a function of channel size for rapid barcoding sequencing Fused silica used to prevent DNA sticking Optical fluorescence micrograph of DNA solution wetting the device via capillary flow. Microchannel (right), pillars (center) and nanochannels (left). SEM micrograph showing fused silica nanochannel device prior to sealing. The nanochannels (center and left) and pillars (top-right) overlap the loading microchannels, which have sloped walls to facilitate DNA injection. MAJOR OBSERVATIONS Sloped nanochannel entrance reduces entropic barrier drastically DNA enter simply via capillary flow, substantially simplifying injection Preliminary channel sizes follow previous studies NNIN University of Minnesota – 2012 MINNESOTA Ratchet Nanofiltration of DNA K. Dorfman (PI), J. Thomas, D.W. Olson, M. Joswiak, S.G. Park, Chemical Engineering and Materials Science, University of Minnesota NNIN Facilities utilized: Nanofabrication Center and Characterization Facility’s JEOL6500) DESCRIPTION OF WORK DNA separation using temporally asymmetric ratchet in a nanofilter array Bi-directional migration of DNA can be tuned to filter DNA Electropherogram of the DNA under alternating electric fields applied in opposite directions. A forward field of 12 V/cm for 17 s and a reverse field of 25 V/cm for 6 s. (A) Schematic of the microfluidic device. The electric potential is controlled at the four fluid reservoirs. (B) Top down SEM image. The periodic array consists of 1 μm long wells, 320 nm deep, and 1 μm long slits, 60 nm MAJOR OBSERVATIONS With properly tuned electric field strengths and pulse times only the smallest DNA fragment migrated towards the exit Separation occurred rapidly, achieving separation in about 10 minutes NNIN University of Minnesota – 2012 MINNESOTA Design of a Tunable Microwave Circulator Anand Gopinath (PI), Siva Puranam Electrical and Computer Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center Objective To design a microwave circulator whose dielectric constant varies with applied electrical bias using Barium Ferrite (BaM) deposited on Barium Strontium Titinate (BSTO) on a glass substrate and to determine the change in permittivity of the sample with bias. Microstrip Fixture Procedure The sample is coated to form a capacitor from which the permittivity with bias is obtained. Contacts of Ti-Pt were deposited in NFC on both sides of the sample to obtain a capacitor. A microstrip fixture was designed and the coated samples was placed on it with silver epoxy and a wire was bonded from the microstrip line to the top of the sample. The combined dielectric constant of the three layers of BaM, BSTO on a glass substrate was measured with bias variations. Since the BSTO permittivity is very large, most of the applied voltage drops across the BaM and substrate and their permittivities do not change with bias. To measure the variation of permittivity of the film, the electrodes have to be placed on the BSTO. New samples are being made for this purpose with the contacts on the BSTO. NNIN University of Minnesota – 2012 MINNESOTA Spectroscopic Studies of Organic Transistors Aaron M. Massari, Chemistry, University of Minnesota NNIN Facility utilized: Nanofabrication Center MAJOR OBSERVATIONS DESCRIPTION OF WORK Use of photolithography to prepare transistor electrodes with appropriate spacings for spectroscopic applications Deposition of photovoltaic electrodes on wedged devices Structural changes in devices is measurable with the fabricated geometries Thermal annealing results in changes to primarily the outer interface Publications Atomic Force Microscopy images of organic thin films before and after thermal annealing on a bare silica surface. T.C. Anglin, Z. Sohrabpour, A.M. Massari, J. Phys. Chem. C, 2011, 115, 20258-20266. http://dx.doi.org/10.1021/jp206523jPub 2 D.B. O’Brien, T.C. Anglin, A.M. Massari, Langmuir, 2011, 27, 13940-13949. http://dx.doi.org/10.1021/la202958a NNIN University of Minnesota – 2012 MINNESOTA High-Throughput Fabrication of Metallic Nanotips Sang-Hyun Oh (PI), Timothy W. Johnson, Nathan C. Lindquist Electrical and Computer Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center DESCRIPTION OF WORK MAJOR OBSERVATIONS Sharp, metallic tips can act as optical antennas and focus light to the nano-scale. Au tips are fabricated and integrated into a near-field scanning optical microscope Au tips are very sharp with tips having < 10 nm ROC Single molecule fluorescence detected with a resolution of 18 nm Fluorescence enhancements up to 200x were shown Publications Johnson et al. ACS Nano (2012) 6, 9168-9174 Lindquist et al. Annalen der Physik (2012) 524, 687-696 NNIN University of Minnesota – 2012 MINNESOTA Spectrally Selective Uncooled Thermal Detectors Joey Talghader (PI), Anand Gawarikar, Ryan Shea Electrical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center Spectrally selective long wave infrared thermal detectors were fabricated using microfabrication techniques. Process integration of non standard materials into challenging MEMS geometries was possible due to extensive use of equipment and staff expertise at UMN NFC. MAJOR OBSERVATIONS Detectivity of 1.3x109 cm Hz1/2 Watt-1 was demonstrated, which is amongst the highest published values. Wavelength dependent responsivity enhancement of 4.3 was observed due to resonant cavity effect. Specific Detectivity 1.4 D* x 10 9 (cm Hz 1/2 Watt-1) 1.2 1 0.8 0.6 0.4 0.2 8,000 9,000 10,000 Wavelength (nm) 11,000 Publications “High Detectivity Uncooled Thermopile Detectors with Spectrally Selective responsivity”, to appear in technical digest, Transducers 2013. NNIN University of Minnesota – 2012 MINNESOTA Buffer Layers for Chalcogenide Thin-Film Solar Cells Prof. Eray Aydil (PI), Dr. Joel T. Abrahamson Chemical Engineering and Materials Science, University of Minnesota NNIN Facility utilized: Nanofabrication Center DESCRIPTION OF WORK Ni/Al/Ni wires 300 nm ITO (transparent electrode) 100 nm n-ZnO (window) 70 nm n-ZnxCd1-xS (buffer) 2 µm p-Cu(In,Ga)Se2 (absorber) 1 µm Mo (electrode) MAJOR OBSERVATIONS Substrate: polymer, stainless steel, glass CdS film on 4” Si wafer CIGS-based solar cells: 20% efficiency in the lab, can be flexible Need uniform buffer layer with precise work function and band gap Synthesizing buffer layers in a lowtemperature, scalable aqueous process Mo, ITO, ZnO sputtering at NFC, plus Mo film stress measurements Work function Buffer thickness varies <10% over 4” wafer Kelvin force microscopy: work function varies ~150 meV over CdS surface Publications B. S. Tosun, J. T. Abrahamson, C. Cheng, S. A. Campbell, and E. S. Aydil. Efficient Continuous-Flow Chemical Bath Deposition of CdS Films as Buffer Layers for Chalcogenide-Based Solar Cells. Proceedings of the 39th Annual IEEE Photovoltaic Specialists Conference, submitted, (2013). NNIN University of Minnesota – 2012 MINNESOTA Variable Modulus Muscular Thin Films For Measuring the Effect of Mechanical Environment on Vascular Contractility Patrick W. Alford (PI), Kerianne E. Steucke Biomedical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center DESCRIPTION OF WORK Employ photolithography techniques to create patterned wafers that yield polydimethysiloxane (PDMS) stamps used to microcontact print guidance cues for tissue formation (fig. 1). Tissues are built on 3-layer vascular muscular thin film (vMTF) constructs (fig 2A). Variable modulus 3-layer vMTF allow us to vary the substrate stiffness and calculate the stress in the tissue layer, thus the contractile function of the tissue can be determined (fig 2B). Figure 2. A. Variable modulus 3-layer vMTF construction. B. PIPAAm release yields a curved beam. The radius of curvature (R) is used to calculate the stress in the tissue layer. Inset: Transmural circumferential stress distribution. MAJOR OBSERVATIONS Figure 1. Microcontact printing. Steps 1-3: Photolithography. Steps 4-6: Stamping. Steps 7-8: Cell seeding. Microcontact printing produces microfabricated tissues that mimic the native tissue structure of the arterial lamella. Engineered tissue constructs, such as the variable modulus 3-layer vMTF, are ideal for observing and isolating the mechanical behavior of the arterial lamella in vitro. Varying the substrate modulus of the PDMS affects the contractile function of the tissue layer. NNIN University of Minnesota – 2012 MINNESOTA Measurement of Carrier Mobility in Single and Multilayer Graphene Quoc Anh Tran, Phil Cohen (PI) Electrical and Computer Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center DESCRIPTION OF WORK E-Beam evaporation for making contacts on graphene Photolithography National University of Singapore , Graphene Research Center <http://graphene.nus.edu.sg/content/graphene> NNIN University of Minnesota – 2012 MINNESOTA Atomically Flat Au Surfaces through a Template Stripping Method C. Daniel Frisbie (PI), Christopher Smith Department of Chemistry, University of Minnesota NNIN Facility utilized : Nanofabrication Center MAJOR OBSERVATIONS DESCRIPTION OF WORK electron beam deposition of Au (5000 Å) on Si (100) surface bond 1x1 cm Si(100) wafers face down on Au film with epoxy cured the template at 150˚ C for 1.5 hr RMS roughness ~ 1nm Template stripped surfaces are stable towards protic solvents, however, the Au film peels of in the presence of CH2Cl2 and DMSO SEM image of the Template stripped Au surface AFM image of the Template stripped Au surface 1 um 1 um Publications 1 um Hegner M.,Wagner P., Semenza G., Surface Science, 1993, 296, 39-46 Choi S. H., Frisbie C. D., J. Am. Chem. Soc., 2010, 132, 16191 NNIN University of Minnesota – 2012 MINNESOTA Mechanical Characterization of Silicon Nanopillars William Gerberich (PI), Yuhong Xiong, Eric Hintsala Chemical Engineering and Materials Science, University of Minnesota NNIN Facility utilized : Nanofabrication Center DESCRIPTION OF WORK MAJOR OBSERVATIONS Brittle-to-ductile transition (BDT) behavior of silicon was investigated in the shape of nano-pillars. Nano-pillars have been fabricated through use of Focused Ion Beam (FIB) machining and tested using nanoindentor. Elastic modulus decreases from about 110 GPa to 53 GPa when nano-pillar size changes from 1.6 microns to 0.3 microns. Brittle to ductile transition occurs with decrease in pillar size, which is associated with the improved mobility of dislocations. NNIN University of Minnesota – 2012 MINNESOTA Understanding Solvent Annealing in Block Copolymer Lithography Chris Leighton (PI), Marc Hillmyer (PI), Andrew Baruth, Chunhao Lin Chemical Engineering and Materials Science, Chemistry University of Minnesota NNIN Facility utilized: Nanofabrication Center In block copolymer lithography, solvent annealing is widely employed as a means to improve ordering of nano-scale features We are investigating the mechanisms at work in solvent annealing, studying the extent of long-range lateral ordering in polystyrene-polylactide block copolymers as a controlled function of solvent loading (measured in situ during annealing) Remarkable enhancements in lateral correlation length are found at certain solvent volume fractions, where singlecrystal ordering over > 10 m occurs 2012 Publications Comparative SAXS studies indicate that this occurs just beneath the order/disorder transition, strongly constraining potential models Rodwogin, Baruth, Leighton and Hillmyer, “Nanoscale rings from silicon-containing triblock terpolymers”, ACS Applied Materials and Interfaces 4, 3550 (2012). NNIN University of Minnesota – 2012 MINNESOTA Grid Design and Fabrication for TEM and AFM Graphene Oxide Studies Andre Mkhoyan, Chemical Engineering and Materials Science, University of Minnesota Gina Mancini-Samuelson, Chemistry, St. Catherine University NNIN Facility utilized: Nanofabrication Center DESCRIPTION OF WORK Design a TEM and AFM compatible grid to deposit singlelayer graphene oxide Perform force curve studies to determine Young’s modulus of single-layer graphene oxide B Figure 3: Mulit-layer and single-layer graphene oxide viewed on fabricated grids using AFM MAJOR OBSERVATIONS Grid was constructed in NFC Graphene oxide was deposited on grid and TEM and AFM measurements were made Figure 1: Working in the clean room . Figure 2: Left – wafer design Right – individual grid design Figure 4: Fabricated grids on right NNIN University of Minnesota – 2012 MINNESOTA Stress and Strain Balanced Films J. Talghader (PI), Andrew Brown Electrical and Computer Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center Growing Stress Balanced Thick Films • • • Thick films require minimal overall stress. Adjusting deposition temperature changes film stress. Multiple layers cancel overall stress. Designing Strain Balanced Films • • Film stress and elastic modulus measured via wafer curvature and nanoindentation. Film strain is found from stress and elastic modulus. *Negative Stress is compressive NNIN University of Minnesota – 2012 MINNESOTA The Effects of Cell-Cell Interaction on Neutrophil Chemotaxis Christy Haynes(PI), Donghyuk Kim, Xiaojie Wu Department of Chemistry, University of Minnesota NNIN Facility utilized: Nanofabrication Center • • DESCRIPTION OF WORK Development of a gradient device to create stable and dynamic chemical gradients Monitor neutrophil chemotaxis within chemoattractant gradients on endothelial cell layer MAJOR OBSERVATIONS Cytokine activation induces different chemotactic behaviors from neutrophils The presence of an endothelial cell layer influences the migration of neutrophils Neutrophil chemotaxis towards a bacteriaderived chemoattractant (MI, CI, ECI: 3 different parameters to describe neutrophil chemotaxis within the microfluidic gradient) NNIN University of Minnesota – 2012 M MINNESOTA INNESOTA The Bumps – a Device to quantify tactile sensation William R. Kennedy1, Donald Simone2, Mona M. Selim1, Thaddeus Brink2, James Hodges3, Gwen WendelschaferCrabb1, Shawn Foster1, Maria Nolano4, Vincenzo Provitera4. Departments of Neurology1, Diagnostic and Biological sciences2, Division of Biostatistics3, University of Minnesota; and Department of Neurology, Salvatore Maugeri Foundation IRCCS-Medical, Center of Telese, Terme4 NNIN Facility utilized: Nanofabrication Center MAJOR OBSERVATIONS DESCRIPTION OF WORK Decreased touch in the hands and feet are common in diabetic and post-chemotherapy neuropathy subjects. There is no practical sensitive method to quantify touch objectively We designed an inexpensive device called the Bumps to quantify touch sensation on the finger pads of normal and neuropathy subjects. Using photolithography at the Nanofabrication center we manufactured the Bumps prototype device (fig 1). It has a smooth surface marked into 12 squares; each square encloses 5 colored circles. One circle in each square contains a small particle (a bump). All bumps are 550µm in diameter but each has a different height. A subject explores the 5 circles with the index finger to locate the one bump on each square. A person’s threshold is the smallest bump located. The Bumps are felt by Meissner corpuscles (MC), touch receptors, located along fingerprint ridges (fig 2). Fig 2:Finger print & MCs Tactile Threshold differences existed between 166 subjects, control group, and 103 subjects with neuropathy (fig 3; p < 0.001). Subjects presenting with symptoms only in their hands had an even higher threshold. Fig 3: Threshold Results CONCLUSIONS The Bumps test clearly discriminates between subjects (fig 3). The Bumps has promise to quantify touch to confirm the clinical suspicion of early neuropathy. It also shows promise in staging neuropathy and for evaluation of progression. ACKNOWLEDGEMENTS Gratitude to: members of the MN Neuropathy Association for participation; Greg Cibuzar of the Nanofabrication center. For funding by Institute for Engineering in Medicine (IEM) and NIH STTR grant 1R21 NS067324-01 Publications Fig 1: The Bumps device Kennedy WR, Selim MM, Brink TS, Hodges JS, Wendelschafer-Crabb G, Foster SX, Nolano M, Provitera V, Simone DA. A new device to quantify tactile sensation in neuropathy. Neurology. 2011; 76:1642-1649. Malpass,K. Discovering the ’Bumps’:a new method to measure symptoms of peripheral neuropathy NNIN University of Minnesota – 2012 MINNESOTA A Novel Cell Release Method for Affinity-based Cell Separation Wei Shen (PI), Wei Song Department of Biomedical Engineering, University of Minnesota NNIN Facility utilized: Nanofabrication Center MAJOR OBSERVATIONS DESCRIPTION OF WORK Fabricate poly(dimethylsiloxane) (PDMS) microluidic channel using UV photolithography and immobilize cell ligand on a glass surface Assemble the microfluidic system and pump cell mixture solution through the channel (the mixture of different types of cells or differentiating stem cells) Capture the target cells through the complementary interactions between cell receptor and ligand immobilized on the glass surface Release captured cells by disrupting interactions between cell receptor and ligand Silicone master and PDMS channel were fabricated (50 mm × 2 mm × 0.076 mm) Human Umbilical Vein Endothelial Cells (HUVECs) were captured in PDMS channel due to the interaction between integrin a4b1 receptor on cell membrane and ligand for a4b1 on glass surface Protein zipper A Cell ligand Cell capture NNIN University of Minnesota – 2012 Protein zipper B Polyethylene glycol (PEG) Cell release MINNESOTA
