The unifying theme of our research is the science of miniaturization and the interface between engineered and living systems
We develop new methods to fabricate very small devices and integrated structures, and characterize these systems using microscopy and spectroscopy. A major thrust of our research is focussed on constructing miniaturized 3D devices which are especially challenging to fabricate at small size scales, as a result of the inherent two dimensionality of lithographic processes.
We utilize a range of experimental techniques including photo-, e-beam and nano-imprint lithography; thin film deposition, molding, etching, culture of prokaryotic (E coli) and and eukaryotic (e.g. fibroblasts, islets, myoblasts) cells, biological assays (e.g. fluorescent stains, ELISA), non-linear optical spectroscopy, electron microscopy (TEM & SEM with fixation), RF measurements such as GHz spectrum analysis, electrochemicial methods such as potentiometry and chronoamperometry and four point electrical testing with femto-amp resolution. We also utilize analytical methods to model data as well finite element methods (HFSS, Surface Evolver). Our lab is multidisciplinary and students in our lab have had backgrounds in Chemical and Biomolecular Engineering, Electrical Engineering, Physics, Chemistry, Materials Science, Biomedical Engineering and Medicine.
Active Research Themes
(NOT in any order of priority)
We acknowledge support from the National Institutes of Health, National Science Foundation, Defense Threat Reduction Agency, Defense Intelligence Agency, Army Research Laboratory, DuPont, Northrop Grumman, Goldman Philanthropic Foundation, Arnold and Mabel Beckman Foundation, Camille & Henry Dreyfus Foundation, Iacocca Family Foundation and Alexander Von Humboldt Foundation
Self-assembly (and self-folding) across length scales
1. Understanding factors that control yield and defect tolerance in self-folding and aggregative self-assembling systems
Representative Publications: Compactness determines the success of cube and octahedron self-assembly, PLoS One (2009); The importance of surface patterns for defect mitigation in three-dimensional self-assembly, Langmuir (2010)
2. Nanoscale self-folding (origami)
Representative Publications: Self-assembly of lithographically patterned nanoparticles, Nanoletters (2009); Three dimensional nanofabrication using surface forces, Langmuir (2010); Nanoscale Origami for 3D Optics Small (2011)
3. Microscale self-folding polyhedra
Representative Publication: Surface tension driven self-folding polyhedra, Langmuir (2007); Three dimensional fabrication at small size scales, Small (2010)
4. Geometrically programmable self-folding materials (sheets) with thousands of folds
Representative Publication: Patterning thin film mechanical properties to drive assembly of complex 3D structures, Advanced Materials (2008); Microassembly based on Hands Free Origami with Bidirectional Curvature, Applied Physics Letters (2009);
5. Self-curving patterned nanostructures
Representative Publication: Curving nanostructures using extrinsic stress, Advanced Materials (2010)
6. Three dimensional cellular self-organization
Representative Publication: Three Dimensional Chemical Patterns for Cellular Self-Organization, Angewandte Chemie (2011)
Chemically actuated and autonomous micro/nanoscale machines
1. Microchemomechanical Systems
Representative Publication: Microchemomechanical Systems,
Advanced Functional Materials
(2011).
2. Bacterial backpacking
Representative Publication: Enabling Cargo-Carrying Bacteria via Surface Attachment and Triggered Release, Small (2011)
Nanomedicine
1. Toward a miniaturized mechanical surgeon (small surgical tools that autonomously respond to disease markers)
Representative Publications: Toward a miniaturized mechanical surgeon, Materials Today (2009); Tetherless thermobiochemically actuated microgrippers, PNAS (2009); Enzymatically Triggered Actuation of Miniaturized Tools, JACS (2010)
2. Nanoscale neuroelectrochemical recording
Representative Publication: Patternable nanowire sensors for electrochemical recording of dopamine, Analytical Chemistry (2009)
3D Microfluidics
1. Precisely structured and patterned 3D microwells and microwell arrays
Representative Publication: Self-loading lithographically structured microcontainers: 3D patterned, mobile microwells, Lab Chip (2008); Three-dimensional microwell arrays for cell culture, Lab Chip (2010)
2. Reconfigurable microfluidics
Representative Publication: Reconfigurable microfluidics with metallic containers, JMEMS (2008)
3. Three dimensional spatio-temporally controlled chemistry and chemical delivery
Representative Publication: Spatially controlled chemistry using remotely guided nanoliter scale containers, JACS (2006)
4. Three dimensional nanoporous membranes for separations
Representative Publication: Size selective sampling using mobile, three-dimensional nanoporous membranes, ABC (2009).
Biomedical devices
1. Precisely patterned polymeric containers for cell, bacteria, macromolecular and small molecule encapsulation and delivery
Representative Publication: Self-folding micropatterned polymeric containers, Biomedical Microdevices (2010)
2. 3D nanoporous immunoisolating devices
Representative Publication: 3D lithographically fabricated nanoliter containers for drug delivery, ADDR (2007)
3. Geometrically complex and anatomically relevant 3D tissue scaffolds
Representative Publication: Directed Growth of Fibroblasts into Three Dimensional Micropatterned Geometries via Self-Assembling Scaffolds, Biomaterials (2010)
Electronics
1. Integration of nanoscale circuits
Representative Publication: Integrating nanowires with substrates using directed assembly and nanoscale soldering, IEEE Transactions on Nanotechnology (2006); Dielectrophoretic assembly of reversible and irreversible metal nanowire networks and verticaly aligned arrays, Applied Phyics Letters (2006)
2. 3-axis sensors and 3D electronics
Representative Publications: Self-assembly of orthogonal 3-axis sensors, Applied Physics Letters (2008); Fabrication of a cylindrical display by patterned assembly, Science (2002); Forming electrical networks in three dimensions by self-assembly, Science (2000)
Optics
1. Metamaterials composed of precisely patterned polyhedral units
Representative Publication: Three-dimensional surface current loops in terahertz responsive microarrays, Applied Physics Letters (2010)
2. Non-Linear (IR+Visible) spectroscopy
Representative Publication: Probing Organic Field Effect Transistors In-Situ During Operation Using SFG, JACS (2006)
3. Precisely patterned 3D nanostructures for optics (Collaboration with IMEC, Belgium)
Representative Publication: Nanoscale Origami for 3D Optics, Small (2011)
Threat sensors
1. Nanowire sensors for threat detection (Collaboration with the Johns
Hopkins
Applied Physics Laboratory)
Representative Publication: Scanning surface-enhanced Raman spectroscopy (SERS) of chemical agent simulants on templated Au-Ag nanowire substrates, Proc. SPIE (2009)
2. Threat responsive microstructures with communicable modules (Collaboration with the
US
Army Research Laboratory)
Tetherless Microgrippers with Transponder Tags, JMEMS (2011)
Curiosity driven research
1. Autonomous movement of gels
Representative Publication: Solvent driven motion of lithographically fabricated gels, Langmuir (2008)
2. Spontaneous pattern formation
Representative Publication: Concentric ring pattern formation in heated chromium-gold thin films on silicon, Applied Physics Letters (2008)
3. Nanoscale wrinkles, saddles and wedges (bifurcation self-assembly)
Representative Publication: Plastic deformation drives wrinkling, saddling and wedging of annular bilayer nanostructures, Nanoletters (2010)
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