Research

The unifying theme in our research group is the science of miniaturization and the interface between engineered and living systems

Watch some of our self-assembling and chemomechanically actuated devices on youtube

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 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 funding from NIH, NSF, DuPont, DTRA, DIA, ARL, Beckman, Dreyfus and Goldman Foundations

Self-assembly

1. Understanding factors that influence yield and defect tolerance in self-assembling systems
Representative Publication: Compactness determines the success of cube and octahedron self-assembly, PLoS One (2009)

2. Nanoscale self-folding
Representative Publication: Self-assembly of lithographically patterned nanoparticles, Nanoletters (2009)

3. Self-assembly of 3D patterned polyhedra and polyhedral arrays
Representative Publication: Surface tension driven self-folding polyhedra, Langmuir (2007)

4. "Hands free" origami
Representative Publication: Microassembly based on Hands Free Origami with Bidirectional Curvature, Applied Physics Letters (2009)

Micro/Nano Chemo Mechanical Systems (MCMS/NCMS)

1. Toward reversible chemically actuated micro and nano scale machines
Representative Publications: Reversible Actuation of Microstructures by Surface Chemical Modification of Thin Film Bilayers, Advanced Materials (2009); Pick-and-place using chemically actuated microgrippers, JACS (2008)

Microfluidics  

1. 3D Microwells
Representative Publication: Self-loading lithographically structured microcontainers: 3D patterned, mobile microwells, Lab Chip (2008)

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 porous membranes for separations
Representative Publication: Size selective sampling using mobile, three-dimensional nanoporous membranes, ABC (2009).

Nanomedicine

1. Toward a miniaturized mechanical surgeon
Representative Publications: Toward a miniaturized mechanical surgeon, Materials Today (2009); Tetherless thermobiochemically actuated microgrippers, PNAS (2009)

2. Nanoscale Neuroelectrochemical Recording
Representative Publication: Patternable nanowire sensors for electrochemical recording of dopamine, Analytical Chemistry (2009)

Biomedical Devices

1. Nanoporous containers for cell encapsulation therapy
Representative Publication: 3D lithographically fabricated nanoliter containers for drug delivery, ADDR (2007);

2. Enabling complex 3D tissue scaffolds
Representative Publication: Directed Growth of Fibroblasts into Three Dimensional Micropatterned Geometries via Self-Assembling Scaffolds, Biomaterials (2009)

Electronics

1. Integration of nanoscale circuits
Representative Publication: Integrating nanowires with substrates using directed assembly and nanoscale soldering, IEEE Transactions on Nanotechnology (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. Non-Linear (IR+Visible) Spectroscopy
Representative Publication: Probing Organic Field Effect Transistors In-Situ During Operation Using SFG, JACS (2006)

2. 3D Self-assembled, Microstructures for THz applications (Collaboration with the Johns Hopkins Applied Physics Laboratory)
Representative Publication: Three dimensional surface current loops in terahertz responsive metamaterials, submitted (2009)

3. 3D patterned nanopolyhedra for plasmonics (Collaboration with IMEC, Belgium)

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)

Curiosity driven research

1. Autonomous movement
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)