Research Topics
Department of Chemistry
Ph.D. (1981) University of Wisconsin-Madison
Research Topics
Research Interests
I. Molecular Gates. We are interested in structures in which it is possible to control biomolecular transport by imposing external control signals. Such structures typically are constituted from polymer membranes with parallel nanometer-diameter channels. The size of the channels and their construction allow us to control flow electrokinetically. Furthermore, under the right conditions the interior of the nanochannels may be coated with molecular recognition elements or changeable volume polymer films to achieve attoliter volume affinity chromatography or size-exclusion chromatography, respectively. Successful efforts here will allow us to fabricate molecular scale analogs of macroscopic fluidic devices, e.g., gates, valves, and pumps, and will open the way to studies of controlled release and single cell sampling. We are also working collaboratively with Sweedler to incorporate our molecular gates with on-chip capillary electrophoresis to effect intelligent sample capture and preconcentration. These efforts will pave the way to performing preparative chromatography at the 10-18 mole level - an unprecedented advance in measurement science which would open completely new kinds of biological experiments at the sub-cellular level.
II. Artificial Chemotaxis. Injection of milliamp currents in ultrathin metal films yields significant in-plane voltage drops to create an in-plane potential gradient, V(x), which can in turn be incorporated in an electrochemical cell, so that relative to a solution reference couple, electrochemical reactions occur at defined spatial positions corresponding to V(x) ~ E0. This capability can be coupled to any electrochemical reaction of interest to produce spatially varying chemistries, e.g., when coupled to electrosorption events it can be used to form two-dimensional molecular maps. Choosing the end-groups to be cell-surface receptor ligands or protein adhesion-resistant moieties means the anisotropic lateral molecular composition can be used to exert lateral forces large enough to move supermolecular objects, like cells. In contrast to existing methods for surface pattern generation, e.g., lithography, stamping, our approach allows the patterns to be changed in real-time, thus raising the possibility of challenging cells to respond to a change in the chemotactic environment. Resulting studies of directed cell motion will inform such fundamentally important processes as wound healing, morphogenesis, and metastasis.
Current Research Funding NSF,
DOE, NIH, DARPA