Research Overview
Our research focuses on developing microfabricated instrumentation and using this instrumentation to study various chemical and biochemical problems. We are currently pursuing projects which fall into the areas of (1) microfluidic separations, (2) nanofluidics, (3) photolithographic mapping, and (4) cell-based assays. Please feel free to contact us if you would like additional information.
(a) Schematic of a spiral design separation chip. (b) N-glycan separation from a breast cancer sample.
Microfluidic Separations. Microfluidic-based separations benefit from the dexterity with which materials can be manipulated and the ability to fabricate microchannel structures having small volume interconnects. In fact, electrokinetically driven separations on microfluidic devices have generated efficiencies per unit length similar to or exceeding that of conventional capillary separations. We are currently developing microfluidic devices for one- and two-dimensional separations that will shorten analysis times and concurrently improve the peak capacity, accuracy, and reproducibility compared to conventional techniques. With improved analytical performance, assays can be developed to study the onset and progression of diseases.
Nanofluidics. In addition to developing sophisticated microscale analysis systems, of particular interest is how device function scales when one or more of the conduit dimensions is on a nanometer length scale, and what advantages, if any, there might be for separations. Nanofluidic systems can be significantly influenced by phenomena such as double layer overlap, surface charge, diffusion, and entropic forces, which are either insignificant or absent in larger microchannels. To develop analytical functions from these unique nanofluidic phenomena, we are studying fundamental fluid and material transport and applying what is learned to separation and sensing problems, e.g., creating tunable particle/molecular filters and monitoring supramolecular assembly.
(a) Schematic of the device used for trapping. (b) Confocal fluorescence image of 200-nm red fluorescent microspheres trapped at nanopores in a microfluidic device. (c) 3D rendering of the trapped microspheres in the device.
Photolithographic Mapping. While evaluating techniques to fabricate feature sizes suitable for our nanofluidic work, we developed a method that provides direct visualization of the three-dimensional light intensity distribution in close proximity to nanoscale apertures. The primary advantages of this method with respect to state-of-the-art techniques using surface probes are higher spatial resolution and non-intrusiveness. Applications employing this method include creating micro- and nanoscale features simultaneously in a single photolithographic exposure and using the optical properties of the polymer (pillar-like) features as detection elements in microfluidic separation devices.
Cell-Based Assays. A long term goal is to be able to screen and analyze cells to determine the chemical basis of cell variability. Microfluidic devices play a key role in handling small quantities of material, delivering those materials to different locations within the device, and controlling the movement of cells within the channels. We have developed microfluidic systems to study sperm chemotaxis, which is oriented cell motion in response to an extracellular chemical concentration gradient, and to produce linear chemical gradients having arbitrary slopes and offsets. Presently, we are exploring bacterial chemotaxis and biofilm formation using similar microfluidic architectures.