Research projects

My current research interest is in the development of a nanodialysis chemical neural probe. Cell-to-cell signaling via neurochemicals is the fundamental basis for communication in the brain. The detection of neurochemical spatial and temporal concentration transients in the brain is an essential and unmet capability for understanding the functionality of neural circuits and for the development of novel drugs for the treatment of various disorders. The goal of this project is to break the fundamental limits of chemical detection to achieve unprecedented chemical, temporal and spatial resolution with minimal tissue damage.

We developed novel conductive nanoporous membrane and achieved electrical control and high flow at the same time. We sputter-deposited conductive layer on top of the commercial anodic aluminum oxide nanoporous membrane. This membrane could regulate the diffusive transport of the charged molecules external gate voltage. The effect of surface charge of the AAO backbone structure on the controllability was also investigated. The removal of the surface charge increased the controllability of positively charged drug molecule and decreased the controllability of negatively charged drug molecule.

We have established a model (based on the Poisson-Nernst-Plank equation) to quantitatively predict the field-effect gating of the charged molecule transport through the nanochannel. We expected that the cylindrical nanochannel with a gate-insulator structure can alter the flux of the charged molecule through the nanochannel. Also, we investigated the effect of the surface charge plays a significant role.

We utilized the novel conductive nanoporous membrane for the nanofluidic diode application. The charge polarities and densities of the nanopores can be regulated externally by the gate potential to change the ionic current rectification property of the device using chromium (Cr) conductive layer deposited directly on an AAO membrane.

We developed the novel double gated nanoporous membrane structure for biomimetic AND nanofluidic logic gate. The voltage-gated cation channel protein achieved precise control of the direction of the transmission by using two stacked gate structure in one channel protein. We modeled and tested the stacked gate structure with our conductive nanoporous membrane. This stacked structure is shown to act as an AND gate for charged molecule transport.

We develop a simple and biocompatible method of patterning proteins on a wettability gradient surface by thermo-transfer printing. The wettability gradient is produced on a poly(dimethylsiloxane) (PDMS)-modified glass substrate through the temperature gradient during thermo-transfer printing. The water contact angle on the PDMS-modified surface is found to gradually increase along the direction of the temperature gradient from a low to a high temperature region. Based on the wettability gradient, the gradual change in the adsorption and immobilization of proteins (cholera toxin B subunit) is achieved in a microfluidic cell with the PDMS-modified surface.