(5ds) Electrokinetics of Nanochannels, Nanocolloids and Nanoporous Membranes: a New Paradigm for Immuno-Assay, Drug Delivery and Ion/Proton Permselective Devices

The main goal of my research program is to develop a microfluidc platform for immuno-assay, drug delivery and ion/proton permselective devices for healthcare, biomedical, energy-related and water purification applications; and to understand the fundamental sciences underlying these problems. I shall focus on electrokinetics: the use of dc and ac electric field to impart a force on the liquid and colloids in microfluidics.

Electrokinetics promises to be the micro-fluidic technique of choice for portable diagnostic chips and for the latest nanofluidic devices (as pressure-gradient driven flow would require unrealistically high pressures). Nanofluidics is not just a scaled-down version of microfluidics, but with fundamental differences with new forces at play. In particular, when the cross section dimensions of the nanochannel approach those of the electric Debye layer (EDL), overlapping of opposite wall EDLs result in its ion-permselective properties. However, despite two centuries of research, our understanding of ion transport and electro-osmotic flow in and near nano-channels and nanoporous membranes remain woefully inadequate.

To develop future generation of nanofluidic devices using electrokinetics, I will advance our understanding of electrokinetics in three distinct research thrusts:

? Non-linear electrokinetics of nanochannels, nanocolloids and nanoporous membranes. A fundamental problem that is barely understood but controls the ionic current of a wide variety of engineering and biological systems such as: desalination membranes, fuel cell membranes, ion-channel, and artificial nanochannels/pores. Here I propose to further pursue the underlying physical mechanisms for the sake of being able to better control the flux through ion-permselective pores, design a more efficient desalination membranes, engineering realization of ion-channel and other exciting future applications.

? Functionalized nano-colloid ? nanochannel array combination for biomolecular detection. An ideal immuno-assay for biomarker/DNA detection platform should is be sensitivite, portable and allow high-throughput multi-target detection. A promising microfluidic platform developed in our group involves functionalized nanocolloids which can be dispersed into a larger sample to capture target molecules and then sorted in large throughputs with a combination of nanochannel array, dielectrophoresis (DEP) and micro-cross flow. Here I propose to pursue various immuno-assay strategies based on this novel approach, while exploiting the non-linear characteristics of nanocolloid-nanochannel array platform for an even more sensitive detection.

? Field-less spontaneous drug delivery. Such a passive device of drug delivery for therapeutic applications is extremely desirable due to its independence from any power supply source, and hence, would be safer and more patient-friendly. Based on my past research, I have formulated several ideas on exploiting the unique osmotic pressure profiles of nanoporous membranes with tailored surface charge and cross-section geometry variations to propel drug carriers across the membrane without an applied force field.