Stuart J. Williams

Ph.D., University of Louisville, Mechanical Engineering




1043 ERF


Dielectrophoresis (DEP) is a technique in microfluidics that has demonstrated trapping, concentration, manipulating, and sorting of biological cells. However, there has been less emphasis on the development of analytical DEP devices. Analytical DEP devices have been rarely pursued due to the inherent non-uniform nature of the dielectrophoretic force, which is proportional to the gradient of the field-squared, thereby generating a highly non-uniform force field within a microfluidic device. Our device overcomes this limitation by applying a unique isomotive dielectrophoresis (isoDEP) field. Decades ago Herbert Pohl first used the phrase “isomotive dielectrophoresis” and suggested an electrode geometry for particle sorting applications. We have modified and adapted his solution for a microfluidic isoDEP device where the gradient of the field-squared is constant thereby enabling a constant DEP force to be applied to all particles in the field of view. In combination with particle tracking velocimetry the Clausius-Mossotti factor for each particle can be extracted. With this approach detailed dielectric measurements of each individual cell is possible with a greater throughput than the current practice using electrorotation.
This presentation will describe the theory and advantages of our isoDEP platform. The unique isoDEP analytical solution will be presented and the procedure for parallel particles analysis will be described. Proof-of- concept results from spherical microparticles will be presented. Future work will include testing of biological samples, specifically freshwater phytoplankton for environmental monitoring.

Stuart J. Williams is an Associate Professor at the University of Louisville in the Department of Mechanical Engineering. Dr. Williams received his Ph.D. at Purdue University under the advisement of Dr. Steven Wereley while being supported by a National Science Foundation Graduate Research Fellowship. Dr. Williams’ work in microscale electrokinetics and colloid self-assembly has received multiple awards including the Young Researcher Poster Award (MicroTAS 2008), highlighted in the Journal of Micromechanics and Microelectronics (IOPSelect, 2010), and featured on the cover of various technical journals (Lab on a Chip #13 2011, Electrophoresis #13 2013 and #15 2015, Biotechnology and Bioengineering #6 2016). Dr. Williams’ ongoing research activities include colloid self-assembly investigations on the International Space Station (NASA NNX14AN28A) and developing a microfluidic electrokinetic platform for impedance analysis of single cells (NSF 1550509).
Host: Dr. Jie Xu