Jingyu Wang's Research Interest
Electrical origin forces such as dielectrophoresis (DEP) and AC electroosmosis (ACEO) have been widely investigated for the purpose of sample pretreatment and analysis. Recent development has witnessed that both DEP and ACEO have great potential in sample transportation, sorting, mixing, etc on microfluidic devices. DEP is a phenomenon of directed motion of electrically polarizable particles in a nonuniform AC electric field. With the variation of field frequency, a changing effective dipole moment is created on the particle, causing the alteration of DEP force direction at a certain crossover frequency. ACEO is an electrokinetic flow caused by the interaction of ions and tangential component of the electric field. It is especially strong near above electrode surface, where large population of ions is formed in electrical double layer.
In order to provide a base for theory development on AC electrokinetic mechanisms like DEP and ACEO, we intend achieving quantification methods of DEP force and ACEO flow on an individual particle. We use optical tweezers as force sensor to trap one single particle. By amplitude modulating AC field square, a combined effect of DEP force and ACEO can be isolated from all other coexisting forces, such as electrophoresis, heat-induced convection and Brownian motion, etc. A complete 3-D mapping of DEP and ACEO signals will well characterize their respective contributions, and give a better guide to future particle manipulating microscale designs.
