Continuous sorting and separation of microparticles by size using AC dielectrophoresis in a PDMS microfluidic device with 3-D conducting PDMS composite electrodes.

Soft lithography technology allows for the development of numerous PDMS-based microfluidic devices for manipulation of particles and cells. However, integrating metallic electrodes with PDMS-based channel structures is challenging due to weak adhesion between metal and PDMS. To overcome this issue, we develop a new PDMS-based microfluidic device for continuous sorting and separation of microparticles by size using AC dielectrophoresis (DEP) with 3-D conducting PDMS composites as sidewall electrodes. The composites are synthesized by mixing silver powders with PDMS gel and such composite electrodes can easily be integrated with the PDMS microchannels. Furthermore, the sidewall electrodes also allow DEP forces to distribute three dimensionally, thus enhancing DEP effects in the entire region of channels. The capability of such PDMS-based microfluidic device is demonstrated for continuously sorting and separating 10 and 15 mum particles, and also for separating 5 from 10 mum particles. Together with experimental results, analysis of particle's trajectory based on Lagrangian approach provides insights into how microparticles transport under the effects of hydrodynamic and DEP forces in the present PDMS-based microfluidic device.