Study on Processing Technique of 3-D PDMS-Ag Composite Microelectrodes Integrated in Microfluidic Systems

Benefited from the development of soft lithography technology, the material polydimethylsiloxane (PDMS) has been widely used serving as a unique material in chip fabrication owing to its properties such as transparency, biocompatibility, and good flexibility. However, PDMS itself is a non-conducting polymer, and the adhesion between metal and PDMS is really weak. Hence, integrating metallic microelectrodes with PDMS-based microchips structures has become an urgent technical issue.

To overcome this problem, we present a method of patterning 3-D microelectrode structures by using a new kind of conductive composite, synthesized by mixing Ag powders with pure PDMS gel. The advantage of this material is the ease of patterning and embedding these microstructures into PDMS-based channels. Compared with other conventional 3-D microelectrode preparations, the technological process was greatly simplified and the cost was effectively reduced.

 In this paper, first, the dimensional electric field distributions induced by sidewall electrodes was simulated. Furthermore, we designed a dentate electrode array based on PDMS-Ag conductive composites for cell electrokinetic operations. Integrating 3D-electrode structures into microchips, chip package and fabrication were accomplished by multiple exposures, developments and plasma bonding. The feasibility of electrodes was validated on cell alignment driven by dielectrophoresis force. The results obtained demonstrate that the method seems to be a valuable solution for 3-D microelectrode processing. It is also compatible with existing micro-processing technology with much simpler operations. Thus, we aim at highlighting the promising prospects of this conductive composite material in microfluidic devices.