Microfluidic Valve Arrays in Thermoplastic Devices

Thermoplastics have been increasingly employed for microfluidic devices due to their manufacturability, low cost, and biocompatibility. A microfluidic device consists of a number of necessary building blocks, including microvalves that are often used for flow regulation. The state-of-the-art of the microfluidic valve technology is polydimethylsiloxane (PDMS)-based elastic membrane valve. This paper is to report the integration of the elastomer valve into a thermoplastic device. The valves were designed for a two-dimensional protein separation device, which was fabricated from cyclic olefin copolymers (COC). To realize the goal of integrating the elastomer-based valves in the device, the key challenge is to achieve strong bonding between COC and PDMS so that the device will not delaminate when a pressure is built up after the valves are closed. Microvalve arrays were fabricated in a COC/PDMS/COC device to facilitate the introduction of two types of separation media, without cross-contamination, into orthogonal channels in order to achieve two-dimensional separation. In addition, we studied thermal actuation in the microvalve, as an alternative to pneumatic actuation in the conventional PDMS-based elastomer valve. The thermally actuated valves can be self-contained, requiring less-bulky external accessories than pneumatically actuated valves.