This paper reports the design, fabrication, characterization, and integration of a thermally actuated microvalve. The valve is made of 4 plastic layers, consisting of a layer for temperature-sensitive fluid, flow channel substrate, elastomeric film and a plastic film patterned with microheaters. When the temperature-sensitive fluid is heated, its volumetric expansion deflects the elastomeric film into the microchannel, closing the valve. Heat supplied to the temperature-sensitive fluid comes from microfabricated heaters. The external power applied to the heaters can be controlled using a printed circuit board (PCB)-based controller. The main challenge of this design is to find a suitable elastomeric film that is both elastic and can be bonded with cyclic olefin copolymer (COC) substrates. Pressure-sensitive tape (PSA) was investigated as an elastomeric film for the valve. A valve using PSA was successfully fabricated and tested. A conductive solution (NaCl) was filled into a microfluidic channel containing the valve. The operation of the valve was investigated by measuring a change in the microchannel’s ionic conduction current mediated by the resistance variation corresponding to the deflection of the microvalve. In addition, we integrated an array of such valves with other components in a device and used the valves to control the introduction of different separation media for two-dimensional protein separation.

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