A microchannel concentrator controlled by integral thermoresponsive valves

A strategy for fabricating a microchannel concentrator having a new type of thermoresponsive valves for the fluid flow switching is described. The function of the valves is based on an actuating flap structure, where the flap is composed of a double-layered sheet, a thermoresponsive hydrogel layer and an acrylic resin layer. Responding to the water swelling/deswelling behavior of the hydrogel layer, the flap bidirectionally bends within several seconds. Likewise, in association with a special valve-sealing concept, two valves showing opposite working (open/close) states were successfully created in a microchip. Consequently, when a microchannel filled with silica gel particles was prepared with two outlet branches having the opposite-working valves, a four-fold enrichment of an analyte was achieved by the single operation of the present concentrator system.