| Abstract
| - A simple integration of both flow control valves and areaction-based sensing function on a single microchip wasperformed by using capillary-assembled microchip (CAs-CHIP: Hisamoto, H.; Nakashima, Y.; Kitamura, C.;Funano, S.-i.; Yasuoka, M.; Morishima, K.; Kikutani, Y.;Kitamori, T.; Terabe, S. Anal. Chem.2004, 76, 3222−3228.). In contrast to the previously reported on-chipvalving systems, where the simple valving functions wereintegrated, our system can integrate not only valvingfunction but also many other chemical functions toperform a complex chemical operation on a single microchip. Here, an enzymatic reaction-based readout systemis employed as an example. A square capillary immobilizing N-isopropylacrylamide polymer monolith (referred toas “valving capillary”) is used as a thermoresponsive“valving part” and the immobilizing enzyme-modifiedglycidyl methacrylate polymer monolith (referred to as“sensing capillary”) is used as a “sensing part” of the CAs-CHIP. These capillaries are embedded into a latticemicrochannel network fabricated on poly(dimethylsiloxane), which has the same channel dimensions as the outerdimensions of the square capillaries. After bonding, asmall Peltier device (2 mm × 2 mm) for temperaturecontrol is placed on the embedded valving capillaries tocontrol fluid flow. Using this for heating or cooling, fastoperation times of 1.4 and 3.2 s for opening and closingvalves, respectively, are successfully achieved. Finally, twovalving capillaries are independently controlled to trapsample solution within a bypass channel, where theenzyme-immobilized capillary is embedded, and thenenzymatic reaction-based sensing of chemical species isperformed as an example. The fundamental characteristics of the valve-integrated microchip are fully investigated,and an application to the analysis of an enzyme substrateby using two independent valving capillaries and a sensingcapillary is demonstrated.
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