Monolithic valves for microfluidic chips based on thermoresponsive polymer gels
Monolithic valves for microfluidic chips based on thermoresponsive polymer gels
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DOI：
10.1002/elps.200305577
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发表时间：
2003-11-01
期刊：
影响因子：
2.9
通讯作者：
Fréchet, JMJ
中科院分区：
文献类型：
--
作者：
Luo, QZ;Mutlu, S;Fréchet, JMJ
本文研究了由N-异丙基丙烯酰胺、N-乙基丙烯酰胺、N，N ′-亚甲基双丙烯酰胺和4，4 ′-偶氮二（4-氰基戊酸）的水溶液组成的液相的水化直接制备温度响应性整体共聚物，并将产物用作微流控装置通道内的阀。与聚合物在其较低临界溶解温度（LCST）下的相变相关的体积变化导致2.5%交联的整体凝胶的快速溶胀和去溶胀，从而使聚合物能够关闭或打开通道并起到非机械致动阀的作用。通过改变聚合混合物中单乙烯基单体的比例，可以容易地将阀门切换时的LCST调节在35 ℃-74 ℃的范围内。关闭的阀门可承受高达18 MPa的压力，而不会出现明显的错位、结构损坏或泄漏。相比之下，在通过将温度升高到LCST以上来消除溶胀之后，阀不会提供明显的流动阻力，因为其大的微米尺寸的孔是开放的。激光触发的光漂白的荧光染料包含在液相中，使监测通过该设备的流量和确定所需的时间打开和关闭阀门。阀门的特点是非常快的致动时间在1-4秒的范围内，这取决于设备的类型。即使在瓣膜重复打开-关闭循环后，也未观察到性能变化。
The direct preparation of thermoresponsive monolithic copolymers by photopatterning of a liquid phase consisting of an aqueous solution of N-isopropylacrylamide, N-ethylacrylamide, N,N'-methylenebisacrylamide, and 4,4'-azobis(4-cyanovaleric acid) has been studied and the products used as valves within the channels of microfluidic devices. The volume change associated with the polymer phase transition at its lower critical solution temperature (LCST) leads to the rapid swelling and the deswelling of the 2.5% cross-linked monolithic gel thus enabling the polymer to close or open the channel and to function as a nonmechanically actuated valve. The LCST at which the valve switches was easily adjusted within a range of 35degreesC-74degreesC by varying the proportions of the monovinyl monomers in the polymerization mixture. The closed valve holds pressures of up to 18 MPa without noticeable dislocation, structural damage, or leakage. In contrast, following deswelling by raising the temperature above LCST the valve offers no appreciable flow resistance since its large, micrometer-size pores are open. Laser-triggered photobleaching of a fluorescent dye contained in the liquid phase enabled monitoring of flow through the device and determination of the times required to open and close the valve. The valves are characterized by very fast actuation times in a range of 1-4 s depending on the type of device. No changes in performance were observed even after repeated open-close cycling of the valves.