Light-actuated high pressure-resisting microvalve for on-chip flow control based on thermo-responsive nanostructured polymer.

A simple light-actuated microvalve using a quartz halogen illuminator with tungsten filament was introduced to manipulate flow path effectively in micro-total analysis systems, which reduces system complexity and the need for on-chip integration. The microvalve device in cyclic olefin copolymer (COC) microchip functions very well based on the thermo-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), whose pressure-tolerance can be tuned by changing the mechanical strength of polymer monolith inside the microchannel with the choice of suitable amount of monomer and crosslinker. The response time and pressure resistance of the valve can be optimized by the tetrahydrofuran composition in the polymerization mixture as well. Very importantly, the microvalve can withstand the leakage pressure up to around 1350 psi, and its opening and closing response time is only 4.0 and 6.2 s respectively. Microchips with such valves will be very useful in drug delivery, chemical analysis and proteomic analysis.