A thermally responsive polymer microvalve without mechanical parts photo-patterned in a parylene channel

A photoresist-like thermally responsive polymer has been formulated, surface micromachined and integrated into parylene microchannels to realize an inline valve. The polymer physically swells below its lower critical solution temperature and shrinks above it. Test showed a 2.5-fold polymer volume increase by changing water temperature from 25 to 10/spl deg/C. Repeated polymer swelling and shrinking were observed inside the channel with a system response time around 7 s. Pressure build-up measurements were used to demonstrate the functionality of the valve. Valve test results using DI water showed that the pressure upstream of the polymer plug increased from 15.3 to 20.3 psi with temperature change from 36/spl deg/C to 15/spl deg/C.