A hydrogel-actuated microvalve for smart flow control

We report on the fabrication and testing of a hydrogel-actuated smart microvalve for biomedical applications. The three-layered microvalve is composed of a stimuli-sensitive "intelligent" hydrogel sandwiched between a porous silicon membrane and a bossed PDMS flexible diaphragm. The entrapped hydrogel in response to changes in the external physiological stimuli (e.g., pH, glucose, etc.), which diffuses through the porous membrane, swell and deswell hence deflecting the flexible PDMS diaphragm and controlling the closure and opening of the microvalve inlet. A microvalve incorporating a 155 /spl mu/m thick hydrogel (poly(methacrylic acid-co-acrylamide), mAA-co-AAm) has a response time of 3.6 min to a sudden pH change (pH=3 to pH=7).