A hydrogel-actuated smart microvalve with a porous diffusion barrier back-plate for active flow control

This paper reports on the fabrication and testing of a hydrogel-actuated microvalve that responds to changes in the concentration of specific chemical species in an external liquid environment. It consists of a hydrogel disc sandwiched between a porous plate and a flexible silicone rubber membrane. Swelling of the hydrogel produced by diffusion of chemical species through the porous plate results in the deflection of the membrane and closure of the valve intake orifice. A phenylboronic acid based hydrogel was used to construct a smart microvalve that opens and closes in response to the changes in the glucose concentration and pH. The fastest response time achieved was 16 minutes using a 70 /spl mu/m thick hydrogel and a 60 /spl mu/m porous back plate.