This paper reports on the fabrication and test of a hydrogel-actuated microvalve that responds to changes in the concentration of specific chemical species in an external liquid environment. The microvalve consists of a thin hydrogel, sandwiched between a stiff porous membrane and a flexible silicone rubber diaphragm. Swelling and deswelling of the hydrogel, which results from the diffusion of chemical species through the porous membrane is accompanied by the deflection of the diaphragm and hence closure and opening of the valve intake orifice. A phenylboronic-acid-based hydrogel was used to construct a smart microvalve that responds to the changes in the glucose and pH concentrations. The fastest response time (for a pH concentration cycle) achieved was 7 min using a 30-μm-thick hydrogel and a 60-μm-thick porous membrane with 0.1 μm pore size and 40% porosity.
Bibliographical noteFunding Information:
Manuscript received September 16, 2002; revised May 13, 2003. This work was supported by the Spanish Ministry of Education, Culture and Sports, the University of Minnesota Drug Delivery Center, and the Graduate school of the University of Minnesota. Subject Editor F. K. Forster.
- Drug delivery
- Smart material