Hydrogel-Based BioMEMS platforms for smart drug delivery.

Environmentally sensitive hydrogels offer unique opportunities for smart flow control in microfluidic systems. These tangled networks of cross-linked polymer chains, immersed in a solvent, manifest a reversible and abrupt swelling phase transition in response to changes in environmental factors such as glucose concentration, pH, electric field, temperature, and light. This transition often results in an abrupt volume change (swelling or shrinking) that can be as large as 1000 fold or more. Because of this property, hydrogels are attractive candidates as components microactuators operating in aqueous media such as body fluids. For example, the volume phase transition in these materials can be harnessed in smart microfluidic components used for implantable drug delivery systems. In this talk, we will discuss several hydrogel-actuated MEMS-based microdevices for smart microflow control developed in out laboratories at th University of Minnesota. These include: 1) a hydrogel-actuated microvalve with a porous back-plate, 2) a hydrogel-gated smart flow controller, 3) a microvalve with double side tethered structure for the entrapment of hydrogel, and 4) a wireless passive glucose transponder. Our emphasis is particularly on lightly crosslinked poly(methacrylamidophenylboronic acid-co-acylamide) hydrogel that swell monotonically at pH 7.4 with exposure to increasing concentration of glucose.