An environmentally responsive microflow controller with double side tethered structure for the entrapment of hydrogel

In this paper, we report on the fabrication and characterization of a new hydrogel-based microflow controller (HFC). The basic HFC structure is a silicon membrane having an array of orifices with an internal structure designed to confine the hydrogel while allowing it to control the flow across the membrane. Each orifice (140 /spl mu/m diameter) in the membrane has a central post held by two sets of tethers on each side. The hydrogel polymerized inside such orifices contracts around the post in the shrunken state, allowing the pass of fluid through the perimeter. In the swollen state, the hydrogel occupies the whole volume of the orifice completely blocking the flow. Fabrication of the structure involve a combination of deep trench etch and KOH etch. Two different hydrogels, temperature-sensitive and glucose-sensitive, have been tested in the HFC. The measured response times were 10 seconds and 10 minutes respectively.