Micromachined Porous Polymer for Bubble Free Electro-Osmotic Pump

A novel porous polymer was microfabricated to serve as a porous plug for a new device, the porous plug electro-osmotic pump (pp-EOP). The plug eliminates any back pressure effects while enhances electro-osmotic flow in a channel. The pp-EOP was batch fabricated by surface micromachining on top of a silicon wafer. The pp-EOP device is driven by a periodic, zero-average injected current signal at low frequencies producing bubble-free electro-osmotic flow with reversible net movement. Testing of the device produced an average water-air interface velocity of $1.8\ \mu {\rm m}/{\rm s}$ at 0.8 Hz. The velocity was increased to 4.8 and to $13.9\ \mu {\rm m}/{\rm s}$ by necking the channel size.