Electroosmotic pumping within a chemical sensor system integrated on silicon

The concept of a multi-manifold flow system integrated on a silicon substrate with valveless switching of flows and electroosmotic pumping of an aqueous solvent is presented. Electroosmotic flow rates of 0.001 cm/s and 0.002 cm/s are obtained with fields of 100 and 180 V/cm, respectively, in an optimized system with thermal oxide insulation. The dielectric breakdown value of an oxide/nitride film 250 nm thick allows application of 200 V to the channels. Sample volumes on the order of 6 to 320 pL can be introduced into the sensing channel. While oxide appears to be a poor choice of insulator, a combination of oxide, nitride, and low-conductivity silicon will allow suitable voltages of 100 to 600 V to be used.<>