Experimental studies of electroosmotic flow dynamics in microfabricated devices during current monitoring experiments.

Electroosmotic flow (EOF) was monitored in glass microfluidic devices at rates up to 2 Hz with a precision of 0.2-1.0% using a technique based on the periodic photobleaching of a dilute, neutral fluorophore added to the running buffer. This EOF monitoring method was used to examine the performance of the current monitoring technique for measuring an average electroosmotic flow in a microfluidic device with a cross-T design. Flow measurements made with the current monitoring method gave a precision of 0.4-2.2%, but the periodic photobleaching method shows that the current monitoring technique causes changes in EOF as high as 41% during a single experiment. The periodic photobleaching method for EOF monitoring was also used to study EOF in channels on opposite sides of a cross-channel intersection. The opposite channels were shown to exhibit substantially different EOF dynamics during a current monitoring experiment as well as different steady-state EOF rates during normal operating conditions.