Improved Current-Monitoring Method for Low Electroosmotic Flow Measurement in Modified Microchip

Current-monitoring method is a widely used approach to measure electroosmotic flow (EOF) in microchip, but low and zero EOF is difficult to be measured. In this report, the mechanism of current-monitoring method was explained with Kohlraush regulation function principle, and an improved current-monitoring method was developed for low EOF measurement with tilting microchip. Fluid flow in the channel was accelerated with the help of hydrostatic pressure generated by tilting microchip, the time of dilute solution displacing the concentrated one in channel was shortened. EOF could be calculated according to the time difference between twice experiments under two different applied voltages by tilting microchip. Low even zero EOF could be measured by this improved current-monitoring method. Three modified microchips were characterized to verify the method. EOF in microchannels modified with poly(vinyl alcohol), bovine serum albumin and myoglobin were 0.27 ± 0.05, 0.16 ± 0.05 and ?0.45 ± 0.04 × 10^?4 cm² V^?1 s^?1, respectively.