A new method to measure zeta potentials of microfabricated channels by applying a time-periodic electric field in a T-channel

A new method is proposed to measure the zeta potential of microfabricated channel surfaces. It is based on the fact that confluent flow streams in a T-channel show oscillation under a time-periodic electric field. When a suitable frequency is chosen, the oscillation amplitude is a monotonic function of the zeta potential of the surfaces. The zeta potential value can be estimated based on the experimentally measured oscillation amplitude and the 3-D numerical simulation results which can convert the oscillation amplitude to the zeta potential. We conducted experiments with three kinds of buffers with different pHs and ionic valences for the validation of the newly proposed method. The zeta potential values predicted by the new method were in good agreement with the previously reported values in the literature.