Frequency dependent AC electroosmotic flow in nanochannels

We report frequency-dependent bidirectional AC electroosmotic flow (AC-EOF) in a nanochannel with double layer overlap. This work follows our report in μTas 2008 of unidirectional AC-EOF in nanochannels [1]. Observed is a bidirectional pumping behavior; simulations of the low frequency pumping confirm a direction opposite to that of AC-EOF in microchannels. By this frequency-dependent bidirectional pumping, nanochannel AC-EOF behaves in fundamentally different way than microchannel AC-EOF. Generally, the results are of importance for the understanding of ion and liquid transport in nanoconfinement.