Field Effect Modulation of Surface Charge Property and Electroosmotic Flow in a Nanochannel: Stern Layer Effect

Abstract

Active control of surface charge property and electroosmotic flow (EOF) in a silica-based nanochannel using a field effect transistor (FET) is analyzed for the first time taking the Stern layer effect into account. Approximations for surface charge property and EOF have been derived and validated by comparing their predictions with experimental data available in the literature. We show that, in addition to the background solution properties such as its pH and salt concentration, the field effect control of the zeta potential of the nanochannel wall and the EOF velocity depends highly on the surface capacitance of the Stern layer, stemming from the attraction of immobile counterions within that layer. The Stern layer effect becomes significant when the background salt concentration, solution pH, and/or the applied gate potential are relatively high. Results gathered provide valuable information for designing relevant gated nanofluidic devices for regulating ion, fluid flow, and biomolecule transport.