(320f) Stern Layer Effect On the Field Effect Regulation of Surface Charge Property and Electroosmotic Flow in a Silica Nanochannel

Electrokinetic transport of ions, fluid, and (bio)particles in micro- and nano-fluidics has attracted considerable attention because of its widespread applications ranging from biosensing to the separation of (bio)molecules. Many of these applications require active control of the surface charge property at the solid/liquid interface of the micro/nanochannel. To achieve this end, field effect transistors (FETs), consisting of gate electrodes embedded beneath dielectric micro/nanochannel walls, have been developed to actively tune the surface charge property. In this study, active control of the surface charge property and electroosmotic flow (EOF) in a silica-based nanochannel by a field effect transistor (FET) is analyzed for the first time with the consideration of the Stern layer effect. Approximate expressions for estimation of the surface charge property and EOF velocity have been derived and validated by comparing to experimental data available from the literature. Results obtained show that field effect regulation of the surface charge property and EOF velocity depend highly on the surface capacitance of the Stern layer and background solution properties including pH and salt concentration. The Stern layer effect becomes appreciable when the magnitude of the surface potential is high, occurring at high pH and/or gate potential imposed.