Mass transport in electrochemical nanogap sensors

Nanofluidic thin-layer cells based on redox cycling allow for extremely sensitive electrochemical detection. Here we establish a physical mass-transfer model for analyte molecules in these transducers which takes into account advective and diffusive transport of both oxidized and reduced species as well as reversible dynamic adsorption at the sensor surfaces. We use finite-element modeling to determine the transient response of nanogap sensors; numerically we predict that the response time can be reduced substantially by pressure-driven advection while the faradaic limiting current remains unaffected by this flow for all experimentally accessible flow rates