Charge regulation in nanopore ionic field-effect transistors.

We studied the ionic conductance through Al₂O₃ nanopore transistors to probe the surface charge density and its dependence on the applied gate field. The observed conductance modulations are entirely attributable to the electrostatic field effect, and their dependence on pH, ionic strength, and gate voltage is described by a quantitative model. Importantly, these experiments revealed how reactive surface groups dominate the response of nanofluidic field-effect devices via a chemical effect called charge regulation. A quantitative understanding of this effect enables the development of new nanofluidic technologies.