Screening model for nanowire surface-charge sensors in liquid

TL;DR

This paper develops an analytical model to evaluate the sensitivity of nanowire surface-charge sensors in ionic liquids, considering Debye screening effects and nanowire geometry.

Contribution

It introduces a theoretical framework combining Thomas-Fermi and Debye-Huckel models to predict sensor sensitivity based on physical parameters.

Findings

Analytical expressions for sensor sensitivity considering screening effects.

Comparison of analytical results with finite-element simulations.

Insights into optimizing nanowire dimensions for improved sensing performance.

Abstract

The conductance change of nanowire field-effect transistors is considered a highly sensitive probe for surface charge. However, Debye screening of relevant physiological liquid environments challenge device performance due to competing screening from the ionic liquid and nanowire charge carriers. We discuss this effect within Thomas-Fermi and Debye-Huckel theory and derive analytical results for cylindrical wires which can be used to estimate the sensitivity of nanowire surface-charge sensors. We study the interplay between the nanowire radius, the Thomas-Fermi and Debye screening lengths, and the length of the functionalization molecules. The analytical results are compared to finite-element calculations on a realistic geometry.