Does Flexoelectricity Drive Triboelectricity?

TL;DR

This paper proposes that flexoelectricity, caused by nanoscale strain gradients, may be the fundamental thermodynamic driver of the triboelectric effect, supported by modeling and experimental correlations.

Contribution

It introduces the hypothesis that flexoelectric potential differences drive tribocharge separation, supported by modeling and experimental evidence.

Findings

Nanoscale flexoelectric potential differences of ±1-10 V can arise during contact.

The hypothesis aligns with observations like bipolar charging and inhomogeneous charge patterns.

Flexoelectricity may be the thermodynamic basis of triboelectricity.

Abstract

The triboelectric effect, charge transfer during sliding, is well established but the thermodynamic driver is not well understood. We hypothesize here that flexoelectric potential differences induced by inhomogeneous strains at nanoscale asperities drive tribocharge separation. Modelling single asperity elastic contacts suggests that nanoscale flexoelectric potential differences of $\pm$1-10 V or larger arise during indentation and pull-off. This hypothesis agrees with several experimental observations, including bipolar charging during stick-slip, inhomogeneous tribocharge patterns, charging between similar materials, and surface charge density measurements.