Interfacial Charge Density and Its Connection to Adhesion and Frictional Forces

TLDR

The study derives a link between intrinsic tribological properties and electronic properties of solid interfaces. The authors develop a figure of merit for charge redistribution and show that inhibiting interfacial charge flow reduces adhesive friction, with examples in common lubricants. They find that adhesion and friction are governed by interfacial charge redistribution, enabling friction measurement via charge evolution and that inhibiting charge flow can reduce adhesive friction.

Abstract

We derive a connection between the intrinsic tribological properties and the electronic properties of a solid interface. In particular, we show that the adhesion and frictional forces are dictated by the electronic charge redistribution occurring due to the relative displacements of the two surfaces in contact. We define a figure of merit to quantify such a charge redistribution and show that simple functional relations hold for a wide series of interactions including metallic, covalent, and physical bonds. This suggests unconventional ways of measuring friction by recording the evolution of the interfacial electronic charge during sliding. Finally, we explain that the key mechanism to reduce adhesive friction is to inhibit the charge flow at the interface and provide examples of this mechanism in common lubricant additives.