Enhancement of non-contact friction between metal surfaces induced by the electrical double layer

TL;DR

This paper demonstrates that the electrical double layer significantly enhances non-contact friction between metal surfaces at nanometer-scale separations, aligning well with experimental data and suggesting new detection methods.

Contribution

It introduces the impact of the electrical double layer on non-contact friction, revealing a substantial increase in friction at extremely close distances, which was not accounted for in previous theories.

Findings

Electrical double layer causes orders-of-magnitude increase in friction at <10nm.

Electrostatic friction matches experimental measurements.

Casimir and electrostatic friction dominate at different separation ranges.

Abstract

Casimir and electrostatic non-contact friction between two gold plates, and a gold tip and a gold plate, are calculated taking into account the contribution of the electrical double layer. It is shown that in an extreme-near field ($d<10$nm) the contribution from the electrical double layer leads to the enhancement of non-contact friction by many orders of magnitude in comparison to the result of the conventional theory without this contribution. Casimir and electrostatic friction dominate for short and large separations, respectively. The calculated electrostatic friction is in good agreement with experimental data. The results obtained open the way to detect the Casimir friction using Atomic Force Microscope.