How charges separate when surfaces are dewetted

TL;DR

This paper uncovers the universal physical mechanism behind charge separation at receding contact lines during dewetting, linking surface charge dynamics to the local electric double layer structure and flow conditions.

Contribution

It introduces an analytical model that explains charge separation during dewetting, validated by experiments and simulations, advancing understanding of dynamic wetting phenomena.

Findings

Charge separation increases with contact angle.

Charge separation decreases with dewetting velocity.

The model aligns with experimental and numerical results.

Abstract

Charge separation at moving three-phase contact lines is observed in nature as well as technological processes. Despite the growing number of experimental investigations in recent years, the physical mechanism behind the charging remains obscure. Here we identify the origin of charge separation as the dewetting of the bound surface charge within the electric double layer by the receding contact line. This charge depends strongly on the local electric double layer structure close to the contact line, which is affected by the gas-liquid interface and the internal flow of the liquid. We summarize the charge separation mechanism in an analytical model that captures parametric dependencies in agreement with our experiments and numerical simulations. Charge separation increases with increasing contact angle and decreases with increasing dewetting velocity. Our findings reveal the universal mechanism of charge separation at receding contact lines, relevant to many dynamic wetting scenarios, and provide a theoretical foundation for both fundamental questions, like contact angle hysteresis, and practical applications.