Bipolar surface charging by evaporating water droplets

TL;DR

This paper investigates how evaporating water droplets cause bipolar surface charging, using microscopy and modeling to understand the underlying physical mechanisms, which is crucial for both technological applications and preventing damage.

Contribution

It provides the first spatially resolved analysis and a quantitative physical model of bipolar surface charging caused by evaporating water droplets.

Findings

Bipolar charge patterns are observed during evaporation.

A physical model explains the origin of bipolar charging.

Implications for nanostructure protection and energy harvesting.

Abstract

Surface charging is a ubiquitous phenomenon with important consequences. On one hand, surface charging underpins emerging technologies such as triboelectric nanogenerators; on the other, uncontrolled charging can damage delicate nanostructures and devices. Despite its significance, surface charging by evaporating water droplets remains poorly understood. Here, using Kelvin Probe Force Microscopy, we spatially resolve the surface-charge patterns from evaporating droplets and propose a physical model that quantitatively explains the origin of bipolar charging.