Discharge dynamics controls the liquid-solid contact electrification of a bouncing drop
Phys. Rev. Fluids 10, 074002 – Published 23 July, 2025
DOI: https://doi.org/10.1103/cfnl-bzss
Abstract
A drop impacting on a superhydrophobic surface acquires an electrical charge. The magnitude of this charge depends both on the hydrodynamics of the impact and on the physicochemical properties of the liquid. Despite its relevance in nature and industry, fundamental understanding of the mechanisms at play in liquid-solid contact electrification remains elusive. Here, we measure the charge acquired by an impacting drop and perform a parametric study by varying drop size, impact speed, salt concentration, viscosity, and liquid conductivity. Our results for pure water confirm that the contact surface area is the dominant hydrodynamic control parameter for charge acquisition [Diaz et al., Soft Matter 18, 1628 (2022)], but drops with varying chemical composition stray away from these predicted trends. We then demonstrate that the amplitude of acquired charge depends directly on a coupling between electric charge transport and hydrodynamic parameters, and more specifically on the ratio of the hydrodynamic impact time and the electrical discharge time.
