SKM 2023 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 44: Wetting, Fluidics and Liquids at Interfaces and Surfaces II (joint session CPP/DY)
CPP 44.10: Vortrag
Donnerstag, 30. März 2023, 12:00–12:15, MER 02
How Charges Separate at Moving Contact Lines — •Aaron D. Ratschow1, Lisa S. Bauer1, Pravash Bista2, Stefan A. L. Weber2,3, Hans-Jürgen Butt2, and Steffen Hardt1 — 1Technische Universität Darmstadt, Darmstadt, Germany — 2Max Planck Institute for Polymer Research, Mainz, Germany — 3Johannes Gutenberg Universtität, Mainz, Germany
Spontaneous charge accumulation in sliding drops is ubiquitous in nature and has been the subject of research activities for over two decades. Despite the growing number of experimental investigations in recent years, the physical mechanism behind the charging remains poorly understood. We identify the origin of charge separation as the dewetting of the immobilized part of the electric double layer (EDL) by the moving contact line. This layer of physically or chemically bound surface charges depends strongly on the local EDL structure, which is disturbed by the vicinity of the gas-liquid interface and the flow in the liquid. We summarize the physics of charge separation in an analytical model that predicts parametric dependencies on surface chemistry, wetting, and liquid properties. The results agree well with our experiments and numerical simulations and uncover decreasing charge separation with decreasing dynamic contact angle and increasing contact line velocity. Our findings reveal the universal mechanism of charge separation at moving contact lines, not limited to drops, with broad implications for the field of wetting.