Solid-Liquid Contact Charge Separation and its Consequences

Understanding the effects and origins of slide electrification, i.e., the spontaneous charge separation in sliding drops [1-4], is of great importance in energy harvesting and wetting. We explored the consequences of spontaneous charge separation in drop motion [3]. We found that the electrostatic force on the sliding drop can be up to almost 50% of the total force. This finding shows that self-induced electrostatics should be considered while studying the drop motion. To understand the molecular processes behind slide electrification, we recently proposed a physical model to describe the dynamics in charge separation as successive water drops slide down a neutral hydrophobic surface. We describe this effect using a three-phase contact line voltage that changes or adapts when the surface is in contact with water. This deeper understanding can open the way for surface engineering to achieve desired wetting properties.<br/><br/>[1] Yatsuzuka, K., Mizuno, Y., & Asano, K. (1994). Electrification phenomena of pure water droplets dripping and sliding on a polymer surface. <i>Journal of electrostatics</i>, <i>32</i>(2), 157-171.<br/>[2] Stetten, A. Z., Golovko, D. S., Weber, S. A., & Butt, H. J. (2019). Slide electrification: charging of surfaces by moving water drops. <i>Soft Matter</i>, <i>15</i>(43), 8667-8679.<br/>[3] Li, X., Bista, P., Stetten, A. Z., Bonart, H., Schür, M. T., Hardt, S., ... & Butt, H. J. (2022). Spontaneous charging affects the motion of sliding drops. <i>Nature Physics</i>, 1-7.<br/>[4] Bista, P., Stetten, A. Z., Wong, W. S., Butt, H. J., & Weber, S. A. (2022). Adaptive two capacitor model to describe slide electrification in moving water drops. <i>arXiv preprint arXiv:2202.03948</i>.