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How Spontaneous Electrowetting and Surface Charge Affect Drop Motion

Chirag Hinduja1,*, Benjamin Leibauer1, Rishi Chaurasia1,2, Nikolaus Knorr1, Aaron D. Ratschow1, Shalini Singh1,3, Hans-Jürgen Butt1,†, and Rüdiger Berger1,‡

  • *Contact author: hindujachirag604@gmail.com
  • †Contact author: butt@mpip-mainz.mpg.de
  • ‡Contact author: berger@mpip-mainz.mpg.de
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Phys. Rev. Lett. 136, 194001 – Published 14 May, 2026

DOI: https://doi.org/10.1103/9mzt-v9cl

Abstract

Water drops sliding on hydrophobic surfaces spontaneously separate charges at their rear. It is unclear how this charge separation affects the contact angles of a sliding drop. We slide grounded and insulated drops on hydrophobic surfaces at low capillary numbers (≤10−4). We find that the drop charge leads to spontaneous electrowetting that decreases the contact angles. The deposited charges lead to a surface charge effect and decrease the contact angle. Both phenomena compensate each other at the receding contact line, resulting in an insignificant change in the receding contact angle of a sliding drop.

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Phys. Rev. Lett. 136, 194001– Published 14 May, 2026
  • Received 10 January 2025
  • Revised 20 August 2025
  • Accepted 17 March 2026
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