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How Spontaneous Electrowetting and Surface Charge Affect Drop Motion
Chirag Hinduja1, Benjamin Leibauer1, Rishi Chaurasia1,2
1Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
Physical Review Letters
|May 29, 2026
Summary
Water drops sliding on hydrophobic surfaces gain charge, causing electrowetting. This effect, however, is balanced by surface charges, leading to no significant change in the receding contact angle of sliding drops.
Area of Science:
- Physics
- Materials Science
- Surface Science
Background:
- Water drops sliding on hydrophobic surfaces exhibit spontaneous charge separation at their rear.
- The impact of this charge separation on the contact angles of sliding drops remains unclear.
Purpose of the Study:
- To investigate how charge separation affects the contact angles of sliding water drops on hydrophobic surfaces.
- To analyze the interplay between electrowetting and surface charge effects.
Main Methods:
- Sliding grounded and insulated water drops on hydrophobic surfaces.
- Conducting experiments at low capillary numbers (≤10⁻⁴).
Main Results:
- The charge on sliding drops induces spontaneous electrowetting, which decreases contact angles.
- Deposited charges create a surface charge effect, further reducing the contact angle.
- Electrowetting and surface charge effects at the receding contact line compensate each other.
Conclusions:
- Sliding drops on hydrophobic surfaces experience opposing electrical effects on their contact angles.
- The net result is an insignificant change in the receding contact angle despite charge separation.
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