Related Experiment Video
Updated: Jun 13, 2025
07:18
Measuring the Interaction Force Between a Droplet and a Super-hydrophobic Substrate by the Optical Lever Method
Published on: June 14, 2019
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Droplet Friction on Superhydrophobic Surfaces Scales With Liquid-Solid Contact Fraction
Sakari Lepikko1,2, Valtteri Turkki1,2, Tomi Koskinen3
1Department of Applied Physics, Aalto University, P.O. Box 15600, Espoo, 02150, Finland.
Small (Weinheim an Der Bergstrasse, Germany)
|September 17, 2024
Summary
Droplet friction on superhydrophobic surfaces strongly depends on liquid-solid contact fraction. This study quantifies this relationship using advanced friction probes and model surfaces, providing a new physical equation for wetting characterization.
Area of Science:
- Surface Science
- Tribology
- Nanotechnology
Background:
- Contact angle hysteresis is assumed to correlate with liquid-solid contact fraction on superhydrophobic surfaces.
- Traditional goniometry lacks the accuracy for precise experimental verification.
- Advancements in friction probes offer superior droplet friction measurements for superhydrophobic surface characterization.
Purpose of the Study:
- To quantify the relationship between droplet friction and liquid-solid contact fraction on superhydrophobic surfaces.
- To validate theoretical predictions with experimental data.
- To establish a physical equation describing this dependency.
Main Methods:
- Utilized well-defined micropillar and microcone structures as model superhydrophobic surfaces.
- Employed cantilever-based friction probes for accurate nanonewton-level droplet friction measurements.
- Combined theoretical analysis with confocal laser scanning microscopy to assess liquid-solid contact.
Main Results:
- Demonstrated that droplets do not significantly penetrate micropillar or microcone structures.
- Revealed a strong dependence of droplet friction on liquid-solid contact fraction across a wide range.
- Established a simple physical equation accurately describing the observed friction dependency.
Conclusions:
- Droplet friction is a more reliable metric than contact angle hysteresis for characterizing superhydrophobic surfaces.
- The developed physical equation provides a quantitative understanding of wetting behavior.
- This work advances the understanding and characterization of superhydrophobic surface interactions with liquids.
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