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Influence of Humidity on Grip and Release Adhesion Mechanisms for Gecko-Inspired Microfibrillar Surfaces
Nicholas Cadirov1, Jamie A Booth1, Kimberly L Turner1
1Department of Chemical Engineering, and ‡Department of Mechanical Engineering, University of California , Santa Barbara, California 93106, United States.
ACS Applied Materials & Interfaces
|April 12, 2017
Summary
Gecko-inspired adhesives maintain strong grip and easy release across humidity levels. Their performance is optimized at intermediate relative humidity (RH) for robust adhesion and friction.
Area of Science:
- Biomimetics and Materials Science
- Adhesion and Friction Physics
Background:
- Gecko feet exhibit remarkable adhesion and friction across diverse environments.
- Gecko-inspired adhesives require similar performance versatility, especially concerning humidity.
- Understanding relative humidity's effect on gecko-inspired adhesion is crucial for practical applications.
Purpose of the Study:
- To investigate the impact of relative humidity (RH) on the frictional-adhesion behavior of gecko-inspired adhesive pads.
- To quantify adhesion and friction forces across a wide range of RH conditions (0-100%).
- To analyze the transition between high-adhesion 'grip' and low-adhesion 'release' states.
Main Methods:
- Utilized a surface forces apparatus to measure adhesion and friction forces.
- Tested microfibrillar, cross-linked polydimethylsiloxane surfaces against a glass disk.
- Varied relative humidity from 0% to 100%, including submersion in water.
Main Results:
- Gecko-inspired microfibers demonstrated distinct 'grip' and 'release' states.
- Grip state adhesion remained constant up to 75% RH, with a grip-to-release ratio above 4.0.
- Friction forces and release adhesion peaked at intermediate RH (40-75%).
Conclusions:
- Relative humidity significantly influences the van der Waals and capillary forces governing adhesion.
- Gecko-inspired adhesives show robust performance across a broad humidity spectrum.
- Optimal frictional-adhesion is achieved at intermediate relative humidity levels.