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Why soft contacts are stickier when breaking than when making them
Antoine Sanner1,2,3, Nityanshu Kumar4,5, Ali Dhinojwala4
1Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany.
Science Advances
|March 6, 2024
Summary
Soft solids exhibit adhesion hysteresis, where separation forces exceed formation forces. This study reveals surface roughness, not just viscoelasticity, causes this phenomenon through stick-slip motion.
Area of Science:
- Physics
- Materials Science
- Soft Matter Physics
Background:
- Soft solids are inherently sticky, readily forming adhesive contacts.
- Adhesion hysteresis, where separation forces exceed formation forces, is typically attributed to viscoelasticity or contact aging.
Purpose of the Study:
- To investigate the origins of adhesion hysteresis in soft solids.
- To determine if adhesion hysteresis occurs in perfectly elastic materials.
- To develop a model for contact formation influenced by surface roughness.
Main Methods:
- Experimental investigations of soft solid adhesion.
- Computational simulations of contact mechanics.
- Derivation of a theoretical equation for contact line dynamics.
Main Results:
- Adhesion hysteresis is observed even in perfectly elastic soft solids.
- Surface roughness induces stick-slip motion of the contact line, dissipating energy.
- A parameter-free equation accurately quantifies contact formation with roughness.
Conclusions:
- Surface roughness is a primary driver of adhesion hysteresis in soft solids.
- The phenomenon of stick-slip motion is crucial for understanding soft adhesion.
- This work offers a fundamental reevaluation of soft adhesion principles.
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