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Linking energy loss in soft adhesion to surface roughness.
Siddhesh Dalvi1, Abhijeet Gujrati2, Subarna R Khanal2
1Department of Polymer Science, The University of Akron, Akron, OH 44325.
Summary
This study reveals that surface roughness, not viscoelasticity, explains adhesion differences in soft materials. Roughness quantifies the energy needed for contact and energy lost during separation, linking topography to adhesion hysteresis.
Area of Science:
- Materials Science
- Surface Science
- Physics
Background:
- Adhesion in soft materials is crucial for applications like tires, biomaterials, and soft robotics.
- Apparent work of adhesion is lower than intrinsic work, with hysteresis during separation, often attributed to viscoelasticity.
- A quantitative link between adhesion and surface topography is missing.
Purpose of the Study:
- To establish an experimentally validated, quantitative link between adhesion and surface topography in soft elastic materials.
- To investigate the role of roughness in adhesion hysteresis.
Main Methods:
- In situ measurements of contact size were used.
- Soft elastic polydimethylsiloxane hemispheres were tested on polycrystalline diamond substrates.
- Substrate topography was characterized across 8 orders of magnitude, down to the angstrom scale.
Main Results:
- The reduction in apparent work of adhesion equals the energy for conformal contact.
- Energy loss during contact and removal equals intrinsic work of adhesion multiplied by true contact area.
- Adhesion hysteresis is quantitatively linked to surface roughness.
Conclusions:
- Surface roughness provides a simple mechanism to explain adhesion hysteresis in soft materials.
- The findings challenge the prevailing explanation of viscoelastic dissipation.
- This work offers a new framework for understanding and predicting adhesion behavior in soft matter.
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