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Friction of a soft hydrogel on rough solid substrates
Taiki Tominaga1, Takayuki Kurokawa1, Hidemitsu Furukawa1
1Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan. gong@sci.hokudai.ac.jp.
Soft Matter
|September 10, 2020
Summary
Friction between soft hydrogels and rough surfaces depends on velocity. At low speeds, roughness increases friction, but at higher speeds, it decreases, influenced by gel properties and surface energy.
Area of Science:
- Materials Science
- Tribology
- Soft Matter Physics
Background:
- Understanding friction is crucial for designing soft materials.
- Hydrogel friction is complex and influenced by surface properties and environmental conditions.
Purpose of the Study:
- To investigate the sliding friction of soft hydrogels on rough substrates in an aqueous environment.
- To elucidate the role of substrate roughness, surface energy, and velocity on hydrogel friction.
Main Methods:
- Utilized polyvinyl alcohol (PVA) hydrogels with varying elastic moduli.
- Employed glass substrates with controlled surface roughness and contact angles.
- Measured friction using a strain-controlled parallel-plate rheometer.
Main Results:
- Friction increased slightly with roughness at low velocities.
- Friction significantly decreased above a critical velocity (>1 μm roughness).
- Frictional stress depended on surface energy below the critical velocity but not above it.
Conclusions:
- Hydrogel friction on rough surfaces exhibits velocity-dependent behavior.
- Two characteristic velocities, vf and vdrainage, govern friction dynamics.
- vf relates to gel diffusion, while vdrainage depends on roughness and pressure.
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