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Bulk elastic fingering instability in Hele-Shaw cells.
B Saintyves1, O Dauchot, E Bouchaud
1CEA-Saclay, IRAMIS, SPEC, F-91191 Gif-sur-Yvette Cedex, France and PSL, 75231 Paris Cedex 05, France.
Physical Review Letters
|August 13, 2013
Summary
Air penetration into elastomers causes a purely elastic fingering instability. This phenomenon, observed in Hele-Shaw cells, occurs once a critical strain is met, independent of material stiffness.
Area of Science:
- Materials Science
- Physics
- Rheology
Background:
- Fingering instabilities are common in fluid dynamics.
- Elastic instabilities in soft materials are less understood.
- Previous studies often focused on viscous effects.
Purpose of the Study:
- To experimentally demonstrate a purely elastic, nonviscous fingering instability.
- To investigate the conditions under which this instability occurs in elastomers.
- To identify the key factors driving the instability.
Main Methods:
- Utilizing a Hele-Shaw cell to confine an elastomer.
- Introducing air to penetrate the elastomer.
- Observing and analyzing the resulting fingering patterns.
- Measuring critical strain thresholds.
Main Results:
- A purely elastic, nonviscous fingering instability was experimentally confirmed.
- Fingers appeared sequentially and propagated within the elastomer bulk.
- Instability onset was linked to a critical strain, independent of elastic modulus.
- Confinement and adhesion to cell plates were identified as key driving forces.
Conclusions:
- Elasticity and confinement, not viscosity, can drive fingering instabilities in gels.
- A critical strain threshold governs the onset of this elastic instability.
- The study provides new insights into the mechanical behavior of soft materials under penetration.
