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Hydrodynamic Elastocapillary Morphing of Hair Bundles
Jonghyun Ha1, Yun Seong Kim1, Kaiying Jiang1
1Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Physical Review Letters
|January 8, 2021
Summary
We discovered that hair bundles can change shape (polymorphism) due to liquid drainage. This self-assembly is driven by physical forces like capillarity and elasticity, leading to reversible changes in bundle structure.
Area of Science:
- Soft Matter Physics
- Materials Science
- Fluid Dynamics
Background:
- Understanding the self-assembly of fibrous materials is crucial in various scientific fields.
- The interplay of capillary forces, hydrodynamics, and material elasticity governs the behavior of microstructures in liquids.
Purpose of the Study:
- To investigate the polymorphic self-assembly of hair-like structures in bundles.
- To elucidate the mechanisms driving the reversible structural changes in these bundles under varying liquid drainage conditions.
Main Methods:
- Experimental observation of hair bundle assembly from a liquid bath.
- Analysis of structural changes under different drainage rates (slow vs. fast).
- Application of scaling laws to predict and model the observed phenomena.
Main Results:
- Hair bundles exhibit polymorphic self-assembly, forming hollow structures.
- At slow drainage, bundles remain hollow due to trapped negative capillary pressure, resisting closure due to fiber stiffening.
- At fast drainage, bundles close before liquid drainage, with a trapped liquid column causing closure while hairs remain soft.
Conclusions:
- Capillarity, hydrodynamics, and elasticity collectively drive reversible hair polymorphism.
- The study reveals a mechanism for tunable structural changes in fibrous assemblies.
- Predicted scaling laws accurately describe the observed reversible polymorphism.
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