Elastocapillarity in wet hairs
Résumé
The hairs of a dog coming out of a pond assemble into bunches giving it a spiny appearance. What is the number of hairs in a clump? The answer relies on a balance between capillary forces and elasticity of the hairs. From a practical point of view, the sticking of flexible elements dramatically damages mechanical microsystems or lung airways, but also allows the self-organization of the hairs of nanotube carpets into well defined structures. Experiments performed with macroscopic brushes teach us that the bundles results from a self-similar cascade of sticking events, which leads to an original form of coalescence process (figure 1). Preliminary results obtained with 1D brushes of parallel strips1 will be completed by recent experiments involving 2D brushes of fibers. Other configurations involving self-crumpling of elastic sheets by capillarity and the fate of a flexible strut pushed through an interface will be finally discussed.