Séminaire SIMM Julien Dervaux, MSC, Univ. Paris Diderot

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22 novembre 2018 14:00 » 15:00 — A1 (Urbain)

Contact lines on soft solids

Julien Dervaux
Laboratoire Matière et Systèmes Complexes, Université Paris Diderot

Elastocapillarity describes the deformations of soft materials by surface tensions and is involved in a broad range of applications, from micro-electromechanical devices to cell patterning on soft surfaces. Within the very rich field of elastocapillarity, studies on the wetting of soft materials by sessile or moving droplets are presently attracting great interest. In contrast with the wetting of liquids on rigid materials, the surface tension of a liquid drop deforms the soft solid at the contact line and leads to the formation of a “ridge”, which in turn drastically affects the static and dynamic wetting properties.

In this talk, I will briefly introduce the linear theory of static elastowetting before presenting experimental and theoretical results beyond the static linear approximation.

First I will show how the viscous dissipation in soft solids controls the velocity of moving contact lines and how this dissipation can be tuned to control the motion of droplets on thin films. Then, I will show that droplets on soft elastomers and gels leave long-lived “footprints” after removal. The observed logarithmic disappearance of these traces is well captured by a poroelastic model and is responsible for a strong time-dependent hysteresis. Finally I will discuss nonlinear effects in elastowetting and highlight a deep connection between elastocapillary ridges in soft materials and topological defects in crystals.

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