Résumé : The role of surface tension in the mechanics of deformable solids is a question raising a growing interest in the soft matter community : in this context, I will present two examples of instabilities featuring liquids on soft materials.
We will begin by revisiting the snap-through instability from an elastocapillary point of view. Snap-through, present in systems ranging from carnivorous plants to MEMS, is a well-known phenomenon in solid mechanics. Here we show that capillary forces are strong enough to trigger a snap-through instability at small scales, and even counterbalance gravity for a droplet deposited below a downward buckled elastic strip. We investigate the statics and dynamics of this phenomenon, and compare droplet-induced snap-through to dry point force indentation on a buckled thin strip.
In a second part, we will focus on the dynamics of droplets sliding on elastomers. The motion of droplets on stiff surfaces has been investigated for a long time, while recent studies have shown the interesting physics underlying the sliding of droplets on soft surfaces. We focus on the dynamics of water-glycerol mixture droplets sliding down vertical plates of commercial silicone elastomers, highlighting an unexpected behavior : the droplet dynamics on such a surface includes two regimes with different constant speeds. Our experiments reveal an unexpected link between microscopic phenomena at the scale of the polymer matrix and the macroscopic dynamics of a droplet.
Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères