Séminaire

Mardi 20 Juin 2017 à 11h00.

Unexpected droplets dynamics on silicone elastomers

''Beyond the importance of understanding the motion of droplets on stiff surfaces, the recent development of soft materials has lead to a growing interest for capillarity problems where soft interfaces and supports come into play. Silicone elastomers are easy-to-make substrates, used in various research fields such as microfluidics, or elastocapillarity where experiments on slender bendable structures or thick soft substrates are performed. We focus on the dynamics of water-glycerol mixture droplets sliding down plates of such silicone elastomers, and highlight an unexpected behavior: we observe two regimes with different constant speeds, and a sharp transition between them. We show that this unexpected behavior is due to the aqueous droplet extracting uncrosslinked oligomers from the silicone elastomer, through a capillarity-induced phase separation at the triple line. We further investigate the dynamics of this phase separation and its consequences on the wetting properties of the system, and discuss the consequences and potential applications of this phenomenon.''