Wed May 10th 2017
16:00 – 17:00
Seminar Shape and stability of drops floating on granular rafts
Etienne Jambon-Puillet


When a droplet is gently deposited on a bath of the same liquid, as soon as the interstitial fluid is squeezed out by the drop's weight, the drop merges with the bath. To prevent this so-called coalescence process one has to prevent contact between the two liquid surfaces, either by renewing constantly the interstitial fluid or by coating the surfaces with a shell that provides steric repulsion. Here we prevent coalescence with a monolayer of large, dense and hydrophobic particles at an oil-water interface: a granular raft. When we deposit a water drop on such rafts, particles are wet by both the drop and the bath while maintaining a thin oil layer in between that prevents contact, a phenomenon known as particle bridging. By modifying the volume of these floating drops, we deform both the drop and the raft, allowing us to experimentally study the mechanical response of this intricate interface. We propose a continuous, heavy membrane model that reproduces very well the shape of the drop and the raft as the drop volume is gradually increased. It also predicts the critical volume for which the raft cannot sustain the drop anymore and destabilises. During this process the drop sinks, dragging down the raft and the oil layer to form what we call an armored capsule: a water in water drop coated with a thin oil-particle shell. Armored capsules' content being transportable and releasable at will, they are great candidates for cheap, underwater, aqueous micro chemical reactors.
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The 10th Complex Motion in Fluids 2021
Max Planck Gesellschaft
Centre for Scientific Computing