Abstract

Small objects trapped at an interface are very common in Nature (insects walking on water, ant rafts, insects laying their eggs on water, bubbles or pollen at the water-air interface, membranes…). They also find an application in industrial processes as they can act as stabilizing agents for emulsions or foams. Their study is therefore of practical as well as fundamental importance. Here we propose an original system which allows us to observe the self-assembly of particles into capillary rafts at an oil-water interface based on the interplay of gravity and capillary effects. When the number of particles in the raft is large enough, the raft becomes unstable and sinks, thus encapsulating the upper oil phase in water. I will first present how and why these rafts may sink and then show how this process allows to contain liquid as millimeter-size droplets with a shell of particles.