Thermal Marangoni bubbles.

When air reaches the surface of a pool (or bath) of pure liquid, it does not form long-lasting bubbles, as opposed to when the bath contains surfactants. Here we describe what happens when the pool is pure (consisting of oil), yet hot. The bubbles dwelling at the surface can then live for minutes or even longer, which we interpret as a consequence of the gradients of temperature generated in this experiment.

When Elasticity Affects Drop Coalescence.

The breakup and coalescence of drops are elementary topological transitions in interfacial flows. The breakup of a drop changes dramatically when polymers are added to the fluid. With the strong elongation of the polymers during the process, long threads connecting the two droplets appear prior to their eventual pinch-off.

Thermophobic Leidenfrost.

We report that a volatile liquid deposited on a hot substrate with a gradient of temperature does not only levitate (Leidenfrost effect), but also spontaneously accelerates to the cold. This thermophobic effect is also observed with sublimating solids, and we attribute it to the ability of temperature differences to tilt (slightly) the base of the "object", which induces a horizontal component to the levitating force. This scenario is tested by varying the drop size (with which the acceleration increases) and the substrate temperature (with which the acceleration decreases), showing that the effect can be used to control, guide and possibly trap the elusive Leidenfrost drops.

Self-excitation of Leidenfrost drops and consequences on their stability.

Volatile liquids (water, alcohol, etc.) poured on hot solids levitate above a layer of vapor. Unexpectedly, these so-called Leidenfrost drops often suddenly start to oscillate with star shapes, a phenomenon first reported about 140 y ago.

Buoyancy-driven convection of droplets on hot nonwetting surfaces.

The global linear stability of a water drop on hot nonwetting surfaces is studied. The droplet is assumed to have a static shape and the surface tension gradient is neglected. First, the nonlinear steady Boussinesq equation is solved to obtain the axisymmetric toroidal base flow.