title: Experimental evidence of the motion of a single out-of-equilibrium drop.
abstract: We show experimentally that when a single, neutrally buoyant drop is injected into a binary mixture either it remains quiescent or it moves, depending on whether the composition of the drop and that of the surrounding phase coincide with the equilibrium concentrations. In general, the movement of out-of-equilibrium drops, which is called diffusiophoresis, is induced by the Korteweg body force. This force is proportional to the chemical potential gradient and is therefore nonzero only when the system is in chemical nonequilibrium. In this letter, we show experimentally that this movement occurs for a single drop as well, even when the initial condition is (almost) isotropic. This instability, although it does not have a complete analytical explanation, has been predicted in the numerical simulations by Vladimirova et al. (Vladimirova, N.; Malagoli, A.; Mauri, R. Phys. Rev. E 1999, 60, 2037).
authors.affiliation: Department of Chemical Engineering, Industrial Chemistry and Material Science, Università di Pisa, 56126 Pisa, Italy.
authors.forename: Dafne
authors.initials: D
authors.lastname: Molin
authors.forename: Roberto
authors.initials: R
authors.lastname: Mauri
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Tricoli