Non-equilibrium dynamics of a binary solvent around heated colloidal particles

Abstract

Using numerical simulations, we study the non-equilibrium coarsening dynamics of a binary solvent around spherical colloids in the presence of a temperature gradient. The coarsening dynamics following a temperature quench is studied by solving the coupled modified Cahn-Hilliard-Cook equation and the heat diffusion equation, which describe the concentration profile and the temperature field, respectively. For the temperature field we apply a suitable boundary condition. We observe the formation of circular layers of different phases around the colloid whereas away from the colloid patterns of spinodal decomposition persist. Additionally, we investigate the dependence of the pattern formation on the quench temperature. Our simulation mimics an experimental system where the colloid is heated by laser illumination. Note that we look at the cooling of a solvent with an upper critical temperature, whereas the experimental analogue is the laser-heating of a solvent with a lower critical temperature. We also study a two colloid system. Here, we observe that a bridge of one phase forms connecting the two colloids. Also, we study the force acting on the colloids that is generated by the chemical potential gradient.