Microrheology close to an equilibrium phase transition

Abstract

We investigate the microstructural and microrheological response to a tracer particle of a two- dimensional colloidal suspension under thermodynamic conditions close to a liquid-gas phase bound- ary. On the liquid side of the binodal, increasing the velocity of the (repulsive) tracer leads to the development of a pronounced cavitation bubble, within which the concentration of colloidal parti- cles is strongly depleted. The tendency of the liquid to cavitate is characterized by a dimensionless colloidal cavitation number. On the gas side of the binodal, a pulled (attractive) tracer leaves behind it an extended trail of colloidal liquid, arising from downstream advection of a wetting layer on its surface. For both situations the velocity dependent friction is calculated.