Non-Equilibrium Interaction Between Catalytic Colloids

Spherical colloids that catalyze the interconversion reaction between solute molecules A and B whose concentration at infinity is maintained away from equilibrium, interact due to the nonuniform fields of solute concentrations. We show that this long range 1/r interaction is suppressed via a mechanism that is superficially reminiscent but qualitatively very different from electrostatic screening: catalytic activity drives the concentrations of solute molecules towards their equilibrium values and reduces the chemical imbalance that drives the interaction between the colloids. The imposed nonequilibrium boundary conditions give rise to a variety of geometry-dependent scenarios; while long range interactions are suppressed (except for a finite penetration depth) in the bulk of the colloid solution in 3D, they can persist in quasi-2D geometry in which the colloids but not the solutes are confined to a surface, resulting in the formation of clusters or Wigner crystals, depending on the sign of the interaction between colloids.