Phoretic flow induced by asymmetric confinement

TL;DR

This paper demonstrates that asymmetric geometric confinement alone can induce internal phoretic flows in chemically homogeneous systems, offering a new way to create tunable microfluidic pumps.

Contribution

It introduces a model for inducing and controlling phoretic flows through geometric asymmetry without chemical patterning, expanding the understanding of phoretic flow mechanisms.

Findings

Flow strength depends on cylinder positioning

Optimal configuration maximizes flow

Analytical solution in diffusive limit

Abstract

Internal phoretic flows due to the interactions of solid boundaries with local chemical gradients may be created using chemical patterning. Alternatively, we demonstrate here that internal flows might also be induced by geometric asymmetries of chemically-homogeneous surfaces. We characterise the circulatory flow created in a cavity enclosed between two eccentric cylindrical walls of uniform chemical activity. Local gradients of the diffusing solute induce a slip flow along the surface of the cylinders, leading to a circulatory bulk flow pattern which can be solved analytically in the diffusive limit. The flow strength can be controlled by adjusting the relative positions of the cylinders and an optimal configuration is identified. These results provide a model system for tunable phoretic pumps.