# Instabilities driven by diffusiophoretic flow on catalytic surfaces

*Corresponding author for this work

## Abstract

We theoretically and numerically investigate the instabilities driven by diffusiophoretic flow, caused by a solutal concentration gradient along a reacting surface. The important control parameters are the Péclet number, which quantifies the ratio of the solutal advection rate to the diffusion rate, and the Schmidt number, which is the ratio of viscosity and diffusivity. First, we study the diffusiophoretic flow on a catalytic plane in two dimensions. From a linear stability analysis, we obtain that for larger than mass transport by convection overtakes that by diffusion, and a symmetry-breaking mode arises, which is consistent with numerical results. For even larger, nonlinear terms become important. For 16{\rm \pi}$]]>, multiple concentration plumes are emitted from the catalytic plane, which eventually merge into a single larger one. When is even larger (for Schmidt number), there are continuous emissions and merging events of the concentration plumes. The newly found flow states have different flow structures for different: for, we observe the chaotic emission of plumes, but the fluctuations of concentration are only present in the region near the catalytic plane. In contrast, for <![CDATA[$Sc, chaotic flow motion occurs also in the bulk. In the second part of the paper, we conduct three-dimensional simulations for spherical catalytic particles, and beyond a critical Péclet number again find continuous plume emission and plume merging, now leading to a chaotic motion of the phoretic particle. Our results thus help us to understand the experimentally observed chaotic motion of catalytic particles in the high regime.

Original language English A10 Journal of fluid mechanics 919 https://doi.org/10.1017/jfm.2021.370 Published - 25 May 2021

## Keywords

• UT-Hybrid-D
• propulsion
• active matter

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