Spontaneous onset of convection in a uniform phoretic channel

Abstract

Phoretic mechanisms, whereby gradients of chemical solutes induce surface-driven flows, have recently been used to generate directed propulsion of patterned colloidal particles. When the chemical solutes diffuse slowly, an instability further provides active but isotropic particles with a route to self-propulsion by spontaneously breaking the symmetry of the solute distribution. Here we show theoretically that, in a mechanism analogous to Bénard-Marangoni convection, phoretic phenomena can create spontaneous and self-sustained wall-driven mixing flows within a straight, chemicallyuniform active channel. Such spontaneous flows do not result in any net pumping for a uniform channel but greatly modify the distribution of transport of the chemical solute. The instability is predicted to occur for a solute Péclet number above a critical value and for a band of finite perturbation wavenumbers. We solve the perturbation problem analytically to characterize the instability, and use both steady and unsteady numerical computations of the full nonlinear transport problem to capture the long-time coupled dynamics of the solute and flow within the channel. * Electronic address: sebastien.michelin@ladhyx.polytechnique.fr arXiv:1912.07667v1 [physics.flu-dyn]

Instabilities driven by diffusiophoretic flow on catalytic surfaces

“…As a final remark, Michelin et al. (2020) have shown the diffusiophoretic instability in a confined phoretic channel, from which they also observe the generation of the plumes. Note that Michelin et al.…”

“…Note that Michelin et al. (2020) have also considered the nonlinear terms in the advection–diffusion equation, however, for the momentum equation, they consider the case of Stokes flow, such that the nonlinear terms and effects of Schmidt number have not been considered. The chaotic plume emission observed in regime IV is the unique feature for high Péclet numbers, which, however, has not been focused on in most of the previous studies.…”

“…Very recently, Michelin et al. (2020) investigated a simplified system, namely a uniform phoretic channel. They reported spontaneous symmetry-breaking of the solute distribution which provides a route to understanding the propulsion of isotropic active particles.…”

Marangoni instability triggered by selective evaporation of a binary liquid inside a Hele-Shaw cell

“…Moreover, the very common use of microfluidic devices in research nowadays makes it important to understand the influence that the confinement has on the Marangoni convection. Indeed, Marangoni flow in microfluidic devices can be used to enhance mixing (Michelin et al 2020).…”

Spontaneous polarization and locomotion of an active particle with surface-mobile enzymes

“…1. The mechanism studied here bears some similarity to the spontaneous symmetry-breaking instability observed for isotropic catalytic particles, which is driven by the advection of the reaction product [28][29][30][31][32][33]. However, here it is the advection along the surface of the enzymes that catalyze the reaction which leads to the spontaneous symmetry-breaking instability.…”