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

Abstract

M. (2020). Spontaneous polarization and locomotion of an active particle with surface-mobile enzymes. Physical Review Fluids, 5(12), [122001].

Interfacially-adsorbed particles enhance the self-propulsion of oil droplets in aqueous surfactant

“…In this regime, it has recently been predicted that droplets in a micellar solution (with bulk surfactant concentration above the ) can spontaneously selfpropel due to a Marangoni instability 18 , resulting from the nonlinear dependence of the advective interfacial flux of surfactant on the interfacial velocity and surfactant concentration. A similar selfpropulsion mechanism for a solid particle coated by enzymes that are mobilized by diffusiophoretic flows, generated by a concentration gradient in the product species of the enzymatic reaction, has also recently been proposed 20 . Indeed, the particle free (0 wt%) bromodecance droplets in Figure 3 do exhibit self-propulsion, which we believe is due to a Marangoni instability.…”

Interfacially-Adsorbed Particles Enhance the Self-Propulsion of Oil Droplets in Aqueous Surfactant

“…In this regime, it has recently been predicted that droplets in a micellar solution (with bulk surfactant concentration above the 𝐶𝐶 𝐶𝐶𝐶𝐶𝐶𝐶 ) can spontaneously selfpropel due to a Marangoni instability 18 , resulting from the nonlinear dependence of the advective interfacial flux of surfactant on the interfacial velocity and surfactant concentration. A similar selfpropulsion mechanism for a solid particle coated by enzymes that are mobilized by diffusiophoretic flows, generated by a concentration gradient in the product species of the enzymatic reaction, has also recently been proposed 20 .…”

Self-propulsion of chemically-active droplets

“…Individual models differ in their description of the solute's relaxation. In interfacial mechanisms, this relaxation originates in surface diffusion, degradation or desorption from the surface (Thutupalli et al 2011, Schmitt & Stark 2013, de Corato et al 2020. For bulk mechanisms, relaxation stems from a bulk degradation (Yoshinaga et al 2012) or diffusive / convective transport away from the particle (Izri et al 2014, Morozov & Michelin 2018, Picella & Michelin 2022.…”

“…By raising the local surface tension, this enhances the initial flow perturbation in a self-reinforcing mechanism at the origin of the spontaneous onset of propulsion (Figure2a). By effectively introducing a spatially-dependent activity directly driven by the surface flow divergence, this tightly-coupled hydro-chemical dynamics resembles the similar problem of surface-mobile enzymes(de Corato et al 2020). A simple hydro-chemical model of such mechanism writes for the reaction-advectiondiffusion dynamics of the relative surface concentration of pristine surfactant(Thutupalli et al 2011, Schmitt & Stark 2013 with the convecting surface flow obtained by solving Stokes' equations inside and outside the droplet in linear response to the Marangoni forcing(Morozov & Michelin 2019a, Schmitt & Stark 2013.…”