Collision between chemically-driven self-propelled drops

Abstract

We consider analytically and numerically head-on collision between two self-propelled drops. Each drop is driven by chemical reactions that produce or consume the concentration isotropically. The isotropic distribution of the concentration field is destabilized by motion of the drop which is itself made by Marangoni flow from concentration-dependent surface tension. This symmetry-breaking self-propulsion is distinct from other self-propulsion mechanisms due to the intrinsic polarity such as squirmers and self-phoretic motion; there is a bifurcation point below which the drop is stationary and above which it moves spontaneously. When two drops moving along the same axis with opposite direction, the interactions arise both from hydrodynamics and concentration overlap. We found that two drops exhibit either elastic collision or fusion depending on the distance from the bifurcation point controlled, for instance, by viscosity. The elastic collision results from the balance between dissipation and energy injection by chemical reactions. We derive the reduced equations for the collision between two drops and analyze the contributions from the two interactions. The concentration-mediated interaction is found to dominate the hydrodynamic interaction.

28 pages, 11 figures

References in corpus (6)

• The hydrodynamics of swimming microorganisms
• Self-motile colloidal particles: from directed propulsion to random walk
• Motility-Induced Phase Separation
• Hydrodynamics of self-propulsion near a boundary: predictions and accuracy of far-field approximations
• Self-propulsion of pure water droplets by spontaneous Marangoni stress driven motion
• Thermocapillary motion

Cited by in corpus (10)

• Self-propulsion of chemically-active droplets
• Phoretic Interactions Between Active Droplets
• Self-propulsion near the onset of Marangoni instability of deformable active droplets
• Emergent Structures in an Active Polar Fluid : dynamics of shape, scattering and merger
• Collisions and rebounds of chemically-active droplets
• Bouncing, chasing or pausing: asymmetric collisions of active droplets
• Alignment and scattering of colliding active droplets
• Lattice Boltzmann study of chemically-driven self-propelled droplets
• Self-propulsion of an active polar drop
• Modeling of chemically active particles at an air-liquid interface