Active spheres induce Marangoni flows that drive collective dynamics

Abstract

For monolayers of chemically active particles at a fluid interface, collective dynamics are predicted to arise owing to activity-induced Marangoni flow even if the particles are not self-propelled. Here we test this prediction by employing a monolayer of spherically symmetric active TiO_2 particles located at an oil-water interface with or without addition of a non-ionic surfactant. Due to the spherical symmetry, an individual particle does not self-propel. However, the gradients produced by the photochemical fuel degradation give rise to long-ranged Marangoni flows. For the case in which surfactant is added to the system, we indeed observe the emergence of collective motion, with dynamics dependent on the particle coverage of the monolayer. The experimental observations are discussed within the framework of a simple theoretical mean field model.

12 pages, to be published in EPJ-E

References in corpus (10)

• The hydrodynamics of swimming microorganisms
• Physics of Microswimmers - Single Particle Motion and Collective Behavior
• Propulsion of a molecular machine by asymmetric distribution of reaction--products
• Phoretic self-propulsion at finite Péclet numbers
• Viscous Marangoni propulsion
• Microscale Marangoni Surfers
• Thermally driven Marangoni surfers
• Self-diffusiophoresis induced by fluid interfaces
• Stability of liquid films covered by a carpet of self-propelled surfactant particles
• Self-motility of an active particle induced by correlations in the surrounding solution