Interfacial activity dynamics of confined active droplets

Active emulsions can spontaneously form self-propelled droplets or phoretic micropumps. However, it remains unclear how these active systems interact with their self-generated chemical fields, which lead to emergent chemodynamic phenomena and multistable interfacial flows. Here, we simultaneously measure the flow concentration fields using dual-channel fluorescence microscopy for micropumps, i.e. immobilised oil that dynamically solubilise in a supramicellar aqueous surfactant solution. With increasing droplet radius, observe (i) migration of vortices from posterior anterior, analogous transition pusher- puller-type swimmers, (ii) bistability between dipolar quadrupolar flows and, eventually, (iii) multipolar modes. We also investigate long-time dynamics. Together, our observations suggest local build-up products leads saturation surface, controls propulsion mechanism. These dynamics be explained by competing time scales slow micellar diffusion governing buildup faster molecular powering underlying transport Our results are directly relevant but shed light on activity other emulsion systems.