Mode switching of active droplets in macromolecular solutions

visualization of the self-generated chemical field around the droplet, we notice unexpectedly high diffusivity of the filled micelles in the presence of high molecular weight polymeric solutes. This highlights the breakdown of continuum approximation due to a significant size difference between the macromolecular solutes and the micelles. It is shown that the Péclet number, defined based on the experimentally determined filled micelle diffusivity (taking into account the local solvent viscosity) successfully captures the transition from smooth to jittery propulsion mode for both molecular and macromolecular solutes. With an increase in macromolecular solute concentration, particle image velocimetry reveals another mode switching from the conventional pusher mode to puller mode of propulsion, characterized by a more persistent droplet motion. By doping the ambient medium with suitable choice of macromolecules, our experiments unveil a novel route to orchestrate complex transitions in active droplet propulsion.