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Abstract

Artificial model swimmers offer a platform to explore the physical principles enabling biological
complexity, for example, multigait motility: a strategy employed by many biomicroswimmers to explore
and react to changes in their environment. Here, we report bimodal motility in autophoretic droplet
swimmers, driven by characteristic interfacial flow patterns for each propulsive mode. We demonstrate
a dynamical transition from quasiballistic to bimodal chaotic propulsion by controlling the viscosity
of the environment. To elucidate the physical mechanism of this transition, we simultaneously visualize
hydrodynamic and chemical fields and interpret these observations by quantitative comparison to
established advection-diffusion models. We show that, with increasing viscosity, higher hydrodynamic
modes become excitable and the droplet recurrently switches between two dominant modes due to
interactions with the self-generated chemical gradients. This type of self-interaction promotes self-avoiding
walks mimicking examples of efficient spatial exploration strategies observed in nature.