Non-Markovian active droplets*

Active droplets are a model system for the chemotactic dynamics of microbes. They propel themselves through solute-mediated interactions. Previously, we showed that the motion of small droplets (~30µm diameter) is akin to active rotational diffusion whose speed and persistence time can be tuned by changing the salt and surfactant concentrations, respectively (Izzet et al., arXiv:1908.00581, 2019). Here we show that the trajectories of larger droplets display complex non-Markovian behaviors, such as self-interacting dynamics, that require a more complicated model than rotational diffusion. These results indicate that our tunable swimmers are ideal candidates for the study of the departure from equilibrium to high levels of activity, on both the single-particle level and their collective behavior, including the motility-induced phase separation (MIPS).