Tuning the random walk of active colloids

Abstract: Active particles such as swimming bacteria or self-propelled colloids are known to spontaneously organize into fascinating large-scale dynamic structures. The emergence of these collective states from the motility pattern of the individual particles, typically a random walk, is yet to be probed in a well-defined synthetic system. Here, we report the experimental realization of intermittent colloidal motion that reproduces the run-and-tumble and Levy trajectories common to many swimming and swarming bacteria. Our strategy enables to tailor the sequence of repeated "runs" (nearly constant-speed straight-line translation) and "tumbles" (seemingly erratic turn) to emulate any random walk. This new paradigm for active locomotion at the microscale opens new opportunities for experimental explorations of the collective dynamics emerging in active suspensions. We find that population of these random walkers exhibit behaviors reminiscent of bacterial suspensions such as dynamic clusters and mesoscale turbulent-like flows.