Stochastic migrations of Marangoni surfers between two lobes of a dumbbell-shaped confinement

Abstract

We report an experimental investigation on the stochastic migration dynamics of Marangoni surfers (camphor-infused paper disks) between the two lobes of a dumbbell-shaped chamber. We characterize the migration dynamics using survival analysis for a given configuration with a unique disk count in each lobe. Qualitatively, all the configurations exhibit stretched exponential decay with time, ascribed to a disk s aging. A given configuration s stability decreases with increasing pairwise interactions. The most stable configuration is always the one with equal partitioning of disks between the lobes, i.e., exactly one-half of disks in each lobe for even-numbered systems but with one extra disk in either of the lobes for odd-numbered systems. Furthermore, we model a camphor disk as a Chiral Active Particle (CAP), as initially proposed by Cruz et al. and show that decreasing motility (or aging) indeed causes the stretched exponential behavior.