Local curvature directs active particles in confinement.

The impact of confinement on the self-organization of active particles has gained much attention. Studying confinement in arbitrary curved geometry is essential to explore realistic scenarios, like particles enclosed in a membrane, and understand the role of curvature. For this purpose, we conducted simulations (in Julia) on active Brownian particles subjected to hard elliptical confinement. Our study reveals a curvature-dependent organization of the particles, wherein particles accumulate at high curvature regions. The degree of curvature-induced collection is sensitive to confinement size, packing fraction, and particles’ size and velocity. Moreover, the number of particles in the high curvature region shows an oscillatory nature. Beyond simulations, we seek experimental evidence of this aggregation based on active Janus particles (Pt/silica) enclosed in micro-wells. We have implemented a novel drop cast method allowing sub-millimeter circular and elliptical wells with smooth walls. The resulting microstructures confine the Janus microparticles, enabling observation of simulation-matching conditions. We anticipate our results might apply to the design of active particles-based microrobots, where environment-induced curvature of the membrane boundary could guide encapsulated active particles.