Pair Interaction of Catalytically Active Colloids: From Assembly to Escape

摘要: The dynamics and pair trajectory of two self-propelled colloids are reported. autonomous motions the due to a catalytic chemical reaction taking place asymmetrically on their surfaces that generates concentration gradient interactive solutes around particles actuate particle propulsion. We consider spherical with symmetric caps extending over local polar angles $\theta^1_{cap}$ $\theta^2_{cap}$ from centers active sectors in an otherwise quiescent fluid. A combined analytical-numerical technique was developed solve coupled mass transfer equation hydrodynamics Stokes flow regime. ensuing is controlled by reacting coverages $\theta^j_{cap}$ initial relative orientation respect each other. Our analysis indicates possible scenarios for trajectories particles: either approach, come into contact assemble or they interact move away other (escape). For arbitrary colloids, it found direction rotations key factor determining escape assembly scenario. Based analysis, phase diagram sketched catalytically as function orientations. believe this study has important implications elucidation collective behaviors auotophoretically colloids.