Slippery boundaries enhance trapping of catalytic micromotors

The locomotion of catalytic micromotors is strongly influenced by nearby boundaries, where hydrodynamic and chemical interactions collectively govern their dynamics. By incorporating hydrodynamic slip into the theoretical framework, we capture the effects of nearby surface wettability on the dynamics of a self-diffusiophoretic micromotor. The hydrodynamic slip alters the balance between phoretic propulsion and wall-induced resistance, resulting in distinct dynamical responses across the space of catalytic coverage and slip length ( l Subscript s l s $l_s$ ). The slip-induced downward attraction, combined with the reduced reorienting torque, disrupts the near-wall ‘cushioning effect’ in no-slip conditions, resulting in the enhanced trapping of micromotors near the boundary. For intermediate catalytic coverages, the micromotor undergoes a sharp transition from escaping trajectories to either wall-collision or stable sliding states. Further, the wall slip lowers the activity threshold required to achieve stable near-wall trapping, thereby expanding the parameter space for controlled transport. The slip-induced changes in hydrodynamic resistance and phoretic thrust result in a counterintuitive reduction in longitudinal velocity as slip increases. In addition, increasing l Subscript s l s $l_s$ systematically shifts the hovering height to larger wall–particle separations. The slip-controlled regimes identified here provide a compact design strategy for manipulating active matter near boundaries. By choosing substrate coating, microtopography and stimulus-responsive materials, one can steer, trap or release micromotors in microfluidic and biological environments without redesigning the swimmers themselves.