Anomalous Dependence on Fuel Concentration for the Dynamics of Catalytic Microswimmers near Obstacles

Efficient exploration of space is a paramount motive for active colloids in practical applications. On the other hand, introducing activity may lead to surface-bound states, posing an impediment to efficient spatial exploration. Here, we study how the interplay between self-propulsion and fuel-dependent affinity for surfaces affects the efficiency of a catalytically-active microswimmer for exploration of an interface decorated with obstacles. In a regime of constant propulsion velocity as a function of fuel concentration, we find that microswimmer-obstacle interactions strongly depend on fuel concentration, leading to a counter-intuitive decrease in exploration efficiency with an increase in available fuel. Additionally, under some conditions, the affinity of a swimmer for obstacles can change significantly over time. Using experiments and theoretical predictions, we show that these largely overlooked phenomena are most likely the result of a change in the surface properties of the microswimmer's catalytic face when exposed to H2O2. Our findings provide far-reaching insights regarding the interpretation of experimental studies of active colloids, as well as new means of controlling their dynamics in complex environments