Interfacial aggregation of self-propelled Janus colloids in sessile droplets

Many living microorganisms experience an affinity to populate boundaries. The reasons for such affinity can be complex. Here we show that a simple synthetic microswimmer (Janus catalytic colloidal particles) tends to accumulate in the vicinity of liquid interfaces in sessile droplets. We show that the main mechanism is related to their active swimming motion, which is dominating even in the presence of evaporation-driven flows within the sessile droplet.