Marangoni self-propelled capsules in a maze: pollutants 'sense and act' in complex channel environments

Environmental remediation is a highly pressing issue in society. Here we demonstrate that autonomous self-propelled millimeter sized capsules can sense the presence of pollutants, mark sites for visible identification and remove the contamination, while navigating in a complex environment of interconnected channels, the maze. Such long-range self-powered capsules propelled by the Marangoni effect are capable of releasing chemicals to alter the pH and induce aggregation during pollutant flocculation at a faster rate than convection or diffusion. These devices are foreseen to have real-world environmental applications in the near future.