Active Particle Accumulation at Boundaries: A Strategy to Measure Contact Angles

Abstract Wetting properties of a substrate are mostly evaluated through the contact angle of droplets on these substrates, a method that works perfectly for a broad range of cases. However, in specific cases it might be difficult to macroscopically measure the contact angle and our experiments show that the behavior of active colloids when approaching edges of liquid–solid interfaces can provide additional information. Here, we present experimental evidence and a simple, geometric model to capture this behavior.