Surface tension gradient invoked path selection

Abstract

Certain active particles execute continuous self-propelled motion at the air–water interface due to Marangoni forces. Here, we report motion of camphor and pentanol infused disks in an L-shaped two path and a Y-shaped three path channel. These channels are open to the sink. In both the cases, these channels have asymmetry in arm-lengths while the arm-widths are equal. The active disks are introduced in the decision region (center) of the channel from where they elect to move along a particular path towards the sink. We observe that these active disks show a preference for reaching the sink along the minimal (in length) path. The camphor disk prefers the minimal path 80% of the time in the two-path and 68% of the time in the three-path channels, while for the pentanol disk, the preference rates for the minimal path selection are 88% and 74%, respectively. Furthermore, we perform numerical analysis to validate the experimental observations.