Active matter consumes local fuel to self-propel; when confined in a closed boundary, they self-organize into a coherent motion such as circulation or a river-like flow. These phenomena originate from the interactions between the active matter and boundaries. Boundaries contain two characteristics: Shape and Surface property i.e. solid or fluidic. Herein, we investigated how fluidic boundaries influenced the self-organization of confined active fluid differently from solid boundaries. To create the fluidic boundary, we confined the active fluid in a water-in-oil droplet, enabling the fluid to interact with the fluidic water-oil interface.
We found that the active fluid in the droplet developed circulatory flows; however, the criterium for the flow formation differed from in solid boundaries of similar shapes. Simultaneously, we found that intra-droplet circulatory flows depended on the parameter outside the droplet: the thickness of the oil layer surrounding the oil-immersed droplet. This result was only possible in the system of fluidic boundaries, demonstrating the unique influence of fluidic boundaries along with the need for understanding their dynamic role on active fluid behaviors. Finally, we developed a millifluidic device to deform the droplet manually to trigger or suppress the formation of the intra-droplet circulatory flow in real time.
Refreshments will be served in Olin Hall 118 at 3:30 P.M.