Controlling Liquid Spreading Using Microfabricated Undercut Edges

A purely topographical method for controlling liquid spreading by using easy-to-fabricate undercut edges is reported. By periodic repetition of such edges, it is shown that multiple droplets can be patterned in well-controlled shapes, and highly anisotropic wetting can also be achieved at a large scale. Apparent contact angles close to 180 degrees at the edge are shown, even for low surface tension liquids.