Topological liquid diode

The last two decades have witnessed an explosion of interest in the field of droplet-based microfluidics for their multifarious applications. Despite rapid innovations in strategies to generate small-scale liquid transport on such devices, the speed of motion is usually slow, the transport distance is limited, and the flow direction is not well controlled because of unwanted pinning of contact lines by defects on the surface. Here we report a new method of microscopic liquid transportation based on a unique topological structure that breaks the contact line pinning through efficient conversion of excess surface energy to kinetic energy at the advancing edge of the droplet whilst simultaneously arresting the reverse motion of the droplet via strong pinning. What results is a novel topological fluid diode that allows for a rapid, directional, and long-distance transport of virtually any kind of liquid without the need for an external energy input.