Digital microfluidics on a wire

In this letter, we discuss the behavior of droplets on fiber networks. An on/off transition is observed when a droplet comes around an intersection between several fibers: large droplets cross the junction while small droplets remain pinned. We show that fibers perform advantageously most operations of digital microfluidics, such as multiplexed biochemical microreactions: intersections are the basic component of fiber-based microfluidic devices.