Climbing droplets driven by mechanowetting

This paper reports a novel technique for droplet transportation using dynamic surface topography. Droplet based microfluidics technology has been increasingly applied in studying cell biology, improving drug delivery and performing chemical and biological analysis on chip in the past decade. A large part of the technology is based on electrowetting, in which droplets placed on a surfaced patterned with electrodes can be transported, merged, mixed and split by selectively activating those electrodes [1]. The manipulation of droplets using electrowetting has been proven to be very effective, however, this technology imposes limitations on the type of fluids, and the electrical field applied to move the droplets can have unwanted effects on substances contained in the drops. Here, we report a new concept to transport droplets with dynamic surface topography undulations, i.e. a surface travelling wave, using a phenomenon called mechanowetting. We analyzed the effect in detail with both experiments and numerical simulations.