title: Additive-free digital microfluidics.
abstract: Digital microfluidics, a technique for manipulation of droplets, is becoming increasingly important for the development of miniaturized platforms for laboratory processes. Despite the enthusiasm, droplet motion is frequently hindered by the desorption of proteins or other analytes to surfaces. Current approaches to minimize this unwanted surface fouling involve the addition of extra species to the droplet or its surroundings, which might be problematic depending on the droplet content. Here, a new strategy is introduced to move droplets containing cells and other analytes on solid substrates, without extra moieties; in particular, droplets with bovine serum albumin could be moved at a concentration 2000 times higher than previously reported (without additives). This capability is achieved by using a soot-based superamphiphobic surface combined with a new device geometry, which favors droplet rolling. Contrasting with electrowetting, wetting forces are not required for droplet motion.
authors.affiliation: Department of Mathematics, Physics and Statistics, University of the Sciences, Philadelphia, Pennsylvania 19104, United States. s.freire@usciences.edu
authors.forename: Sergio L S
authors.initials: SL
authors.lastname: Freire
authors.forename: Brendan
authors.initials: B
authors.lastname: Tanner