Multifunctional Superhydrophobic Platform for Control of Water Microdroplets by Non-Uniform Electrostatic Field

At the moment, manipulation of liquid microdroplets is required in various microfluidic and lab-on-a-chip devices, as well as advanced sensors. The platforms used for these purposes should provide the possibility of controlled selective movement and coalesce of droplets, also the manipulation speed should be sufficiently high (more than 10 mm/s). In addition, to facilitate their practical application, such platforms should have a simple planar geometry and low manufacturing cost. We report here a new method for microdroplets manipulation, based on the use non-uniform electrostatic fields. Our platform uses an electrode array embedded in a dielectric planar superhydrophobic substrate (50x50 mm). When a voltage is applied to a certain sequence of electrodes, a non-uniform electrostatic field is produced, which acts to attract a droplet on the substrate to the electrodes. This achieves a stepwise movement of the droplet. We realized non-contact, selective and high speed (up to 80 mm/s) movement of the individual droplets along specified trajectories (like a chess game) and their selective coalescence. It allowed us to demonstrate several controllable chemical reactions including an analytical one. In our opinion, this approach has a huge potential for chemical technology applications especially in advanced sensors.