Deflection of sliding droplets by dielectrophoresis force on a superhydrophobic surface

Abstract

In this study, we experimentally identify the effect of liquid dielectrophoresis (LDEP) force on a superhydrophobic surface in directing the trajectory of moving water droplets across designed interdigitated electrodes and show that this method is capable of rapidly selecting droplets at a high speed (200 mm/s). As the droplets traverse down the surface by the electric field, their deflection on the edge of these electrodes is achieved successively, allowing for the selective manipulation of discrete droplets. A series of experiments were conducted to validate the relationships among droplet deflections, applied electric fields, and dynamic contact angles. Our findings reveal that the principal driving force behind the droplet deflections is the LDEP force, which can provide instant manipulation of moving droplets rather than a variation in contact angles brought about by electrowetting. This study presents a proof-of-concept experiment utilizing LDEP for high-throughput droplet selection and also highlights the potential applications of this mechanism in high-speed digital microfluidics (DMF) and biological separation methodologies.