Control of sliding droplet movement through electrowetting on dielectrics

Through the electrowetting on dielectric effect, we attempted to control the movement of a droplet sliding on an inclined plate owing to gravity. The electrode boundary of the substrate was deflected from the in-plane gravitational direction, and the behavior of a droplet sliding on the substrate was investigated. The maximum volume that could slide along the electrode boundary was obtained theoretically from the force balance between the surface tension acting on the contact line and the gravitational force. The calculated results were in good agreement with the experimental results. For the substrate manufactured in this experiment, a maximum deflection angle of 55° was obtained for a 28 μL droplet. We created a device to sort the volume of droplets from different sliding paths depending on each volume. By installing electrode boundaries with different inclinations on the substrate, it was confirmed that the droplets actually slid in different paths and were classified in a predetermined position according to their volumes.