Wide-range single droplet generator using electrostatic manipulation by corona discharge

This study introduces a novel method for generating droplets of varying sizes using corona discharge with needle-plate electrodes. By precisely adjusting the needle tip position and applied electric field, the forces acting on the droplets can be modulated, enabling the production of droplets across a broad size range. Large droplets form on a superhydrophobic surface and slide down an inclined plane under the influence of gravity once they reach a critical volume. In contrast, small droplets are predominantly influenced by the electric field, with their detachment from the syringe needle governed by the droplet's charge and the electric field's strength. Droplet sizes, ranging from 0.08 to 108 μl, can be precisely controlled by tuning parameters such as needle tip position, applied voltage, and surface inclination angle. Furthermore, effective droplet sorting is demonstrated by exploiting differences in the rolling speed and trajectory on the inclined plane, determined by the applied voltage. This approach provides a versatile and precise platform for droplet manipulation with potential applications in microfluidics, material delivery, and related fields.