Voltage build-up time responses of Kelvin's water droplet generator: Variations due to different geometric configurations

• Voltage build-up charging time responses were measured for Kelvin's water dropper.
• Charging performances were examined for different geometric configurations.
• Charging performances depended considerably on several geometric dimensions.
• Charging rate may be optimized by adjusting the relevant geometric dimensions.
• Results may be of importance to actuation methods used in droplet microfluidics.

Systematic measurements of the voltage build-up charging time responses were performed on a two-beaker Kelvin's water droplet electrostatic induction generator. Measurement results showed that the droplet generator charging rate depended considerably on variations in several different geometric configurations or dimensions of the water dropper. Higher voltages were achieved when the water flow rates were higher, when the induction rings were closer to the liquid outlets, and when larger rings were employed. Our measurement results were not only consistent with previous related measurements, but also qualitatively explainable using the lumped systems equivalent circuit theory as found in the literature.