Vibration of a water droplet on a polymeric insulating material subjected to AC voltage stress

The behavior of a water droplet on a silicone rubber plate was observed with a high-speed camera under ac voltage application. It was confirmed that a water droplet vibrated and that a remarkable deformation from the original droplet form occurred at the mechanical resonance frequency. Vibration frequency of an uncharged water droplet was double the frequency of the applied voltage. On the contrary, in the case of an artificially charged droplet, vibration frequency was the same with that of the applied voltage. A macroscopic mechanical model was devised, to which the experimental data were well correlated. Flashover voltage via the water droplet was also measured. Lower flashover voltage was obtained at the mechanical resonance frequency.