Equilibrium droplet shape and transient dynamics during (di)electrowetting and dewetting on dielectric are electric field–dependent. We present a lubrication model incorporating the Young–Lippmann law that accurately predicts the equilibrium droplet shape and its transient dynamics. The droplet contact line position $x_{cl}$ follows a field-dependent power law $x_{cl}\propto t^n$, where the magnitude of $n$ increases with the applied electric field. When the field strength equals the critical value required for complete wetting, the electrospreading dynamics reduce to the classical Tanner's law ($n=1/7$), in agreement with past experiments. The magnitude of $n$ for electrodewetting is shown to be greater compared with wetting, attributed to a lesser viscous dissipation in the former case. Despite a difference in the power-law exponent $n$, the transient dynamics for both (di)electrowetting and electrodewetting are shown to follow the Cox–Voinov law. These observations qualitatively extend beyond the lubrication regime to large contact-angle droplets as well, as confirmed using Navier–Stokes simulations.

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• Contact line dynamics
• Drop & bubble phenomena
• Electrohydrodynamic effects
• Laminar flows
• Lubrication theory
• Thin fluid films
• Wetting
• Microfluidics
• Stokes equations