Electric field induced deformation of hemispherical sessile droplets of ionic liquid

• Sessile droplets of an ionic liquid subjected to transverse electric fields.
• Liquid and surface treatment provide contact angles reproducibly close to 90°.
• Small electric field induced changes in droplet height studied, Δh(E), up to 5%.
• Capacitor plate gaps wider than 3 times the drop height do not influence Δh(E).
• Scaling law obeyed: Δh(E) ∝ [(Voltage × drop radius)/(gap between plates)]2.

Sessile droplets of an ionic liquid with contact angles close to 90° were subjected to an electric field E = V/w inside a capacitor with plate separation w and potential difference V. For small field induced deformations of the droplet shape the change in maximum droplet height, Δh = h(E) – h(0), was found to be virtually independent of the plate separation provided that w > 3h(0). In this regime a scaling law obtains Δh α E2r2, where r is the constant droplet radius, in agreement with the asymptotic predictions of Basaran and Scriven (J. Coll. Int. Sci. 140, 10, 1990).

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