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).

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide