Abstract

Devices that undergo reversible optical changes upon application of an electrical field can be based on a modification of the surface tension at liquidsolid or liquid-liquid interfaces, which causes a displacement of a liquid. The surface tension may be altered by either electrocapillarity or electrowetting.¹ In a three-phase system (solid, liquid electrolyte, and a second fluid, which may be liquid or gas), electrowetting is the change in surface tension due to a potential difference applied across the solid-electrolyte interface. Electrocapillarity is the change in surface tension at a liquid electrolyte-liquid metal interface when a potential is applied across it. In both cases the change In surface tension Δγ _SL. at the (polarizable) electronic conductor-electrolyte Interface is given by the Lippman equation Δγ_SL = −qΔV, where q is the charge per unit area, and ΔV is the interfacial potential difference.

© 1981 Optical Society of America