Deciphering the mechanism of electrowetting on conductors with immiscible electrolytes

The effect of potential bias on the wettability of graphite using immiscible electrolyte solutions (ITIES) is investigated. The mechanism of the phenomenon is elucidated by decoupling the effects of the electrochemical processes, i.e., double layer charging/discharging, adsorption of ions and charge/ion transfer reactions occurring at the graphite|aqueous electrolyte, graphite|non-aqueous electrolyte and liquid|liquid interfaces, on the electrowetting response. The derived findings are interpreted in terms of potential-induced changes in the total free energy of the system. On this basis, a complete phenomenological model is presented for electrowetting directly on conductors using an ITIES that combines the established interfacial theories of the solid|liquid and liquid| liquid interfaces. Our work should complement the existing, relatively scarce literature in the area and contribute to the design of practical systems, such as low voltage optofluidic devices, that exploit the properties of the ITIES.