Elektrowetting

Elektrowetting, also known as electrowetting on dielectric (EWOD), is a phenomenon where the wetting properties of a liquid on a solid surface are modified by the application of an electric potential. Typically, a droplet of liquid is placed on a dielectric layer that covers a conductive electrode. When a voltage is applied between the liquid and the electrode, the surface tension at the liquid-solid interface changes, leading to a decrease in the contact angle of the droplet. This means the liquid spreads out more on the surface.

The fundamental principle behind elektrowetting involves the formation of an electrical double layer at the interface between the liquid and the dielectric. The applied electric field polarizes the liquid and induces charges in the electrode. This charge separation at the interface reduces the interfacial energy, which in turn alters the equilibrium contact angle according to the Lippmann-Young equation. The magnitude of the contact angle change is dependent on the applied voltage, the dielectric constant and thickness of the insulating layer, and the dielectric properties of the liquid.

Elektrowetting has a wide range of potential applications. It can be used to precisely manipulate and move liquid droplets, making it suitable for microfluidic devices, lab-on-a-chip systems, and digital microfluidics. Other applications include adaptive optics for adjusting lens shapes, variable-focus lenses, and creating dynamic wetting surfaces. The ability to control liquid behavior with electrical signals offers advantages in terms of speed, reversibility, and minimal energy consumption.