Dielectrowetting

Dielectrowetting is a wettability control phenomenon in which an applied electric field across a dielectric layer alters the contact angle of a liquid on a solid substrate. The effect arises from dielectric polarization of the liquid and the substrate, which generates Maxwell stresses at the solid–liquid interface. These stresses modify the interfacial tensions and can cause the droplet to spread, move, or change shape without the need for direct electrical contact with the liquid.

Typically, dielectrowetting uses alternating current fields to minimize electrochemical reactions at electrodes and to enable actuation of insulating or nonconductive liquids. An electrode array beneath an insulating coating applies a controlled AC voltage, and the resulting field induces polarization and interfacial stress that adjust the apparent wettability. The phenomenon can enable controlled droplet spreading, transport, splitting, and merging on a microfabricated surface.

Applications of dielectrowetting are concentrated in digital microfluidics and lab-on-a-chip systems, where precise, low-power droplet manipulation is valuable. It is particularly advantageous for handling nonconductive fluids such as oils or silicone-based liquids, and for operations where avoiding charge transfer to the liquid is beneficial. The approach supports programmable routing of droplets along predefined paths, enabling tasks such as mixing, dilution, and reagent addition.

Advantages include compatibility with insulating liquids, potential for low-voltage operation when designed properly, and reduced electrode degradation through high-frequency actuation. Limitations involve dependence on the dielectric properties of the materials, possible heating from dielectric losses, contact angle hysteresis, and fabrication complexity of insulating layers.

See also: electrowetting on dielectrics, electrowetting, dielectrophoresis, microfluidics.