The ability of a liquid to maintain contact with a solid surface is a property called wetting. It is determined by the balance between adhesive and cohesive forces resulting from intermolecular interactions. Adhesive forces cause the liquid to spread across a surface while cohesive forces cause the liquid to ball up and avoid contact. Water-repellant fabrics are an example of non-wetting materials because they minimize interactions between the surface and water droplets.
Electrowetting is a technique to modify the wetting properties of a surface using an external electric field. Dielectric arrays can be used to create microfluidic devices that allow for programatic control of droplet motion. Scientists have used these techniques to perform biological automation and are now exploring the possibility of water-based computer interfaces.
Learn More: https://doi.org/10.1145/3170427.3186607 (CHI 2018)