The wetting of a liquid droplet on a solid substrate is a fundamental phenomenon in both nature and technology. It has a wide range of applications in scientific and industrial fields, such as microfluidic mixing, painting, coating, droplet transport, and liquid displacement events. Understanding the interaction between a droplet and a solid surface in the presence of an external field is essential for effective droplet manipulation and control. In this review, we summarize recent progress in wetting and spreading phenomena under an externally applied electric field from both theoretical and experimental aspects. First, we provide an overview of the theoretical background for droplets on flat surfaces, including the basic principles of wetting and electrowetting-on-dielectric (EWOD). Next, we present the latest research advances on droplet wetting behaviors on topographically structured surfaces, followed by a discussion of the current research status of liquid-liquid displacement phenomena driven by capillary. Finally, we outline future trends and challenges.
Xiao et al. (Wed,) studied this question.