A review of droplet bouncing behaviors on superhydrophobic surfaces: Theory, methods, and applications

The phenomenon of droplet bouncing on superhydrophobic surfaces has received extensive attention in the academic and industrial fields, as it is critical for various engineering applications, such as anti-icing, spray cooling, and metal quenching. In this review, the research of droplet bouncing behaviors is comprehensively introduced from the bouncing mechanism, research methods, and potential applications. The bouncing mechanism is related to three aspects: droplet properties, surface characteristics, and ambient conditions. Among them, droplet size, impact velocity, gas film, surface morphology, surface temperature, and applied electric field are frequently concerned. Surface wettability is critical for droplet bouncing behaviors, which affects the droplet movement on the surface. Momentum and mass distribution are essential to reduce contact time, which can be achieved through the surface morphology design. The manipulation of solid-liquid contact lines and surface tension can achieve directional droplet transportation. In addition, typical droplet bouncing experiments are presented, and experimental studies of single and successive droplets in recent decades are collated. Volume of fluid, the lattice Boltzmann method, and molecular dynamics are described, which are typical simulation methods for droplet bouncing dynamics at different scales. Potential engineering applications such as surface self-cleaning, digital microfluidics, and enhanced heat transfer have been developed through theoretical foundations and research methods. Finally, the conclusions and the possible future research directions are outlined. The durability of superhydrophobic surfaces becomes a bottleneck for engineering applications. The life cycle research perspective may be applied to future studies.