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.

Dust deposition on solar photovoltaic (PV) cell surface will significantly decrease the PV power efficiency, as the transmittance of the solar cells would be greatly decreased by the deposited dust particles. This paper aims to study the anti-dust performance of super-hydrophilic coatings for the solar PV cells with water spraying condition. The solar cell covering glass was treated to be super-hydrophilic and compared with the bare glass sample. It was found that many dust particles adhere and aggregate on the uncoated glass while the particles deposited on the super-hydrophilic glass surface are densely distributed. When the water spraying process was conducted, the dust deposition mass for the bare and the coated glass samples are both reduced obviously with the increase time of water spraying. In addtion, dust deposition mass is significantly reduced with the increase of deposition and spraying tilt angles. The self-cleaning efficiency of super-hydrophilic coating on dust deposition is 92% higher than the bare glass cases. The spectral transmittance of glass samples for all the coated cases are significantly higher than that for all the bare cases. The maximum transmittance improvement can reach 26.5% when the deposition tilt angle is 30° and the spraying tilt angle is 60°.

Large-scale solar photovoltaic (PV) power plants tend to be set in desert areas, which enjoy high irradiation and large spaces. However, due to frequent sandstorms, large amounts of contaminants and dirt are suspended in the air and deposited on photovoltaic modules, which greatly decreases the power efficiency and service life. To clean PV to improve efficiency, many methods were proposed. It was found that the application of the self-cleaning coating on PV modules can effectively reduce dust deposition and improve the efficiency of PV. This paper reviews the dust deposition mechanism on photovoltaic modules, classifies the very recent dust removal methods with a critical review, especially focusing on the mechanisms of super-hydrophobic and super-hydrophilic coatings, to serve as a reference for researchers and PV designers, and presents the current state of knowledge of the aspects mentioned above to promote sustainable improvement in PV efficiency. It was found that the behaviors of dust on photovoltaic modules are mainly deposition, rebound, and resuspension. Particles with a diameter of 1–100 μm are most easily deposited on photovoltaic modules. The use of self-cleaning coatings, especially super-hydrophobic coatings, is beneficial to the rebound and resuspension of particles. The research gaps and development prospects of self-cleaning coatings are also discussed in this paper.