Recent progress in optimal design of superhydrophobic surfaces

Superhydrophobic surfaces have received tremendous attention due to their extraordinary physical characteristics and potential applications in various fields. However, the design of robust superhydrophobic surfaces showing both low adhesion and high antiwetting remains a great challenge. Here, we first introduce some important parameters for the characterization of the adhesion property of superhydrophobic surfaces and its physical meaning, including the apparent contact angle, rolling angle, and hysteresis angle. Then, we summarize the antiwetting property of superhydrophobic surfaces through thermodynamic and dynamic methods, and we point out the contradiction between low adhesion and high antiwetting of superhydrophobic surfaces. To achieve a trade-off between low adhesion and high antiwetting in superhydrophobic materials, we also review the recent progress made in regard to the optimal design of superhydrophobic surfaces by using chemical modification and physical design of microstructures. Finally, we review the application of superhydrophobic surfaces for drag reduction, with a few discussions and outlook. This Research Update is expected to provide useful guidance to rationally design superhydrophobic materials with low adhesion and high antiwetting properties and, thus, speed up the development of superhydrophobic materials or anti-icing materials.