Dynamical behaviors of water drop impact on superhydrophobic surfaces with the macro-textured cavity

Drop impact on superhydrophobic surfaces (SHSs) is of significant importance to many engineering applications. Drop impact dynamics on micro-nano structured SHSs has been widely investigated, however, that on macro-textured SHSs is still lacking, especially the macro-textured cavities. In this work, water drops impact on rigid SHSs with or without cavities were experimentally investigated through a high-speed camera. We number (We =rho du(2)/sigma) is chosen to quantify the drop impact intensity. Compared to plane SHSs, the cavity with different geometries reduces both the maximum spreading diameter and the contact time, and leads to complex drop deformation with two times expanding process under higher We numbers. The maximum spreading ratios increase with We numbers and are scaled by a power-law with exponents of 0.20 for plane SHSs and 0.17 for cavity-textured SHSs. The dimensionless contact time on plane SHSs remains constant about 0.88, while that on the cavity-textured SHSs is about 0.82. Drop impact on SHSs with macro-textured cavities exhibits different behaviors, which anticipates to throw an insight into the applications of self-cleaning, anti-icing and so on.