Enhanced superhydrophobic robustness of black silicon employing nanojungle structures

Superhydrophobic surfaces are essential in various industries such as textiles, aviation, electronics and biomedical devices due to their exceptional water-repellent properties. Black silicon (b-Si) would be an ideal candidate for some applications due to its nanoscale topography made with a convenient lithography-free step and complementary metal-oxide-semiconductor (CMOS) compatible fabrication process. However, its use is hindered by serious issues with mechanical robustness. This study presents 'nanojungle b-Si', characterized by elongated and deep nanostructures and fabricated through photoresist micromasks associating with Bosch etching. These nanojungle structures exhibit enhanced robustness and sustain superhydrophobicity under abrasive conditions, outperforming traditional 'nanograss b-Si'. Optical analysis indicates that the nanojungle structures dissipate abrasive impact energy more effectively, preserving surface roughness and hydrophobicity. Notably, nanojungle b-Si maintains its superhydrophobicity even after impinging by 20 g of sand impacting from a height of 40 cm. This advancement in b-Si surfaces holds significant potential for enhancing future technological applications.