A Superhydrophilic Silicon Surface Enhanced by Multiscale Hierarchical Structures Fabricated by Laser Direct Writing.

Many biological surfaces with hierarchical structures exhibit super wetting properties, but a multiscale hierarchical metal surface with superhydrophilic performance is difficult to be fabricated using a simple method. In this work, we report a large area micro/nanotextured superhydrophilic silicon surface fabricated by a laser direct writing technique. The combination of a microscale column structure and randomization-distributed nano-bumps decorated on the column enhances the superhydrophilic properties, with the contact angle reduced substantially from about 46° to 0°, where the droplets are able to spread rapidly within 591 ms. The water wetting orientation can be regulated by controlling the shape of microcolumns on the surface. Moreover, our results show that the fabricated surface with the hierarchical structure has better droplet shape control performance and higher fog collection efficiency compared to a smooth surface. These surfaces have potential applications in heat exchangers, biosensors, cell adhesives, and self-cleaning solar cells.