Comparison of structures and hydrophobicity of femtosecond and nanosecond laser-etched surfaces on silicon

The rough micro- and nano- scale hierarchical structures on surfaces of materials render the surfaces superhydrophobic. In this context, we obtain both microscale grating structures and nanoscale induced structures (with some splashes) on silicon-based surfaces by means of laser etching and inducing. Our research focuses on the differences of morphology and hydrophobicity for silicon-based microstructured surfaces fabricated by femtosecond laser and nanosecond laser. The results indicated that the grating microstructures fabricated by femtosecond laser are smoother and with smaller top width of groove. Moreover, better micro-nanoscale hierarchical structures can be obtained by femtosecond laser overlapped etching for many times. On the surface with such structures, the water droplet is at Cassie-Baxter state and the contact angle (CA) is 144.6°, which indicates that the surface is middle hydrophobic. This work may provide an effective approach for fabrication of self-cleaning functional surfaces and devices.

► Gratings with induced structures on silicon surfaces were etched by fs and ns laser. ► The fs laser etched structures are smoother and with smaller top widths of grooves. ► Etching by fs laser can result in better micro-nanoscale hierarchical structures. ► The hierarchical structures contribute a lot to the enhancement of hydrophobicity. ► This work provides a basis for fabricating silicon-based superhydrophobic surfaces.