A femtosecond laser-induced superhygrophobic surface: beyond superhydrophobicity and repelling various complex liquids

Surfaces that can strongly repel various complex liquids, not just pure water, are highly desirable and the fabrication of such surfaces still remains a huge challenge because the liquids one wants to repel usually have a complex chemical composition, viscosity, and concentration. Here, a superhygrophobic surface microstructure was created on a polytetrafluoroethylene (PTFE) surface by femtosecond laser treatment. The laser-ablated surface was composed of a micro/nanoscale hierarchical structure and micropores with a certain degree of re-entrant curvature. After femtosecond laser ablation, the sample surface is directly endowed with superhygrophobicity and has great ability to repel various pure and complex liquids, such as water, 10 000 ppm bovine serum albumin, cola, 10 000 ppm glucose, juice, and saline. It is because the combined effect of the ultralow surface energy of the PTFE material, the laser-induced hierarchical rough microstructure, and the partly re-entrant surface curvature of the porous structure allows the complex liquid droplets to be at the robust Cassie state on the laser-induced surface microstructure. Such superhygrophobic surfaces can be potentially applied in cell engineering, medical instruments, food packaging, microfluidics technology, chemical engineering, and so on.