Superhydrophobicity-memory surfaces prepared by a femtosecond laser

Abstract

Superhydrophobicity-memory surface that can transform its surface morphology and wettability in response to heat was successfully prepared by using femtosecond laser to directly induce hierarchical micropillar array on the surface of a thermal-responsive shape-memory polymer (SMP). When the resultant surface was pressed by an external load to make the micropillars lean to one side, the superhydrophobicity would weaken caused by the deformation of the micro/nanoscale structures. Interestingly, the original surface morphology and wettability could recover just through a simple heating process due to the excellent macro/microscopic shape-memory effect of such polymer. Even after 10 cycles of pressing-heating treatments, the surface was also able to re-obtain its original ultralow-adhesive superhydrophobicity. In addition to the restorable property, the superhydrophobicity of the as-prepared surface was very stable since the laser-induced microstructure on the SMP could withstand various harsh treatments/environments, such as sandpaper abrasion, tape peeling, UV irradiation, and the immersion in different pH solutions. The superhydrophobicity-memory surface was successfully used as a rewritable platform for directional liquid transportation. It is anticipated that the laser-induced hierarchical micropillars with superhydrophobicity-memory property will have significant applications in tunable wettability, liquid/droplet manipulation, and chemical engineering.