Toward application of hierarchical structures by ultrashort pulsed laser ablation

Abstract

Surface structuring is a versatile tool to modify the physical interplay at the interface to gaseous or liquid media. The two industrial used approaches are, in general, a chemical modification via coating or/and an introduced topography. Here, the structuring is carried out with a direct technique using an ultrashort pulsed laser with infrared and green wavelengths. Two hierarchical structural units are generated at the surface on copper, aluminum, and an amorphous alloy. Structures in the micrometer regime are produced via 2.5D layered laser ablation. Laser induced periodic surface structures (LIPSSs), an inherent phenomenon of self-generated periodic features, can be utilized to generate subdiffraction limit features. LIPSSs are demonstrated in the high spatial frequency regime with a periodicity of 320 and 600 nm for green and infrared radiations, accordingly. This work concerns the use of direct laser structuring for potential applications. Specifically, a change in the optical and wetting properties is addressed. Broadband absorbing behavior and static contact angles of up to 152° are reported. Laser ablation processes and experimental routines are presented to upscale the structuring process. Production rates up to 100 mm2/h for 2.5D ablation and 0.6 m2/h for LIPSSs can be reached.