Mimicking lizard-like surface structures upon ultrashort laser pulse irradiation of inorganic materials

Highlights: • Two laser processing strategies were evaluated to process hierarchical nano- and microstructures on carbon alloyed steel surfaces. • Self-assembled ripples, grooves and spikes were generated by fs-laser irradiation. • Capillary channels with micro-dimple patterns were fabricated by ps-laser irradiation. • Lizard-like fluid transport properties can be realized by laser processing. - Abstract: Inorganic materials, such as steel, were functionalized by ultrashort laser pulse irradiation (fs- to ps-range) to modify the surface's wetting behavior. The laser processing was performed by scanning the laser beam across the surface of initially polished flat sample material. A systematic experimental study of the laser processing parameters (peak fluence, scan velocity, line overlap) allowed the identification of different regimes associated with characteristic surface morphologies (laser-induced periodic surface structures, grooves, spikes, etc.). Analyses of the surface using optical as well as scanning electron microscopy revealed morphologies providing the optimum similarity to the natural skin of lizards. For mimicking skin structures of moisture-harvesting lizards towards an optimization of the surface wetting behavior, additionally a two-step laser processing strategy was established for realizing hierarchical microstructures. In this approach, micrometer-scaled capillaries (step 1) were superimposed by a laser-generated regular array of small dimples (step 2). Optical focus variation imaging measurements finally disclosed the three dimensional topography of the laser processed surfaces derived from lizard skin structures. The functionality of these surfaces was analyzed in view of wetting properties.