Long term superhydrophobic and hybrid superhydrophobic/superhydrophilic surfaces produced by laser surface micro/nano surface structuring

Abstract

Stable superhydrophobic and superhydrophilic surfaces were created using laser surface micro/nano patterning. These were based on periodic 3D micro/nanostructures produced on 316L stainless steel over large areas using nanosecond and picosecond laser surface fabrication. The effects of laser processing parameters on controlling the micro-/nano-topographical characteristics of 24 different types of structures were presented. Surface roughness, surface chemical composition and wettability (via water contact angle) of these surfaces were characterised. Aging experiments were carried out for up to 8 months to analyse the durability of the prepared surfaces under three conditions of water (hot, normal and icy). Samples with superhydrophobic characteristics, processed with the ps or ns lasers in air, kept dry (water repellent) for over 8 months when tested in ice water (0C-4C), whilst those stored in hot water (80C) or room temperature water could only be kept dry for 3-14 weeks. Samples processed in water had shorter water repellent life and samples processed with the ns laser in air had the longest water repellent periods. The hybrid superhydrophobic and superhydrophobic surfaces had a stability life for water repellent and water spreading of over 6 months.

The influence of picosecond laser generated periodic structures on bacterial behaviour

“…As we focused on examine the laser treated surface after one day and one month of laser treatment, the EDX results showed that the carbon percentage increased with time. Indeed, it was reported by our previous work that the carbon layer was decreased by immersing the surfaces in water [24]. Therefore, the best explanation for the mechanism involved is that these carbon layer is related to the adsorption of the organic component from the atmosphere onto the laser produced oxide surface [36][37][38].…”

“…Such decreases in the surfaces wettability can be significant altered directly after laser treatment, due to the adsorption of organic and carbon contents onto the surface from the atmosphere [23]. In order to control such changes in the surface wettability and energy, surface may be chemically treated following laser ablation [15,[20][21][22]24]. In this work, the effect of laser generated structures with and without chemical modification and their effect on bacterial retention over time was characterised.…”

“…Work Rajab et al [24], which focused on studying the effect of processing time on the surface wettability of laser treated stainless steel surfaces, demonstrated that chemical treatment stabilises surface hydrophobicity and helps laser treated surfaces to maintain hydrophobicity for longer time than control surface. This might be the reason behind the reduced bacterial retention on laser treated surface after chemical treatment.…”

Superhydrophobic surfaces review: Functional application, fabrication techniques and limitations

“…Laser micro-and nanomachining can also be used to generate asperities on surfaces which behave as hydrophobic or superhydrophobic depending on the base material, the type of microstructure created, the processing atmosphere and the laser machining parameters. [57][58][59][60] Both laser-induced periodic surface structures (LIPSS) and unstructured bumps can be generated over surfaces using various kinds of pulse lasers, such as nano- 61 or femtosecond lasers, 62 and so on, just by varying various laser parameters. 63 Figure 22 shows SEM images of laser-patterned surfaces under different machining conditions.…”

Study on the Fabrication of Super-Hydrophobic Surface on Inconel Alloy via Nanosecond Laser Ablation

“…Many previous papers reported that surface topography and surface chemistry contributed to the super-hydrophobicity of the laser ablated surfaces [39,40]. However, the relationship between laser-induced surface topography and surface chemistry was seldom investigated.…”