The use of pulsed laser irradiation techniques has proven to be a clearly effective procedure for the achievement of surface properties modification via micro-/nano-structuration, different conceptual approaches having been the subject of research and extensively reported in the literature. Beyond the broad spectrum of applications developed for the generation of structured surfaces of metallic materials with specific contact, friction and wear functionalities, the application of laser sources to the surface structuration of metal surfaces for the modification of their wettability and corrosion resistance properties is considered. Multi-scaled hierarchical surface microstructures fabricated on characteristic alloys (the concrete case of Ti6Al4V alloy is considered as example) by the combination of two complementary laser micro/nano-structuring techniques (Direct Laser Writing and Direct Laser Interference Patterning) are reported. Static contact angle measurements show a clearly hydrophobicity enhancement for both types of processing options and a clear improvement on the corrosion resistance of patterned samples of either type is observed. A discussion of the reported features in view of the applicability of the technique to industrial-scope problems is provided.

The use of pulsed laser irradiation techniques has proven to be a clearly effective procedure for the achievement of surface properties modification via micro-/nano-structuration, different conceptual approaches having been the subject of research and extensively reported in the literature. Completing the broad spectrum of applications developed mostly involving the generation of structured surfaces (particularly of metallic materials) with specific contact, friction and wear functionalities, the application of laser sources to the surface structuration of metal surfaces for the modification of their wetability and corrosion resistance properties is considered. The particular problems found for the generation of the appropriate surface microstructure able to replicate the hydrophobic behaviour of some live structures present in nature, their long term stability and their amenability to macroscopic scale are discussed along with innovative methods to generate the required hierarchical micro-/nano-structures by a combination of the DLW and DLIP techniques.

Ice accretion on external surfaces of aircraft due to the impingement of supercooled liquid water droplets can be tackled by the implementation of icephobic surfaces. Among these, superhydrophobic surfaces represent a promising solution, due to their water repellent nature. In the last decade, short/ultra-short pulsed laser technologies have been proposed as a one-step process to manufacture superhydrophobic surfaces. However, the effectiveness and durability of such surfaces in operational icing conditions has not yet been validated. In this work, we investigate ice adhesion strength and the chemical stability of metal alloys textured with a UV nanosecond laser via Direct Laser Writing. (C) 2019 The Authors. Published by Elsevier B.V.

In the present work, a study of laser-based surface structuring of aerospace-grade titanium alloy (Ti-6Al-4V) with subsequent ageing by employing two different storage methods is undertaken. The titanium alloy samples were patterned using UV-ns and IR-fs pulsed lasers in a two-step process to fabricate bio-inspired hierarchical structures. The resulting surface structure consisted in regular periodic square-shaped micro-pillars covered by 810 nm-periodic LIPSS. After the laser processing the samples were kept in two different storage conditions: exposed to ambient air and inside polyethylene bags. The polyethylene bags were found to be beneficial for the surface ageing of laser-fabricated titanium surfaces, increasing the ageing time when compared to ageing by exposure to ambient air. Hierarchical surface topographies exhibited higher water-repellency when compared to non-hierarchical structures. Especially, hierarchical structures reached a hydrophobic state with water contact angle over 160 degrees after 3 weeks storage in polyethylene bags. The micro-structured surfaces were characterized by using confocal microscopy, scanning electron microscopy, static contact angle measurements and X-ray photoelectron spectroscopy.

1. Introduction: The Search for Hydrophobic Surfaces. 2. Basic Experimental Setup and Initial Results: Hydrophobicity Induced by Surface Patterning with Individual ns Laser Pulses. 3. The Next Step: Extended Surfaces Patterning with ns Laser Generated Channels. a) Effect of repetition rate / processing speed. b) Effect of hatch distance. 4. Generation of Withstanding Superhydrophobic Surfaces with 2DMicropillar Patterns 5. The Way for the Generation of Low Wettability and Bio-inspired Self-Cleaning Surfaces 6. Conclusions

Multi-scaled hierarchical surface microstructures are fabricated on A12024 alloy using Direct Laser Writing and Direct Laser Interference Patterning. During the manufacturing procedure two distinct laser sources are used, including an ultra-violet nanosecond laser system that produces microcell structures with different dimensions through Direct Laser Writing. Posteriorly, an infrared picosecond laser source is used to fabricate sub-micron features on the previously patterned microcells. Thus, the fabricated multi-scaled hierarchical structures are a closer representation of what is observed in nature. Water contact angle measurements are carried out in order to assess the wettability response, which revealed superhydrophobicity one week posterior to the fabrication, with measured contact angles up to 161.5 +/- 3 degrees.

Micro cell structures of different sizes were patterned using a nanosecond near-infrared laser source on Al2024 aluminium alloy plates with 2 mm thickness. The influence of laser parameters on the shape and size of the produced patterns were studied together with the evolution of wettability properties over time for different storage conditions. Samples were found to be superhydrophobic from a single step laser patterning, requiring no further treatment. Exposure to ambient air was shown to be a key factor in the property changes of the samples over time. The produced surface patterns with different laser parameter settings were correlated with the contact angle measurements, revealing a great influence of the amount of recast material on the hydrophobic properties. X-Ray photoelectron spectroscopy was used to study the impact of surface chemistry changes on hydrophobicity, analysis of elemental composition proved that chemisorbed organic molecules present in the ambient air were responsible for the hydrophilic to superhydrophobic transition.

In this work, hierarchical surface patterns fabricated on Ti-6Al-4V alloy combining two laser micro-machining techniques are presented. The used technologies are based on nanosecond Direct Laser Writing and picosecond Direct Laser Interference Patterning. Squared shape micro-cells with different hatch distances were produced by Direct Laser Writing with depths values in the micro-scale, forming a well-defined closed packet. Subsequently, cross-like periodic patterns were fabricated by means of Direct Laser Interference Patterning using a two-beam configuration, generating a dual-scale periodic surface structure in both micro- and nano-scale due to the formation of Laser-Induced Periodic Surface Structure after the picosecond process. As a result a triple hierarchical periodic surface structure was generated. The surface morphology of the irradiated area was characterized with scanning electron microscopy and confocal microscopy. Additionally, static contact angle measurements were made to analyze the wettability behavior of the structures, showing a hydrophobic behavior for the hierarchical structures. (C) 2017 Elsevier Ltd. All rights reserved.