Ultra fast laser machined hydrophobic stainless steel surface for drag reduction in laminar flows

Hydrophobic surfaces have attracted much attention due to their potential in microfluidics, lab on chip devices and as functional surfaces for the automotive and aerospace industry. The combination of a dual scale roughness with an inherent low-surface-energy coating material is the pre-requisite factor for the development of an artificial superhydrophobic surfaces. Ultra short pulse laser (USPL) machining/structuring is a promising technique to obtain the dual scale roughness. Moreover, ultra short laser pulses allow machining without or with limited thermal effects. Flat stainless steel (AISI 304L) were laser machined with ultraviolet laser pulses of 6.7ps, at different laser processing parameters. Next, the samples were coated with a monolayer of\ud perfluorinated octyltrichlorosilane (FOTS) to get a superhydrophobic surface. The degree of hydrophobicity was accessed by static contact angle measurement. Laser patterned surface has longitudinal micro channels. Drag reduction in liquid flow can be obtained due to the shear free boundary condition at air-liquid menisci. The geometry of the patterns was analyzed with optical and scanning electron microscopy. Micro-Particle Image Velocimetry (μPIV) has been employed to measure and visualize the flow over such pattern

Influence of ambient conditions on the evolution of wettability properties of an IR-, ns-laser textured aluminium alloy

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

Chemical analysis on laser processed Ultrahydrophobic Ti-6Al-4V surface by high vacuum Process

A technique has been developed for fabrication of ultrahydrophobic Ti-6Al-4V surface by vacuum process. This report has the data related to the article “Hybrid laser and vacuum process for rapid ultrahydrophobic Ti-6Al-4 V surface formation” on the fabrication of ultrahydrophobic Ti-6Al-4V by Vacuum process (Jagdheesh et al., 2019). The present data consist of X-ray photo electron spectroscopy spectrums recorded for the laser patterned ultrahydrophobic samples, droplet image and surface chemical composition of laser patterned Ti-6Al-4V samples before vacuum process(b. v. p.) and after vacuum process (a. v. p.) for 120 min. The presented data give a clear idea about the chemical modification evolved during the vacuum process

Fabrication of functional superhydrophobic surfaces on carbon fibre reinforced plastics by IR and UV direct laser interference patterning

The fabrication of functional microstructures on surfaces by laser enables unique material properties and is presently a leading research topic. This work addresses the production of functional hierarchical microstructures on carbon fibre reinforced polymer composites in order to control the wettability properties of the material. Two-beam Direct Laser Interference Patterning using either ultraviolet (263 nm) or infrared (1053 nm) nanosecond laser source is employed to produce melt-free and well-defined hierarchical microstructures on carbon fibre reinforced plastics. The resulting water contact angles after thin film deposition of 1H,1H,2H,2H-Perflorodecyl-triethoxysilane were analysed with respect to structure depth and quality. The maximum static contact angle of 171° is demonstrated for dual hierarchical microstructures composed of 11 µm deep large-scale pillars, covered by 1.7 µm pillars, both fabricated in a single step

Sliding/Rolling Phobic Droplets along a Fiber: Measurement of Interfacial Forces

Phobic droplet–fiber systems possess complex geometries, which have made full characterization of such systems difficult. This work has used atomic force microscopy (AFM) to measure droplet–fiber forces for oil droplets on oleophobic fibers over a range of fiber diameters. The work adapted a previous method and a theoretical model developed by the authors for philic droplet–fiber systems. A Bayesian statistical model was also used to account for the influence of surface roughness on the droplet–fiber force. In general, it has been found that the force required to move a liquid droplet along an oleophobic filter fiber will be less than that required to move a droplet along an oleophilic fiber. However, because of the effects of pinning and/or wetting behavior, this difference may be less than would otherwise be expected. Droplets with a greater contact angle ( 110°) were observed to roll along the fiber, whereas droplets with a lesser contact angle (<90°) would slide