Laser drilling of metals and alloys is a well-established process widely utilised in industries such as aerospace, medical, and automotive. However, the laser drilling of ceramics, particularly alumina of thickness greater than 5 mm, remains a significant challenge. This difficulty arises from alumina’s high melting temperature, brittleness that leads to cracking, and its low absorption of standard fibre laser wavelength. This study investigates laser trepanning drilling of 6 mm thick alumina, focusing on understanding the material removal characteristics and the influence of key process parameters on hole geometry and thermal damages. The effects of pulse energy, frequency, assist gas composition, and trepanning speed were systematically examined. A minimum specific energy requirement of 80 J/mm was established for through-hole formation, while crack initiation occurred beyond 640 J/mm. Among various assist gases tested, oxygen demonstrated superior performance with minimal taper despite no reactive fusion. Optimal drilling performance can be achieved by balancing pulse energy (for hole geometry stability and minimal thermal affected zone), frequency (for controlled thermal effects), and trepanning speed (for minimal taper and reduced thermal affected zone).

High-performance ceramic material composites (CMCs) have excellent applications in aerospace industries. However, the machining of the CMSs is challenging due to the inherent properties such as high hardness, heterogeneous structure, and brittleness. Understanding the machinability, ablation mechanism, and the magnitude of the damage is essential to control the machining quality. The study investigates the characteristics of laser process parameters on the machinability of the Al2O3/Al2O3 CMCs in the femtosecond regime. The laser-machined slots were subjected to geometrical analysis, surface roughness measurements, and material removal rates with respect to the process parameters. The laser-machined surface structures and the microstructures of the cross-sections were analysed by scanning electron microscope. The study reveals that high laser power favours the maximum material removal rate irrespective of the scan rates. The peak material removal rate of 2.36 mm3/min was achieved at the power level of 14.23 W. High laser power and slow scan rates produced a smooth machined surface of the slots due to the melting and resolidification of the surface. Some microcracks were observed at the bottom of the laser-machined slots. The microcracks were more prominent in the transverse direction compared to the longitudinal direction. The formation of microcracks is due to the expansion and shrinkage caused during the laser machining process. The elemental analysis of the slots reveals a thick oxide layer at the bottom of the slots, and the thickness of the oxide layer is a function of laser power and scan rates.

The interaction of water droplets to the engineered hierarchical surface structures depends on the synergy between the topographical and chemical modifications. In this work, we develop an ultrafast laser processing technology to create a robust superhydrophobic nanostructured titanium nitride (TiN) surface based on the surface geometry and accelerated adsorption of Volatile Organic Compounds (VOC) by low-pressure technique. The laser processed surfaces are composed of nanoscale geometry overlapped with porous, spongy structures. The metal oxides formed on the TiN surface was hydrophilic and it was subjected to accelerated adsorption of VOC by low-pressure technique via condensation reaction with surface hydroxyl groups formed by heterolityc adsorption of water molecules from the environment. The decrease of surface energy due to the presence of a layer of adsorbed hydrocarbons along with the topography of the nanostructures allows the trapping of small volumes of air that favour the Cassie-Baxter state of wetting. Static contact angle ranging from 155 to 180˚ have been reached depending on the nanostructures geometry. A comparative study of vacuum processed and aged (15 days) samples under atmospheric conditions were also performed. The chemical analysis by XPS demonstrates that the water molecules attached to hydroxyl groups passivate these reactive sites and hinder the adsorption of VOC, decreasing drastically the adsorption rate, under aging in air conditions, whereas it is enhanced under low pressure conditions.

The laser cleaning process has the potential to become an alternative to the existing chemical-based cleaning process if integrated with an effective in-process monitoring system that could serve as a control mechanism over surface damages or contaminants through which the desired surface cleanliness could be achieved. This paper presents results of an investigation into the characteristics and viability of utilizing probe beam reflection (PBR) and laser plume-emission spectroscopy (PES) as respective integrated monitoring systems during and after cleaning of titanium alloy sheets using a frequency-tripled Nd:YAG laser. The results present the probe beam reflection as a better system with the ability to differentiate between cleaned and un-cleaned surfaces for both small and large surface areas.

In this study, self-organised microspiked surface structures were fabricated with a picosecond laser source on austenite stainless steel. The laser-processed surface structures were subjected to low-temperature annealing for chemical modification to reduce the surface free energy of the metal oxides formed due to laser processing. The low-temperature treatment accelerates the adsorption of organic contamination, leading to the formation of ultralow water adhesion surface in few hours compared to the prolonged ageing process. The effect of the number of pulses/spot (PPS) and fluence with respect to the geometrical shape and its impact on wetting behaviour has been systematically investigated. The density of the nanoscale protrusions and the overlay of spongy porous nanoscale structures were influenced by the number of PPS and applied energy density. The multi-scale structures generated with a fluence of 1.3 J/cm(2) showed superhydrophobic character with a high contact angle about 158 +/- 3 degrees and low contact angle hysteresis <5 degrees.

The non-linear energy deposition associated with ultrafast laser processing enables us to create sub-wavelength nanostructures on a variety of materials; therefore, ultrafast laser processing is proved to be a versatile tool for the generation of surface functionalities such as superhydrophobic and self-cleaning surfaces. Float glass is an important material used in automobile for the windshields and mirrors. Windshields with functional properties like self-cleaning without compromising the transparency and bulk material properties is a tough challenge. In this direction, a successful attempt has been made by creating laser-induced surface structures on the float glass surface without reducing the transparency by picosecond laser processing. The initiation and growth of laser-induced surface structures have been studied with respect to number of pulses applied to the spot and the variation of density of the nanostructures by a spatial shift of laser beam. The wetting property evaluation was found to be superhydrophobic and oleophobic.

Using four beam direct laser interference patterning (DLIP) Laser Induced Periodic Surface Structures (LIPSS, ripples) are simultaneously generated on surface of AISI 316L steel in more than thousands of spots at once. Both low-spatial frequency LIPSS (LSFL) and high-spatial frequency LIPSS (HFSL) are possible to fabricate with optimized parameters of 1030 nm, 1.7 ps PERLA laser system, developed and operated at HiLASE center. A novel large-beam DLIP technique applied for the redistribution of initial laser energy per pulse results in fabrication of similar to 1520 spots with LSFL in 50 ms and similar to 1016 spots with HSFL in 5 ms, thus significantly improving the productivity in comparison with the single beam approach. Efficient production of LIPSS structures over large area, required for applications such as a production of security diffractive elements and surfaces with super-hydrophobic properties is also demonstrated. Possible steps for further increase of processing speed are discussed.

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 degrees is demonstrated for dual hierarchical microstructures composed of 11 mu m deep large-scale pillars, covered by 1.7 mu m pillars, both fabricated in a single step.

Ultralow water adhesion aluminum surface has been fabricated by eco friendly low pressure processing technique. The laser patterned surface shows interconnected spongy porous nanostructures with micro packets at regular intervals. The micro volume of air present inside the interconnected porous surface structure together with the adsorbed hydrocarbons by low pressure processing leads to ultralow water adhesion surface. Application of bigger droplet volumes to the patterned surface showed a decrease in static contact angle measurement due to larger radius of curvature and axisymmetrical compared to the smaller droplets. (C) 2020 Elsevier B.V. All rights reserved.

In this paper, we introduce a method to efficiently use a high-energy pulsed 1.7 ps HiLASE Perla laser system for two beam interference patterning. The newly developed method of large-beam interference patterning permits the production of micro and sub-micron sized features on a treated surface with increased processing throughputs by enlarging the interference area. The limits for beam enlarging are explained and calculated for the used laser source. The formation of a variety of surface micro and nanostructures and their combinations are reported on stainless steel, invar, and tungsten with the maximum fabrication speed of 206 cm2/min. The wettability of selected hierarchical structures combining interference patterns with 2.6 µm periodicity and the nanoscale surface structures on top were analyzed showing superhydrophobic behavior with contact angles of 164°, 156°, and 150° in the case of stainless steel, invar, and tungsten, respectively.

A lot of research efforts have been invested in the fabrication of superhydrophobic surfaces in recent years due to many protentional applications in science and industry including anti-icing, self-cleaning and anti-corrosive surfaces. Laser as a non-polluting, precise and flexible tool can be applied to replicate surface microstructures of extremely water repellent lotus leave surface. In this study, a common nanosecond laser source is used to fabricate a super/ultrahydrophobic surfaces with different microstructure designs, contact angles above 170 degrees and sliding angles below 5 degrees. The freshly processed surface is hydrophilic and becomes hydrophobic and superhydrophobic in a certain time period, which could be dramatically reduced by storing samples in high vacuum. The transformation in wetting properties are analysed with respect to surface geometry and surface chemistry.

Growing demand for superhydrophobic surfaces in recent years is associated to many attractive science and engineering applications including self-cleaning, anti-icing and anti-corrosive behaviours. Stainless steel type AISI 316L is one of the most versatile and widely used engineering material in industries. Inspired by the "lotus effect" nano/microstructures has been fabricated by direct laser writing method with nanosecond laser source using two ablation regimes. Primarily, microstructures were fabricated with a tightly focused beam and covered by nano-scale structures by defocused laser beam in the second fabrication step. However, freshly prepared laser patterned metal surface shows hydrophilic behaviour. The hydrophilic to superhydrophobic transformation takes several days or weeks by aging technique in atmospheric condition. In this study, the transition time has been drastically reduced by high vacuum processing technique. Wetting properties with respect to laser processing parameters and surface morphology were examined and found to be consistent for large droplet volumes.

A technique has been developed for fabrication of ultra hydrophobic Ti-6A1-4V surface by vacuum process. This report has the data related to the article "Hybrid laser and vacuum process for rapid ultrahydrophobic Ti-6A1-4V surface formation" on the fabrication of ultrahydrophobic Ti-6A1-4V 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-6A1-4V 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. (C) 2018 Published by Elsevier Inc.

Fabrication of superhydrophobic surfaces is a popular topic in research and industry due to many potential applications including self-cleaning, anti-icing or drag reduction. Laser micro and nanostructuring is an efficient method to replicate lotus leaves double-scale structures to achieve superhydrophobicity without chemical treatment. Immediately after laser processing, samples are hydrophilic and become hydrophobic in a few days, exposed to atmospheric conditions. This time was significantly reduced by vacuum processing to only 4 h. Two-step fabrication method of superhydrophobic surfaces have been developed using nanosecond laser system. In the first step, large scale micropillars are fabricated and covered by nano-scale protrusions in the following step using defocused laser beam. The nanostructure formation increased the apparent contact angle from 149 degrees to 175 degrees. (C) 2019 Elsevier B.V. All rights reserved.

The metallic surfaces with low affinity or high repellence towards water molecules are extremely desirable. The present investigation reports the development of non-fluorinated super or ultrahydrophobic aerospace aluminum alloy (Al7075) surface by laser patterning and high vacuum process for 4 h. Lamellar and lotus leaf papillae like structures covered with nanoscale protrusions are found to be formed depends on the laser fluence and spatial shifts of laser scans. The fresh laser processed hydrophilic surface was vacuum processed to create layer of hydrocarbon to reduce the surface free energy for the wetting property transformation. The analysis of the results shows the synergistic effect of hierarchical structures and dominant presence of non-polar elements is critical for superhydrophobic property. The surface geometry is primarily responsible for the wetting property transformation by entrapping mu-volume of air to generate a composite interface of solid-gas-liquid. Micro and nanoscale (dual scale) surface structures are essential for the durable and consistent superhydrophobic property with high degree of water repellence for bigger volume of water droplets. Further, sole presence of nanoscale structures on inherent hydrophilic aluminum alloy surface with predominant presence of non-polar elements can yield only near superhydrophobic surface due to random spacing of nanoscale protrusions.

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.

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

This paper presents a novel structural piezoresistive pressure sensor with four-grooved membrane combined with rood beam to measure low pressure. In this investigation, the design, optimization, fabrication, and measurements of the sensor are involved. By analyzing the stress distribution and deflection of sensitive elements using finite element method, a novel structure featuring high concentrated stress profile (HCSP) and locally stiffened membrane (LSM) is built. Curve fittings of the mechanical stress and deflection based on FEM simulation results are performed to establish the relationship between mechanical performance and structure dimension. A combination of FEM and curve fitting method is carried out to determine the structural dimensions. The optimized sensor chip is fabricated on a SOI wafer by traditional MEMS bulk-micromachining and anodic bonding technology. When the applied pressure is 1 psi, the sensor achieves a sensitivity of 30.9 mV/V/psi, a pressure nonlinearity of 0.21% FSS and an accuracy of 0.30%, and thereby the contradiction between sensitivity and linearity is alleviated. In terms of size, accuracy and high temperature characteristic, the proposed sensor is a proper choice for measuring pressure of less than 1 psi.

A novel technique of post-vacuum processing the laser patterned surface was used for high speed fabrication of Ultrahydrophobic Ti6Al4V surface and the basics behind the transformation of surface chemistry is investigated in this paper. The wetting property of the laser patterned dual geometry structures transforms to ultrahydrophobic in 120 min of vacuum process without any chemical treatments to suppress the surface polarity. The surface recorded static contact angle of 180 degrees, sliding angle less than 5, and exhibits bouncing and roll-off characteristic due to the presence of composite interface. The transformation of hydrophobic property establish a clear relationship between the vacuum process period and the improvement in static contact angle. The surface chemical analyses by XPS reveals that the amount of surface carbon content increases 2.3 times higher because of the adsorption of unstable organic molecules by vacuum process. The low partial pressure of the water molecules (120 min.) compared to those occurs at standard atmospheric pressure (days). The transformation of freshly laser processed Ti6Al4V hydrophilic surfaces into ultrahydrophobic surface is due to the development of carbonaceous layer over the laser patterned structures, which helps to sustain the Cassi-Baxter state.

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.