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Laser Applications in Micromachining and Surface Functionalization of Materials

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Optical and Photonic Materials".

Deadline for manuscript submissions: closed (20 July 2022) | Viewed by 16531

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Special Issue Editors

Dr. Tim Kunze

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Guest Editor

Fusion Bionic GmbH, Winterbergstraße 28, 01277 Dresden, Germany
Interests: laser texturing; laser-based surface functionalization; surface engineering; laser micromachining; advanced technology development; materials processing

Dr. Sabri Alamri

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Guest Editor

Fusion Bionic GmbH, Winterbergstraße 28, 01277 Dresden, Germany
Interests: laser texturing; laser-based surface functionalization; surface engineering; advanced technology development; materials processing; process modeling

Special Issue Information

Dear Colleagues,

Laser micromachining and surface functionalization of materials by laser processes have increasingly attracted the attention of scientists and technologists. Various approaches, from conventional laser micromachining to advanced processes and technologies, provide remarkable capabilities for processing several classes of materials. Consequently, complex surface textures and functionalities previously unattainable have been realized and investigated in view of their practical use. Of particular significance is the possibility of using higher laser powers and peculiar beam deflection systems to speed up laser processes in view of their industrial scalability. In this context, laser-generated surface functions such as self-cleaning, decoration, and biocompatibility are becoming more and more recognized in industry since they add a significant value to existing products. This so-called functional laser texturing arose in recent years and represents a very powerful tool for attaining advanced surface properties by creating well-defined surface patterns with micro- and nanometer resolution. In some areas, functional laser texturing has enabled disruptive technology approaches that were not possible before.

In this Special Issue, modern trends of laser micromachining approaches, ranging from direct laser writing to multibeam patterning approaches, will be highlighted and discussed. This includes the processing fundamentals, optimization schemes, and beam shaping methods, as well as the machining of novel and sophisticated materials. The focus is directed on laser-based surface functionalization for a wide set of applications such as tailored wettability, tribology, biocompatibility, decoration, antisticking surfaces, and antireflection. This explicitly includes use cases from industrial environments.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Dr. Tim Kunze
Dr. Sabri Alamri
Guest Editors

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Keywords

laser micromachining
laser (multibeam) texturing
laser-based surface functionalization
surface engineering
surface processing
materials processing

Published Papers (7 papers)

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Research

13 pages, 4016 KiB

Open AccessArticle

Laser Structuring and DLC Coating of Elastomers for High Performance Applications

by Sönke Vogel, Andreas Brenner, Bernadette Schlüter, Bernhard Blug, Franziska Kirsch and Tamara van Roo

Materials 2022, 15(9), 3271; https://doi.org/10.3390/ma15093271 - 02 May 2022

Cited by 1 | Viewed by 1557

Abstract

Even though hard, low friction coatings such as diamond like carbon (DLC) would be beneficial for the performance and longevity of rubber seals, a crucial challenge remains. The elastic mismatch of rubber substrate and DLC coating prevents a fracture free coating application. In this work, a nature inspired approach is applied to render the stiff coating flexible and resilient to delamination at the same time by direct patterning. Rubber substrates were laser structured with tile patterns and subsequently DLC coated. Tensile and tribology tests were performed on structured and unstructured samples. Unstructured DLC coatings showed a crack pattern induced by the coating process, which was further fragmented by tensile stress. Coatings with tile patterns did not experience a further fragmentation under load. During continuous tribological loading, less heterogenous damage is produced for tile structured samples. The findings are ascribed to the relief of induced coating stress by the tile structure, meaning a more resilient coating. Full article

(This article belongs to the Special Issue Laser Applications in Micromachining and Surface Functionalization of Materials)

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27 pages, 26874 KiB

Open AccessArticle

Evolution of Surface Topography and Microstructure in Laser Polishing of Cold Work Steel 1.2379 (AISI D2) Using Quadratic, Top-Hat Shaped Intensity Distributions

by André Temmler, Magdalena Cortina, Ingo Ross, Moritz E. Küpper and Silja-Katharina Rittinghaus

Materials 2022, 15(3), 769; https://doi.org/10.3390/ma15030769 - 20 Jan 2022

Cited by 4 | Viewed by 1883

Abstract

Within the scope of this study, basic experimental research was carried out on macro-laser polishing of tool steel 1.2379 (D2) using a square intensity distribution and continuous wave laser radiation. The influence of the individual process parameters on surface topography was analyzed by a systematic investigation of a wide range of process parameters for two different, square laser beam diameters. Contrary to a typical laser polishing approach, it was shown that short interaction times (high scanning velocity and small laser beam dimensions) are required to reduce both micro-roughness and meso-roughness. A significant reduction of surface roughness of approx. 46% was achieved from Ra_ini = 0.33 ± 0.026 µm to Ra_min = 0.163 ± 0.018 µm using a focused square laser beam with an edge length of d_L,E = 100 µm at a scanning velocity of v_scan = 200 mm/s, a laser power P_L = 60 W and n = 2 passes. However, characteristic surface features occur during laser polishing and are a direct consequence of the laser polishing process. Martensite needles in the micro-roughness region, undercuts in the meso-roughness region, and surface waviness in the macro-roughness region can dominate different regions of the resulting surface roughness spectrum. In terms of mechanical properties, average surface hardness was determined by hundreds of nano-indentation measurements and was approx. 390 ± 21 HV0.1 and particularly homogeneous over the whole laser polished surface. Full article

(This article belongs to the Special Issue Laser Applications in Micromachining and Surface Functionalization of Materials)

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13 pages, 3852 KiB

Open AccessEditor’s ChoiceArticle

Utilizing a Diffractive Focus Beam Shaper to Enhance Pattern Uniformity and Process Throughput during Direct Laser Interference Patterning

by Mikhael El-Khoury, Bogdan Voisiat, Tim Kunze and Andrés Fabián Lasagni

Materials 2022, 15(2), 591; https://doi.org/10.3390/ma15020591 - 13 Jan 2022

Cited by 8 | Viewed by 2535

Abstract

Uniform periodic microstructure formation over large areas is generally challenging in Direct Laser Interference Patterning (DLIP) due to the Gaussian laser beam intensity distribution inherent to most commercial laser sources. In this work, a diffractive fundamental beam-mode shaper (FBS) element is implemented in a four-beam DLIP optical setup to generate a square-shaped top-hat intensity distribution in the interference volume. The interference patterns produced by a standard configuration and the developed setup are measured and compared. In particular, the impact of both laser intensity distributions on process throughput as well as fill-factor is investigated by measuring the resulting microstructure height with height error over the structured surface. It is demonstrated that by utilizing top-hat-shaped interference patterns, it is possible to produce on average 44.8% deeper structures with up to 60% higher homogeneity at the same throughput. Moreover, the presented approach allows the production of microstructures with comparable height and homogeneity compared to the Gaussian intensity distribution with increased throughput of 53%. Full article

(This article belongs to the Special Issue Laser Applications in Micromachining and Surface Functionalization of Materials)

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12 pages, 6026 KiB

Open AccessArticle

A Novel Process for Manufacturing High-Friction Rings with a Closely Defined Coefficient of Static Friction (Relative Standard Deviation 3.5%) for Application in Ship Engine Components

by Wojciech S. Gora, Jesper V. Carstensen, Krystian L. Wlodarczyk, Mads B. Laursen, Erica B. Hansen and Duncan P. Hand

Materials 2022, 15(2), 448; https://doi.org/10.3390/ma15020448 - 07 Jan 2022

Cited by 2 | Viewed by 1862

Abstract

In recent years, there has been an increased uptake for surface functionalization through the means of laser surface processing. The constant evolution of low-cost, easily automatable, and highly repeatable nanosecond fibre lasers has significantly aided this. In this paper, we present a laser surface-texturing technique to manufacture a surface with a tailored high static friction coefficient for application within driveshafts of large marine engines. The requirement in this application is not only a high friction coefficient, but a friction coefficient kept within a narrow range. This is obtained by using nanosecond-pulsed fibre lasers to generate a hexagonal pattern of craters on the surface. To provide a suitable friction coefficient, after laser processing the surface was hardened using a chromium-based hardening process, so that the textured surface would embed into its counterpart when the normal force was applied in the engine application. Using the combination of the laser texturing and surface hardening, it is possible to tailor the surface properties to achieve a static friction coefficient of ≥0.7 with ~3–4% relative standard deviation. The laser-textured and hardened parts were installed in driveshafts for ship testing. After successfully performing in 1500 h of operation, it is planned to adopt the solution into production. Full article

(This article belongs to the Special Issue Laser Applications in Micromachining and Surface Functionalization of Materials)

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15 pages, 4233 KiB

Open AccessArticle

Effects of Insertion of Ag Mid-Layers on Laser Direct Ablation of Transparent Conductive ITO/Ag/ITO Multilayers: Role of Effective Absorption and Focusing of Photothermal Energy

by Younggon Choi, Hong-Seok Kim, Haunmin Lee, Wonjoon Choi, Sang Jik Kwon, Jae-Hee Han and Eou-Sik Cho

Materials 2021, 14(18), 5136; https://doi.org/10.3390/ma14185136 - 07 Sep 2021

Cited by 7 | Viewed by 2050

Abstract

From the viewpoint of the device performance, the fabrication and patterning of oxide–metal–oxide (OMO) multilayers (MLs) as transparent conductive oxide electrodes with a high figure of merit have been extensively investigated for diverse optoelectronic and energy device applications, although the issues of their general concerns about possible shortcomings, such as a more complicated fabrication process with increasing cost, still remain. However, the underlying mechanism by which a thin metal mid-layer affects the overall performance of prepatterned OMO ML electrodes has not been fully elucidated. In this study, indium tin oxide (ITO)/silver (Ag)/ITO MLs are fabricated using an in-line sputtering method for different Ag thicknesses on glass substrates. Subsequently, a Q-switched diode-pumped neodymium-doped yttrium vanadate (Nd:YVO₄, λ = 1064 nm) laser is employed for the direct ablation of the ITO/Ag/ITO ML films to pattern ITO/Ag/ITO ML electrodes. Analysis of the laser-patterned results indicate that the ITO/Ag/ITO ML films exhibit wider ablation widths and lower ablation thresholds than ITO single layer (SL) films. However, the dependence of Ag thickness on the laser patterning results of the ITO/Ag/ITO MLs is not observed, despite the difference in their absorption coefficients. The results show that the laser direct patterning of ITO/Ag/ITO MLs is primarily affected by rapid thermal heating, melting, and vaporization of the inserted Ag mid-layer, which has considerably higher thermal conductivity and absorption coefficients than the ITO layers. Simulation reveals the importance of the Ag mid-layer in the effective absorption and focusing of photothermal energy, thereby supporting the experimental observations. The laser-patterned ITO/Ag/ITO ML electrodes indicate a comparable optical transmittance, a higher electrical current density, and a lower resistance compared with the ITO SL electrode. Full article

(This article belongs to the Special Issue Laser Applications in Micromachining and Surface Functionalization of Materials)

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12 pages, 2602 KiB

Open AccessEditor’s ChoiceArticle

Simultaneous Micro-Structuring and Surface Smoothing of Additive Manufactured Parts Using DLIP Technique and Its Influence on the Wetting Behaviour

by Florian Kuisat, Fabian Ränke, Fernando Lasagni and Andrés Fabián Lasagni

Materials 2021, 14(10), 2563; https://doi.org/10.3390/ma14102563 - 14 May 2021

Cited by 7 | Viewed by 2147

Abstract

It is well known that the surface topography of a part can affect its function as well as its mechanical performance. In this context, we report on the surface modification of additive manufactured components made of Titanium 64 and Scalmalloy^®, using Direct Laser Interference Patterning technique. In our experiments, a nanosecond-pulsed near-infrared laser source with a pulse duration of 10 ns was used. By varying the process parameters, periodic structures with different depths and associated roughness values are produced. Additionally, the influence of the resultant morphological characteristics on the wettability behaviour of the fabricated textures is investigated by means of contact angle measurements. The results demonstrated a reduction of the surface roughness of the additive manufactured parts (in the order of some tens of micrometres) and simultaneously the production of well-defined micro-patterns (in the micrometre range), which allow the wettability of the surfaces from 26° and 16° up to 93° and 131° to be tuned for Titanium 6Al 4V and Al-Mg-Sc (Scalmalloy^®), respectively. Full article

(This article belongs to the Special Issue Laser Applications in Micromachining and Surface Functionalization of Materials)

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15 pages, 6130 KiB

Open AccessEditor’s ChoiceArticle

Hierarchical Microtextures Embossed on PET from Laser-Patterned Stamps

by Felix Bouchard, Marcos Soldera, Robert Baumann and Andrés Fabián Lasagni

Materials 2021, 14(7), 1756; https://doi.org/10.3390/ma14071756 - 02 Apr 2021

Cited by 12 | Viewed by 2603

Abstract

Nowadays, the demand for surface functionalized plastics is constantly rising. To address this demand with an industry compatible solution, here a strategy is developed for producing hierarchical microstructures on polyethylene terephthalate (PET) by hot embossing using a stainless steel stamp. The master was structured using three laser-based processing steps. First, a nanosecond-Direct Laser Writing (DLW) system was used to pattern dimples with a depth of up to 8 µm. Next, the surface was smoothed by a remelting process with a high-speed laser scanning at low laser fluence. In the third step, Direct Laser Interference Patterning (DLIP) was utilized using four interfering sub-beams to texture a hole-like substructure with a spatial period of 3.1 µm and a depth up to 2 µm. The produced stamp was used to imprint PET foils under controlled temperature and pressure. Optical confocal microscopy and scanning electron microscopy imaging showed that the hierarchical textures could be accurately transferred to the polymer. Finally, the wettability of the single- and multi-scaled textured PET surfaces was characterized with a drop shape analyzer, revealing that the highest water contact angles were reached for the hierarchical patterns. Particularly, this angle was increased from 77° on the untreated PET up to 105° for a hierarchical structure processed with a DLW spot distance of 60 µm and with 10 pulses for the DLIP treatment. Full article

(This article belongs to the Special Issue Laser Applications in Micromachining and Surface Functionalization of Materials)

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