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Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures

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A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "D：Materials and Processing".

Deadline for manuscript submissions: closed (20 March 2024) | Viewed by 21236

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Special Issue Editors

Dr. Congyi Wu

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Guest Editor

School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: laser manufacturing; ultrafast laser processing; flexible electronics; polymer laser processing; flexible sensor; wearable devices; human–machine interface
Special Issues, Collections and Topics in MDPI journals

Dr. Longchao Cao

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Guest Editor

School of Mechanical Engineering & Automation, Wuhan Textile University, Wuhan 430200, China
Interests: laser material processing; laser welding; laser-based additive manufacturing; processing parameter optimization; numerical simulation; process monitoring; machine learning
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Guojun Zhang

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Guest Editor

School of Mechanical Science and Engineering, Huazhong University of Science Technology, Wuhan 430074, China
Interests: non-traditional machining; laser manufacturing; ultrafast laser processing

Ya Lu

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Guest Editor Assistant

Special Issue Information

Dear Colleagues,

Carbon fibre reinforced plastics, brittle materials, cemented carbide, organic polymer materials, biomass materials, and other difficult-to-machine materials are widely used in aviation, aerospace, navigation, biology, etc. For example, Carbon fibre reinforced plastics are used in satellite manufacturing, photovoltaic glass is used in solar panels, titanium alloy is used in deep submersibles, polymer materials are used in flexible electronics, and fibrin is used in heart valves. Traditional processing methods such as turning and milling are difficult to achieve precision processing of the above difficult-to-machine materials, and there is an urgent need to introduce revolutionary processing methods. Ultrafast laser with short pulse width and high peak power is an important tool for low damage and high precision processing of difficult-to-machine materials. As an emerging processing technology, there is still a need to continuously explore the interaction mechanism between ultrafast lasers and materials, develop advanced process technologies, and expand the application prospects of ultrafast lasers.

This Special Issue of Micromachines, “Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures”, seeks to showcase research papers, communications, and review articles that focus on ultrafast laser processing of difficult-to-machine materials such as carbon fibre reinforced plastics, brittle materials(glass, diamond, etc.), cemented carbide, organic polymer materials, biomass materials, highly reflective material, matrix composite and explore the application of short-pulsed lasers in various fields. We hope that the papers will encompass the next key technological leaps that will further extend the applications of short-pulsed lasers. Suitable contributions can be related to (but are not restricted to) ultrafast laser processing mechanisms, processes, and equipment for difficult-to-machine materials and micro/nano structures, as well as expanded applications of ultrafast lasers in aviation, aerospace, navigation, biology, etc.

Dr. Congyi Wu
Dr. Longchao Cao
Prof. Dr. Guojun Zhang
Guest Editors
Ya Lu
Guest Editor Assistant

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

ultrafast laser
difficult machining materials
process technology
interaction mechanism
functional structure

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Published Papers (8 papers)

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Research

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14 pages, 5029 KiB

Open AccessArticle

Characterization of Micro-Holes Drilled Using a UV Femtosecond Laser in Modified Polyimide Flexible Circuit Boards

by Lijuan Zheng, Shuzhan Lin, Huijuan Lu, Bing Huang, Yu Liu, Jun Wang, Xin Wei, Jun Wang and Chengyong Wang

Micromachines 2024, 15(9), 1078; https://doi.org/10.3390/mi15091078 - 26 Aug 2024

Viewed by 1403

Abstract

Modified polyimide (MPI) flexible printed circuits (FPCs) are used as chip carrier boards. The quality of the FPC directly affects the reliability of the integrated circuit. Furthermore, micro-holes are critical components of FPCs. In this study, an ultraviolet (UV) femtosecond laser is used to drill micro-holes in double-layer flexible circuit boards with MPI as the substrate. The morphology of the micro-hole wall in the copper foil and MPI layer is observed, and the effects of the laser processing parameters on the diameter and depth of the micro-holes are analyzed. The drilling process and mechanism of micro-holes obtained using a UV femtosecond laser in MPI FPCs are discussed. The results show that the morphology of femtosecond laser-machined copper is closely related to the laser energy, and a periodic structure is observed during the machining process. Copper, MPI, and copper oxides are the most common molten deposits in micro-holes during drilling. The depth of the micro-holes increases with an increase in the energy of a single pulse, scanning time, and scanning overlap rate of the laser beam. However, the diameter exhibits no discernible alteration. The material removal rate increased significantly when laser processing was applied to the MPI resin layer. Full article

(This article belongs to the Special Issue Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures)

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13 pages, 28047 KiB

Open AccessArticle

Study on Laser Polishing of Ti₆Al₄V Fabricated by Selective Laser Melting

by Shuo Huang, Junyong Zeng, Wenqi Wang and Zhenyu Zhao

Micromachines 2024, 15(3), 336; https://doi.org/10.3390/mi15030336 - 28 Feb 2024

Cited by 2 | Viewed by 1703

Abstract

Laser-based additive manufacturing has garnered significant attention in recent years as a promising 3D-printing method for fabricating metallic components. However, the surface roughness of additive manufactured components has been considered a challenge to achieving high performance. At present, the average surface roughness (Sa) of AM parts can reach high levels, greater than 50 μm, and a maximum distance between the high peaks and the low valleys of more than 300 μm, which requires post machining. Therefore, laser polishing is increasingly being utilized as a method of surface treatment for metal alloys, wherein the rapid remelting and resolidification during the process significantly alter both the surface quality and subsurface material properties. In this paper, the surface roughness, microstructures, microhardness, and wear resistance of the as-received, continuous wave laser polishing (CWLP), and pulsed laser polishing (PLP) processed samples were investigated systematically. The results revealed that the surface roughness (Sa) of the as-received sample was 6.29 μm, which was reduced to 0.94 μm and 0.84 μm by CWLP and PLP processing, respectively. It was also found that a hardened layer, about 200 μm, was produced on the Ti₆Al₄V alloy surface after laser polishing, which can improve the mechanical properties of the component. The microhardness of the laser-polished samples was increased to about 482 HV with an improvement of about 25.2% compared with the as-received Ti₆Al₄V alloy. Moreover, the coefficient of friction (COF) was slightly reduced by both CWLP and LPL processing, and the wear rate of the surface layer was improved to 0.790 mm³/(N∙m) and 0.714 mm³/(N∙m), respectively, under dry fraction conditions. Full article

(This article belongs to the Special Issue Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures)

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19 pages, 21957 KiB

Open AccessArticle

Numerical and Experimental Analysis of Dual-Beam Laser Polishing Additive Manufacturing Ti6Al4V

by Junyong Zeng, Wei Zhang, Ting Guo, Yan Lou, Wenqi Wang, Zhenyu Zhao and Chao Wang

Micromachines 2023, 14(9), 1765; https://doi.org/10.3390/mi14091765 - 13 Sep 2023

Cited by 4 | Viewed by 1535

Abstract

Laser polishing is an emerging efficient technique to remove surface asperity without polluting the environment. However, the insufficient understanding of the mechanism of laser polishing has limited its practical application in industry. In this study, a dual-beam laser polishing experiment was carried out to reduce the roughness of a primary Ti6Al4V sample, and the polishing mechanism was well studied using simulation analysis. The results showed that the surface roughness of the sample was efficiently reduced from an initial 10.96 μm to 1.421 μm using dual-beam laser processing. The simulation analysis regarding the evolution of material surface morphology and the flow behavior of the molten pool during laser the polishing process revealed that the capillary force attributed to surface tension was the main driving force for flattening the large curvature surface of the molten pool at the initial stage, whereas the thermocapillary force influenced from temperature gradient played the key role of eliminating the secondary roughness at the edge of the molten pool during the continuous wave laser polishing process. However, the effect of thermocapillary force can be ignored during the second processing stage in dual-beam laser polishing. The simulation result is well in agreement with the experimental result, indicating the accuracy of the mechanism for the dual-beam laser polishing process. In summary, this work reveals the effect of capillary force and thermocapillary force on molten pool flows during the dual-beam laser polishing processes. Moreover, it is also proved that the dual-beam laser polishing process can further reduce the surface roughness of a sample and obtain a smoother surface. Full article

(This article belongs to the Special Issue Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures)

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11 pages, 8081 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Surface Nanotexturing of Boron-Doped Diamond Films by Ultrashort Laser Pulses

by Matteo Mastellone, Eleonora Bolli, Veronica Valentini, Stefano Orlando, Antonio Lettino, Riccardo Polini, Josephus Gerardus Buijnsters, Alessandro Bellucci and Daniele Maria Trucchi

Micromachines 2023, 14(2), 389; https://doi.org/10.3390/mi14020389 - 4 Feb 2023

Cited by 7 | Viewed by 2318

Abstract

Polycrystalline boron-doped diamond (BDD) films were surface nanotextured by femtosecond pulsed laser irradiation (100 fs duration, 800 nm wavelength, 1.44 J cm⁻² single pulse fluence) to analyse the evolution of induced alterations on the surface morphology and structural properties. The aim was to identify the occurrence of laser-induced periodic surface structures (LIPSS) as a function of the number of pulses released on the unit area. Micro-Raman spectroscopy pointed out an increase in the graphite surface content of the films following the laser irradiation due to the formation of ordered carbon sites with respect to the pristine sample. SEM and AFM surface morphology studies allowed the determination of two different types of surface patterning: narrow but highly irregular ripples without a definite spatial periodicity or long-range order for irradiations with relatively low accumulated fluences (<14.4 J cm⁻²) and coarse but highly regular LIPSS with a spatial periodicity of approximately 630 nm ± 30 nm for higher fluences up to 230.4 J cm⁻². Full article

(This article belongs to the Special Issue Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures)

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11 pages, 2728 KiB

Open AccessArticle

High-Contrast Marking of Stainless-Steel Using Bursts of Femtosecond Laser Pulses

by Simas Butkus, Vytautas Jukna, Evaldas Kažukauskas, Žilvinas Svirksas, Domas Paipulas and Valdas Sirutkaitis

Micromachines 2023, 14(1), 194; https://doi.org/10.3390/mi14010194 - 12 Jan 2023

Cited by 3 | Viewed by 2637

Abstract

The marking and surface structuring of various materials is important in various industrial fields such as biomaterials, luxury goods, anti-counterfeiting, automotive and aerospace, electronics and semiconductor industries, and others. Recent advances in laser technology, such as burst-mode lasers, have opened new ways of affecting the surfaces of various materials, inducing a different appearance and/or properties of the laser-exposed areas. From earlier studies, it is known that when splitting a single pulse into multiple pulses and thus creating a quasi-MHz–GHz repetition rate regime, it is possible to increase not only the ablation efficiency but it also provides the possibility to tune the heat in-flow into the surface. Such new regimes enable the control of the surface roughness as well as the optical properties and corrosion resistance. In this work, we analyze the effect of the different burst-mode regimes for the marking of stainless-steel samples, aiming to produce high-contrast marking having different shades of black/white color (black-gray-white). Moreover, we investigate the angular dependence of the reflected light after laser treatment numerically from the measured surface morphology Full article

(This article belongs to the Special Issue Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures)

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15 pages, 6528 KiB

Open AccessArticle

Effects of Ambient Temperature on Nanosecond Laser Micro-Drilling of Polydimethylsiloxane (PDMS)

by Ya Lu, Chaoran Lin, Minghui Guo, Youmin Rong, Yu Huang and Congyi Wu

Micromachines 2023, 14(1), 90; https://doi.org/10.3390/mi14010090 - 29 Dec 2022

Viewed by 1993

Abstract

In this research, effects of ambient temperature (−100 °C–200 °C) on nanosecond laser micro-drilling of polydimethylsiloxane (PDMS) was investigated by simulation and experiment. A thermo-mechanical coupled model was established, and it was indicated that the top and bottom diameter of the micro-hole decreased with the decrease of the ambient temperature, and the micro-hole taper increased with the decrease of the ambient temperature. The simulation results showed a good agreement with the experiment results in micro-hole geometry; the maximum prediction errors of the top micro-hole diameter, the bottom micro-hole diameter and micro-hole taper were 2.785%, 6.306% and 9.688%, respectively. The diameter of the heat-affected zone decreased with the decrease of the ambient temperature. The circumferential wrinkles were controlled by radial compressive stress. As the ambient temperature increased from 25 °C to 200 °C, the radial compressive stress gradually decreased, which led to the circumferential wrinkles gradually evolving in the radial direction. This work provides a new idea and method based on ambient temperature control for nanosecond laser processing of PDMS, which provides exciting possibilities for a wider range of engineering applications of PDMS. Full article

(This article belongs to the Special Issue Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures)

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10 pages, 3561 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Sapphire Selective Laser Etching Dependence on Radiation Wavelength and Etchant

by Agnė Butkutė, Romualdas Sirutkaitis, Darius Gailevičius, Domas Paipulas and Valdas Sirutkaitis

Micromachines 2023, 14(1), 7; https://doi.org/10.3390/mi14010007 - 20 Dec 2022

Cited by 10 | Viewed by 4431

Abstract

Transparent and high-hardness materials have become the object of wide interest due to their optical and mechanical properties; most notably, concerning technical glasses and crystals. A notable example is sapphire—one of the most rigid materials having impressive mechanical stability, high melting point and a wide transparency window reaching into the UV range, together with impressive laser-induced damage thresholds. Nonetheless, using this material for 3D micro-fabrication is not straightforward due to its brittle nature. On the microscale, selective laser etching (SLE) technology is an appropriate approach for such media. Therefore, we present our research on C-cut crystalline sapphire microprocessing by using femtosecond radiation-induced SLE. Here, we demonstrate a comparison between different wavelength radiation (1030 nm, 515 nm, 343 nm) usage for material modification and various etchants (hydrofluoric acid, sodium hydroxide, potassium hydroxide and sulphuric and phosphoric acid mixture) comparison. Due to the inability to etch crystalline sapphire, regular SLE etchants, such as hydrofluoric acid or potassium hydroxide, have limited adoption in sapphire selective laser etching. Meanwhile, a 78% sulphuric and 22% phosphoric acid mixture at 270 °C temperature is a good alternative for this process. We present the changes in the material after the separate processing steps. After comparing different processing protocols, the perspective is demonstrated for sapphire structure formation. Full article

(This article belongs to the Special Issue Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures)

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Review

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21 pages, 7449 KiB

Open AccessReview

A Review of Research Progress on Machining Carbon Fiber-Reinforced Composites with Lasers

by Junke Jiao, Xiangyu Cheng, Jiale Wang, Liyuan Sheng, Yuanming Zhang, Jihao Xu, Chenghu Jing, Shengyuan Sun, Hongbo Xia and Haolei Ru

Micromachines 2023, 14(1), 24; https://doi.org/10.3390/mi14010024 - 22 Dec 2022

Cited by 24 | Viewed by 4056

Abstract

Carbon fiber-reinforced composites are widely used in automobile, aerospace and military lightweight manufacturing due to their excellent mechanical properties such as light weight, excellent fracture resistance, corrosion resistance and wear resistance, etc. However, because of their high hardness, anisotropy and low interlayer strength characteristics, there are many problems with machine carbon fiber-reinforced composites with traditional methods. As a non-contact processing technology, laser machining technology has lots of advantages in carbon fiber-reinforced composites processing. However, there are also some defects produced in laser machining process such the heat affected zone, delamination and fiber extraction due to the great difference of physical properties between the carbon fibers and the resin matrix. To improve the quality of carbon fiber-reinforced composites laser machining, lots of works have been carried out. In this paper, the research progress of carbon fiber-reinforced composites laser machining parameters optimization and numerical simulation was summarized, the characteristics of laser cutting carbon fiber-reinforced composites and cutting quality influence factors were discussed, and the developing trend of the carbon fiber-reinforced composites laser cutting was prospected. Full article

(This article belongs to the Special Issue Ultrafast Laser Processing of Difficult-to-Machine Materials and Micro/Nano Structures)

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