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Micromachines
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Laser Micromachining
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Laser Micromachining

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E：Engineering and Technology".

Deadline for manuscript submissions: closed (20 January 2021) | Viewed by 28108

Special Issue Editor

Prof. Dr. Man-Seop Lee

E-Mail Website
Guest Editor
School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
Interests: ultra-short pulsed laser micromachining; laser processing; material surface modification

Special Issue Information

Dear Colleagues,

Due to the advent of new laser sources with high beam quality and small spot size, or high power ultra-short pulses, or ultraviolet radiation, laser-based micromachining process offers local and large-area material deposition, surface modification, compound formation, surface and volume patterning, drilling and etching. Those applications are essential in various application areas of technology, such as mechanics, metallurgy, microelectronics, integrated optics, optoelectronics, biomedical applications, nanotechnology, life science and chemical technology.

Furthermore, ultra-short pulsed lasers such as picosecond lasers and femtosecond lasers have been widely used in the micro and nanomachining of a variety of materials due to their unique features such as the eradication of thermal effect and contribution in a variety of non-linear processes compared to long pulsed and continuous wave lasers. One of the most important advantages of ultra-short pulsed laser ablation is that the energy deposited by the ultra-short pulses doesn’t move into the bulk material during the laser pulses, which characteristic makes it easy to fabricate precise micro and nanostructures. Therefore, laser micromachining opened a new era, where micromachining with other available technologies is quite impossible. Moreover, in recent years, R&D activities in the field of laser micromachining technology is progressively more important to meet technologies required in such new era. This special issue solicits contributions like research articles and review articles as well as short communications on all areas of laser micromachining. Topics include but are not limited to the keywords listed below:

  • Laser-material interactions
  • Applications of laser ablation and deposition
  • Surface micro structuring/modification
  • Laser drilling/patterning/direct writing
  • Laser processing in nanotechnology
  • Laser processing applications for biology and life sciences

Prof. Dr. Man-Seop Lee
Guest Editor

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 2600 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.

Related Special Issue

Published Papers (11 papers)

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Research

Jump to: Review

12 pages, 4662 KiB  
Article
Analytical Model for the Depth Progress during Laser Micromachining of V-Shaped Grooves
by Daniel Holder, Rudolf Weber and Thomas Graf
Micromachines 2022, 13(6), 870; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13060870 - 31 May 2022
Cited by 3 | Viewed by 1883
Abstract
An analytical model is presented that allows predicting the progress and the final depth obtained by laser micromachining of grooves in metals with ultrashort laser pulses. The model assumes that micromachined grooves feature a V-shaped geometry and that the fluence absorbed along the [...] Read more.
An analytical model is presented that allows predicting the progress and the final depth obtained by laser micromachining of grooves in metals with ultrashort laser pulses. The model assumes that micromachined grooves feature a V-shaped geometry and that the fluence absorbed along the walls is distributed with a linear increase from the edge to the tip of the groove. The depth progress of the processed groove is recursively calculated based on the depth increments induced by successive scans of the laser beam along the groove. The experimental validation confirms the model and its assumptions for micromachining of grooves in a Ti-alloy with femtosecond pulses and different pulse energies, repetition rates, scanning speeds and number of scans. Full article
(This article belongs to the Special Issue Laser Micromachining)
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11 pages, 8753 KiB  
Article
Investigations on 2Cr13 Stainless Valves after Dry-Type Laser Degumming
by Guang Li, Kai Li, Lu Zhang, Chen Liang, Chen Wang, Benhai Li, Junlong Wang, Xiaohua Wang, Mingwei Lei and Zhipeng Wei
Micromachines 2022, 13(5), 666; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13050666 - 24 Apr 2022
Cited by 1 | Viewed by 1425
Abstract
The disabled glue on valve surfaces is known to reduce aircraft durability and performance. In this paper, glue contaminants were removed from 2Cr13 stainless valves by dry-type laser processing with a cold air gun and compared with the chemical soaking method. The laser-processed [...] Read more.
The disabled glue on valve surfaces is known to reduce aircraft durability and performance. In this paper, glue contaminants were removed from 2Cr13 stainless valves by dry-type laser processing with a cold air gun and compared with the chemical soaking method. The laser-processed surface was examined by white-light interferometer, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometer, hardness tester, and metallographic microscopy. The substrate surface became a little smoother but also had deeper dips due to laser thermal melting. After laser degumming, the new constituent was found in the laser-irradiated region and analyzed as FeCr0.29Ni0.16C0.06, since the ratio of chemical compositions changed. Based on our simulation and experiments, the temperature of the workpiece was effectively controlled by the cold air gun, and its physical properties, including hardness and metallographic structure, were hardly changed. It was shown that laser degumming provides an alternative method for metal valve cleaning. Full article
(This article belongs to the Special Issue Laser Micromachining)
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14 pages, 2342 KiB  
Article
Femtosecond Single Cycle Pulses Enhanced the Efficiency of High Order Harmonic Generation
by Abdelmalek Taoutioui and Hicham Agueny
Micromachines 2021, 12(6), 610; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12060610 - 26 May 2021
Cited by 4 | Viewed by 2437
Abstract
High-order harmonic generation is a nonlinear process that converts the gained energy during light-matter interaction into high-frequency radiation, thus resulting in the generation of coherent attosecond pulses in the XUV and soft x-ray regions. Here, we propose a control scheme for enhancing the [...] Read more.
High-order harmonic generation is a nonlinear process that converts the gained energy during light-matter interaction into high-frequency radiation, thus resulting in the generation of coherent attosecond pulses in the XUV and soft x-ray regions. Here, we propose a control scheme for enhancing the efficiency of HHG process induced by an intense near-infrared (NIR) multi-cycle laser pulse. The scheme is based on introducing an infrared (IR) single-cycle pulse and exploiting its characteristic feature that manifests by a non-zero displacement effect to generate high-photon energy. The proposed scenario is numerically implemented on the basis of the time-dependent Schrödinger equation. In particular, we show that the combined pulses allow one to produce high-energy plateaus and that the harmonic cutoff is extended by a factor of 3 compared to the case with the NIR pulse alone. The emerged high-energy plateaus is understood as a result of a vast momentum transfer from the single-cycle field to the ionized electrons while travelling in the NIR field, thus leading to high-momentum electron recollisions. We also identify the role of the IR single-cycle field for controlling the directionality of the emitted electrons via the IR-field induced electron displacement effect. We further show that the emerged plateaus can be controlled by varying the relative carrier-envelope phase between the two pulses as well as the wavelengths. Our findings pave the way for an efficient control of light-matter interaction with the use of assisting femtosecond single-cycle fields. Full article
(This article belongs to the Special Issue Laser Micromachining)
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14 pages, 4988 KiB  
Article
Femtosecond Laser-Pulse-Induced Surface Cleavage of Zinc Oxide Substrate
by Xi Yu, Fumihiro Itoigawa and Shingo Ono
Micromachines 2021, 12(6), 596; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12060596 - 21 May 2021
Cited by 3 | Viewed by 1824
Abstract
The induction of surface cleavage along the crystalline structure of a zinc oxide substrate (plane orientation: 0001) by femtosecond laser pulses (wavelength: 1030 nm) has been reported; a scanning electron microscope image of the one-pulse (pulse energy: 6–60 μJ) irradiated surface shows very [...] Read more.
The induction of surface cleavage along the crystalline structure of a zinc oxide substrate (plane orientation: 0001) by femtosecond laser pulses (wavelength: 1030 nm) has been reported; a scanning electron microscope image of the one-pulse (pulse energy: 6–60 μJ) irradiated surface shows very clear marks from broken hexagons. This cleavage process differs from the general laser-induced melt process observed on the surfaces of narrower-bandgap semiconductors and other metal materials. This phenomenon is discussed using a multi-photon absorption model, and the pulse-energy dependence of the cleavage depth (less than 3 μm) is quantitatively analyzed. Laser-induced cleavage is found not to occur under multi-pulse irradiation; when more than four pulses are irradiated upon the same spot, the general laser-induced melt process becomes dominant. This cleavage–melt shift is considered to be caused by the enhancement of absorption due to the initial pulses, which is supported by our measurement of cathodoluminescence. Full article
(This article belongs to the Special Issue Laser Micromachining)
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15 pages, 4248 KiB  
Article
Laser–Material Interactions of High-Quality Ultrashort Pulsed Vector Vortex Beams
by Yue Tang, Walter Perrie, David Rico Sierra, Qianliang Li, Dun Liu, Stuart P. Edwardson and Geoff Dearden
Micromachines 2021, 12(4), 376; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12040376 - 01 Apr 2021
Cited by 13 | Viewed by 2817
Abstract
Diffractive multi-beams based on 1 × 5 and 2 × 2 binary Dammann gratings applied to a spatial light modulator (SLM) combined with a nanostructured S-wave plate have been used to generate uniform multiple cylindrical vector beams with radial and azimuthal polarizations. The [...] Read more.
Diffractive multi-beams based on 1 × 5 and 2 × 2 binary Dammann gratings applied to a spatial light modulator (SLM) combined with a nanostructured S-wave plate have been used to generate uniform multiple cylindrical vector beams with radial and azimuthal polarizations. The vector quality factor (concurrence) of the single vector vortex beam was found to be C = 0.95 ± 0.02, hence showing a high degree of vector purity. The multi-beams have been used to ablate polished metal samples (Ti-6Al-4V) with laser-induced periodic surface structures (LIPSS), which confirm the polarization states unambiguously. The measured ablation thresholds of the ring mode radial and azimuthal polarizations are close to those of a Gaussian mode when allowance is made for the expected absolute intensity distribution of a ring beam generated from a Gaussian. In addition, ring mode vortex beams with varying orbital angular momentum (OAM) exhibit the same ablation threshold on titanium alloy. Beam scanning with ring modes for surface LIPSS formation can increase micro-structuring throughput by optimizing fluence over a larger effective beam diameter. The comparison of each machined spot was analysed with a machine learning method—cosine similarity—which confirmed the degree of spatial uniformity achieved, reaching cosθ > 0.96 and 0.92 for the 1 × 5 and 2 × 2 arrays, respectively. Scanning electron microscopy (SEM), optical microscopy and white light surface profiling were used to characterize and quantify the effects of surface modification. Full article
(This article belongs to the Special Issue Laser Micromachining)
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13 pages, 3840 KiB  
Article
Numerical Simulation on Pulsed Laser Ablation of the Single-Crystal Superalloy Considering Material Moving Front and Effect of Comprehensive Heat Dissipation
by Bin Wang, Yihui Huang, Junke Jiao, Hao Wang, Ji Wang, Wenwu Zhang and Liyuan Sheng
Micromachines 2021, 12(2), 225; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12020225 - 23 Feb 2021
Cited by 10 | Viewed by 2247
Abstract
In the present research, an iterative numerical model is proposed to investigate the nanosecond pulsed laser ablation (PLA) mechanism of the DD6 single-crystal superalloy. In the numerical model, two subroutines are introduced to trace the moving boundary and update the thermal load. The [...] Read more.
In the present research, an iterative numerical model is proposed to investigate the nanosecond pulsed laser ablation (PLA) mechanism of the DD6 single-crystal superalloy. In the numerical model, two subroutines are introduced to trace the moving boundary and update the thermal load. The iteration between the main governing equation and the two subroutines enables the PLA numerical simulation to consider material moving front and effect of comprehensive heat dissipation including thermal convection and radiation. The basic experimental results exhibit a good agreement with simulation results which indicates the good accuracy of the simulation model. Therefore, the PLA mechanism of the DD6 single-crystal superalloy is studied base on the improved iterative model, which indicates the evolution of temperature field, ablation zone morphology, formation of recast layer and heat-affected zone are closely related with time. The temperature of the laser spot center increases sharply at the first stage, reaching a maximum value of 5252 K, and then decreases gradually. The thermal dissipation postpones the ablation rate but promotes the formation of a recast layer and heat-affected zone. Due to the evaporation and thermal dissipation, the depth of the molten layer exhibits two rapid increasing stages. The comprehensive analysis of the PLA processing by the improved simulation model helps the understanding of the intrinsic mechanism, which would contribute to the further optimizing parameters of PLA fabrication of the DD6 single-crystal superalloy. Full article
(This article belongs to the Special Issue Laser Micromachining)
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15 pages, 10673 KiB  
Article
Green Picosecond Laser Machining of Thermoset and Thermoplastic Carbon Fiber Reinforced Polymers
by Insung Choi, Su-Jin Lee, Dongsig Shin and Jeong Suh
Micromachines 2021, 12(2), 205; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12020205 - 17 Feb 2021
Cited by 14 | Viewed by 3505
Abstract
There has been an increase in demand for the development of lightweight and high-strength materials for applications in the transportation industry. Carbon fiber reinforced polymer (CFRP) is known as one of the most promising materials owing to its high strength-to-weight ratio. To apply [...] Read more.
There has been an increase in demand for the development of lightweight and high-strength materials for applications in the transportation industry. Carbon fiber reinforced polymer (CFRP) is known as one of the most promising materials owing to its high strength-to-weight ratio. To apply CFRP in the automotive industry, various machining technologies have been reported because it is difficult to machine. Among these technologies, picosecond laser beam-induced machining has attracted great interest because it provides negligible heat transfer and can avoid tool wear. In this work, we conducted and compared machining of 2.15 mm-thick thermoset and 1.85 mm-thick thermoplastic CFRPs by using a green picosecond laser. The optimized experimental conditions for drilling with a diameter of 7 mm led to a small taper angle (average ~ 3.5°). The tensile strength of the laser-drilled specimens was evaluated, and the average value was 570 MPa. Our study indicates that green picosecond laser processing should be considered as a promising option for the machining of CFRP with a small taper angle. Full article
(This article belongs to the Special Issue Laser Micromachining)
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11 pages, 3183 KiB  
Article
Clinical Applications of Laser Technology: Laser Balloon Ablation in the Management of Atrial Fibrillation
by Jamario R. Skeete, Jeanne M. Du-Fay-de-Lavallaz, David Kenigsberg, Carlos Macias, Jeffrey R. Winterfield, Parikshit S. Sharma, Richard G. Trohman and Henry D. Huang
Micromachines 2021, 12(2), 188; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12020188 - 12 Feb 2021
Cited by 4 | Viewed by 3046
Abstract
Catheter-based ablation techniques have a well-established role in atrial fibrillation (AF) management. The prevalence and impact of AF is increasing globally, thus mandating an emphasis on improving ablation techniques through innovation. One key area of ongoing evolution in this field is the use [...] Read more.
Catheter-based ablation techniques have a well-established role in atrial fibrillation (AF) management. The prevalence and impact of AF is increasing globally, thus mandating an emphasis on improving ablation techniques through innovation. One key area of ongoing evolution in this field is the use of laser energy to perform pulmonary vein isolation during AF catheter ablation. While laser use is not as widespread as other ablation techniques, such as radiofrequency ablation and cryoballoon ablation, advancements in product design and procedural protocols have demonstrated laser balloon ablation to be equally safe and effective compared to these other modalities. Additionally, strategies to improve procedural efficiency and decrease radiation exposure through low fluoroscopy protocols make this technology an increasingly promising and exciting option. Full article
(This article belongs to the Special Issue Laser Micromachining)
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18 pages, 8339 KiB  
Article
Effect of Interface Pretreatment of Al Alloy on Bonding Strength of the Laser Joined Al/CFRTP Butt Joint
by Yiyun Ye, Qi Zou, Yinan Xiao, Junke Jiao, Beining Du, Yuezhan Liu and Liyuan Sheng
Micromachines 2021, 12(2), 179; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12020179 - 11 Feb 2021
Cited by 27 | Viewed by 2175
Abstract
In the present research, the carbon fiber reinforced thermoplastic (CFRTP) was laser joined with the Al alloy whose joining interface was pretreated by laser micro-texturing, anodizing, and hybrid of laser micro-texturing and anodizing. The surface morphology of the pretreated Al joining interface and [...] Read more.
In the present research, the carbon fiber reinforced thermoplastic (CFRTP) was laser joined with the Al alloy whose joining interface was pretreated by laser micro-texturing, anodizing, and hybrid of laser micro-texturing and anodizing. The surface morphology of the pretreated Al joining interface and bonding strength of the corresponding Al/CFRTP butt joint were investigated. The results show that the laser micro-texturing has fabricated the micro-pit or micro-furrow in the Al joining interface. With the increasing of laser scanning times, the size of the micro-pit or micro-furrow decreases, when the laser scanning distance is constant. The bonding strength of the Al/CFRTP butt joint with Al joining interface pretreated by micro-texturing fluctuates with the increasing of laser scanning distance and times, reaching the maximum value of 20 MPa at laser scanning distance of 0.1 mm and 1 time. The anodizing pretreatment has formed the Al2O3 oxide layer on the Al joining interface. The Al/CFRTP butt joint with Al joining interface pretreated by anodizing obtains the maximum bonding strength of 11 MPa at anodizing time of 10 min. The hybrid pretreatment of micro-texturing and subsequent anodizing fabricates the regular grid structure with smooth micro-furrow and micro-pit, while the hybrid pretreatment of anodizing and subsequent micro-texturing fabricates the Al joining interface with explosive micro-pit and micro-furrow. The bonding strength of the Al/CFRTP butt joint with hybrid-pretreated Al joining interface is relative better than that of the Al/CFRTP butt joint with anodizing-pretreated Al joining interface but almost lower than that of the Al/CFRTP butt joint with micro-texturing pretreated Al joining interface. Such results should be attributed to the surface morphology of the Al joining interface. Full article
(This article belongs to the Special Issue Laser Micromachining)
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14 pages, 7054 KiB  
Article
Evaluation of the Cross-Sectional Shape of μ–Grooves Produced in Stainless Steel 304 by Laser-Induced Etching Technique
by Jonghun Kim and Kwang H. Oh
Micromachines 2021, 12(2), 144; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12020144 - 30 Jan 2021
Viewed by 2164
Abstract
The variation in cross-sectional profile of a microgroove fabricated with focused and diverging laser irradiation is demonstrated with ray tracing. To verify the result of ray tracing, stainless-steel 304 microgrooves were manufactured utilizing the conventional lens-based and optical fiber-based laser-induced etching techniques in [...] Read more.
The variation in cross-sectional profile of a microgroove fabricated with focused and diverging laser irradiation is demonstrated with ray tracing. To verify the result of ray tracing, stainless-steel 304 microgrooves were manufactured utilizing the conventional lens-based and optical fiber-based laser-induced etching techniques in phosphoric acid solution. Three distinctive groove geometries, i.e., a flat surface with no groove, an intermediate stage groove, and a fully developed V-groove, were rendered for numerical analysis. For focusing mode, the first and second reflections were caused by high laser intensity and the second reflected beam could lead to variation in the groove shape such as a U-shaped groove or a V-shaped groove in accordance with etchant concentration. On the contrary, a weak laser entirely distributed at the groove sidewall could not induce a chemical reaction, leading to a V-shaped groove. The effect of process variables such as laser power (intensity) and etchant concentration on the cross-sectional profiles of a groove are closely examined through the computed simulation results. Full article
(This article belongs to the Special Issue Laser Micromachining)
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Review

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16 pages, 2316 KiB  
Review
A Review on Microstructural Features and Mechanical Properties of Wheels/Rails Cladded by Laser Cladding
by Xinlin Wang, Lei Lei and Han Yu
Micromachines 2021, 12(2), 152; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12020152 - 04 Feb 2021
Cited by 25 | Viewed by 3276
Abstract
The service life of rails would be remarkably reduced owing to the increase of axle load, which can induce the occurrence of damages such as cracks, collapse, fat edges, etc. Laser cladding, which can enhance the mechanical properties of the rail by creating [...] Read more.
The service life of rails would be remarkably reduced owing to the increase of axle load, which can induce the occurrence of damages such as cracks, collapse, fat edges, etc. Laser cladding, which can enhance the mechanical properties of the rail by creating a coating, has received great attention in the area of the rails due to the attractive advantages such as low input heat, small heat-affected zone, and small deformation. In this paper, recent developments in the microstructural characteristics and mechanical properties of a cladded layer on the rail are reviewed. The method of process optimization for enhancing the properties of a cladded layer are discussed. Finally, the trend of future development is forecasted. Full article
(This article belongs to the Special Issue Laser Micromachining)
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