New Trends and Applications in Femtosecond Laser Micromachining

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

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 46080

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Special Issue Editors


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Guest Editor
Institute for Photonics and Nanotechnologies, CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
Interests: femtosecond laser micromachining; integrated optics; optofluidics; lab on a chip
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Guest Editor
Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
Interests: fluorescence imaging; photonics; microfluidics; biophotonics; optical manipulation of cells; lab on a chip
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
Interests: femtosecond laser micromachining; photonics; microfluidics; biophotonics; lab on a chip

Special Issue Information

Dear colleagues,

Since the first pioneering work by Hirao in 1996, who demonstrated modifications induced in a transparent material by focusing a sub-picosecond pulse, femtosecond laser micromachining has been widely used in many research and industrial fields in applications ranging from material processing to microdevices’ fabrication. Indeed, the strong versatility of femtosecond laser micromachining allows working with both transparent and absorptive materials by inducing permanent modifications in the bulk of substrates, by removing material or structuring surfaces or even by growing three-dimensional free-standing structure by direct laser writing. This Special Issue aims to highlight the latest achievements in various applications of femtosecond laser micromachining, with particular interest in new approaches that will pave the way to the future in this technology field. We are looking for research papers, short communications, and review articles that focus on new routes in the exploitation of femtosecond laser machining in the following applications:

  • Surface structuring and patterning
  • Drilling, cutting and welding
  • Multiphoton polymerization
  • Lab-on-chip
  • Biophotonics
  • Integrated optics

Dr. Rebeca Martínez Vázquez
Dr. Francesca Bragheri
Dr. Petra Paiè
Guest Editors

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Keywords

  • material processing
  • femtosecond lasers
  • laser direct writing
  • lab-on-chip
  • multiphoton polymerization
  • biophotonics
  • microfluidics

Published Papers (11 papers)

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Editorial

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2 pages, 189 KiB  
Editorial
Editorial for the Special Issue on New Trends and Applications in Femtosecond Laser Micromachining
by Francesca Bragheri, Petra Paiè and Rebeca Martínez Vázquez
Micromachines 2022, 13(2), 150; https://doi.org/10.3390/mi13020150 - 19 Jan 2022
Cited by 1 | Viewed by 1464
Abstract
Femtosecond laser micromachining is becoming an established fabrication technique for transparent material processing in three dimensions [...] Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)

Research

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10 pages, 767 KiB  
Article
Effects of Thermal Annealing on Femtosecond Laser Micromachined Glass Surfaces
by Federico Sala, Petra Paié, Rebeca Martínez Vázquez, Roberto Osellame and Francesca Bragheri
Micromachines 2021, 12(2), 180; https://doi.org/10.3390/mi12020180 - 11 Feb 2021
Cited by 18 | Viewed by 3257
Abstract
Femtosecond laser micromachining (FLM) of fused silica allows for the realization of three-dimensional embedded optical elements and microchannels with micrometric feature size. The performances of these components are strongly affected by the machined surface quality and residual roughness. The polishing of 3D buried [...] Read more.
Femtosecond laser micromachining (FLM) of fused silica allows for the realization of three-dimensional embedded optical elements and microchannels with micrometric feature size. The performances of these components are strongly affected by the machined surface quality and residual roughness. The polishing of 3D buried structures in glass was demonstrated using different thermal annealing processes, but precise control of the residual roughness obtained with this technique is still missing. In this work, we investigate how the FLM irradiation parameters affect surface roughness and we characterize the improvement of surface quality after thermal annealing. As a result, we achieved a strong roughness reduction, from an average value of 49 nm down to 19 nm. As a proof of concept, we studied the imaging performances of embedded mirrors before and after thermal polishing, showing the capacity to preserve a minimum feature size of the reflected image lower than μ5μm. These results allow for us to push forward the capabilities of this enabling fabrication technology, and they can be used as a starting point to improve the performances of more complex optical elements, such as hollow waveguides or micro-lenses. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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11 pages, 4728 KiB  
Article
Femtosecond Laser Direct Writing of Integrated Photonic Quantum Chips for Generating Path-Encoded Bell States
by Meng Li, Qian Zhang, Yang Chen, Xifeng Ren, Qihuang Gong and Yan Li
Micromachines 2020, 11(12), 1111; https://doi.org/10.3390/mi11121111 - 15 Dec 2020
Cited by 16 | Viewed by 3835
Abstract
Integrated photonic quantum chip provides a promising platform to perform quantum computation, quantum simulation, quantum metrology and quantum communication. Femtosecond laser direct writing (FLDW) is a potential technique to fabricate various integrated photonic quantum chips in glass. Several quantum logic gates fabricated by [...] Read more.
Integrated photonic quantum chip provides a promising platform to perform quantum computation, quantum simulation, quantum metrology and quantum communication. Femtosecond laser direct writing (FLDW) is a potential technique to fabricate various integrated photonic quantum chips in glass. Several quantum logic gates fabricated by FLDW have been reported, such as polarization and path encoded quantum controlled-NOT (CNOT) gates. By combining several single qubit gates and two qubit gates, the quantum circuit can realize different functions, such as generating quantum entangled states and performing quantum computation algorithms. Here we demonstrate the FLDW of integrated photonic quantum chips composed of one Hadamard gate and one CNOT gate for generating all four path-encoded Bell states. The experimental results show that the average fidelity of the reconstructed truth table reaches as high as 98.8 ± 0.3%. Our work is of great importance to be widely applied in many quantum circuits, therefore this technique would offer great potential to fabricate more complex circuits to realize more advanced functions. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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9 pages, 5246 KiB  
Article
AFM Analysis of Micron and Sub-Micron Sized Bridges Fabricated Using the Femtosecond Laser on YBCO Thin Films
by Patrice Umenne
Micromachines 2020, 11(12), 1088; https://doi.org/10.3390/mi11121088 - 8 Dec 2020
Cited by 2 | Viewed by 2295
Abstract
The research arose as a result of the need to use the femtosecond laser to fabricate sub-micron and nano-sized bridges that could be analyzed for the Josephson effect. The femtosecond laser has a low pulse duration of 130 femtoseconds. Hence in an optical [...] Read more.
The research arose as a result of the need to use the femtosecond laser to fabricate sub-micron and nano-sized bridges that could be analyzed for the Josephson effect. The femtosecond laser has a low pulse duration of 130 femtoseconds. Hence in an optical setup it was assumed that it could prevent the thermal degradation of the superconductive material during fabrication. In this paper a series of micron and sub-micron sized bridges where fabricated on superconductive yttrium barium copper oxide (YBCO) thin film using the femtosecond laser, a spherical convex lens of focal length 30 mm and the G-code control programming language applied to a translation stage. The dimensions of the bridges fabricated where analyzed using the atomic force microscope (AFM). As a result, micron sized superconductive bridges of width 1.68 μm, 1.39 μm, 1.23 μm and sub-micron sized bridges of width 858 nm, 732 nm where fabricated. The length of this bridges ranged from 9.6 μm to 12.8 μm. The femtosecond laser technique and the spherical convex lens can be used to fabricate bridges in the sub-micron dimension. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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19 pages, 5622 KiB  
Article
Fabrication of a 3D Multi-Depth Reservoir Micromodel in Borosilicate Glass Using Femtosecond Laser Material Processing
by Ebenezer Owusu-Ansah and Colin Dalton
Micromachines 2020, 11(12), 1082; https://doi.org/10.3390/mi11121082 - 6 Dec 2020
Cited by 8 | Viewed by 3760
Abstract
Micromodels are ideal candidates for microfluidic transport investigations, and they have been used for many applications, including oil recovery and carbon dioxide storage. Conventional fabrication methods (e.g., photolithography and chemical etching) are beset with many issues, such as multiple wet processing steps and [...] Read more.
Micromodels are ideal candidates for microfluidic transport investigations, and they have been used for many applications, including oil recovery and carbon dioxide storage. Conventional fabrication methods (e.g., photolithography and chemical etching) are beset with many issues, such as multiple wet processing steps and isotropic etching profiles, making them unsuitable to fabricate complex, multi-depth features. Here, we report a simpler approach, femtosecond laser material processing (FLMP), to fabricate a 3D reservoir micromodel featuring 4 different depths—35, 70, 140, and 280 µm, over a large surface area (20 mm × 15 mm) in a borosilicate glass substrate. The dependence of etch depth on major processing parameters of FLMP, i.e., average laser fluence (LFav), and computer numerically controlled (CNC) processing speed (PSCNC), was studied. A linear etch depth dependence on LFav was determined while a three-phase exponential decay dependence was obtained for PSCNC. The accuracy of the method was investigated by using the etch depth dependence on PSCNC relation as a model to predict input parameters required to machine the micromodel. This study shows the capability and robustness of FLMP to machine 3D multi-depth features that will be essential for the development, control, and fabrication of complex microfluidic geometries. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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13 pages, 1848 KiB  
Article
Single-Cell Elasticity Measurement with an Optically Actuated Microrobot
by István Grexa, Tamás Fekete, Judit Molnár, Kinga Molnár, Gaszton Vizsnyiczai, Pál Ormos and Lóránd Kelemen
Micromachines 2020, 11(9), 882; https://doi.org/10.3390/mi11090882 - 22 Sep 2020
Cited by 17 | Viewed by 3387
Abstract
A cell elasticity measurement method is introduced that uses polymer microtools actuated by holographic optical tweezers. The microtools were prepared with two-photon polymerization. Their shape enables the approach of the cells in any lateral direction. In the presented case, endothelial cells grown on [...] Read more.
A cell elasticity measurement method is introduced that uses polymer microtools actuated by holographic optical tweezers. The microtools were prepared with two-photon polymerization. Their shape enables the approach of the cells in any lateral direction. In the presented case, endothelial cells grown on vertical polymer walls were probed by the tools in a lateral direction. The use of specially shaped microtools prevents the target cells from photodamage that may arise during optical trapping. The position of the tools was recorded simply with video microscopy and analyzed with image processing methods. We critically compare the resulting Young’s modulus values to those in the literature obtained by other methods. The application of optical tweezers extends the force range available for cell indentations measurements down to the fN regime. Our approach demonstrates a feasible alternative to the usual vertical indentation experiments. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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12 pages, 6579 KiB  
Article
Improvement of Etching Anisotropy in Fused Silica by Double-Pulse Fabrication
by Valdemar Stankevič, Jonas Karosas, Gediminas Račiukaitis and Paulius Gečys
Micromachines 2020, 11(5), 483; https://doi.org/10.3390/mi11050483 - 8 May 2020
Cited by 10 | Viewed by 3023
Abstract
Femtosecond laser-induced selective etching (FLISE) is a promising technology for fabrication of a wide range of optical, mechanical and microfluidic devices. Various etching conditions, together with significant process optimisations, have already been demonstrated. However, the FLISE technology still faces severe limitations for a [...] Read more.
Femtosecond laser-induced selective etching (FLISE) is a promising technology for fabrication of a wide range of optical, mechanical and microfluidic devices. Various etching conditions, together with significant process optimisations, have already been demonstrated. However, the FLISE technology still faces severe limitations for a wide range of applications due to limited processing speed and polarization-dependent etching. In this article, we report our novel results on the double-pulse processing approach on the improvement of chemical etching anisotropy and >30% faster processing speed in fused silica. The effects of pulse delay and pulse duration were investigated for further understanding of the relations between nanograting formation and etching. The internal sub-surface modifications were recorded with double cross-polarised pulses of a femtosecond laser, and a new nanograting morphology (grid-like) was demonstrated by precisely adjusting the processing parameters in a narrow processing window. It was suggested that this grid-like morphology impacts the etching anisotropy, which could be improved by varying the delay between two orthogonally polarized laser pulses. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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11 pages, 3469 KiB  
Article
One-Step Femtosecond Laser Stealth Dicing of Quartz
by Caterina Gaudiuso, Annalisa Volpe and Antonio Ancona
Micromachines 2020, 11(3), 327; https://doi.org/10.3390/mi11030327 - 22 Mar 2020
Cited by 38 | Viewed by 6273
Abstract
We report on a one-step method for cutting 250-µm-thick quartz plates using highly focused ultrashort laser pulses with a duration of 200 fs and a wavelength of 1030 nm. We show that the repetition rate, the scan speed, the pulse overlap and the [...] Read more.
We report on a one-step method for cutting 250-µm-thick quartz plates using highly focused ultrashort laser pulses with a duration of 200 fs and a wavelength of 1030 nm. We show that the repetition rate, the scan speed, the pulse overlap and the pulse energy directly influence the cutting process and quality. Therefore, a suitable choice of these parameters was necessary to get single-pass stealth dicing with neat and flat cut edges. The mechanism behind the stealth dicing process was ascribed to tensile stresses generated by the relaxation of the compressive stresses originated in the laser beam focal volume during irradiation in the bulk material. Such stresses produced micro-fractures whose controlled propagation along the laser beam path led to cutting of the samples. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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8 pages, 1832 KiB  
Article
A Microfluidic Mixer of High Throughput Fabricated in Glass Using Femtosecond Laser Micromachining Combined with Glass Bonding
by Jia Qi, Wenbo Li, Wei Chu, Jianping Yu, Miao Wu, Youting Liang, Difeng Yin, Peng Wang, Zhenhua Wang, Min Wang and Ya Cheng
Micromachines 2020, 11(2), 213; https://doi.org/10.3390/mi11020213 - 19 Feb 2020
Cited by 16 | Viewed by 3749
Abstract
We demonstrate a microfluidic mixer of high mixing efficiency in fused silica substrate using femtosecond laser-induced wet etching and hydroxide-catalysis bonding method. The micromixer has a three-dimensional geometry, enabling efficient mixing based on Baker’s transformation principle. The cross-sectional area of the fabricated micromixer [...] Read more.
We demonstrate a microfluidic mixer of high mixing efficiency in fused silica substrate using femtosecond laser-induced wet etching and hydroxide-catalysis bonding method. The micromixer has a three-dimensional geometry, enabling efficient mixing based on Baker’s transformation principle. The cross-sectional area of the fabricated micromixer was 0.5 × 0.5 mm2, enabling significantly promotion of the throughput of the micromixer. The performance of the fabricated micromixers was evaluated by mixing up blue and yellow ink solutions with a flow rate as high as 6 mL/min. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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Review

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28 pages, 7232 KiB  
Review
3D Manufacturing of Glass Microstructures Using Femtosecond Laser
by Agnė Butkutė and Linas Jonušauskas
Micromachines 2021, 12(5), 499; https://doi.org/10.3390/mi12050499 - 28 Apr 2021
Cited by 42 | Viewed by 7684
Abstract
The rapid expansion of femtosecond (fs) laser technology brought previously unavailable capabilities to laser material processing. One of the areas which benefited the most due to these advances was the 3D processing of transparent dielectrics, namely glasses and crystals. This review is dedicated [...] Read more.
The rapid expansion of femtosecond (fs) laser technology brought previously unavailable capabilities to laser material processing. One of the areas which benefited the most due to these advances was the 3D processing of transparent dielectrics, namely glasses and crystals. This review is dedicated to overviewing the significant advances in the field. First, the underlying physical mechanism of material interaction with ultrashort pulses is discussed, highlighting how it can be exploited for volumetric, high-precision 3D processing. Next, three distinct transparent material modification types are introduced, fundamental differences between them are explained, possible applications are highlighted. It is shown that, due to the flexibility of fs pulse fabrication, an array of structures can be produced, starting with nanophotonic elements like integrated waveguides and photonic crystals, ending with a cm-scale microfluidic system with micro-precision integrated elements. Possible limitations to each processing regime as well as how these could be overcome are discussed. Further directions for the field development are highlighted, taking into account how it could synergize with other fs-laser-based manufacturing techniques. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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21 pages, 4356 KiB  
Review
Femtosecond-Laser Assisted Surgery of the Eye: Overview and Impact of the Low-Energy Concept
by Catharina Latz, Thomas Asshauer, Christian Rathjen and Alireza Mirshahi
Micromachines 2021, 12(2), 122; https://doi.org/10.3390/mi12020122 - 24 Jan 2021
Cited by 28 | Viewed by 5613
Abstract
This article provides an overview of both established and innovative applications of femtosecond (fs)-laser-assisted surgical techniques in ophthalmology. Fs-laser technology is unique because it allows cutting tissue at very high precision inside the eye. Fs lasers are mainly used for surgery of the [...] Read more.
This article provides an overview of both established and innovative applications of femtosecond (fs)-laser-assisted surgical techniques in ophthalmology. Fs-laser technology is unique because it allows cutting tissue at very high precision inside the eye. Fs lasers are mainly used for surgery of the human cornea and lens. New areas of application in ophthalmology are on the horizon. The latest improvement is the high pulse frequency, low-energy concept; by enlarging the numerical aperture of the focusing optics, the pulse energy threshold for optical breakdown decreases, and cutting with practically no side effects is enabled. Full article
(This article belongs to the Special Issue New Trends and Applications in Femtosecond Laser Micromachining)
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