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Micromachines
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Laser Micro- and Nano- Processing
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Laser Micro- and Nano- Processing

A special issue of Micromachines (ISSN 2072-666X).

Deadline for manuscript submissions: closed (31 July 2014) | Viewed by 152143

Special Issue Editors

Dr. Maria Farsari

E-Mail Website
Guest Editor
IESL-FORTH, 100 N.Plastira str., Vassilika Vouton, 70013 Heraklion, Crete, Greece
Interests: nonlinear optics; nanophotonics; 3D laser printing; laser-based additive manufacturing; metamaterials
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Costas Fotakis

E-Mail Website
Guest Editor
IESL-FORTH, 100 N.Plastira str., Vassilika Vouton, 70013 Heraklion, Crete, Greece
Interests: light-matter interactions; laser materials processing; biophotonics

Special Issue Information

Dear Colleagues,

Numerous recent technological advances rely on controllable micro- and nano-fabrication techniques to improve the performance of devices in various applications (e.g., in biomedicine, communications, and energy harvesting). Lasers are uniquely suited for a wide variety of fabrication applications at both the micro- and the nano- scales, in both the production and research environments. In light of this, we announce a Special Issue on "Laser Micro- and Nano Processing" and invite original contributions. We seek not only to report recent developments, but also to mold the future of the field. Example topics include matter interactions, direct write processes, ultra-short pulse laser processing, surface treatment, and 3-D micro- and nano-fabrication.

We look forward to receiving your contributions.

Prof. Dr. Costas Fotakis
Dr. Maria Farsari
Guest Editors

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.


Keywords

  • Laser-Matter Interaction
  • Fundamental aspects (dynamics, modeling)
  • Nanotechnology
  • Direct write processes (MAPLE DW, LIFT, etc.)
  • Ultra-short pulse laser processing
  • VUV laser processing
  • Surface treatment (texturing, cleaning, annealing, modification, etc.)
  • Micro-patterning and micro-structuring
  • Micro-machining
  • 3-D micro- and nano-fabrication
  • Drilling and cutting
  • Micro-forming
  • Lithography (including EUV sources and applications)
  • Manufacture of micro devices and systems
  • Film deposition and synthesis of advanced materials
  • Nano- and micro-particles
  • Medical and biological applications
  • Photochemistry
  • Glass/Ceramic processing

Published Papers (17 papers)

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Research

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6173 KiB  
Article
Effects of Laser Operating Parameters on Piezoelectric Substrates Micromachining with Picosecond Laser
by Lamia EL Fissi, Victor Xhurdebise and Laurent A. Francis
Micromachines 2015, 6(1), 19-31; https://doi.org/10.3390/mi6010019 - 23 Dec 2014
Cited by 12 | Viewed by 5951
Abstract
Ten picoseconds (200 kHz) ultrafast laser micro-structuring of piezoelectric substrates including AT-cut quartz, Lithium Niobate and Lithium Tantalate have been studied for the purpose of piezoelectric devices application ranging from surface acoustic wave devices, e.g., bandpass filters, to photonic devices such as optical [...] Read more.
Ten picoseconds (200 kHz) ultrafast laser micro-structuring of piezoelectric substrates including AT-cut quartz, Lithium Niobate and Lithium Tantalate have been studied for the purpose of piezoelectric devices application ranging from surface acoustic wave devices, e.g., bandpass filters, to photonic devices such as optical waveguides and holograms. The study examines the impact of changing several laser parameters on the resulting microstructural shapes and morphology. The micromachining rate has been observed to be strongly dependent on the operating parameters, such as the pulse fluence, the scan speed and the scan number. The results specifically indicate that ablation at low fluence and low speed scan tends to form a U-shaped cross-section, while a V-shaped profile can be obtained by using a high fluence and a high scan speed. The evolution of surface morphology revealed that laser pulses overlap in a range around 93% for both Lithium Niobate (LiNbO3) and Lithium Tantalate (LiTaO3) and 98% for AT-cut quartz can help to achieve optimal residual surface roughness. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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3197 KiB  
Article
Impacts of Ambient and Ablation Plasmas on Short- and Ultrashort-Pulse Laser Processing of Surfaces
by Nadezhda M. Bulgakova, Alexei N. Panchenko, Vladimir P. Zhukov, Sergey I. Kudryashov, Antonio Pereira, Wladimir Marine, Tomas Mocek and Alexander V. Bulgakov
Micromachines 2014, 5(4), 1344-1372; https://doi.org/10.3390/mi5041344 - 09 Dec 2014
Cited by 31 | Viewed by 10566
Abstract
In spite of the fact that more than five decades have passed since the invention of laser, some topics of laser-matter interaction still remain incompletely studied. One of such topics is plasma impact on the overall phenomenon of the interaction and its particular [...] Read more.
In spite of the fact that more than five decades have passed since the invention of laser, some topics of laser-matter interaction still remain incompletely studied. One of such topics is plasma impact on the overall phenomenon of the interaction and its particular features, including influence of the laser-excited plasma re-radiation, back flux of energetic plasma species, and massive material redeposition, on the surface quality and processing efficiency. In this paper, we analyze different plasma aspects, which go beyond a simple consideration of the well-known effect of plasma shielding of laser radiation. The following effects are considered: ambient gas ionization above the target on material processing with formation of a “plasma pipe”; back heating of the target by both laser-driven ambient and ablation plasmas through conductive and radiative heat transfer; plasma chemical effects on surface processing including microstructure growth on liquid metals; complicated dynamics of the ablation plasma flow interacting with an ambient gas that can result in substantial redeposition of material around the ablation spot. Together with a review summarizing our main to-date achievements and outlining research directions, we present new results underlining importance of laser plasma dynamics and photoionization of the gas environment upon laser processing of materials. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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1587 KiB  
Article
Laser Controlled Synthesis of Noble Metal Nanoparticle Arrays for Low Concentration Molecule Recognition
by Enza Fazio, Fortunato Neri, Rosina C. Ponterio, Sebastiano Trusso, Matteo Tommasini and Paolo Maria Ossi
Micromachines 2014, 5(4), 1296-1309; https://doi.org/10.3390/mi5041296 - 01 Dec 2014
Cited by 15 | Viewed by 5949
Abstract
Nanostructured gold and silver thin films were grown by pulsed laser deposition.Performing the process in an ambient gas (Ar) leads to the nucleation and growth ofnanoparticles in the ablation plasma and their self-organization on the substrate. Thedependence of surface nanostructuring of the films [...] Read more.
Nanostructured gold and silver thin films were grown by pulsed laser deposition.Performing the process in an ambient gas (Ar) leads to the nucleation and growth ofnanoparticles in the ablation plasma and their self-organization on the substrate. Thedependence of surface nanostructuring of the films on the deposition parameters is discussedconsidering in particular the number of laser pulses and the ambient gas nature and pressure.The performance of the deposited thin films as substrates for surface-enhanced Ramanspectroscopy (SERS) was tested against the detection of molecules at a low concentration.Taking Raman maps on micrometer-sized areas, the spatial homogeneity of the substrateswith respect to the SERS signal was tested. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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4603 KiB  
Article
Femtosecond Laser Irradiation of Plasmonic Nanoparticles in Polymer Matrix: Implications for Photothermal and Photochemical Material Alteration
by Anton A. Smirnov, Alexander Pikulin, Natalia Sapogova and Nikita Bityurin
Micromachines 2014, 5(4), 1202-1218; https://doi.org/10.3390/mi5041202 - 19 Nov 2014
Cited by 13 | Viewed by 5727
Abstract
We analyze the opportunities provided by the plasmonic nanoparticles inserted into the bulk of a transparent medium to modify the material by laser light irradiation. This study is provoked by the advent of photo-induced nano-composites consisting of a typical polymer matrix and metal [...] Read more.
We analyze the opportunities provided by the plasmonic nanoparticles inserted into the bulk of a transparent medium to modify the material by laser light irradiation. This study is provoked by the advent of photo-induced nano-composites consisting of a typical polymer matrix and metal nanoparticles located in the light-irradiated domains of the initially homogeneous material. The subsequent irradiation of these domains by femtosecond laser pulses promotes a further alteration of the material properties. We separately consider two different mechanisms of material alteration. First, we analyze a photochemical reaction initiated by the two-photon absorption of light near the plasmonic nanoparticle within the matrix. We show that the spatial distribution of the products of such a reaction changes the symmetry of the material, resulting in the appearance of anisotropy in the initially isotropic material or even in the loss of the center of symmetry. Second, we analyze the efficiency of a thermally-activated chemical reaction at the surface of a plasmonic particle and the distribution of the product of such a reaction just near the metal nanoparticle irradiated by an ultrashort laser pulse. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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2597 KiB  
Article
Effect of Laser Power on the Quality of Drilled Micro Hole Using Cu50Zr50 Amorphous Alloys Foils
by Chuan-Jie Wang, Gang Chen, Dong Luan and Peng Zhang
Micromachines 2014, 5(4), 1061-1068; https://doi.org/10.3390/mi5041061 - 11 Nov 2014
Cited by 10 | Viewed by 5727
Abstract
The rapid growth of the micro-electro-mechanical systems (MEMS) is being driven by the rapid development of the micro manufacturing processes. Laser beam machining is one of the micro manufacturing processes which can shape almost all ranges of engineering materials. In this study, the [...] Read more.
The rapid growth of the micro-electro-mechanical systems (MEMS) is being driven by the rapid development of the micro manufacturing processes. Laser beam machining is one of the micro manufacturing processes which can shape almost all ranges of engineering materials. In this study, the effect of laser power on the quality of drilled micro holes using Cu50Zr50 amorphous alloys foils is experimentally investigated. It indicates that both entrance and exit circularities diameters increase with laser power. The circularities of the holes at the entry and the exit are in the range of 0.893 to 0.997. The taper of drilled holes increases quickly to a stable value with the increase of laser power from 60 to 110 W, then decreases quickly when the laser power becomes larger than 170 W. The micro holes with a diameter of 400 to 1200 μm are manufactured successfully by laser drilling processes. The formation mechanism of the quality of the laser drilled hole is analyzed based on the laser beam and the properties of amorphous alloys foils. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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407 KiB  
Article
Micromachining of AlN and Al2O3 Using Fiber Laser
by Florian Preusch, Benedikt Adelmann and Ralf Hellmann
Micromachines 2014, 5(4), 1051-1060; https://doi.org/10.3390/mi5041051 - 10 Nov 2014
Cited by 39 | Viewed by 7704
Abstract
We report on high precision high speed micromachining of Al2O3 and AlN using pulsed near infrared fiber laser. Ablation thresholds are determined to be 30 J/cm2 for alumina and 18 J/cm2 for aluminum nitride. The factors influencing the [...] Read more.
We report on high precision high speed micromachining of Al2O3 and AlN using pulsed near infrared fiber laser. Ablation thresholds are determined to be 30 J/cm2 for alumina and 18 J/cm2 for aluminum nitride. The factors influencing the efficiency and quality of 3D micromachining, namely the surface roughness, the material removal rate and the ablation depth accuracy are determined as a function of laser repetition rate and pulse overlap. Using a fluence of 64 J/cm², we achieve a material removal rate of up to 94 mm³/h in Al2O3 and 135 mm³/h in AlN for high pulse overlaps (89% and 84%). A minimum roughness of 1.5 μm for alumina and 1.65 μm for aluminum nitride can be accomplished for medium pulse overlaps (42% to 56%). In addition, ablation depth deviation of the micromachining process of smaller than 8% for alumina and 2% for aluminum nitride are achieved. Based on these results, by structuring exemplarily 3D structures we demonstrate the potential of high quality and efficient 3D micromachining using pulsed fiber laser. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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3044 KiB  
Article
Characterization of Laser Beam Shaping Optics Based on Their Ablation Geometry of Thin Films
by Stefan Rung, Johannes Barth and Ralf Hellmann
Micromachines 2014, 5(4), 943-953; https://doi.org/10.3390/mi5040943 - 27 Oct 2014
Cited by 33 | Viewed by 13642
Abstract
Thin film ablation with pulsed nanosecond lasers can benefit from the use of beam shaping optics to transform the Gaussian beam profile with a circular footprint into a Top-Hat beam profile with a rectangular footprint. In general, the quality of the transformed beam [...] Read more.
Thin film ablation with pulsed nanosecond lasers can benefit from the use of beam shaping optics to transform the Gaussian beam profile with a circular footprint into a Top-Hat beam profile with a rectangular footprint. In general, the quality of the transformed beam profile depends strongly on the beam alignment of the entire laser system. In particular, the adjustment of the beam shaping element is of upmost importance. For an appropriate alignment of the beam shaper, it is generally necessary to observe the intensity distribution near the focal position of the applied focusing optics. Systems with a low numerical aperture (NA) can commonly be qualified by means of laser beam profilers, such as a charge-coupled device (CCD) camera. However, laser systems for micromachining typically employ focus lenses with a high NA, which generate focal spot sizes of only several microns in diameter. This turns out to be a challenge for common beam profiling measurement systems and complicates the adjustment of the beam shaper strongly. In this contribution, we evaluate the quality of a Top-Hat beam profiling element and its alignment in the working area based on the ablated geometry of single pulse ablation of thin transparent conductive oxides. To determine the best achievable adjustment, we develop a quality index for rectangular laser ablation spots and investigate the influences of different alignment parameters, which can affect the intensity distribution of a Top-Hat laser beam profile. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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7247 KiB  
Article
3D Microporous Scaffolds Manufactured via Combination of Fused Filament Fabrication and Direct Laser Writing Ablation
by Mangirdas Malinauskas, Sima Rekštytė, Laurynas Lukoševičius, Simas Butkus, Evaldas Balčiūnas, Milda Pečiukaitytė, Daiva Baltriukienė, Virginija Bukelskienė, Arūnas Butkevičius, Povilas Kucevičius, Vygandas Rutkūnas and Saulius Juodkazis
Micromachines 2014, 5(4), 839-858; https://doi.org/10.3390/mi5040839 - 30 Sep 2014
Cited by 111 | Viewed by 20810
Abstract
A 3D printing fused filament fabrication (FFF) approach has been implemented for the creation of microstructures having an internal 3D microstructure geometry. These objects were produced without any sacrificial structures or additional support materials, just by precisely tuning the nozzle heating, fan cooling [...] Read more.
A 3D printing fused filament fabrication (FFF) approach has been implemented for the creation of microstructures having an internal 3D microstructure geometry. These objects were produced without any sacrificial structures or additional support materials, just by precisely tuning the nozzle heating, fan cooling and translation velocity parameters. The manufactured microporous structures out of polylactic acid (PLA) had fully controllable porosity (20%–60%) and consisted of desired volume pores (~0.056 μm3). The prepared scaffolds showed biocompatibility and were suitable for the primary stem cell growth. In addition, direct laser writing (DLW) ablation was employed to modify the surfaces of the PLA structures, drill holes, as well as shape the outer geometries of the created objects. The proposed combination of FFF printing with DLW offers successful fabrication of 3D microporous structures with functionalization capabilities, such as the modification of surfaces, the generation of grooves and microholes and cutting out precisely shaped structures (micro-arrows, micro-gears). The produced structures could serve as biomedical templates for cell culturing, as well as biodegradable implants for tissue engineering. The additional micro-architecture is important in connection with the cell types used for the intention of cell growing. Moreover, we show that surface roughness can be modified at the nanoscale by immersion into an acetone bath, thus increasing the hydrophilicity. The approach is not limited to biomedical applications, it could be employed for the manufacturing of bioresorbable 3D microfluidic and micromechanic structures. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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1963 KiB  
Article
Compact Birefringent Waveplates Photo-Induced in Silica by Femtosecond Laser
by Matthieu Lancry, Rudy Desmarchelier, Kevin Cook, Bertrand Poumellec and John Canning
Micromachines 2014, 5(4), 825-838; https://doi.org/10.3390/mi5040825 - 30 Sep 2014
Cited by 14 | Viewed by 6772
Abstract
Recently, we showed that femtosecond laser induced “nanogratings” consist of thin regions with a low refractive index (Δn = −0.15), due to the formation of nanoporous silica surrounded by regions with a positive index change. In this paper, we investigate a wide [...] Read more.
Recently, we showed that femtosecond laser induced “nanogratings” consist of thin regions with a low refractive index (Δn = −0.15), due to the formation of nanoporous silica surrounded by regions with a positive index change. In this paper, we investigate a wide range of laser parameters to achieve very high retardance within a single layer; as much as 350 nm at λ = 546 nm but also to minimize the competing losses. We show that the total retardance depends on the number of layers present and can be accumulated in the direction of laser propagation to values higher than 1600 nm. This opens the door to using these nanostructures as refined building blocks for novel optical elements based on strong retardance. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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4824 KiB  
Article
Multifunctional Material Structures Based on Laser-Etched Carbon Nanotube Arrays
by Aline Emplit, Ester Tooten, Victor Xhurdebise and Isabelle Huynen
Micromachines 2014, 5(3), 756-765; https://doi.org/10.3390/mi5030756 - 22 Sep 2014
Cited by 6 | Viewed by 5986
Abstract
High-power electronics in the transportation and aerospace sectors need size and weight reduction. Multifunctional and multistructured materials are currently being developed to couple electromagnetic (EM) and thermal properties, i.e., shielding against electromagnetic impulsions, and thermal management across the thermal interface material (TIM). [...] Read more.
High-power electronics in the transportation and aerospace sectors need size and weight reduction. Multifunctional and multistructured materials are currently being developed to couple electromagnetic (EM) and thermal properties, i.e., shielding against electromagnetic impulsions, and thermal management across the thermal interface material (TIM). In this work, we investigate laser-machined patterned carbon nanotube (CNT) micro-brushes as an alternative to metallic structures for driving simultaneously EM and heat propagation. The thermal and electromagnetic response of the CNT array is expected to be sensitive to the micro-structured pattern etched in the CNT brush. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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6765 KiB  
Article
Three-Dimensional Glass Monolithic Micro-Flexure Fabricated by Femtosecond Laser Exposure and Chemical Etching
by Viktor Tielen and Yves Bellouard
Micromachines 2014, 5(3), 697-710; https://doi.org/10.3390/mi5030697 - 11 Sep 2014
Cited by 36 | Viewed by 13836
Abstract
Flexures are components of micro-mechanisms efficiently replacing classical multi-part joints found at the macroscale. So far, flexures have been limited to two-dimensional planar designs due to the lack of a suitable three-dimensional micromanufacturing process. Here we demonstrate and characterize a high-strength transparent monolithic [...] Read more.
Flexures are components of micro-mechanisms efficiently replacing classical multi-part joints found at the macroscale. So far, flexures have been limited to two-dimensional planar designs due to the lack of a suitable three-dimensional micromanufacturing process. Here we demonstrate and characterize a high-strength transparent monolithic three-dimensional flexural component fabricated out of fused silica using non-ablative femtosecond laser processing combined with chemical etching. As an illustration of the potential use of this flexure, we propose a design of a Hoecken linkage entirely made with three-dimensional cross-spring pivot hinges. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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2370 KiB  
Article
Design, Fabrication and Computational Characterization of a 3D Micro-Valve Built by Multi-Photon Polymerization
by Stratos Galanopoulos, Nikoleta Chatzidai, Vasileia Melissinaki, Alexandros Selimis, Charalampos Schizas, Maria Farsari and Dimitris Karalekas
Micromachines 2014, 5(3), 505-514; https://doi.org/10.3390/mi5030505 - 06 Aug 2014
Cited by 15 | Viewed by 7394
Abstract
We report on the design, modeling and fabrication by multi-photon polymerization of a complex medical fluidic device. The physical dimensions of the built micro-valve prototype are compared to those of its computer-designed model. Important fabrication issues such as achieving high dimensional resolution and [...] Read more.
We report on the design, modeling and fabrication by multi-photon polymerization of a complex medical fluidic device. The physical dimensions of the built micro-valve prototype are compared to those of its computer-designed model. Important fabrication issues such as achieving high dimensional resolution and ability to control distortion due to shrinkage are presented and discussed. The operational performance of both multi-photon and CAD-created models under steady blood flow conditions was evaluated and compared through computational fluid dynamics analysis. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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1232 KiB  
Article
Laser Direct Writing of Thick Hybrid Polymers for Microfluidic Chips
by Akanksha Singh, Gianmario Scotti, Tiina Sikanen, Ville Jokinen and Sami Franssila
Micromachines 2014, 5(3), 472-485; https://doi.org/10.3390/mi5030472 - 22 Jul 2014
Cited by 20 | Viewed by 9291
Abstract
This work presents patterning of thick (10–50 µm) hybrid polymer structures of ORMOCER® by laser direct writing. ORMOCER® combine polymer-like fabrication processes with glass-like surface chemistry that is beneficial for many bio-microfluidic applications. ORMOCER® is liquid before exposure, so patterning [...] Read more.
This work presents patterning of thick (10–50 µm) hybrid polymer structures of ORMOCER® by laser direct writing. ORMOCER® combine polymer-like fabrication processes with glass-like surface chemistry that is beneficial for many bio-microfluidic applications. ORMOCER® is liquid before exposure, so patterning is done by contact-free lithography, such as proximity exposure. With laser direct writing, we obtained higher resolution patterns, with smaller radius of curvature (~2–4 µm), compared to proximity exposure (~10–20 µm). Process parameters were studied to find the optimal dose for different exposure conditions and ORMOCER® layer thicknesses. Two fluidic devices were successfully fabricated: a directional wetting device (fluidic diode) and an electrophoresis chip. The fluidic diode chip operation depends on the sharp corner geometry and water contact angle, and both have been successfully tailored to obtain diodicity. Electrophoresis chips were used to separate of two fluorescent dyes, rhodamine 123 and fluorescein. The electrophoresis chip also made use of ORMOCER® to ORMOCER® bonding. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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1039 KiB  
Article
Sequential Atmospheric Pressure Plasma-Assisted Laser Ablation of Photovoltaic Cover Glass for Improved Contour Accuracy
by Christoph Gerhard, Maximilian Dammann, Stephan Wieneke and Wolfgang Viöl
Micromachines 2014, 5(3), 408-419; https://doi.org/10.3390/mi5030408 - 02 Jul 2014
Cited by 9 | Viewed by 6651
Abstract
In this paper, we present sequential atmospheric pressure plasma-assisted laser ablation of photovoltaic cover glass. First, glass samples were plasma pre-treated using a hydrogenous plasma process gas in order to accomplish a modification of the near-surface glass network by a chemical reduction and [...] Read more.
In this paper, we present sequential atmospheric pressure plasma-assisted laser ablation of photovoltaic cover glass. First, glass samples were plasma pre-treated using a hydrogenous plasma process gas in order to accomplish a modification of the near-surface glass network by a chemical reduction and the implantation of hydrogen. As a result, the transmission at a wavelength of 355 nm was reduced by approximately 2% after plasma treatment duration of 60 min. Further, the surface polarity was increased by approximately 78%, indicating an increase of the near-surface index of refraction. Subsequently to the plasma pre-treatment, the samples were laser ablated applying the above-mentioned laser wavelength of a Nd:YAG nanosecond laser. Compared to untreated samples, a significant decrease of the form error by 45% without any mentionable change in the ablation rate was obtained in the case of pre-treated samples. For comparison, the results and findings are discussed with respect to previous work, where the presented plasma-assisted ablation procedure was applied to optical glasses. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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661 KiB  
Article
Laser Micro Bending Process of Ti6Al4V Square Bar
by Gang Chen and Peng Zhang
Micromachines 2014, 5(2), 359-372; https://doi.org/10.3390/mi5020359 - 11 Jun 2014
Cited by 2 | Viewed by 6083
Abstract
Laser micro bending process of Ti6Al4V square bar are carried out using a 3D thermo-mechanical finite element analytical model (FEM). The transient temperature fields, displacement fields, stress fields and strain fields are obtained and analyzed. The results show that the bending angel during [...] Read more.
Laser micro bending process of Ti6Al4V square bar are carried out using a 3D thermo-mechanical finite element analytical model (FEM). The transient temperature fields, displacement fields, stress fields and strain fields are obtained and analyzed. The results show that the bending angel during laser micro bending process is in good agreement with experimental measurements. The effects of process parameters on temperature and deformation are also investigated here. During the bending process the temperature increases with the increase of the laser power and the irradiation time. Radiation of the laser beam yields to a rapid temperature increase at the irradiated surface, which leads to the high temperature gradients between the irradiated surface and the unirradiated surface, which suggest that the mechanism of laser micro bending is the temperature gradient mechanism. The z displacement of forward direction and reverse direction increase when the laser power and irradiation time increase. Laser micro bending process can obtain the larger bending angles reverse to laser beam using higher laser power and shorter irradiation time. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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2194 KiB  
Article
Optimization of Femtosecond Laser Polymerized Structural Niches to Control Mesenchymal Stromal Cell Fate in Culture
by Manuela T. Raimondi, Michele M. Nava, Shane M. Eaton, Arianna Bernasconi, Krishna C. Vishnubhatla, Giulio Cerullo and Roberto Osellame
Micromachines 2014, 5(2), 341-358; https://doi.org/10.3390/mi5020341 - 11 Jun 2014
Cited by 45 | Viewed by 7830
Abstract
We applied two-photon polymerization to fabricate 3D synthetic niches arranged in complex patterns to study the effect of mechano-topological parameters on morphology, renewal and differentiation of rat mesenchymal stromal cells. Niches were formed in a photoresist with low auto-fluorescence, which enabled the clear [...] Read more.
We applied two-photon polymerization to fabricate 3D synthetic niches arranged in complex patterns to study the effect of mechano-topological parameters on morphology, renewal and differentiation of rat mesenchymal stromal cells. Niches were formed in a photoresist with low auto-fluorescence, which enabled the clear visualization of the fluorescence emission of the markers used for biological diagnostics within the internal niche structure. The niches were structurally stable in culture up to three weeks. At three weeks of expansion in the niches, cell density increased by almost 10-fold and was 67% greater than in monolayer culture. Evidence of lineage commitment was observed in monolayer culture surrounding the structural niches, and within cell aggregates, but not inside the niches. Thus, structural niches were able not only to direct stem cell homing and colony formation, but also to guide aggregate formation, providing increased surface-to-volume ratios and space for stem cells to adhere and renew, respectively. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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Review

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10770 KiB  
Review
Femtosecond Laser 3D Fabrication in Porous Glass for Micro- and Nanofluidic Applications
by Yang Liao and Ya Cheng
Micromachines 2014, 5(4), 1106-1134; https://doi.org/10.3390/mi5041106 - 17 Nov 2014
Cited by 17 | Viewed by 10524
Abstract
The creation of complex three-dimensional (3D) fluidic systems composed of hollow micro- and nanostructures embedded in transparent substrates has attracted significant attention from both scientific and applied research communities. However, it is by now still a formidable challenge to build 3D micro- and [...] Read more.
The creation of complex three-dimensional (3D) fluidic systems composed of hollow micro- and nanostructures embedded in transparent substrates has attracted significant attention from both scientific and applied research communities. However, it is by now still a formidable challenge to build 3D micro- and nanofluidic structures with arbitrary configurations using conventional planar lithographic fabrication methods. As a direct and maskless fabrication technique, femtosecond laser micromachining provides a straightforward approach for high-precision, spatially-selective, modification inside transparent materials through nonlinear optical absorption. In this paper, we demonstrate rapid fabrication of high-aspect-ratio micro- and/or nanofluidic structures with various 3D configurations by femtosecond laser direct writing in porous glass substrates. Based on this approach, we demonstrate several functional micro- and nanofluidic devices including a 3D passive microfluidic mixer, a capillary electrophoresis (CE) analysis chip, and an integrated micro-nanofluidic system for single DNA analysis. The possible mechanisms behind the formation of high-aspect-ratio micro- and nanochannels are also discussed. This technology offers new opportunities to develop novel 3D micro-nanofluidic systems for a variety of lab-on-a-chip applications. Full article
(This article belongs to the Special Issue Laser Micro- and Nano- Processing)
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