Special Issue "Micro/Nano-surfaces: Fabrication and Applications"

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

Deadline for manuscript submissions: closed (30 April 2021).

Special Issue Editors

Prof. Dr. Yoshiaki Nishijima
E-Mail Website
Guest Editor
Department of Electrical & Computer Engineering, Yokohama National University, Yokohama, Japan
Interests: metamaterials for IR sensors; hydrogen detection; radiative cooling; photonic crystal sensors
Prof. Dr. Saulius Juodkazis
E-Mail Website1 Website2
Guest Editor
Optical Sciences Centre, Swinburne University of Technology, John Street, Hawthorn, VIC 3122, Australia
Interests: nanofabrication; nanophotonics; micro-optics; 3D laser fabrication (additive and subtractive); ablation; light-matter interaction; solar hydrogen
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Special Issue Information

Dear Colleagues,

Future breakthroughs in science and applications are expected from a better understanding and harnessing of mesoscale phenomena. The mesoscale length spans from nanometers to millimeters (nm-to-mm) and usually implies a hierarchical character of structural organization and complex composition. This creates challenges in theoretical modeling and fabrication of materials/structures with mesoscale characteristics. With increasing computing power required for modeling processes on different length and time scales and modern trends in high fabrication throughput and the 3D character of innovative nanotechnology techniques, a new class of materials can be created with tailored optical, mechanical, thermal, and electrical properties. In photonics, metamaterials with tailored optical properties are one of the fastest developing fields.

The proposed Special Issue of Nanomaterials “Micro/Nano-Surfaces: Fabrication and Applications” aims to highlight the multi-disciplinary character of fabrication solutions and reflect the breadth of application fields. Papers covering fundamental and modeling aspects of various functional mesoscale phenomena are also most welcome. The fast-changing state-of-the-art in 3D nano-micro-fabrication techniques warrants the most recent snapshot of this dynamic field which can be illustrated by a variety of specific applications. Applications from the widest range in nano-, bio-, and chemo-sensors, manipulation of light over vis-IR-THz spectral ranges, solar cell, photo-catalysis, surface property control (wetting, friction, bactericidal), etc. are invited.

Prof. Dr. Yoshiaki Nishijima
Prof. Dr. Saulius Juodkazis
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 papers will be 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 1800 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

  • Metamaterials for photo-catalysis
  • Sensors
  • Micro-fluidics
  • Waveguides
  • Solar cells
  • Bactericidal surfaces
  • Energy harvesting

Published Papers (12 papers)

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Research

Article
Femtosecond Laser Trimming with Simultaneous Nanostructuring to Fine Piercing Punch to Electrical Amorphous Steel Sheets
Micromachines 2021, 12(5), 568; https://doi.org/10.3390/mi12050568 - 17 May 2021
Viewed by 434
Abstract
A CVD (Chemical Vapor Deposition) diamond coated tungsten carbide (WC) and cobalt (Co) sintered alloy punch was trimmed by the femtosecond laser machining to sharpen its edge with about 2 μm and to simultaneously make nanostructuring to its side surface. In addition to [...] Read more.
A CVD (Chemical Vapor Deposition) diamond coated tungsten carbide (WC) and cobalt (Co) sintered alloy punch was trimmed by the femtosecond laser machining to sharpen its edge with about 2 μm and to simultaneously make nanostructuring to its side surface. In addition to the sharpened edge, its edge profile was formed to be homogeneous enough to reduce the damage layer width by piercing the electrical amorphous steel sheet stack. Each brittle sheet in the stacked work was damaged to have three kinds of defects by piercing; e.g., the droop-like cracking in the thickness and at the vicinity of hole, the wrinkling in peak-to-valley with partial cracking on the peaks, and the circumferential cracking. When using the WC (Co) punch with the inhomogeneous edge profile in the sharpened edge width, these three damages were induced into each sheet and the maximum damage width exceeded 80 μm. When using the punch with the sharpened edge and homogeneous edge profile, the wrinkling mode was saved and the total affected layer width was significantly reduced to less than 20 μm. Through the precise embossing experiments, this effect of punch edge profile condition to the induced damages was discussed with a statement on the nanostructuring effect on the reduction of damaged width in electrical amorphous steel sheets. The developed tool with the sharpened edge and homogenous edge condition contributes to the realization of a low iron loss motor with a reduced affected layer width. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Article
Chemosensing on Miniaturized Plasmonic Substrates
Micromachines 2021, 12(3), 275; https://doi.org/10.3390/mi12030275 - 06 Mar 2021
Viewed by 531
Abstract
Round, small-sized coverslips were coated for the first time with thin layers of indium tin oxide (ITO, 10–40 nm)/gold (Au, 2–8 nm) and annealed at 550 °C for several hours. The resulting nanostructures on miniaturized substrates were further optimized for the localized surface [...] Read more.
Round, small-sized coverslips were coated for the first time with thin layers of indium tin oxide (ITO, 10–40 nm)/gold (Au, 2–8 nm) and annealed at 550 °C for several hours. The resulting nanostructures on miniaturized substrates were further optimized for the localized surface plasmon resonance (LSPR) chemosensing of a model molecule—1,2-bis-(4-ppyridyl)-ethene (BPE)—with a detection limit of 10−12 M BPE in an aqueous solution. All the fabrication steps of plasmonic-annealed platforms were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Article
Omnidirectional and Broadband Antireflection Effect with Tapered Silicon Nanostructures Fabricated with Low-Cost and Large-Area Capable Nanosphere Lithography
Micromachines 2021, 12(2), 119; https://doi.org/10.3390/mi12020119 - 23 Jan 2021
Viewed by 524
Abstract
In this report, we present a process for the fabrication and tapering of a silicon (Si) nanopillar (NP) array on a large Si surface area wafer (2-inch diameter) to provide enhanced light harvesting for Si solar cell application. From our N,N [...] Read more.
In this report, we present a process for the fabrication and tapering of a silicon (Si) nanopillar (NP) array on a large Si surface area wafer (2-inch diameter) to provide enhanced light harvesting for Si solar cell application. From our N,N-dimethyl-formamide (DMF) solvent-controlled spin-coating method, silica nanosphere (SNS in 310 nm diameter) coating on the Si surface was demonstrated successfully with improved monolayer coverage (>95%) and uniformity. After combining this method with a reactive ion etching (RIE) technique, a high-density Si NP array was produced, and we revealed that controlled tapering of Si NPs could be achieved after introducing a two-step RIE process using (1) CHF3/Ar gases for SNS selective etching over Si and (2) Cl2 gas for Si vertical etching. From our experimental and computational study, we show that an effectively tapered Si NP (i.e., an Si nanotip (NT)) structure could offer a highly effective omnidirectional and broadband antireflection effect for high-efficiency Si solar cell application. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Communication
Optically Transparent Metasurface Absorber Based on Reconfigurable and Flexible Indium Tin Oxide Film
Micromachines 2020, 11(12), 1032; https://doi.org/10.3390/mi11121032 - 24 Nov 2020
Viewed by 675
Abstract
In this paper, we present a flexible, breathable and optically transparent metasurface with ultra-wideband absorption. The designed double layer of indium tin oxide (ITO) films with specific carved structure realizes absorption and electromagnetic (EM) isolation in dual-polarization, as well as good air permeability. [...] Read more.
In this paper, we present a flexible, breathable and optically transparent metasurface with ultra-wideband absorption. The designed double layer of indium tin oxide (ITO) films with specific carved structure realizes absorption and electromagnetic (EM) isolation in dual-polarization, as well as good air permeability. Under the illumination of x- and y-polarization incidence, the metasurface has low reflectivity and transmission from about 2 to 18 GHz. By employing ITO film based on polyethylene terephthalate (PET), the presented metasurface also processes the excellent flexibility and optically transparency, which can be utilized for wearable device application. In addition, the dual-layer design enables mechanically-reconfigurable property of the metasurface. The transmission and reflection coefficients in two polarizations show distinct difference when arranging the different relevant positions of two layers of the metasurface. A sample with 14*14 elements is designed, fabricated and measured, showing good agreement with the simulation results. We envision this work has various potentials in the wearable costume which demands both EM absorption and isolation. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Article
Surface-Tension-Confined Channel with Biomimetic Microstructures for Unidirectional Liquid Spreading
Micromachines 2020, 11(11), 978; https://doi.org/10.3390/mi11110978 - 30 Oct 2020
Viewed by 844
Abstract
Unidirectional liquid spreading without energy input is of significant interest for the broad applications in diverse fields such as water harvesting, drop transfer, oil–water separation and microfluidic devices. However, the controllability of liquid motion and the simplification of manufacturing process remain challenges. Inspired [...] Read more.
Unidirectional liquid spreading without energy input is of significant interest for the broad applications in diverse fields such as water harvesting, drop transfer, oil–water separation and microfluidic devices. However, the controllability of liquid motion and the simplification of manufacturing process remain challenges. Inspired by the peristome of Nepenthes alata, a surface-tension-confined (STC) channel with biomimetic microcavities was fabricated facilely through UV exposure photolithography and partial plasma treatment. Perfect asymmetric liquid spreading was achieved by combination of microcavities and hydrophobic boundary, and the stability of pinning effect was demonstrated. The influences of structural features of microcavities on both liquid spreading and liquid pinning were investigated and the underlying mechanism was revealed. We also demonstrated the spontaneous unidirectional transport of liquid in 3D space and on tilting slope. In addition, through changing pits arrangement and wettability pattern, complex liquid motion paths and microreactors were realized. This work will open a new way for liquid manipulation and lab-on-chip applications. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Article
Second Harmonic Generation from Phase-Engineered Metasurfaces of Nanoprisms
Micromachines 2020, 11(9), 848; https://doi.org/10.3390/mi11090848 - 12 Sep 2020
Cited by 1 | Viewed by 904
Abstract
Metasurfaces of gold (Au) nanoparticles on a SiO2-Si substrate were fabricated for the enhancement of second harmonic generation (SHG) using electron beam lithography and lift-off. Triangular Au nanoprisms which are non-centro-symmetric and support second-order nonlinearity were examined for SHG. The thickness of the SiO2 spacer is shown to be an effective parameter to tune for maximising SHG. Electrical field enhancement at the fundamental wavelength was shown to define the SHG intensity. Numerical modeling of light enhancement was verified by experimental measurements of SHG and reflectivity spectra at the normal incidence. At the plasmonic resonance, SHG is enhanced up to ∼3.5 × 103 times for the optimised conditions. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Article
Kirchhoff’s Thermal Radiation from Lithography-Free Black Metals
Micromachines 2020, 11(9), 824; https://doi.org/10.3390/mi11090824 - 30 Aug 2020
Cited by 3 | Viewed by 936
Abstract
Lithography-free black metals composed of a nano-layered stack of materials are attractive not only due to their optical properties but also by virtue of fabrication simplicity and the cost reduction of devices based on such structures. We demonstrate multi-layer black metal layered structures [...] Read more.
Lithography-free black metals composed of a nano-layered stack of materials are attractive not only due to their optical properties but also by virtue of fabrication simplicity and the cost reduction of devices based on such structures. We demonstrate multi-layer black metal layered structures with engineered electromagnetic absorption in the mid-infrared (MIR) wavelength range. Characterization of thin SiO2 and Si films sandwiched between two Au layers by way of experimental electromagnetic radiation absorption and thermal radiation emission measurements as well as finite difference time domain (FDTD) numerical simulations is presented. Comparison of experimental and simulation data derived optical properties of multi-layer black metals provide guidelines for absorber/emitter structure design and potential applications. In addition, relatively simple lithography-free multi-layer structures are shown to exhibit absorber/emitter performance that is on par with what is reported in the literature for considerably more elaborate nano/micro-scale patterned metasurfaces. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Article
Direct Measurement of Temperature Diffusivity of Nanocellulose-Doped Biodegradable Composite Films
Micromachines 2020, 11(8), 738; https://doi.org/10.3390/mi11080738 - 29 Jul 2020
Cited by 5 | Viewed by 1239
Abstract
The thermal properties of novel nanomaterials play a significant role in determining the performance of the material in technological applications. Herein, direct measurement of the temperature diffusivity of nanocellulose-doped starch–polyurethane nanocomposite films was carried out by the micro-contact method. Polymer films containing up [...] Read more.
The thermal properties of novel nanomaterials play a significant role in determining the performance of the material in technological applications. Herein, direct measurement of the temperature diffusivity of nanocellulose-doped starch–polyurethane nanocomposite films was carried out by the micro-contact method. Polymer films containing up to 2 wt%. of nanocellulose were synthesised by a simple chemical process and are biodegradable. Films of a high optical transmittance T80% (for a 200 μm thick film), which were up to 44% crystalline, were characterised. Two different modalities of temperature diffusivity based on (1) a resistance change and (2) micro-thermocouple detected voltage modulation caused by the heat wave, were used for the polymer films with cross sections of ∼100 μm thickness. Twice different in-plane α and out-of-plane α temperature diffusivities were directly determined with high fidelity: α=2.12×107 m2/s and α=1.13×107 m2/s. This work provides an example of a direct contact measurement of thermal properties of nanocellulose composite biodegradable polymer films. The thermal diffusivity, which is usually high in strongly interconnected networks and crystals, was investigated for the first time in this polymer nanocomposite. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Article
Wetting Properties of Transparent Anatase/Rutile Mixed Phase Glancing Angle Magnetron Sputtered Nano-TiO2 Films
Micromachines 2020, 11(6), 616; https://doi.org/10.3390/mi11060616 - 25 Jun 2020
Cited by 1 | Viewed by 781
Abstract
Transparent polycrystalline TiO2 thin films have been deposited on unheated glass substrates using RF reactive magnetron sputtering. Depositions were carried out at different glancing angles and with different total gas mixture pressures. The variation of these parameters affected the crystal phase composition [...] Read more.
Transparent polycrystalline TiO2 thin films have been deposited on unheated glass substrates using RF reactive magnetron sputtering. Depositions were carried out at different glancing angles and with different total gas mixture pressures. The variation of these parameters affected the crystal phase composition and the surface morphology. Depending on the glancing angle and the pressure, rutile, mixed anatase/ rutile and pure anatase were deposited at low substrate temperature. Both hydrophilic and hydrophobic TiO2 were obtained, exhibiting fast photoconversion to superhydrophilic upon UV irradiation. The effect of the materials physicochemical properties on the wettability and rate of the UV induced superhydrophilicity is evaluated. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Communication
Randomly Multiplexed Diffractive Lens and Axicon for Spatial and Spectral Imaging
Micromachines 2020, 11(4), 437; https://doi.org/10.3390/mi11040437 - 21 Apr 2020
Cited by 10 | Viewed by 1221
Abstract
A new hybrid diffractive optical element (HDOE) was designed by randomly multiplexing an axicon and a Fresnel zone lens. The HDOE generates two mutually coherent waves, namely a conical wave and a spherical wave, for every on-axis point object in the object space. [...] Read more.
A new hybrid diffractive optical element (HDOE) was designed by randomly multiplexing an axicon and a Fresnel zone lens. The HDOE generates two mutually coherent waves, namely a conical wave and a spherical wave, for every on-axis point object in the object space. The resulting self-interference intensity distribution is recorded as the point spread function. A library of point spread functions are recorded in terms of the different locations and wavelengths of the on-axis point objects in the object space. A complicated object illuminated by a spatially incoherent multi-wavelength source generated an intensity pattern that was the sum of the shifted and scaled point spread intensity distributions corresponding to every spatially incoherent point and wavelength in the complicated object. The four-dimensional image of the object was reconstructed using computer processing of the object intensity distribution and the point spread function library. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Article
Detailed Experiment-Theory Comparison of Mid-Infrared Metasurface Perfect Absorbers
Micromachines 2020, 11(4), 409; https://doi.org/10.3390/mi11040409 - 14 Apr 2020
Cited by 8 | Viewed by 1093
Abstract
Realisation of a perfect absorber A = 1 with transmittance and reflectance T = R = 0 by a thin metasurface is one of the hot topics in recent nanophotonics prompted by energy harvesting and sensor applications ( A + R + T = 1 is the energy conservation). Here we tested the optical properties of over 400 structures of metal–insulator–metal (MIM) metasurfaces for a range of variation in thickness of insulator, diameter of a disc and intra-disc distance both experimentally and numerically. Conditions of a near perfect absorption A > 95 % with simultaneously occurring anti-reflection property ( R < 5 % ) was experimentally determined. Differences between the bulk vs. nano-thin film properties at mid-IR of the used materials can be of interest for plasmonic multi-metal alloys and high entropy metals. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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Article
Black Metals: Optical Absorbers
Micromachines 2020, 11(3), 256; https://doi.org/10.3390/mi11030256 - 28 Feb 2020
Cited by 5 | Viewed by 1784
Abstract
We demonstrate a concept and fabrication of lithography-free layered metal-SiO2 thin-film structures which have reduced reflectivity (black appearance), to as low as 0.9%, with 4.9% broadband reflectance (8.9% for soda lime) in the 500–1400 nm range. The multi-layered (four layers) thin-film metamaterial [...] Read more.
We demonstrate a concept and fabrication of lithography-free layered metal-SiO2 thin-film structures which have reduced reflectivity (black appearance), to as low as 0.9%, with 4.9% broadband reflectance (8.9% for soda lime) in the 500–1400 nm range. The multi-layered (four layers) thin-film metamaterial is designed so that optical impedance matching produces minimal reflectance and transmittance within the visible and infra-red (IR) spectral region for a range of incident angles. The structure has enhanced absorbance and is easily tuned for reduced minimal transmission and reflection. This approach should allow for novel anti-reflection surfaces by impedance matching to be realized. Full article
(This article belongs to the Special Issue Micro/Nano-surfaces: Fabrication and Applications)
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