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Feature Papers in Micro- or Nanoscale Materials Sciences and Technology
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Feature Papers in Micro- or Nanoscale Materials Sciences and Technology

A special issue of Micro (ISSN 2673-8023). This special issue belongs to the section "Microscale Materials Science".

Deadline for manuscript submissions: closed (30 September 2023) | Viewed by 21110

Special Issue Editor

Dr. Ajit Roy

E-Mail Website
Guest Editor
Air Force Research Laboratory, Materials and Manufacturing Directorate, Dayton, OH 45433-7728, USA
Interests: nano materials; heterostructure; nanomaterials interface; nano materials design; modeling and simulation; nano and micro scale metrology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear colleagues，

Future materials are expected to perform in a disparate and dynamic environment with enhanced performance efficiency. In this pursuit, efficient materials often exhibit simultaneous multifunctionality (structural, electrical, thermal, optical, dielectric, etc.), even in very dynamic environments. Towards boosting materials performance or work efficiency, a compelling approach is to extract the same amount of work at every point of the materials volume, even in the gradient field. This may require placing different materials selectively at different locations (i.e., materials hybridization) to extract almost the same amount of work, whose effectiveness improves significantly if we can take such selectivity in a smaller (micron or atomic) scale—hence the importance of microscale or nanoscale materials science. Science-related materials selection and design at the micro- or nanoatomic scale materials hybridization (such as materials interface optimization and its validation) is still evolving and offers unprecedented opportunities in expanding the materials design and performance space.

In this Special Issue on “Feature Papers in Micro- or Nanoscale Materials Sciences and Technology”, we solicit foundational work in materials processing, innovative materials characterization techniques, metrology, and materials modeling approaches towards advancing micro- or nanoscale materials science. We invite original research work in the broad materials application space (structural, thermal, electrical, magnetic, dielectric, and more), discovering innovative micro- or nanoscale materials science issues.

Dr. Ajit Roy
Guest Editor

Manuscript Submission Information

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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. Micro is an international peer-reviewed open access quarterly 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 1000 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

  • materials processing
  • innovative materials
  • micro- or nanoscale materials science
  • materials application
  • materials hybridization

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Published Papers (16 papers)

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12 pages, 2238 KiB  
Article
Enhancing the Photovoltaic Performance of Cd(1−x)ZnxS Thin Films Using Seed Assistance and EDTA Treatment
by Gayan W. C. Kumarage, Ruwan P. Wijesundera, Elisabetta Comini and Buddhika S. Dassanayake
Micro 2023, 3(4), 867-878; https://doi.org/10.3390/micro3040059 - 12 Nov 2023
Viewed by 646
Abstract
This research article provides a comprehensive investigation into the optoelectronic characteristics of three distinct types of cadmium sulfide (CdS) thin films, namely: (a) conventionally prepared CdS thin films using chemical bath deposition (CBD-CdS), (b) CdS thin films produced via chemical bath deposition with [...] Read more.
This research article provides a comprehensive investigation into the optoelectronic characteristics of three distinct types of cadmium sulfide (CdS) thin films, namely: (a) conventionally prepared CdS thin films using chemical bath deposition (CBD-CdS), (b) CdS thin films produced via chemical bath deposition with the inclusion of zinc (CBD-Cd(1−x)ZnxS, x = 0.3), and (c) CdS thin films synthesized using a seed-assisted approach, treated with ethylenediaminetetraacetic acid (EDTA), and incorporating zinc (ED/CBD + EDTA-Cd(1−x)ZnxS). The investigation reveals that the crystallite size of these thin films decreases upon the addition of EDTA to the reaction solution, leading to an increase in the inter-planar spacing and dislocation density. Furthermore, a blue shift in the transmittance edge of the ED/CBD + EDTA-Cd(1−x)ZnxS samples compared to CBD-CdS implies modifications in the band gaps of the deposited films. The incorporation of Zn2+ into the reaction solution results in an increased band gap value of up to 2.42 eV. This suggests that Cd(1−x)ZnxS thin films permit more efficient photon transmission compared to conventional CdS. Among the three types of films studied, ED/CBD + EDTA-Cd(1−x)ZnxS exhibits the highest optical band gap of 2.50 eV. This increase in the optical band gap is attributed to the smaller crystallite size and the splitting of the tail levels from the band structure. Additionally, the increment in the optical band gap leads to reduced light absorption at longer wavelengths, thereby enhancing the electrical properties. Notably, ED/CBD + EDTA-Cd(1−x)ZnxS thin films demonstrate improved photovoltaic performance in a photoelectrochemical (PEC) cell, characterized by enhanced open-circuit voltage (363 mV, VOC), short-circuit current (35.35 μA, ISC), and flat-band voltage (−692 mV, Vfb). These improvements are attributed to the better adhesion of CdS to the fluorine-doped tin oxide (FTO) substrate and improved inter-particle connectivity. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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10 pages, 11778 KiB  
Communication
Improved Properties of Post-Deposition Annealed Ga2O3/SiC and Ga2O3/Al2O3/SiC Back-Gate Transistors Fabricated by Radio Frequency Sputtering
by Hee-Jae Lee, Geon-Hee Lee, Seung-Hwan Chung, Dong-Wook Byun, Michael A. Schweitz, Dae Hwan Chun, Nack Yong Joo, Minwho Lim, Tobias Erlbacher and Sang-Mo Koo
Micro 2023, 3(4), 775-784; https://doi.org/10.3390/micro3040055 - 30 Sep 2023
Viewed by 1033
Abstract
The high breakdown electric field, n-type doping capability, availability of high-quality substrates, and high Baliga’s figure of merit of Ga2O3 demonstrate its potential as a next-generation power semiconductor material. However, the thermal conductivity of Ga2O3 is lower [...] Read more.
The high breakdown electric field, n-type doping capability, availability of high-quality substrates, and high Baliga’s figure of merit of Ga2O3 demonstrate its potential as a next-generation power semiconductor material. However, the thermal conductivity of Ga2O3 is lower than that of other wide-bandgap materials, resulting in the degradation of the electrical performance and reduced reliability of devices. The heterostructure formation on substrates with high thermal conductivity has been noted to facilitate heat dissipation in devices. In this work, Ga2O3 thin films with an Al2O3 interlayer were deposited on SiC substrates by radio frequency sputtering. Post-deposition annealing was performed at 900 °C for 1 h to crystallize the Ga2O3 thin films. The Auger electron spectroscopy depth profiles revealed the interdiffusion of the Ga and Al atoms at the Ga2O3/Al2O3 interface after annealing. The X-ray diffraction (XRD) results displayed improved crystallinity after annealing and adding the Al2O3 interlayer. The crystallite size increased from 5.72 to 8.09 nm as calculated by the Scherrer equation using the full width at half maximum (FWHM). The carrier mobility was enhanced from 5.31 to 28.39 cm2 V−1 s−1 in the annealed Ga2O3 thin films on Al2O3/SiC. The transfer and output characteristics of the Ga2O3/SiC and Ga2O3/Al2O3/SiC back-gate transistors reflect the trend of the XRD and Hall measurement results. Therefore, this work demonstrated that the physical and electrical properties of the Ga2O3/SiC back-gate transistors can be improved by post-deposition annealing and the introduction of an Al2O3 interlayer. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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13 pages, 5522 KiB  
Article
Experimental Wear Analysis of Nano-Sized Titania Particles as Additives in Automotive Lubricants
by Ádám István Szabó, Álmos Dávid Tóth, Hebah Abdallah and Hajnalka Hargitai
Micro 2023, 3(3), 715-727; https://doi.org/10.3390/micro3030050 - 21 Aug 2023
Viewed by 1132
Abstract
This study focuses on the wear effects of nano-sized titania as a potential engine lubricant additive. Titanium dioxide nanoparticles have promising wear-reducing properties and significant tribological potential. In this article, titania nanoparticles were homogenized in Group III automotive oil at five different concentrations [...] Read more.
This study focuses on the wear effects of nano-sized titania as a potential engine lubricant additive. Titanium dioxide nanoparticles have promising wear-reducing properties and significant tribological potential. In this article, titania nanoparticles were homogenized in Group III automotive oil at five different concentrations (0.1; 0.2 … 0.5 wt%). The nanodoped oil samples were tested on a linear oscillating tribometer with oil circulation. Based on the tribological results, titania nanoparticles increased friction by 20–32% but can reduce the wear area by up to 32%. According to the confocal microscopic examination, wear volume can be reduced by up to 57% with titania nanoparticles. Titania nanoparticles improved the repeatability of tribological measurements. A scanning electron microscopy examination of the wear track revealed that the characteristic wear of the tribological system was abrasive, but a significant amount of adhesive wear was also observed. Energy dispersive X-ray spectroscopy analysis found that the nanoparticles fill the deeper trenches of the wear. The worn surface uniformly contains TiO2 particles and the quantified normalized titanium concentration was between 0.56 and 0.62%. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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16 pages, 4976 KiB  
Article
Matrix Effect of Properties of Au, ZnO and Eu2O3: Silica, Titania and Alumina Matrices
by Carlos Díaz, Olga Cifuentes-Vaca and María Luisa Valenzuela
Micro 2023, 3(3), 699-714; https://doi.org/10.3390/micro3030049 - 19 Aug 2023
Viewed by 703
Abstract
The composites Au/SiO2, Au/TiO2, Au/Al2O3, ZnO/TiO2, ZnO/TiO2, ZnO/Al2O3 and Eu2O3/SiO2, Eu2O3/TiO2 and Eu2O3/Al [...] Read more.
The composites Au/SiO2, Au/TiO2, Au/Al2O3, ZnO/TiO2, ZnO/TiO2, ZnO/Al2O3 and Eu2O3/SiO2, Eu2O3/TiO2 and Eu2O3/Al2O3 were prepared using a solid-state method. The effect of the polymer precursors was investigated using two precursor polymers, Chitosan and Poly(styrene-co-4vinylpyridine), (PS-co-4-PVP) in the M/MxLy•Chitosan//M’xO’y as well as M/MxLy•PS-co-4-PVP//M’xO’y with M’xO’y = SiO2, TiO2 and Al2O3. The effects on the particle size and morphology were observed. The new composites were characterized using X-ray powder diffraction, SEM-EDS mapping and HRTEM analysis. The distribution of the metallic nanoparticles as well as the metal oxide nanoparticles inside the matrices depend on the matrix. Marked optical and photocatalytic effects of the Au, ZnO and Eu2O3 inside the SiO2, TiO2 and Al2O3 matrices are expected. An experiment is in course. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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18 pages, 3398 KiB  
Article
Extraction and Modification of Cellulose Microfibers Derived from Biomass of the Amazon Ochroma pyramidale Fruit
by Ana Luisa Farias Rocha, Bianca de Andrade Feitosa, Adriano de Souza Carolino, Ronald Zico de Aguiar Nunes, Célio Matias Airone Macalia, Kalil Araújo da Silva, Cleverton Oliveira Dias, Sérgio Michielon de Souza, Pedro Henrique Campelo, Jaqueline de Araújo Bezerra and Edgar Aparecido Sanches
Micro 2023, 3(3), 653-670; https://doi.org/10.3390/micro3030046 - 28 Jul 2023
Viewed by 1480
Abstract
Microfibers are important to several areas of human lifestyle, and the knowledge about their physicochemical characteristics allows for proposing new technological applications. The in natura microfiber of Ochroma pyramidale fruit (IN sample) and its extracted pulp (PU sample) were evaluated by X-ray Diffraction [...] Read more.
Microfibers are important to several areas of human lifestyle, and the knowledge about their physicochemical characteristics allows for proposing new technological applications. The in natura microfiber of Ochroma pyramidale fruit (IN sample) and its extracted pulp (PU sample) were evaluated by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetry and Differential Scanning Calorimetry (TG/dTG and DSC). Microfibers were composed mainly of (68 ± 1)% holocellulose, (35.8 ± 0.1)% cellulose, (32 ± 3)% lignin and (3.7 ± 0.3)% extractives. The XRD pattern of the PU sample revealed that the mercerization process resulted in the change of the cellulose crystal structure from Iα type (triclinic) to type II (monoclinic). The SEM technique showed that the IN sample presented regular cylindrical/hollow-shaped wire-like microfibers with diameters ranging from 5 µm to 25 µm. However, the mercerization process changed their natural morphology. A significant change in the FTIR spectra after the removal of hemicellulose and lignin components was observed: weak bands at 1739 cm−1 (C=O stretching of lignin and hemicellulose fractions), 1463 cm−1 (CH3 of lignin) and 1246 cm−1 (C-O of lignin) were still observed in the PU sample, indicating that the lignin was not completely removed due to the natural difficulty of isolating pure cellulose. The TG/dTG and DSC evaluation revealed a temperature increase of the second thermal event (starting at 235 °C) in the PU sample, which was assigned to the cellulose and residual hemicellulose degradation. Then, this work aimed to disseminate and characterize a microfiber with unusual characteristics still little explored by the scientific community, as well as its cellulosic pulp, providing information that may be useful in its application in different industries, enabling the positive development of new biocompatible, renewable and sustainable materials. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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10 pages, 5217 KiB  
Article
Selective Hydrodeoxygenation of Guaiacol to Cyclohexane over Ru-Catalysts Based on MFI Nanosheets
by Dmitry Tsaplin, Alexey Sadovnikov, Dzhamalutdin Ramazanov, Dmitry Gorbunov, Valeriya Ryleeva, Anton Maximov, Kaige Wang and Evgeny Naranov
Micro 2023, 3(2), 610-619; https://doi.org/10.3390/micro3020042 - 20 Jun 2023
Cited by 2 | Viewed by 991
Abstract
Bio-oils derived from the pyrolysis of lignin-based biomass often contain a variety of oxygenated compounds, which can compromise their usefulness as a fuel. To improve the quality of bio-oil, catalytic hydrodeoxygenation (HDO) is a crucial step that removes oxygen from the oil in [...] Read more.
Bio-oils derived from the pyrolysis of lignin-based biomass often contain a variety of oxygenated compounds, which can compromise their usefulness as a fuel. To improve the quality of bio-oil, catalytic hydrodeoxygenation (HDO) is a crucial step that removes oxygen from the oil in the form of water. In this study, we showed that MFI nanosheets are excellent supports for Ru-catalysts. We synthesized highly crystalline MFI nanosheets using a simple hydrothermal seeding procedure; the final material was obtained in 56 h of crystallization. We investigated the activity of Ru supported on different materials. Our findings indicated that Ru supported on hierarchical MFI demonstrated excellent activity in HDO of guaiacol. Our results demonstrated that Ru/ZNS-56 achieved nearly 100% selectivity towards cyclohexane under mild conditions (200 °C, 50 bar H2, 1 h). Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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14 pages, 7348 KiB  
Article
Tensile Behavior of [0/90]7 Hemp/Elium Biocomposites after Water Aging: In-Situ Micro-CT Testing and Numerical Analysis
by Quentin Drouhet, Fabienne Touchard and Laurence Chocinski-Arnault
Micro 2023, 3(2), 496-509; https://doi.org/10.3390/micro3020033 - 02 May 2023
Cited by 1 | Viewed by 1185
Abstract
This paper aims to study the tensile behavior of a woven [0/90]7 hemp/Elium composite after three different conditionings: “Ambient storage”, “Saturated at 60 °C” and “15 wet/dry cycles”. Instrumented repeated progressive tensile loading tests were carried out and showed an unexpected increase [...] Read more.
This paper aims to study the tensile behavior of a woven [0/90]7 hemp/Elium composite after three different conditionings: “Ambient storage”, “Saturated at 60 °C” and “15 wet/dry cycles”. Instrumented repeated progressive tensile loading tests were carried out and showed an unexpected increase in the secant modulus for the aged samples at the end of the test. An in-situ micro-CT tensile test was then performed on a “15 wet/dry cycles” aged sample. The analysis of the tomographic images showed the damage development with interfacial debonding and matrix cracks in the specimen volume, and also the decrease in the curvature radius of the warp yarns during tensile loading facilitated by the plasticization of the resin. Finite element calculations were thus performed and demonstrated that the increase in the modulus is directly linked to the straightening of warp yarns, showing that the evolution of the modulus on a macroscopic scale can be explained by the deformations of the yarns on a microscopic level. These results allow us to better understand the mechanical behavior and the damage mechanisms that occur in biocomposites during tensile testing after water aging. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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12 pages, 2460 KiB  
Article
Effect of CdSTe QDs’ Crystal Size on Viability and Cytochrome P450 Activity of CHO-K1 and HEP-G2 Cells
by Luis Alamo-Nole, Adriana Ponton-Almodovar and Ivan Ortiz-Laboy
Micro 2023, 3(1), 308-319; https://doi.org/10.3390/micro3010021 - 02 Mar 2023
Viewed by 1352
Abstract
In the last few years, quantum dots (QDs) have attracted research interest in different fields of science and technology. Despite their applications, it is essential to understand how nanomaterials (with different crystal sizes) are metabolized inside organisms. Thus, the focus of this study [...] Read more.
In the last few years, quantum dots (QDs) have attracted research interest in different fields of science and technology. Despite their applications, it is essential to understand how nanomaterials (with different crystal sizes) are metabolized inside organisms. Thus, the focus of this study was on an evaluation of how crystal sizes of CdSTe QDs affect the viability and response of the cytochrome P450 system in CHO-K1 and HEP-G2 cells. CdSTe QDs were synthesized using a microwave-assisted system at different reaction temperatures (60, 120, 150, and 180 °C) to obtain different crystal sizes. The optical and structural characterization confirmed four crystal sizes from 3 to 8 nm. Fluorescence microscopy confirmed that CdSTe QDs are incorporated into both cell lines. Viability studies suggested that CHO-K1 cells are more sensitive than HEP-G2 cells to CdSTe QDs and Cd+2 ions. The responsible mechanisms for the toxicity of QDs and Cd+2 are apoptosis followed by necrosis. The activity of CYP 1A1, 1A2, and 3A4 isoenzymes suggests that the smallest CdSTe crystals are recognized in a manner similar to that of Cd+2. Furthermore, the largest CdSTe crystals can have different metabolic routes than Cd+2. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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8 pages, 1434 KiB  
Article
Structural Consequences of Post-Synthetic Modification of Cu2P3I2
by Gregory R. Schwenk, John T. Walters and Hai-Feng Ji
Micro 2023, 3(1), 256-263; https://doi.org/10.3390/micro3010018 - 01 Mar 2023
Viewed by 1327
Abstract
In an attempt to widen the family of Phosphorus Metal Halides (MxPyXz) and enable new applications, post-synthetic modifications to the MxPyXz, Cu2P3I2 have been reported. While such [...] Read more.
In an attempt to widen the family of Phosphorus Metal Halides (MxPyXz) and enable new applications, post-synthetic modifications to the MxPyXz, Cu2P3I2 have been reported. While such a technique suggests access to an entirely new family of MxPyXz-based materials, we report, in this work, that the ion-exchange process seemingly influences important properties such as the crystallographic pattern and vibrational modes. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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17 pages, 80791 KiB  
Article
Influence of the Chromium Content on the Characteristics of the Matrix, the Tantalum Carbides Population, and the Hardness of Cast Co(Cr)-0.4C-6Ta Alloys
by Patrice Berthod, Merzouk Bouaraba and Junfu Cai
Micro 2023, 3(1), 239-255; https://doi.org/10.3390/micro3010017 - 16 Feb 2023
Cited by 1 | Viewed by 1293
Abstract
The mechanical and chemical behaviors of cast cobalt-base superalloys are governed by the carbides and by a reactive element, which is often chromium. The content of this later element, which is efficient in resisting hot oxidation and also hot corrosion, may have consequences [...] Read more.
The mechanical and chemical behaviors of cast cobalt-base superalloys are governed by the carbides and by a reactive element, which is often chromium. The content of this later element, which is efficient in resisting hot oxidation and also hot corrosion, may have consequences on the melting temperature, microstructure, and mechanical properties at high temperatures and at room temperature. Seemingly, the effect of chromium content on the microstructure and properties of cast equi-axed Co-Cr-Ta-C superalloys containing TaC as single reinforcing carbide and in high-enough quantities to achieve a high level of creep resistance has not been the subject of previous investigations. The present work is devoted to the exploration of this influence of Cr content on the as-cast microstructure of a model alloy in this category, as well as on its microstructure transformations at high temperatures. The work aims to help rate the Cr content to achieve the best characteristics in machinability and high-temperature properties. This is of great importance for fabricability (production cost) and sustainability in service (long enough lifetime performance). A series of six alloys derived from a rather well-known alloy and presenting various Cr contents were thus elaborated by casting. Their microstructures were investigated in their as-cast state as well as in an aged state resulting from a 4-day stage at 1400 K. Vickers indentation was also carried out to study how hardness may evolve with Cr content. It was seen that the higher the Cr content, the lower the solidus temperature, the coarser the TaC population, the harder the alloy, and the higher the risk of brittleness. In order to reach the best compromise, the preferred Cr weight content range, as identified by this work, is 20–30%; indeed, for such Cr contents: (1) the matrix is austenitic, then dense, and then hard and not brittle, and thus is mechanically resistant and tough; (2) the TaC carbides are script-shaped and resistant against morphology changes at high temperatures, and thus efficiently preserve interdendritic cohesion for a long time, and, consequently, (3) the alloys are machinable, have expected good toughness, and can be resistant against creep deformation as well as oxidation and corrosion at high temperatures thanks to the Cr content, allowing for chromium-forming behavior. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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16 pages, 11185 KiB  
Article
Barrier Performance of Spray Coated Cellulose Nanofibre Film
by Kirubanandan Shanmugam, Narendhar Chandrasekar and Ramachandran Balaji
Micro 2023, 3(1), 192-207; https://doi.org/10.3390/micro3010014 - 03 Feb 2023
Cited by 1 | Viewed by 1800
Abstract
Cellulose nanofibre (CNF) is the sustainable nanomaterial used for developing high-performance barrier materials that are renewable, recyclable, and biodegradable. The CNF film has very low oxygen permeability; however, its water vapor permeability is significantly higher than that of conventional packaging plastics. The fabrication [...] Read more.
Cellulose nanofibre (CNF) is the sustainable nanomaterial used for developing high-performance barrier materials that are renewable, recyclable, and biodegradable. The CNF film has very low oxygen permeability; however, its water vapor permeability is significantly higher than that of conventional packaging plastics. The fabrication method influences their barrier properties of the film. A spray-coating CNF on a stainless-steel plate was developed to form a compact film with two unique surfaces, namely a smooth layer on the base side and rough layer on the free side. It improves both the ease of preparation of the film and reduces the water vapour permeability via tailoring the basis weight and thickness of the film through simple adjusting CNF content in the suspension. The air permanence of the film from 1.0 wt.% to 2.0 wt.% CNF suspension is less than 0.003 µm/Pa·S confirming that is an impermeable film and proves a good packaging material. SEM, optical profilometry, and AFM revealed that the spray-coated surface was smooth and glossy. For sprayed CNF films with basis weight between 86.26 ± 13.61 and 155.85 ± 18.01 g/m2, WVP were ranged from 6.99 ± 1.17 × 10−11 to 4.19 ± 1.45 × 10−11 g/m·Pa·S. In comparison, the WVP of 100 g/m2 vacuum filtered CNF film was 5.50 ± 0.84 × 10−11 g/m·Pa·S, spray-coated film (of 96.6 g/m2) also show similar permeability at around 5.34 ± 0.603 × 10−11 g/m·Pa·S. The best performance was achieved with spraying of 2.0 wt.% CNF and a water vapour permeability of 3.91 × 10−11 g/m·s·Pa. Spray coated CNF film is impermeable against air and water vapour and a potential alternative to synthetic plastics. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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20 pages, 6490 KiB  
Article
Polyaniline Hybrids with Biological Tissue, and Biological Polymers as Physiological—Electroactive Materials
by Mai Ichikawa, Masashi Otaki and Hiromasa Goto
Micro 2023, 3(1), 172-191; https://doi.org/10.3390/micro3010013 - 01 Feb 2023
Cited by 1 | Viewed by 1325
Abstract
A sprout/polyaniline was synthesized via the chemical oxidative polymerization of aniline in the presence of natural sprout, based on a concept of cyborg plant composite. The composite consisted of both polyaniline and plants. The chemical structure was confirmed by infrared absorption spectroscopy measurements. [...] Read more.
A sprout/polyaniline was synthesized via the chemical oxidative polymerization of aniline in the presence of natural sprout, based on a concept of cyborg plant composite. The composite consisted of both polyaniline and plants. The chemical structure was confirmed by infrared absorption spectroscopy measurements. Optical microscopy observation revealed that polyaniline was deposited into the micro-tissue of the sprout to form the conductive polymer bio-composite. Micro-optical fiber functions for the composite were visually confirmed. Furthermore, the sprout/polyaniline based organic diode exhibited an avalanche breakdown phenomenon. Next, a fucoidan/polyaniline composite as a physiological active material/conducting polymer composite was prepared. This composite showed good film-forming ability, electrochromism, and a micro-porous surface. This paper reports the preparation of conducting polymer composites with a combination of bio-tissue and bio-substance for the creation of bio-based electrically active organized architecture. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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16 pages, 5023 KiB  
Article
In-Vitro Cell Response to Strontium/Magnesium-Doped Calcium Phosphate Nanoparticles
by Kathrin Kostka, Shabnam Hosseini and Matthias Epple
Micro 2023, 3(1), 156-171; https://doi.org/10.3390/micro3010012 - 01 Feb 2023
Cited by 2 | Viewed by 1449
Abstract
Calcium phosphate nanoparticles are highly biocompatible and biodegradable in bone regeneration. On the other hand, strontium and magnesium enhance the formation of bone. The substitution of calcium by strontium and magnesium is an efficient way to improve the biological properties of calcium phosphate-based [...] Read more.
Calcium phosphate nanoparticles are highly biocompatible and biodegradable in bone regeneration. On the other hand, strontium and magnesium enhance the formation of bone. The substitution of calcium by strontium and magnesium is an efficient way to improve the biological properties of calcium phosphate-based biomaterials. Strontium-doped calcium phosphate nanoparticles and magnesium-doped calcium phosphate nanoparticles with degrees of cation substitution of 5, 10, 15, and 20 mol% with respect to calcium were prepared by precipitation, followed by surface functionalization with polyethyleneimine (PEI, cationic) or carboxymethylcellulose (CMC, anionic). The nanoparticles were characterized by dynamic light scattering (DLS), zeta potential measurement, scanning electron microscopy (SEM), atomic absorption spectrometry (AAS), energy dispersive X-ray analysis (EDX), and X-ray powder diffraction (XRD). The particles were approximately spherical (diameter 40–70 nm). The addition of magnesium and strontium considerably decreased the internal crystallinity, i.e., the doped particles were almost X-ray amorphous. The cell-biological effects were assessed on three different cell lines, i.e., HeLa cells, MG63 cells, and MC3T3 cells. Cell viability tests (MTT) showed a low cytotoxicity, the alkaline phosphatase (ALP) activity was strongly increased, and the nanoparticles were taken up well by the three cell lines. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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13 pages, 10358 KiB  
Article
Graphene Formation through Spontaneous Exfoliation of Graphite by Chlorosulfonic Acid: A DFT Study
by Alfredo Bol-Arreba, Isabel G. Ayala and Nicolás A. Cordero
Micro 2023, 3(1), 143-155; https://doi.org/10.3390/micro3010011 - 31 Jan 2023
Cited by 1 | Viewed by 1237
Abstract
Using exfoliating agents is one of the most promising ways for large-scale production of liquid dispersed graphenic materials from graphite. Therefore, it is crucial to know the reason why some molecules have a larger exfoliating power than others. The highest reported experimental yield [...] Read more.
Using exfoliating agents is one of the most promising ways for large-scale production of liquid dispersed graphenic materials from graphite. Therefore, it is crucial to know the reason why some molecules have a larger exfoliating power than others. The highest reported experimental yield for the liquid phase single-surfactant spontaneous exfoliation of graphite, i.e., without sonication, has been obtained using chlorosulfonic acid. The ability of this acid to disperse graphite is studied within the framework of Density Functional Theory (DFT). Equilibrium configurations, electron transfers, binding energies, and densities of states are presented for two acid concentrations and for two situations: adsorption (on monolayer and bilayer graphene) and intercalation (in between simple hexagonal and Bernal-stacked bilayer graphene). Experimental exfoliation power and dispersion stability are explained in terms of charge transfer—the largest found among several studied exfoliating and surfactant agents—facilitated by the good geometrical matching of chlorosulfonic acid molecules to constituent carbon rings of graphene. This matching is in the origin of the tendency toward adsorption of chlorosulfonic acid molecules on graphene monolayers when they separate, originating the charging of the monolayers that precludes their reaggregation. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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25 pages, 4773 KiB  
Article
Chitosan/Hydroxyapatite Scaffolds with P28 as a Promising Osteoinductive Scaffold for Bone Healing Applications
by Farah Alwani Azaman, Florence Daubiné, Amélie Lebatard, Margaret E. Brennan Fournet and Declan M. Devine
Micro 2023, 3(1), 118-142; https://doi.org/10.3390/micro3010010 - 31 Jan 2023
Cited by 2 | Viewed by 1658
Abstract
Despite bone’s inherent ability to heal, large bone defects remain a major clinical concern. This study proposes an off-the-shelf treatment combining chitosan/hydroxyapatite (CS/HAp) scaffolds, covalently linked with either bone morphogenetic protein-2 (BMP-2) or its related peptide P28 via a UV crosslinking process. Although [...] Read more.
Despite bone’s inherent ability to heal, large bone defects remain a major clinical concern. This study proposes an off-the-shelf treatment combining chitosan/hydroxyapatite (CS/HAp) scaffolds, covalently linked with either bone morphogenetic protein-2 (BMP-2) or its related peptide P28 via a UV crosslinking process. Although covalently binding the growth factors was reported as a great alternative to the conventionally physical adsorption and encapsulation methods, this method presents the risk of altering the molecular activity and interaction of the growth factors. Therefore, alkaline phosphatase (ALP) activity and alizarin red staining (ARS) with a quantitative cetylpyridinium chloride (CPC) assay were conducted to validate that our photo-crosslinking fabrication method did not interfere with the functionality of the growth factors. The ALP activity of C2C12 with 100 µg/mL P28 was found to be comparable to 0.5 µg/mL BMP-2 after two weeks, where 0.001 U/mL was recorded for both treatments. The C2C12 cultured with CS/HAp/BMP-2 and CS/HAp/P28 scaffolds also showed an increased ALP activity compared to the negative control. ARS-CPC assay presented the highest optical density in 0.3 µg/mL BMP-2 and 50 µg/mL P28, while the highest intensity of ARS was observed in C2C12 cultured with CS/HAp/BMP-2 and CS/HAp/P28 scaffolds compared to the negative controls. The osteoconductive capability of this delivery system was then investigated through a rat femoral condyle defect model, where the new bone mineral density and the bone volume increased for all CS/HAp scaffolds compared to the collagen sponge control treatment. The histological assessment showed a favourable bone regeneration efficacy of the CS/HAp/P28 compared to the CS/HAp/BMP-2 treatment, thus showing the use of CS/HAp scaffolds with P28 as a promising osteoinductive scaffold for bone healing applications. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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Review

Jump to: Research

13 pages, 768 KiB  
Review
Nanometals and Metal Ion Pollution from Dental Materials in Dental Environment
by Ana Carla B. C. J. Fernandes and Rodrigo França
Micro 2023, 3(2), 471-483; https://doi.org/10.3390/micro3020031 - 17 Apr 2023
Viewed by 1760
Abstract
The dental environment is being polluted with metals from dental materials in many ways, mainly due to aerosol-generating procedures; this could affect the long-term well-being of dentists, dental students, and dental personnel. The current dental pollution incorporates metallic nanoparticles, which are highly reactive [...] Read more.
The dental environment is being polluted with metals from dental materials in many ways, mainly due to aerosol-generating procedures; this could affect the long-term well-being of dentists, dental students, and dental personnel. The current dental pollution incorporates metallic nanoparticles, which are highly reactive and quickly become airborne, especially those particles that become unbound in the bulk composition. In addition, liquid mercury or mercury vapors may be released from dental amalgam, causing concerns in the dental community. In our study, we reviewed the behavior of metallic elements present in dental materials, their routes of exposure, and their potentially toxic effects on the dental team. This review found that skin and lung disorders are the most harmful effects of metallic exposure for dentists, dental students, and dental personnel. Therefore, chronic exposure to low concentrations of metals in the dental environment, especially in nanosized forms, should be further investigated to improve the environmental matrix, material choice, and safety protocols. Full article
(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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