Journal Description
Micro
Micro
is an international, peer-reviewed, open access journal on microscale and nanoscale research and applications in physics, chemistry, materials, biology, medicine, food, environment technology, engineering, etc., published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 22.5 days after submission; acceptance to publication is undertaken in 2.8 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Piezoelectric and Pyroelectric Properties of Organic MDABCO-NH4Cl3 Perovskite for Flexible Energy Harvesting
Micro 2024, 4(2), 196-205; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4020014 (registering DOI) - 27 Mar 2024
Abstract
This study describes the synthesis and characterization of the lead-free organic ferroelectric perovskite N-methyl-N’-diazabicyclo [2.2.2]octonium)-ammonium trichloride (MDABCO-NH4Cl3). The electrospinning technique was employed to obtain nanofibers embedded with this perovskite in a PVC polymer for hybrid fiber
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This study describes the synthesis and characterization of the lead-free organic ferroelectric perovskite N-methyl-N’-diazabicyclo [2.2.2]octonium)-ammonium trichloride (MDABCO-NH4Cl3). The electrospinning technique was employed to obtain nanofibers embedded with this perovskite in a PVC polymer for hybrid fiber production. The dielectric, piezoelectric, and pyroelectric properties of these fibers were carefully examined. Based on measurements of the dielectric permittivity temperature and frequency dependence, together with the pyroelectric results, a transition from a high temperature paraelectric to a ferroelectric phase that persisted at room temperature was found to occur at 438 K. The measured pyroelectric coefficient yielded values as high as 290 μC K−1 m−2, which is in between the values reported for MDABCO-NH4I3 and the semiorganic ferroelectric triglycine sulfate (TGS). The hybrid nanofibers exhibited good morphological characteristics and demonstrated very good piezoelectric properties. Specifically, a piezoelectric coefficient of 42 pC/N was obtained when applying a periodical force of 3 N and a piezoelectric voltage coefficient of geff = 0.65 V mN−1. The performance of these fibers is on par with that of materials discussed in the existing literature for the fabrication of nano energy-harvesting generators. Importantly, the perovskite nanocrystals within the fibers are protected from degradation by the surrounding polymer, making them a promising environmentally friendly platform for flexible mechanical energy harvesting.
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(This article belongs to the Section Microscale Physics)
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Janus Particles in Acoustofluidic Setup: The Interplay between Self-Propulsion and Acoustic Trapping
by
Lisa Marie Benko, Vyacheslav R. Misko, Larysa Baraban, Denys Makarov, Antonio Maisto and Wim De Malsche
Micro 2024, 4(1), 185-195; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010013 - 16 Mar 2024
Abstract
Acoustic focusing of particle flow in microfluidics has been shown to be an efficient tool for particle separation for various chemical and biomedical applications. The mechanism behind the method is the selective effect of the acoustic radiation force on distinct particles. In this
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Acoustic focusing of particle flow in microfluidics has been shown to be an efficient tool for particle separation for various chemical and biomedical applications. The mechanism behind the method is the selective effect of the acoustic radiation force on distinct particles. In this way, they can be selectively focused and separated. The technique can also be applied under stationary conditions, i.e., in the absence of fluid flows. In this study, the manipulation of self-propelled particles, such as Janus particles, in an acoustofluidic setup was investigated. In experiments with self-propelled Janus particles and passive beads, we explored the interplay between self-propulsion and the acoustic radiation force. Our results demonstrated unusual and potentially useful effects such as selective trapping, escape, and assisted escape in binary mixtures of active and passive particles. We also analyzed various aspects related to the behavior of Janus particles in acoustic traps in the presence and absence of flows.
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(This article belongs to the Collection Advances in Microtechnology for Cell/Tissue Engineering and Biosensing)
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Open AccessArticle
An Investigation into the Effect of Length Scale of Reinforcement on the Cryogenic Response of a Mg/2wt.%CeO2 Composite
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Shwetabh Gupta, Michael Johanes, Gururaj Parande and Manoj Gupta
Micro 2024, 4(1), 170-184; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010012 - 14 Mar 2024
Abstract
The present study attempted for the first time an investigation on the effect of deep cryogenic treatment in liquid nitrogen (LN) on magnesium–cerium oxide (Mg/2wt.%CeO2) composites containing equal amounts of different length scales (micron and nanosize) cerium oxide (CeO2)
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The present study attempted for the first time an investigation on the effect of deep cryogenic treatment in liquid nitrogen (LN) on magnesium–cerium oxide (Mg/2wt.%CeO2) composites containing equal amounts of different length scales (micron and nanosize) cerium oxide (CeO2) particles. The disintegrated melt deposition method was used to synthesize Mg-2CeO2 micro- and nanocomposites, followed by hot extrusion as the secondary processing. Further liquid nitrogen treatment was performed at a cryogenic temperature of −196 °C. The combined effects of cryogenic treatment and reinforcement length scale on physical, mechanical, and thermal behaviors were studied. The results indicate that LN-treated micro- and nanocomposite samples exhibit, in common, a reduction in porosity, similar grain size, and a limited effect on the original texture of the matrix. However, microhardness, 0.2% Compressive Yield Strength (CYS), failure strain, and energy absorbed increased for both micro- and nanocomposite samples. Overall, results clearly indicate the capability of deep cryogenic treatment with LN to positively diversify the properties of both micro- and nanocomposite samples.
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(This article belongs to the Special Issue Advances in Micro- and Nanomaterials: Synthesis and Applications)
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Influence of Pt Ultrathin Interlayers on Magnetic Anisotropy in Ni/NiO Multilayers
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Dimitrios I. Anyfantis, Alexandros Barnasas, Nikolaos C. Diamantopoulos, Constantinos M. Tsakiris, Georg Schmidt, Evangelos Th. Papaioannou and Panagiotis Poulopoulos
Micro 2024, 4(1), 157-169; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010011 - 29 Feb 2024
Abstract
Perpendicular magnetic anisotropy at transition metal/oxide interfaces plays a significant role in technological applications such as magnetic storage and spintronics. In this study, we investigate the effects of thermal annealing and Pt ultrathin interlayers on the magnetic anisotropy in Ni/NiO multilayers. Ni/NiO/Pt multilayers
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Perpendicular magnetic anisotropy at transition metal/oxide interfaces plays a significant role in technological applications such as magnetic storage and spintronics. In this study, we investigate the effects of thermal annealing and Pt ultrathin interlayers on the magnetic anisotropy in Ni/NiO multilayers. Ni/NiO/Pt multilayers were fabricated via radiofrequency magnetron sputtering and natural oxidation. The static magnetic properties of the samples were studied using temperature-dependent SQUID magnetometry. We focus on a sample with a Nickel thickness of 6.7 nm in each multilayer period. This multilayer in Ni/NiO form showed the maximum enhancement of perpendicular magnetic anisotropy after mild thermal annealing in past work. In this work, we study the effects of ultrathin Pt interlayers on the magnetic properties of such a Ni/NiO multilayer before and after annealing. We have observed a further increase in perpendicular magnetic anisotropy, and we study the temperature-dependent magnetic properties of this system, which combines the favorable magnetic properties of Ni/Pt and Ni/NiO multilayers.
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(This article belongs to the Section Microscale Materials Science)
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Open AccessArticle
Characterization of Thin AlN/Ag/AlN-Reflector Stacks on Glass Substrates for MEMS Applications
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Christian Behl, Regine Behlert, Jan Seiler, Christian Helke, Alexey Shaporin and Karla Hiller
Micro 2024, 4(1), 142-156; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010010 - 29 Feb 2024
Abstract
Thin metal layers such as silver (Ag) are being utilized for various optical and plasmonic applications as well as for electrical purposes, e.g., as transparent electrodes in display devices or solar cells. This paper focuses on optical MEMS applications such as the Fabry–Pérot
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Thin metal layers such as silver (Ag) are being utilized for various optical and plasmonic applications as well as for electrical purposes, e.g., as transparent electrodes in display devices or solar cells. This paper focuses on optical MEMS applications such as the Fabry–Pérot interferometer (FPI). Within such filters, reflector materials such as distributed Bragg reflectors (DBRs) or subwavelength gratings (SWGs) have been widely used so far, whereas metallic thin films (MTFs) were limited in application due to their comparatively higher absorption. In this paper, thin sputtered Ag layers with thicknesses of 20, 40 and 60 nm on glass substrates have been investigated, and it is shown that the absorption is very low in the visible spectral range (VIS) and increases only in near-infrared (NIR) with increasing wavelength. Thus, we consider Ag-thin layers to be an interesting reflector material at least for the VIS range, which can be easily fabricated and integrated. However, Ag is not inert and stable when exposed to the atmosphere. Hence, it needs a passivation material. For this purpose, AlN has been chosen in this contribution, which can be deposited by sputtering as well. In this contribution, we have chosen thin AlN layers for this purpose, which can also be deposited by sputtering. Thus, various AlN/Ag/AlN-reflector stacks were created and patterned by lift-off technology preferably. The fabricated reflectors were characterized with respect to adhesion, stress, cohesion, homogeneity, and most importantly, their optical properties. It was found that the thickness of the AlN can be used to adjust the reflectance–transmittance ratio in the VIS range, and influences the adsorption in the NIR range as well. Based on the measured values of the reflectors with 40 nm Ag, an exemplary transmission filter characteristics has been predicted for a wavelength range from 400 to 800 nm. Both the maximum transmittance and the full width at half maximum (FWHM) can be tuned by variation of the AlN thickness from 20 to 60 nm.
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(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)
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Open AccessReview
Nanomedicine-Based Drug Delivery Systems and the Treatment of Autism Spectrum Disorders: A Review
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Zaria Jean-Baptiste, Yashwant Pathak and Kevin B. Sneed
Micro 2024, 4(1), 132-141; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010009 - 27 Feb 2024
Abstract
Nanotechnology has played a pioneering role in advancing medical applications, aiming to enhance healthcare through innovation and collaboration. Nanomedicine can be seen expanding into many fields from cancer therapies, cosmetics, tissue regeneration, biosensing, and infectious diseases, and now, it is seen venturing into
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Nanotechnology has played a pioneering role in advancing medical applications, aiming to enhance healthcare through innovation and collaboration. Nanomedicine can be seen expanding into many fields from cancer therapies, cosmetics, tissue regeneration, biosensing, and infectious diseases, and now, it is seen venturing into the realm of research geared toward autism spectrum disorder (ASD). ASD is a neurodevelopmental disorder characterized by restrictive, monotonous activities or fixed interests as well as difficulties with social communication. As of now, there are no validated quantitative metrics for diagnosing autism, nor is there a drug that is specifically designed to treat the condition. As identifiers of ASD have improved, the diagnosis of individuals who meet established criteria have dramatically increased over the years. Although there is still no recognized nanomedicine treatment specifically intended for ASD, research is looking into how nanotechnology might be used in a number of ASD-related areas. This comprehensive review examines prior research efforts aimed at preventing, treating, and diagnosing individuals with ASD. It particularly focuses on the significance of prenatal care and investigates advancements in drug delivery methods through the blood–brain barrier concerning ASD treatment and management.
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(This article belongs to the Section Microscale Biology and Medicines)
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The Decorated Garden Grotto of Condes de Basto Palace in Évora, Portugal: Microbial Community Characterization and Biocide Tests for Conservation
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Inês Silva, Cátia Salvador, Sílvia Arantes, Ana Z. Miller, António Candeias and Ana Teresa Caldeira
Micro 2024, 4(1), 117-131; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010008 - 17 Feb 2024
Abstract
The Eugénio de Almeida Foundation’s Casa de Fresco is a historical monument of valuable historic–artistic significance, which currently reveals an assortment of biofilms due to the proliferation of microorganisms in the stone and rocaille elements. The biodeterioration in this area was studied as
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The Eugénio de Almeida Foundation’s Casa de Fresco is a historical monument of valuable historic–artistic significance, which currently reveals an assortment of biofilms due to the proliferation of microorganisms in the stone and rocaille elements. The biodeterioration in this area was studied as part of the Conservation and Restoration Project. We effectively characterized the local microbial community using modern high-throughput DNA analysis. Our results suggested the existence of a variety of lichens or lichenized fungi, including genera such as Variospora, Verrucaria, Circinaria, and Caloplaca. Furthermore, we detected several prokaryote microorganisms related to the identification of these lichens. To properly deal with this microbiological issue and avoid fungal recolonization, we evaluated available commercial antimicrobial treatments.
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(This article belongs to the Section Microscale Biology and Medicines)
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Electrodeposition of Zn and Cu Nanoparticles into TiO2 Nanotubes on Ti6Al4V: Antimicrobial Effect against S. Epidermidis and Cytotoxicity Assessment
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Bruno Ribeiro, Ruben Offoiach, Claudia Monteiro, Miguel R. G. Morais, M. Cristina L. Martins, Ana Paula Pêgo, Elisa Salatin, Lorenzo Fedrizzi and Maria Lekka
Micro 2024, 4(1), 97-116; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010007 - 08 Feb 2024
Abstract
Surface modification of the Ti6Al4V alloy (ASTM grade 5), with the fabrication of vertically oriented TiO2 nanotubes, has been receiving increasing attention both as a way to provide advanced bioactive features and the ability to act as reservoirs for a localized, controlled
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Surface modification of the Ti6Al4V alloy (ASTM grade 5), with the fabrication of vertically oriented TiO2 nanotubes, has been receiving increasing attention both as a way to provide advanced bioactive features and the ability to act as reservoirs for a localized, controlled drug release. In this work, TiO2 nanotubes were grown on the surface of a Ti6Al4V alloy through electrochemical anodization. An ethylene glycol-based electrolyte containing 0.5 wt.% NH4F and 2.5% (v/v) H2O was used. Post-anodizing heat treatments at 500 °C in air atmosphere were performed to achieve a crystalline oxide layer with a higher mechanical stability. Following these treatments, Zn or Cu nanoparticles were incorporated into the nanotubular structures through electrodeposition processes. Then, the antimicrobial performance of the obtained surfaces was assessed against Staphylococcus epidermidis, a Gram-positive bacterium common in implant-related infections. Lastly, the cytotoxicity of the produced surface was evaluated against MC3T3-E1 mouse pre-osteoblast cells. In general, Cu-doped TiO2 nanotubes presented an almost total antimicrobial action, while Zn doped samples had a lower, but still significant antibacterial effect. However, a highly cytotoxic effect against MC3T3-E1 cells was observed on all anodized samples due to the release of vanadium from the alloy. In spite of this, the surface modification reported in this work can be a valid solution for existing commercially available orthopedic implants, considering that similar solutions were already studied in in vivo assays.
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(This article belongs to the Section Microscale Materials Science)
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A Method for Directly Observing Mechanical Oscillations in Photonic Structures Based on Porous Silicon Nanostructures
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Miller Toledo Solano, Hector H. Cerecedo-Nuñez, Martha Alicia Palomino Ovando, Jocelyn Faubert, Khashayar Misaghian and J. Eduardo Lugo
Micro 2024, 4(1), 80-96; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010006 - 01 Feb 2024
Abstract
Due to their unique properties, porous silicon nanostructures have garnered much attention in photonics. For example, these structures can exhibit photoluminescence and are highly efficient in trapping light, making them ideal for applications such as biosensors, optical communication, and solar cells. The production
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Due to their unique properties, porous silicon nanostructures have garnered much attention in photonics. For example, these structures can exhibit photoluminescence and are highly efficient in trapping light, making them ideal for applications such as biosensors, optical communication, and solar cells. The production of electromagnetic forces by light is a well-established concept, and the mechanism behind it is well-understood. In the past, we have used these forces to induce mechanical oscillations in a photonic structure based on porous silicon. Usually, to detect the oscillations, a high-precision vibrometer is utilized. However, we report a novel approach to visualizing photonic structure oscillations here. The traditional method of using a vibrometer as an indirect measurement tool has been replaced by one that involves directly observing the changes using a camera, digital movement amplification, a theoretical approximation, and FDTE simulations. This original technique provides researchers with a less expensive means of studying photonic structure movements. This proposal could be extended to other microscopic movements or for dynamical interferometric fringe analysis.
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(This article belongs to the Section Microscale Physics)
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Enhanced Gypsum Boards with Activated Carbon Composites and Phase Change Materials for Advanced Thermal Energy Storage and Electromagnetic Interference Shielding Properties
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Christina Gioti, Konstantinos C. Vasilopoulos, Maria Baikousi, Constantinos E. Salmas, Angelos Ntaflos, Alkiviadis S. Paipetis, Zacharias Viskadourakis, Rabia Ikram, Simeon Agathopoulos, George Kenanakis and Michael A. Karakassides
Micro 2024, 4(1), 61-79; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010005 - 24 Jan 2024
Abstract
This work presents the development of novel gypsum board composites for advanced thermal energy storage (TES) and electromagnetic interference (EMI) shielding applications. Activated carbon (AC) derived from spent coffee with a high surface area (SBET = 1372 m2/g) was used
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This work presents the development of novel gypsum board composites for advanced thermal energy storage (TES) and electromagnetic interference (EMI) shielding applications. Activated carbon (AC) derived from spent coffee with a high surface area (SBET = 1372 m2/g) was used as a shape stabilizer, while the commercial paraffin, RT18HC, was used as organic encapsulant phase change material (PCM). The AC showed a remarkable encapsulation efficiency as a shape stabilizer for PCM, with ~120.9 wt% (RT18HC), while the melting enthalpy (ΔHm) of the shape-stabilized PCM was 117.3 J/g. The performance of this PCM/carbon nanocomposite as a thermal energy storage material was examined by incorporating it into building components, such as gypsum wallboards. The microstructure of these advanced panels, their density, and their dispersion of additives were examined using X-ray microtomography. Their thermal-regulated performance was measured through a self-designed room model with a similar homemade environmental chamber that was able to create a uniform temperature environment, surrounding the test room during heating and cooling. The measurements showed that the advanced panels reduce temperature fluctuations and the indoor temperature of the room model, in comparison with normal gypsum panels, by a range of 2–5%. The investigated gypsum board composite samples showed efficient electromagnetic shielding performance in a frequency range of 3.5–7.0 GHz, reaching an EMI value of ~12.5 dB, which is adequate and required for commercial applications, when filled with PCMs.
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(This article belongs to the Section Microscale Materials Science)
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Open AccessArticle
Toward Remote Detection of Chemical Warfare Simulants Using a Miniature Potentiostat
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Amer Dawoud, Rashid Mia, Jesy Alka Motchaalangaram, Wujian Miao and Karl Wallace
Micro 2024, 4(1), 49-60; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010004 - 22 Jan 2024
Abstract
A miniaturized electrochemical sensor was developed for the remote detection of chemical warfare agent (CWA) simulants. To facilitate drone-based remote sensing, this present study focuses on advancing the miniaturized and compact electrochemical sensor for monitoring two CWA simulants, diisopropyl fluorophosphate (DFP) and O,S-diethylmethylphosphonothioate
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A miniaturized electrochemical sensor was developed for the remote detection of chemical warfare agent (CWA) simulants. To facilitate drone-based remote sensing, this present study focuses on advancing the miniaturized and compact electrochemical sensor for monitoring two CWA simulants, diisopropyl fluorophosphate (DFP) and O,S-diethylmethylphosphonothioate (O,S-DEMPT). The differential pulse voltammetry (DPV) signal was processed, and the DPV signature features were extracted on the basis of the redox properties associated with the absence and the presence of DFP and O,S-DEMPT. Upon the addition of 0.10 equivalence of DFP or O,S-DEMPT, a shift in potential (E) of ~0.13 V was recorded. The limit of detection (LOD) was calculated to be 0.25 µM (0.046 ppm) and 0.10 µM (0.017 ppm) for DFP and O,S-DEMPT, respectively. These results were validated using a portable Palmsens Emstat HR potentiostat, which corroborated the results obtained using a lab benchtop potentiostat. Additionally, Boolean logic (“AND” operation) was implemented for future drone technology deployment. This advancement enables the fabrication of a networked device capable of autonomously executing tasks without constant oversight.
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(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)
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Photochromic Responses and Stability of Functional Inks Applied on Sustainable Packaging Materials
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Sanja Mahović Poljaček, Maja Strižić Jakovljević and Tamara Tomašegović
Micro 2024, 4(1), 33-48; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010003 - 15 Jan 2024
Abstract
Photochromism refers to a reversible colour change induced by the irradiation of photochromic materials with ultraviolet (UV) or visible light that reverts to the original colour after the light source is removed. This effect arises from chemical transformations between two isomers with different
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Photochromism refers to a reversible colour change induced by the irradiation of photochromic materials with ultraviolet (UV) or visible light that reverts to the original colour after the light source is removed. This effect arises from chemical transformations between two isomers with different absorption spectra, involving processes like proton transfer, chemical-bond formation, and isomerisation. These photochromic inks, appearing as crystalline powders with micro-sized particles, require dissolution in a suitable matrix to achieve the colour change. Photochromic inks are used in security, as functional coatings for paper and packaging, in the fabric industry, and in other ways. This study examines the influence of varying concentrations of micro-sized photochromic pigments and different ink-coating thicknesses on the photochromic effect on sustainable paperboard substrates. Artificial ageing was performed to assess the photochromic response and lightfastness in relation to pigment concentration, ink-coating thickness, and the influence of the paperboard substrates. The results of this research could contribute to enhancing knowledge on employing photochromic inks for diverse packaging applications.
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(This article belongs to the Section Microscale Materials Science)
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Preparation of Zeolitic Imidazolate Framework and Carbon Nanofiber Composites for Nitrofurazone Detection
by
Haobo Wang, Subramanian Sakthinathan, Arjunan Karthi Keyan, Chung-Lun Yu, Satoshi Kameoka, Te-Wei Chiu and Karuppiah Nagaraj
Micro 2024, 4(1), 14-32; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010002 - 09 Jan 2024
Abstract
Metal–organic frame (MOF) materials may have the advantages of a regular pore structure, large porosity, and large specific surface area, which could provide better catalytic activity, but they have some disadvantages in electrocatalysis. In contrast, carbon nanofibers (CNFs) prepared by electrospinning methods have
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Metal–organic frame (MOF) materials may have the advantages of a regular pore structure, large porosity, and large specific surface area, which could provide better catalytic activity, but they have some disadvantages in electrocatalysis. In contrast, carbon nanofibers (CNFs) prepared by electrospinning methods have good conductivity and stability. Therefore, this research aimed to generate MOF/CNFs composite materials to improve the electrochemical properties of MOF materials and apply them to the field of electrochemical sensing. This experiment was based on the preparation of straight unidirectional CNFs by an electrospinning method at 2000 RPM. The original method of preparing zeolitic imidazolate frameworks (ZIF-8) was improved and ZIF-8 was uniformly dispersed on the surface of CNFs to form a ZIF-8/CNF composite with a fiber diameter of about 0.10 to 0.35 µm. The specific surface area of the CNFs was about 42.28 m2/g, while that of the ZIF-8/CNF composite was about 999.82 m2/g. The specific surface area of the ZIF-8/CNF composite was significantly larger than that of CNFs. The GCE/ZIF-8/CNF electrode had an excellent electrochemical reaction, with an oxidation peak at about 216 μA, which proved that the ZIF-8/CNF composite material would have good catalytic activity and excellent electrochemical properties for the detection of nitrofurazone compared to other modified electrodes.
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(This article belongs to the Section Microscale Materials Science)
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Open AccessArticle
Design Guideline for a Cantilever-Type MEMS Switch with High Contact Force
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Ilia V. Uvarov and Igor A. Belozerov
Micro 2024, 4(1), 1-13; https://0-doi-org.brum.beds.ac.uk/10.3390/micro4010001 - 20 Dec 2023
Abstract
Micromechanical switches are of significant interest for advanced radio frequency and microwave systems, but their practical implementation is limited by low reliability. Electrodes of a microscopic size develop weak contact force that leads to high and unstable contact resistance. The force is typically
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Micromechanical switches are of significant interest for advanced radio frequency and microwave systems, but their practical implementation is limited by low reliability. Electrodes of a microscopic size develop weak contact force that leads to high and unstable contact resistance. The force is typically increased by using a sophisticated switch design with extended lateral dimensions, although a simple and compact cantilever is more preferable. The paper describes for the first time a comprehensive approach to enhance the force of an electrostatically actuated switch. The strategy is applied to a miniature device based on a 50 µm long cantilever. The contact force is increased from 10 to 112 µN, making the switch strong enough to achieve low and stable contact resistance. The restoring force is also enhanced in order to ensure reliable de-actuation. The growth of forces is accompanied by a reduction in the pull-in voltage. Connecting several cantilevers in parallel and manipulating the number and position of contact bumps additionally improves the force and mechanical stability of the switch. An optimal design contains a triple cantilever with two bumps. It provides 50% higher force per contact compared to the single-cantilever switch at the same pull-in voltage and keeps the advantages of a miniature device. The proposed design strategy may be used for building reliable MEMS switches.
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(This article belongs to the Special Issue Microsystem and Nanosystem Researches for Sensors, Actuators and Energy Conversion Devices)
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Structural Inhomogeneities and Nonlinear Phenomena in Charge Transfer under Cold Field Emission in Individual Closed Carbon Nanotubes
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S. V. von Gratowski, Z. Ya. Kosakovskaya, V. V. Koledov, V. G. Shavrov, A. M. Smolovich, A. P. Orlov, R. N. Denisjuk, Cong Wang and Junge Liang
Micro 2023, 3(4), 941-954; https://0-doi-org.brum.beds.ac.uk/10.3390/micro3040064 - 05 Dec 2023
Abstract
The structure and phenomena arising from charge transfer in cold field emission mode in a single closed carbon nanotube (CNT) under cold field emission conditions are studied. Inhomogeneities of the structure of CNT in the form of two types of superlattices are found
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The structure and phenomena arising from charge transfer in cold field emission mode in a single closed carbon nanotube (CNT) under cold field emission conditions are studied. Inhomogeneities of the structure of CNT in the form of two types of superlattices are found by studying microphotographs obtained by AFM, SEM, and TEM. The features of charge transfer in a quasi-one-dimensional carbon nanotube emitter with a small gap between the anode and cathode are studied under conditions of low-voltage field emission. It is established that the characteristics reveal voltage thresholds and resonant peaks, which are associated with the opening of conduction channels in the region of van Hove singularities. In the region of peaks in the characteristics, the emission current exceeds the one calculated using the Fowler–Nordheim ( ) function by one to three orders of magnitude. The characteristic is not that the curve straightens in F-N coordinates. It is found that the peaks in the characteristics have distinct regions of negative differential conductivity.
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(This article belongs to the Section Microscale Materials Science)
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Open AccessArticle
Effect of Complexation with Closo-Decaborate Anion on Photophysical Properties of Copolyfluorenes Containing Dicyanophenanthrene Units in the Main Chain
by
Anton A. Yakimanskiy, Ksenia I. Kaskevich, Tatiana G. Chulkova, Elena L. Krasnopeeva, Serguei V. Savilov, Vera V. Voinova, Nikolay K. Neumolotov, Andrey P. Zhdanov, Anastasia V. Rogova, Felix N. Tomilin, Konstantin Yu. Zhizhin and Alexander V. Yakimansky
Micro 2023, 3(4), 930-940; https://0-doi-org.brum.beds.ac.uk/10.3390/micro3040063 - 30 Nov 2023
Abstract
The functionalization of copolyfluorenes containing dicyanophenanthrene units by closo-decaborate anion is described. Target copolyfluorenes were analyzed using SEM, UV-vis, luminescence, NMR, and Fourier-transform infrared (FTIR) spectroscopy. The effect of complexation with the closo-decaborate anion on the photophysical properties was studied both
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The functionalization of copolyfluorenes containing dicyanophenanthrene units by closo-decaborate anion is described. Target copolyfluorenes were analyzed using SEM, UV-vis, luminescence, NMR, and Fourier-transform infrared (FTIR) spectroscopy. The effect of complexation with the closo-decaborate anion on the photophysical properties was studied both experimentally and theoretically. The PL data indicate an efficient charge transfer from fluorene to the dicyanophenanthrene units coordinated to the closo-decaborate. The coordination of closo-decaborate clusters to the nitrile groups of copolyfluorenes provides an important route to new materials for sensors and light-emitting devices while, at the same time, serving as a platform for further study of the nature of boron clusters.
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(This article belongs to the Section Microscale Materials Science)
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Chitin-Derived Silver Nanoparticles for Enhanced Food Preservation: Synthesis, Characterization, and Antimicrobial Potential
by
R. Vijayaraj, K. Altaff, M. Jayaprakashvel, R. Muthezhilan, B. Saran, P. Kurinjinathan, Selvakumari Jeyaperumal, Venkatesan Perumal, R. M. Saravana Kumar and Lakshmanan Govindan
Micro 2023, 3(4), 912-929; https://0-doi-org.brum.beds.ac.uk/10.3390/micro3040062 - 30 Nov 2023
Abstract
In this research article we report the potentials of chitin-based silver nanoparticles (chitin AgNPs) derived from Indian mimic goatfish (Mulloidichthys ayliffe) scales as an effective food preservation agent. The study comprehensively presents the multifaceted attributes of chitin AgNPs, including their synthesis,
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In this research article we report the potentials of chitin-based silver nanoparticles (chitin AgNPs) derived from Indian mimic goatfish (Mulloidichthys ayliffe) scales as an effective food preservation agent. The study comprehensively presents the multifaceted attributes of chitin AgNPs, including their synthesis, characterization, and antimicrobial properties. Chitin yield from M. ayliffe scales and three-spot swimming crab (P. sanguinolentus) exoskeleton was determined, with the insoluble content quantified. FTIR analysis unveiled distinct absorption peaks for chitin, and scanning electron microscopy revealed the ultrastructure of chitin from both the sources. Using UV–visible spectroscopy, the biosynthesis of AgNPs was accomplished and characterized, with the color shift of the solution serving as proof of a successful synthesis. UV–vis spectra provided insights into nanoparticle size and shape. SEM micrographs exhibited spherical particle morphology, while FTIR spectra indicated amino group interactions contributing to AgNP stabilization. The antimicrobial potential of chitin AgNPs was assessed against the food pathogen, Vibrio spp. Chitin films displayed significant antimicrobial activity, particularly AgNP-synthesized chitin from M. ayliffe scales, demonstrated the highest Vibrio spp. inhibition activity. Furthermore, chitin AgNPs were incorporated into the common chili, Capsicum annuum and the tomato, Solanum lycopersicum to extend their shelf life at room temperature. This study reveals the efficacy of chitin AgNPs from M. ayliffe scales as potent agents for food preservation, offering insights into their physical, mechanical, and antimicrobial attributes. The application of chitin AgNPs to perishable food items highlights their potential in enhancing shelf life and quality, opening innovative avenues for sustainable food preservation.
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(This article belongs to the Section Microscale Biology and Medicines)
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Open AccessArticle
Formulation of Pharmaceutical Tablets Containing β-Cyclodextrin-4-Methyl-Umbelliferone (Hymecromone) Inclusion Complexes and Study of the Dissolution Kinetics
by
Eleni Kavetsou, Ioanna Pitterou, Nikos G. Dimitrioglou, Stefanos Kikionis, Eftichia Kritsi, Panagiotis Zoumpoulakis, Eleni Pontiki, Dimitra Hadjipavlou-Litina, Dimitris T. Hatziavramidis and Anastasia Detsi
Micro 2023, 3(4), 892-911; https://0-doi-org.brum.beds.ac.uk/10.3390/micro3040061 - 22 Nov 2023
Abstract
The present study focuses on the synthesis of the natural product 4-methyl-umbelliferone (4-MU, hymecromone), the preparation, characterization, and biological activity evaluation of 4-MU inclusion complexes with β-cyclodextrin (β-CD), as well as their incorporation into pharmaceutical tablets. The inclusion complexes (ICs)
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The present study focuses on the synthesis of the natural product 4-methyl-umbelliferone (4-MU, hymecromone), the preparation, characterization, and biological activity evaluation of 4-MU inclusion complexes with β-cyclodextrin (β-CD), as well as their incorporation into pharmaceutical tablets. The inclusion complexes (ICs) were characterized using DLS, SEM, TGA as well as FT-IR, UV-vis, and NMR spectroscopies. The release profile of 4-MU from the β-CD-4-MU ICs was studied in three different pH: 1.2 (aqueous hydrochloric acid), 7.4, and 6.8 (phosphate-buffered solutions), to simulate the stomach, physiological, and intestine pH, respectively. The ICs were incorporated in pharmaceutical tablets which were prepared by direct compression and were characterized for their mechanical properties. The optimal composition of 4-MU as the active pharmaceutical ingredient (API) and excipients was determined using design of experiment (DoE), and the dissolution studies were performed at pH 1.2 at 37 ± 0.5 °C. The sustained release profile of the pharmaceutical tablets showed a delayed burst release effect at 20 min (20% drug release) compared to that of the ICs at the same time interval (70%). The results indicated that the kinetic model describing the release profile of 4-MU from the ICs and tablets is the Higuchi model, while the release mechanism is swelling and diffusion, as was indicated by the Korsmeyer–Peppas kinetic model. The optimization analysis revealed that the optimum composition contains x1 = 150.95 mg of β-CD-4-MU ICs, x2 = 82.65 mg of microcrystalline cellulose, and x3 = 12.40 mg of calcium phosphate.
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(This article belongs to the Section Microscale Biology and Medicines)
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Open AccessArticle
Impact of Two Lavender Extracts on Silver Nanoparticle Synthesis, and the Study of Nanoparticles’ Antibiofilm Properties and Their Ability to Transfer them into a Nontoxic Polymer
by
Lívia Mačák, Oksana Velgosova and Silvia Dolinská
Micro 2023, 3(4), 879-891; https://0-doi-org.brum.beds.ac.uk/10.3390/micro3040060 - 17 Nov 2023
Abstract
In this work, we aimed to analyze the impact of extracts prepared from dried Lavandula angustifolia (lavender) flowers and leaves on the synthesis of silver nanoparticles (AgNPs) (wherein the shape and size of AgNPs and the efficiency of the process were analyzed) and
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In this work, we aimed to analyze the impact of extracts prepared from dried Lavandula angustifolia (lavender) flowers and leaves on the synthesis of silver nanoparticles (AgNPs) (wherein the shape and size of AgNPs and the efficiency of the process were analyzed) and to prove the possibility of transferring the AgNPs’ properties into a polymer matrix. An ex situ method was used to incorporate AgNPs and prepare polymer matrix composite (PVP-AgNPs) films (via casting) and fibers (via electrospinning). We used UV-vis absorption spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM) to analyze and characterize the AgNPs and prepared composites. The results of FTIR analysis confirmed the presence of phytochemicals that can reduce silver ions from Ag+ to Ag0 in both extracts. The presence of spherical nanoparticles was confirmed via TEM regardless of the type of extract used. However, leaf extract caused the formation of AgNPs with a narrower size interval (an average size of 20 nm), and with higher efficiency, compared to the nanoparticles prepared using the flower extract. The nanoparticles prepared using the leaf extract were then incorporated into the polymer matrix, and thin polymer composite films and fibers were successfully prepared. The anti-biofilm activity of AgNPs colloids and prepared polymer nanocomposites against green algae Chlorella kessleri was studied. The anti-biofilm properties of the AgNPs were proved, along with the efficient transfer of their toxic properties into nontoxic polymer.
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(This article belongs to the Section Microscale Materials Science)
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Open AccessArticle
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://0-doi-org.brum.beds.ac.uk/10.3390/micro3040059 - 12 Nov 2023
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
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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.
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(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)
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