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.
- High Visibility: indexed within Scopus, ESCI (Web of Science) and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 22.4 days after submission; acceptance to publication is undertaken in 3.8 days (median values for papers published in this journal in the first half of 2024).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
- Micro is a companion journal of Micromachines.
Latest Articles
Pullulan/Collagen Scaffolds Promote Chronic Wound Healing via Mesenchymal Stem Cells
Micro 2024, 4(4), 599-620; https://doi.org/10.3390/micro4040037 - 28 Oct 2024
Abstract
This study investigated the development of Pullulan/Collagen nanofiber scaffolds integrated with mesenchymal stem cells (MSCs) to enhance chronic wound healing. The combination of these biopolymers aims to optimize the scaffold properties for cell growth, viability, and tissue regeneration. Materials and Methods: Pullulan, Collagen,
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This study investigated the development of Pullulan/Collagen nanofiber scaffolds integrated with mesenchymal stem cells (MSCs) to enhance chronic wound healing. The combination of these biopolymers aims to optimize the scaffold properties for cell growth, viability, and tissue regeneration. Materials and Methods: Pullulan, Collagen, and Pullulan/Collagen composite nanofibers were fabricated using electrospinning. The fibers were characterized using scanning electron microscopy (SEM) to determine the fiber diameter, and Fourier-transform infrared spectroscopy (FTIR) was employed to assess the molecular interactions. Cell viability was evaluated using MSCs cultured on the scaffolds and apoptosis assays were conducted to assess cell health. Distilled water was used as the solvent to maximize biocompatibility. Results: SEM analysis revealed that Pullulan nanofibers exhibited a larger average diameter (274 ± 20 nm) compared to Collagen fibers (167.03 ± 40.04 nm), while the Pullulan/Collagen composite fibers averaged 280 ± 102 nm. FTIR confirmed the molecular interactions between Pullulan and Collagen. Regarding biocompatibility, the Pullulan/Collagen scaffold demonstrated superior cell viability at 99% compared to 91% for Pullulan alone. Apoptosis assays indicated significantly lower necrosis rates for the composite scaffold (1.29%) than for the Pullulan-only scaffolds (2.35%). Conclusion: The use of distilled water as a solvent played a critical role in increasing cell viability and facilitating healthy proliferation of MSCs without cellular damage. Additionally, the reduced platelet activation and macrophage activity (0.75-fold for both) further supported the biocompatibility of the Pullulan/Collagen scaffold, demonstrating its potential for tissue engineering and chronic wound healing applications.
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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
Enhanced Acoustic Mixing in Silicon-Based Chips with Sharp-Edged Micro-Structures
by
Mehrnaz Hashemiesfahan, Pierre Gelin, Han Gardeniers and Wim De Malsche
Micro 2024, 4(4), 585-598; https://doi.org/10.3390/micro4040036 - 20 Oct 2024
Abstract
The small dimensions of microfluidic channels allow for fast diffusive or passive mixing, which is beneficial for time-sensitive applications such as chemical reactions, biological assays, and the transport of to-be-detected species to sensors. In microfluidics, the need for fast mixing within milliseconds arises
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The small dimensions of microfluidic channels allow for fast diffusive or passive mixing, which is beneficial for time-sensitive applications such as chemical reactions, biological assays, and the transport of to-be-detected species to sensors. In microfluidics, the need for fast mixing within milliseconds arises primarily because these devices are often used in fields where rapid and efficient mixing significantly impacts the performance and outcome of the processes. Active mixing with acoustics in microfluidic devices involves using acoustic waves to enhance the mixing of fluids within microchannels. Using sharp corners and wall patterns in acoustofluidic devices significantly enhances the mixing by acoustic streaming around these features. The streaming patterns around the sharp edges are particularly effective for the mixing because they can produce strong lateral flows that rapidly homogenize liquids. This work presents extensive characterizations of the effect of sharp-edged structures on acoustic mixing in bulk acoustic wave (BAW) mode in a silicon microdevice. The effect of side wall patterns in different angles and shapes, their positions, the type of piezoelectric transducer, and its amplitude and frequency have been studied. Following the patterning of the channel walls, a mixing time of 25 times faster was reached, compared to channels with smooth side walls exhibiting conventional BAW behavior. The average locally determined acoustic streaming velocity inside the channel becomes 14 times faster if sharp corners of 10° are added to the wall.
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(This article belongs to the Section Analysis Methods and Instruments)
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Open AccessArticle
Evaluation of the Influence of Lorentz Forces on the Natural Frequencies of a Dual-Microcantilever Sensor for Ultralow Mass Detection
by
Luca Banchelli, Georgi Todorov, Vladimir Stavrov, Borislav Ganev and Todor Todorov
Micro 2024, 4(4), 572-584; https://doi.org/10.3390/micro4040035 - 12 Oct 2024
Abstract
In this paper, the impact of Lorentz forces and temperature on the natural frequencies of a piezoresistive sensor composed of two microcantilevers with integrated U-shaped thin-film aluminum heaters are investigated. Two types of experiments were performed. In the first, the sensor was placed
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In this paper, the impact of Lorentz forces and temperature on the natural frequencies of a piezoresistive sensor composed of two microcantilevers with integrated U-shaped thin-film aluminum heaters are investigated. Two types of experiments were performed. In the first, the sensor was placed in a magnetic field so that the current flowing in the heater, in addition to raising the temperature, produced Lorentz forces, inducing normal stresses in the plane of one of the microcantilevers. In the second, which were conducted without magnetic fields, only the temperature variation of the natural frequency was left. In processing of the results, the thermal variations were subtracted from the variations due to both Lorentz forces and temperature in the natural frequency, resulting in the influence of the Lorentz forces only. Theoretical relations for the Lorentz frequency offsets were derived. An indirect method of estimating the natural frequency of one of the cantilevers, through a particular cusp point in the amplitude–frequency response of the sensor, was used in the investigations. The findings show that for thin microcantilevers with silicon masses on the order of 4 × 10−7 g and currents of 25 µA, thermal eigenfrequency variations are dominant. The results may have applications in the design of similar microsensors with vibrational action.
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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
Chemistry and Physics of Wet Foam Stability for Porous Ceramics: A Review
by
Kamrun Nahar Fatema, Md Rokon Ud Dowla Biswas, Jung Gyu Park and Ik Jin Kim
Micro 2024, 4(4), 552-571; https://doi.org/10.3390/micro4040034 - 30 Sep 2024
Abstract
The unique structural properties of porous ceramics, such as low thermal conductivity, high surface area, controlled permeability, and low density, make this material valuable for a wide range of applications. Its uses include insulation, catalyst carriers, filters, bio-scaffolds for tissue engineering, and composite
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The unique structural properties of porous ceramics, such as low thermal conductivity, high surface area, controlled permeability, and low density, make this material valuable for a wide range of applications. Its uses include insulation, catalyst carriers, filters, bio-scaffolds for tissue engineering, and composite manufacturing. However, existing processing methods for porous ceramics, namely replica techniques and sacrificial templates, are complex, release harmful gases, have limited microstructure control, and are expensive. In contrast, the direct foaming method offers a simple and cost-effective approach. By modifying the surface chemistry of ceramic particles in a colloidal suspension, the hydrophilic particles are transformed into hydrophobic ones using surfactants. This method produces porous ceramics with interconnected pores, creating a hierarchical structure that is suitable for applications like nano-filters. This review emphasizes the importance of interconnected porosity in developing advanced ceramic materials with tailored properties for various applications. Interconnected pores play a vital role in facilitating mass transport, improving mechanical properties, and enabling fluid or gas infiltration. This level of porosity control allows for the customization of ceramic materials for specific purposes, including filtration, catalysis, energy storage, and biomaterials.
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(This article belongs to the Special Issue Advances in Micro- and Nanomaterials: Synthesis and Applications)
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Open AccessArticle
Textile Organic Electrochemical Transistor for Non-Invasive Glucose Sensing
by
Rike Brendgen, Thomas Grethe and Anne Schwarz-Pfeiffer
Micro 2024, 4(4), 530-551; https://doi.org/10.3390/micro4040033 - 30 Sep 2024
Abstract
The global rise in diabetes has highlighted the urgent need for continuous, non-invasive health monitoring solutions. Traditional glucose monitoring methods, which are invasive and often inconvenient, have created a demand for alternative technologies that can offer comfort, accuracy, and real-time data. In this
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The global rise in diabetes has highlighted the urgent need for continuous, non-invasive health monitoring solutions. Traditional glucose monitoring methods, which are invasive and often inconvenient, have created a demand for alternative technologies that can offer comfort, accuracy, and real-time data. In this study, the development of a textile-based organic electrochemical transistor (OECT) is presented, designed for non-invasive glucose sensing, aiming to integrate this technology seamlessly into everyday clothing. The document details the design, optimization, and testing of a one-component textile-based OECT, featuring a porous PEDOT:PSS structure and a glucose oxidase-modified electrolyte for effective glucose detection in sweat. The research demonstrates the feasibility of using this textile-based OECT for non-invasive glucose monitoring, with enhanced sensitivity and specificity achieved through the integration of glucose oxidase within the electrolyte and the innovative porous PEDOT:PSS design. These findings suggest a significant advancement in wearable health monitoring technologies, providing a promising pathway for the development of smart textiles capable of non-invasively tracking glucose levels. Future work should focus on refining this technology for clinical use, including individual calibration for accurate blood glucose correlation and its integration into commercially available smart textiles.
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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
Updates on an Even More Compact Precision NMR Spectrometer and a Wider Range V-T Probe, for General Purpose NMR and for NMR Cryoporometric Nano- to Micro-Pore Measurements
by
John Beausire Wyatt Webber
Micro 2024, 4(3), 509-529; https://doi.org/10.3390/micro4030032 - 13 Sep 2024
Abstract
There is an increasing need for compact low-cost NMR apparatus that can be used on the laboratory bench and in the field. There are four main usage variants of usage: (a) time-domain apparatus, particularly for physical measurements; (b) frequency-domain apparatus, particularly for chemical
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There is an increasing need for compact low-cost NMR apparatus that can be used on the laboratory bench and in the field. There are four main usage variants of usage: (a) time-domain apparatus, particularly for physical measurements; (b) frequency-domain apparatus, particularly for chemical analysis, (c) NMR Cryoporometry apparatus for measuring pore-size distributions; and (d) MRI apparatus for imaging. For all of these, variable temperature capability may be vital. We have developed compact low-cost apparatus targeted at these applications. We discuss a hand-held NMR Spectrometer, and three different holdable NMR magnets, with sufficiently large internal bores for the Lab-Tools compact Peltier thermo-electric cooled variable-temperature probes. Currently, the NMR Spectrometer is very suitable for (a) NMR time-domain relaxation and (c) NMR Cryoporometry. With a suitable high-homogeneity magnet, it is also appropriate for simple use (b), spectral analysis, or, with a suitable gradient set, (d) MRI. Together, the NMR Spectrometer, one of the NMR variable-temperature probes, and any of these NMR magnets make excellent NMR Cryoporometers, as demonstrated by this paper and previously published research. Equally, they make versatile general-purpose variable-temperature NMR systems for materials science.
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(This article belongs to the Section Analysis Methods and Instruments)
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Open AccessReview
Advances in 3D Bioprinting for Neuroregeneration: A Literature Review of Methods, Bioinks, and Applications
by
Abrar Islam, Nuray Vakitbilir, Nátaly Almeida and Rodrigo França
Micro 2024, 4(3), 490-508; https://doi.org/10.3390/micro4030031 - 31 Aug 2024
Abstract
Recent advancements in 3D-bioprinting technology have sparked a growing interest in its application for brain repair, encompassing tissue regeneration, drug delivery, and disease modeling. This literature review examines studies conducted over the past five years to assess the current state of research in
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Recent advancements in 3D-bioprinting technology have sparked a growing interest in its application for brain repair, encompassing tissue regeneration, drug delivery, and disease modeling. This literature review examines studies conducted over the past five years to assess the current state of research in this field. Common bioprinting methods and key parameters influencing their selection are explored, alongside an analysis of the diverse types of bioink utilized and their associated parameters. The extrusion-based 3D-bioprinting method emerged as the most widely studied and popular topic, followed by inkjet-based and laser-based bioprinting and stereolithography. Regarding bioinks, fibrin-based and collagen-based bioinks are predominantly utilized. Furthermore, this review elucidates how 3D bioprinting holds promise for neural tissue repair, regeneration, and drug screening, detailing the steps involved and various approaches employed. Neurovascular 3D printing and bioscaffold 3D printing stand out as the top two preferred methods for brain repair. The recent studies’ shortcomings and potential solutions to address them are also examined and discussed. Overall, by synthesizing recent findings, this review provides valuable insights into the potential of 3D bioprinting for advancing brain repairment strategies.
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(This article belongs to the Section Microscale Biology and Medicines)
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Open AccessArticle
The Design, Simulation, and Parametric Optimization of an RF MEMS Variable Capacitor with an S-Shaped Beam
by
Shakila Shaheen, Tughrul Arslan and Peter Lomax
Micro 2024, 4(3), 474-489; https://doi.org/10.3390/micro4030030 - 14 Aug 2024
Abstract
This study presents the design and simulation of an RF MEMS variable capacitor with a high tuning ratio and high linearity factor of capacitance–voltage response. An electrostatic torsion actuator with planar and non-planar structures is presented to obtain the high tuning ratio by
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This study presents the design and simulation of an RF MEMS variable capacitor with a high tuning ratio and high linearity factor of capacitance–voltage response. An electrostatic torsion actuator with planar and non-planar structures is presented to obtain the high tuning ratio by avoiding the occurrence of pull-in point. In the proposed design, the capacitor plate is connected to the electrostatic actuators by using the s-shaped beam. The proposed design shows a 138% tuning ratio with the planar structure of the actuator and 167% tuning ratio by implementing the non-planar structure. A linearity factor of 99% is attained by adjusting the rates at which the capacitor plate rises as the actuation voltage increases and the rate at which the capacitance decreases as the plate rises. Parametric optimization of the design is performed by utilizing the finite element method (FEM) analysis and high-frequency structural simulator (HFSS) analysis to obtain an optimized high-tuning ratio RF MEMS varactor at low actuation voltage. S-parameters of the design are presented on HFSS, with a 50 ohm coplanar waveguide (CPW) serving as the transmission line. The proposed RF MEMS varactor can be utilized in tunable RF devices.
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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 AccessArticle
Synthesis and Functionalities of Blade-Coated Nanographite Films
by
Paloma E. S. Pellegrini, Luana de Moraes Leitão Gonçalves Vaz, Silvia Vaz Guerra Nista, Hugo Enrique Hernández-Figueroa and Stanislav Moshkalev
Micro 2024, 4(3), 460-473; https://doi.org/10.3390/micro4030029 - 27 Jul 2024
Abstract
The manufacturing and characterization of nanographite films on substrates form the foundation for advances in materials science. Conductive graphite films are challenging products, as isolating graphite oxide is often necessary. In this study, nanographite suspensions containing non-oxidized graphite flakes were used to fabricate
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The manufacturing and characterization of nanographite films on substrates form the foundation for advances in materials science. Conductive graphite films are challenging products, as isolating graphite oxide is often necessary. In this study, nanographite suspensions containing non-oxidized graphite flakes were used to fabricate novel thin and ultrathin films via blade coating on industry-standard substrates. Films as thin as 346 nm were successfully fabricated. Moreover, it was possible to induce the orientation of the graphite nanoflakes via blade coating. This orientation led to electrical anisotropy; thus, the electrical behavior of the films in each orthogonal direction differed. After adjusting the coating parameters and the concentration of the nanographite flakes, the electrical conductivity ranged from 0.04 S/cm to 0.33 S/cm. In addition, with such adjustments, the transparency of the films in the visible range varied from 20% to 75%. By establishing a methodology for the tuning of both electrical and optical properties via adjustments in the nanographite suspension and coating parameters, we can fabricate resistant, conductive, and transparent films satisfying certain requirements. The results presented here can be extrapolated to enhance applications, especially for photonics and solar cells, in fields that require electrical conductive materials with high levels of transparency.
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(This article belongs to the Special Issue Advances in Micro- and Nanomaterials: Synthesis and Applications)
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Open AccessArticle
Exploring Microstructure Patterns: Influence on Hydrophobic Properties of 3D-Printed Surfaces
by
Mark Lohatepanont, Melody Chen, Luis Carlos Mendoza Nova, John-Thomas Murray and Wilson Merchan-Merchan
Micro 2024, 4(3), 442-459; https://doi.org/10.3390/micro4030028 - 23 Jul 2024
Abstract
This study investigates the influence of microstructure patterns on the hydrophobic properties of surfaces of 3D-printed objects generated using photopolymer resin. Various arrangements and designs of microstructures on the surface of 3D-printed objects were examined. Leveraging the superior resolution of stereolithography printers (SLA)
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This study investigates the influence of microstructure patterns on the hydrophobic properties of surfaces of 3D-printed objects generated using photopolymer resin. Various arrangements and designs of microstructures on the surface of 3D-printed objects were examined. Leveraging the superior resolution of stereolithography printers (SLA) over fused deposition modeling, intricate microfeature designs were well-implemented. The experiments involved a range of structures on the surface of the 3D-printed objects, including precisely defined arrays of microcylinders, microchannels, and other complex designs generated by parametric equations. The hydrophobicity of the 3D-printed objects was assessed through the water droplet test, revealing a spectrum of results ranging from hydrophobic to weakly hydrophobic, and to hydrophilic surfaces. Light microscopy was employed to characterize the surface morphological properties of the 3D-printed objects, which were then correlated with the measured contact angles. It was discovered that the 3D-printed objects with microstructures formed using parametric functions exhibited patterns with irregularities and fluctuations along all directions or axes, resulting in a higher degree of hydrophobicity compared to structured matrices with pillared arrays. However, some surfaces created with parametric functions resulted in an anisotropic system where the material properties varied along one direction, while the other direction exhibited a flat, planar surface. These anisotropic systems were found to be less hydrophobic according to the water droplet test.
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(This article belongs to the Section Microscale Engineering)
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Open AccessArticle
Optical and Morphological Characterization of Nanoscale Oxides Grown in Low-Energy H+-Implanted c-Silicon
by
Anna Szekeres, Sashka Alexandrova, Mihai Anastasescu, Hermine Stroescu, Mariuca Gartner and Peter Petrik
Micro 2024, 4(3), 426-441; https://doi.org/10.3390/micro4030027 - 18 Jul 2024
Abstract
Nanoscale oxides grown in c-silicon, implanted with low-energy (2 keV) H+ ions and fluences ranging from 1013 cm−2 to 1015 cm−2 by RF plasma immersion implantation (PII), have been investigated. The oxidation of the implanted Si layers proceeded
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Nanoscale oxides grown in c-silicon, implanted with low-energy (2 keV) H+ ions and fluences ranging from 1013 cm−2 to 1015 cm−2 by RF plasma immersion implantation (PII), have been investigated. The oxidation of the implanted Si layers proceeded in dry O2 at temperatures of 700 °C, 750 °C and 800 °C. The optical characterization of the formed Si/SiOx structures was conducted by electroreflectance (ER) and spectroscopic ellipsometric (SE) measurements. From the ER and SE spectra analysis, the characteristic energy bands of direct electron transitions in Si are elaborated. The stress in dependence on hydrogenation conditions is considered and related to the energy shifts of the Si interband transitions around 3.4 eV. Silicon oxides, grown on PII Si at a low H+ fluence, have a non-stoichiometric nature, as revealed by IR-SE spectra analysis, while with an increasing H+ fluence in the PII Si substrates and/or the subsequent oxidation temperature the stoichiometric Si-O4 units in the oxides become predominant. The development of surface morphology is studied by atomic force microscopy (AFM) imaging. Oxidation of the H+-implanted Si surface region flattens out the surface pits created on the Si surface by H+ implants. Based on the evaluation of the texture index and mean fractal dimension, the isotropic and self-similar character of the studied surfaces is emphasized.
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(This article belongs to the Special Issue Advances in Micro- and Nanomaterials: Synthesis and Applications)
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Open AccessArticle
Observation of the Transition Phenomenon of High-Density Cell Distribution in a Two-Dimensional Microspace of the Unicellular Green Alga Chlamydomonas reinhardtii
by
Yuka Goda, Kyohei Yamashita, Tetsuo Aono, Kentaro Aizawa, Masafumi Hashimoto and Eiji Tokunaga
Micro 2024, 4(3), 412-425; https://doi.org/10.3390/micro4030026 - 28 Jun 2024
Abstract
Understanding the spatial distribution (SD) of unicellular organisms is crucial for comprehending population dynamics and adaptive strategies at the microbial scale. These behaviors include the formation of ordered structures through intercellular interactions and the broader implications for ecosystem interactions. In this study, the
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Understanding the spatial distribution (SD) of unicellular organisms is crucial for comprehending population dynamics and adaptive strategies at the microbial scale. These behaviors include the formation of ordered structures through intercellular interactions and the broader implications for ecosystem interactions. In this study, the spatial distribution of the motile unicellular alga Chlamydomonas reinhardtii was investigated, with a focus on high-density conditions approximated by an area fraction of φ = 10%. Cell counting was carried out by image analysis, which applies the quasi-two-dimensional observation technique developed in our previous studies to analyze cell interactions in microspaces with thicknesses of 80 µm and 200 µm using both variance-to-mean ratio (VMR) and Eberhardt statistics (ES). The study reveals that experimental results, when evaluated using both VMR and ES, confirmed a similar trend and a density-dependent transition in cellular interaction. This transition ranges from swarming at lower densities to dispersal at higher densities, with a critical boundary observed at approximately φ = 8%. The findings suggest that cell behavior in dense populations shifts due to limited space and resources, offering a new perspective on the adaptive strategies of cells. These insights could enhance understanding of the mechanisms governing cell behavior in crowded environments.
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(This article belongs to the Section Microscale Biology and Medicines)
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Open AccessArticle
Preparation of Antimony Tin Oxide Thin Film Using Green Synthesized Nanoparticles by E-Beam Technique for NO2 Gas Sensing
by
Chaitra Chandraiah, Hullekere Mahadevaiah Kalpana, Challaghatta Muniyappa Ananda and Madhusudan B. Kulkarni
Micro 2024, 4(3), 401-411; https://doi.org/10.3390/micro4030025 - 21 Jun 2024
Abstract
This work delves into the preparation of ATO thin films and their characterization, fabrication, and calibration of a NO2 gas sensor, as well as the development of the packaged sensor. ATO thin films were prepared by e-beam evaporation using green synthesized ATO
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This work delves into the preparation of ATO thin films and their characterization, fabrication, and calibration of a NO2 gas sensor, as well as the development of the packaged sensor. ATO thin films were prepared by e-beam evaporation using green synthesized ATO nanomaterials on different substrates and annealed at 500 and 600 °C for one hour. The structural and morphological properties of the developed thin films were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. An orthorhombic SnO2 crystal structure was recognized through XRD analysis. The granular-shaped nanoparticles were revealed through SEM and TEM images. The films annealed at 600 °C exhibited improved crystallinity. ATO films prepared on normal 5 µm interdigitated electrodes (IDEs) and annealed at 600 °C exhibited a response of 10.31 ± 0.25 with an optimum temperature of 200 °C for a 4.8 ppm NO2 gas concentration. The packaged NO2 gas sensor developed using IDEs with a microheater demonstrated an improved response of 16.20 ± 0.25 for 4.8 ppm of NO2 gas.
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(This article belongs to the Special Issue Advances in Micro- and Nanomaterials: Synthesis and Applications)
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Open AccessArticle
Extending Polymer Opal Structural Color Properties into the Near-Infrared
by
Giselle Rosetta, Matthew Gunn, John J. Tomes, Mike Butters and Chris E. Finlayson
Micro 2024, 4(2), 387-400; https://doi.org/10.3390/micro4020024 - 5 Jun 2024
Abstract
We report the fabrication and characterisation of near-IR reflecting films and coatings based on shear-assembled crystalline ensembles of polymer composite microspheres, also known as “polymer opals”. Extension of the emulsion polymerisation techniques for synthesis of tractable larger core-interlayer-shell (CIS) particles, of up to
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We report the fabrication and characterisation of near-IR reflecting films and coatings based on shear-assembled crystalline ensembles of polymer composite microspheres, also known as “polymer opals”. Extension of the emulsion polymerisation techniques for synthesis of tractable larger core-interlayer-shell (CIS) particles, of up to half a micron diameter, facilitates the engineering and processing of thin-film synthetic opals, with a tunable photonic stopband spanning an extended spectral range of λ ≈ 700–1600 nm. Samples exhibit strong “scattering cone” interactions, with considerable angular dependence and angle tuning possible, as measured with a goniometric technique. These intense optical resonances in the near-IR, particularly within the important region around λ ~ 800 nm, combined with an appreciable translucency within the visible light spectrum, is indicative of the potential applications in coatings technologies and solar cells.
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(This article belongs to the Special Issue Advances in Micro- and Nanomaterials: Synthesis and Applications)
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Open AccessArticle
Implementation of Numerical Model for Prediction of Temperature Distribution for Metallic-Coated Firefighter Protective Clothing
by
Jawad Naeem, Adnan Mazari, Zdenek Kus, Antonin Havelka and Mohamed Abdelkader
Micro 2024, 4(2), 368-386; https://doi.org/10.3390/micro4020023 - 21 May 2024
Abstract
The aim of this study is to predict the distribution of temperature at various positions on silver-coated firefighter protective clothing when subjected to external radiant heat flux. This will be helpful in the determination of thermal protective performance. Firefighter clothing consists of three
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The aim of this study is to predict the distribution of temperature at various positions on silver-coated firefighter protective clothing when subjected to external radiant heat flux. This will be helpful in the determination of thermal protective performance. Firefighter clothing consists of three layers, i.e., the outer shell, moisture barrier and thermal liner. The outer shell is the exposed surface, which was coated with silver particles through a physical vapor deposition process called magnetron sputtering. Afterwards, these uncoated and silver-coated samples were exposed to radiant heat transmission equipment at 10 kW/m2 as per the ISO 6942 standard. Silver-coated samples displayed better thermal protective performance as the rate of temperature rise in silver-coated samples slowed. Later, a numerical approach was employed, contemplating the impact of metallic coating on the exterior shell. The finite difference method was utilized for solving partial differential equations and the implicit method was employed to discretize the partial differential equations. The numerical model displayed a good prediction of the distribution of temperature at different nodes with respect to time. The comparison of time vs. temperature graphs at different nodes for uncoated and silver-coated samples acquired from numerical solutions showed similar patterns, as witnessed in the experimental results.
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(This article belongs to the Section Microscale Materials Science)
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Open AccessArticle
A Microfluidic Paper-Based Lateral Flow Device for Quantitative ELISA
by
Ashutosh Kumar, Cameron Hahn, Stephen Herchen, Alex Soucy, Ethan Carpio, Sophia Harper, Nassim Rahmani, Constantine Anagnostopoulos and Mohammad Faghri
Micro 2024, 4(2), 348-367; https://doi.org/10.3390/micro4020022 - 16 May 2024
Cited by 1
Abstract
This study presents an innovative lateral flow microfluidic paper-based analytical device (μPAD) designed for conducting quantitative paper-based enzyme-linked immunosorbent assays (p-ELISA), seamlessly executing conventional ELISA steps in a paper-based format. The p-ELISA device utilizes a passive fluidic circuit with functional elements such as
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This study presents an innovative lateral flow microfluidic paper-based analytical device (μPAD) designed for conducting quantitative paper-based enzyme-linked immunosorbent assays (p-ELISA), seamlessly executing conventional ELISA steps in a paper-based format. The p-ELISA device utilizes a passive fluidic circuit with functional elements such as a multi-bi-material cantilever (B-MaC) assembly, delay channels, and a buffer zone, all enclosed within housing for autonomous, sequential loading of critical reagents onto the detection zone. This novel approach not only demonstrates a rapid assay completion time of under 30 min, but also boasts reduced reagent requirements, minimal equipment needs, and broad applicability across clinical diagnostics and environmental surveillance. Through detailed descriptions of the design, materials, and fabrication methods for the multi-directional flow assay (MDFA), this manuscript highlights the device’s potential for complex biochemical analyses in a user-friendly and versatile format. Analytical performance evaluation, including a limit of detection (LOD) of 8.4 pM for Rabbit IgG, benchmarks the device’s efficacy compared to existing p-ELISA methodologies. This pioneering work lays the groundwork for future advancements in autonomous diagnostics, aiming to enhance global health outcomes through accessible and reliable testing solutions.
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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
Coupled Mode Design of Low-Loss Electromechanical Phase Shifters
by
Nathnael S. Abebe, Sunil Pai, Rebecca L. Hwang, Payton Broaddus, Yu Miao and Olav Solgaard
Micro 2024, 4(2), 334-347; https://doi.org/10.3390/micro4020021 - 6 May 2024
Cited by 1
Abstract
Micro-electromechanical systems (MEMS) have the potential to provide low-power phase shifting in silicon photonics, but techniques for designing low-loss devices are necessary for adoption of the technology. Based on coupled mode theory (CMT), we derive analytical expressions relating the loss and, in particular,
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Micro-electromechanical systems (MEMS) have the potential to provide low-power phase shifting in silicon photonics, but techniques for designing low-loss devices are necessary for adoption of the technology. Based on coupled mode theory (CMT), we derive analytical expressions relating the loss and, in particular, the phase-dependent loss, to the geometry of the MEMS phase shifters. The analytical model explains the loss mechanisms of MEMS phase shifters and enables simple optimization procedures. Based on that insight, we propose phase shifter geometries that minimize coupling power out of the waveguide. Minimization of the loss is based on mode orthogonality of a waveguide and phase shifter modes. We numerically model such geometries for a silicon nitride MEMS phase shifter over a silicon nitride waveguide, predicting less than −1.08 dB loss over a range and −0.026 dB loss when optimized for a range. We demonstrate this design framework with a custom silicon nitride process and achieve −0.48 dB insertion loss and less than 0.05 dB transmission variation over a phase shift. Our work demonstrates the strength of the coupled mode approach for the design and optimization of MEMS phase shifters.
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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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Silver Nanoparticles’ Localized Surface Plasmon Resonances Emerged in Polymeric Environments: Theory and Experiment
by
Maria Tsarmpopoulou, Dimitrios Ntemogiannis, Alkeos Stamatelatos, Dimitrios Geralis, Vagelis Karoutsos, Mihail Sigalas, Panagiotis Poulopoulos and Spyridon Grammatikopoulos
Micro 2024, 4(2), 318-333; https://doi.org/10.3390/micro4020020 - 2 May 2024
Cited by 3
Abstract
Considering that the plasmonic properties of metallic nanoparticles (NPs) are strongly influenced by their dielectric environment, comprehension and manipulation of this interplay are crucial for the design and optimization of functional plasmonic systems. In this study, the plasmonic behavior of silver nanoparticles encapsulated
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Considering that the plasmonic properties of metallic nanoparticles (NPs) are strongly influenced by their dielectric environment, comprehension and manipulation of this interplay are crucial for the design and optimization of functional plasmonic systems. In this study, the plasmonic behavior of silver nanoparticles encapsulated in diverse copolymer dielectric environments was investigated, focusing on the analysis of the emerging localized surface plasmon resonances (LSPRs) through both experimental and theoretical approaches. Specifically, two series of nanostructured silver ultrathin films were deposited via magnetron sputtering on heated Corning Glass substrates at 330 °C and 420 °C, respectively, resulting in the formation of self-assembled NPs of various sizes and distributions. Subsequently, three different polymeric layers were spin-coated on top of the silver NPs. Optical and structural characterization were carried out by means of UV–Vis spectroscopy and atomic force microscopy, respectively. Rigorous Coupled Wave Analysis (RCWA) was employed to study the LSPRs theoretically. The polymeric environment consistently induced a red shift as well as various alterations in the LSPR amplitude, suggesting the potential tunability of the system.
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(This article belongs to the Section Microscale Materials Science)
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Micro-Spectrometer-Based Interferometric Spectroscopy and Environmental Sensing with Zinc Oxide Thin Film
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Ciao-Ming Tsai, Yu-Chen Hsu, Chang-Ting Yang, Wei-Yi Kong, Chitsung Hong and Cheng-Hao Ko
Micro 2024, 4(2), 305-317; https://doi.org/10.3390/micro4020019 - 1 May 2024
Abstract
This study introduces a novel approach for analyzing thin film interference spectra by employing a micro-spectrometer equipped with a spectral chip. Focusing on zinc oxide (ZnO) thin films prepared via the sol–gel method, this research aims to explore the films’ physical properties through
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This study introduces a novel approach for analyzing thin film interference spectra by employing a micro-spectrometer equipped with a spectral chip. Focusing on zinc oxide (ZnO) thin films prepared via the sol–gel method, this research aims to explore the films’ physical properties through spectral analysis. After obtaining the interference spectrum of the ZnO thin films, the peak positions within the spectrum were cataloged. Mathematical simulation was used to adjust the refractive index and thickness of the films to match the simulated interference peak positions with the observed peak positions. The thickness of the prepared ZnO film was estimated to be 4.9 μm and its refractive index at 80 °C was estimated to be 1.96. In addition, the measurement system was used to detect environmental changes, including temperature changes and gas exposure. It was observed that the optical characteristics of ZnO films exhibit marked variations with temperature shifts, enabling the establishment of a temperature calibration curve based on spectral feature displacement. In addition, experiments using a variety of gases showed that NO2 and gaseous isopropanol significantly affect the interference spectrum of ZnO, with the peak of the interference spectrum shifted by 2.3 nm and 5.2 nm, respectively, after injection of the two gases. This indicates that interferometric spectroscopy can serve as an effective tool for ZnO monitoring, capable of selectively detecting specific gases.
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(This article belongs to the Section Analysis Methods and Instruments)
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Single-Cell Screening through Cell Encapsulation in Photopolymerized Gelatin Methacryloyl
by
Venkatesh Kumar Panneer Selvam, Takeru Fukunaga, Yuya Suzuki, Shunya Okamoto, Takayuki Shibata, Tuhin Subhra Santra and Moeto Nagai
Micro 2024, 4(2), 295-304; https://doi.org/10.3390/micro4020018 - 27 Apr 2024
Abstract
This study evaluated the potential of gelatin methacryloyl (GelMA) for single-cell screening compared to polyethylene glycol diacrylate (PEGDA). GelMA photopolymerized at 1000–2000 mJ/cm2 produced consistent patterns and supported HeLa cell viability. GelMA (5%w/v) facilitated better cell collection within 2 days due
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This study evaluated the potential of gelatin methacryloyl (GelMA) for single-cell screening compared to polyethylene glycol diacrylate (PEGDA). GelMA photopolymerized at 1000–2000 mJ/cm2 produced consistent patterns and supported HeLa cell viability. GelMA (5%w/v) facilitated better cell collection within 2 days due to its shape retention. GelMA demonstrated biocompatibility with HeLa cells exhibiting exponential proliferation and biodegradation over 5 days. The average cell displacement over 2 days was 16 µm. Two targeted cell recovery strategies using trypsin were developed: one for adherent cells encapsulated at 800 mJ/cm2, and another for floating cells encapsulated at 800 mJ/cm2, enabling the selective removal of unwanted cells. These findings suggest GelMA as a promising biomaterial for single-cell screening applications, offering advantages over PEGDA in cell encapsulation and targeted recovery.
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(This article belongs to the Collection Advances in Microtechnology for Cell/Tissue Engineering and Biosensing)
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