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Micromachines, Volume 14, Issue 7 (July 2023) – 206 articles

Cover Story (view full-size image): Silicon–glass microfluidic devices offer chemical resistivity towards corrosive solvents, mechanical strength, long-term endurance, and mass-production compatibility. In this research, a generic manufacturing approach is presented that enables three-dimensional glass–silicon–glass microfluidic structures to be fabricated based on the implementation of vertical vias and a redistribution layer. This device architecture is exemplarily used to create droplet-generation microfluidic devices with an increasing number of flow-focusing junctions operated in parallel and being feed from one single source. Increasing the number of junctions boosts the production rate without compromising droplet monodispersity, despite the more complex 3D fluid routing. High-throughput screening applications in biomedicine and biochemistry may benefit from the high performance of 3D silicon microfluidics. View this paper
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10 pages, 4334 KiB  
Article
An Ultra-Low-Power Analog Multiplier–Divider Compatible with Digital Code for RRAM-Based Computing-in-Memory Macros
Micromachines 2023, 14(7), 1482; https://doi.org/10.3390/mi14071482 - 24 Jul 2023
Viewed by 763
Abstract
This manuscript presents an ultra-low-power analog multiplier–divider compatible with digital code words, which is applicable to the integrated structure of resistive random-access memory (RRAM)-based computing-in-memory (CIM) macros. Current multiplication and division are accomplished by a current-mirror-based structure. Compared with digital dividers to achieve [...] Read more.
This manuscript presents an ultra-low-power analog multiplier–divider compatible with digital code words, which is applicable to the integrated structure of resistive random-access memory (RRAM)-based computing-in-memory (CIM) macros. Current multiplication and division are accomplished by a current-mirror-based structure. Compared with digital dividers to achieve higher precision and operation speed, analog dividers present the advantages of a reduced power consumption and a simple circuit structure in lower precision operations, thus improving the energy efficiency. Designed and fabricated in a 55 nm CMOS process, the proposed work is capable of achieving 8-bit precision for analog current multiplication and division operations. Measurement results show that the signal delay is 1 μs when performing 8-bit operation, with a bandwidth of 1.4 MHz. The power consumption is less than 6.15 μW with a 1.2 V supply voltage. The proposed multiplier–divider can increase the operation capacity by dividing the input current and digital code while reducing the power consumption and complexity required by division, which can be further utilized in real-time operation of edge computing devices. Full article
(This article belongs to the Special Issue State-of-the-Art CMOS and MEMS Devices)
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19 pages, 87789 KiB  
Communication
Research on IMU-Assisted UWB-Based Positioning Algorithm in Underground Coal Mines
Micromachines 2023, 14(7), 1481; https://doi.org/10.3390/mi14071481 - 24 Jul 2023
Viewed by 893
Abstract
The application of an ultra-wideband (UWB) positioning system in a Global Positioning System (GPS) denial environment such as an underground coal mine, mainly focuses on position information and rarely involves information such as direction attitude. Position accuracy is often affected by multipath, non-visible [...] Read more.
The application of an ultra-wideband (UWB) positioning system in a Global Positioning System (GPS) denial environment such as an underground coal mine, mainly focuses on position information and rarely involves information such as direction attitude. Position accuracy is often affected by multipath, non-visible ranges, base station layout, and more. We proposed an IMU-assisted UWB-based positioning system for the provision of positioning and orientation services to coal miners in underground mines. The Error-State Kalman Filter (ESKF) is used to filter the errors in the measured data from the IMU-assisted UWB positioning system to obtain the best estimate of the error for the current situation and correct for inaccuracies due to approximations. The base station layout of the IMU-assisted UWB positioning system was also simulated. The reasonable setting of the reference base station location can suppress multi-access interference and improve positioning accuracy to a certain extent. Numerous simulation experiments have been conducted in GPS denial environments, such as underground coal mines. The experimental results show the effectiveness of the method for determining the position, direction, and attitude of the coal miner under the mine, which provides a better reference value for positioning and orientation in a GPS rejection environment such as under the mine. Full article
(This article belongs to the Special Issue MEMS Sensors: Past, Present and Future)
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30 pages, 9382 KiB  
Review
A Review of the Residual Stress Generation in Metal Additive Manufacturing: Analysis of Cause, Measurement, Effects, and Prevention
Micromachines 2023, 14(7), 1480; https://doi.org/10.3390/mi14071480 - 24 Jul 2023
Cited by 8 | Viewed by 3839
Abstract
Metal additive manufacturing (AM) is capable of producing complex parts, using a wide range of functional metals that are otherwise very difficult to make and involve multiple manufacturing processes. However, because of the involvement of thermal energy in the fabrication of metallic AM [...] Read more.
Metal additive manufacturing (AM) is capable of producing complex parts, using a wide range of functional metals that are otherwise very difficult to make and involve multiple manufacturing processes. However, because of the involvement of thermal energy in the fabrication of metallic AM parts, residual stress remains one of the major concerns in metal AM. This residual stress has negative effects on part quality, dimensional accuracy, and part performance. This study aims to carry out a comprehensive review and analysis of different aspects of residual stress, including the causes and mechanisms behind the generation of residual stress during metal AM, the state-of-the-art measurement techniques for measuring residual stress, various factors influencing residual stress, its effect on part quality and performance, and ways of minimizing or overcoming residual stress in metal AM parts. Residual stress formation mechanisms vary, based on the layer-by-layer deposition mechanism of the 3D printing process. For example, the residual stress formation for wire-arc additive manufacturing is different from that of selective laser sintering, direct energy deposition, and powder bed fusion processes. Residual stress formation mechanisms also vary based on the scale (i.e., macro, micro, etc.) at which the printing is performed. In addition, there are correlations between printing parameters and the formation of residual stress. For example, the printing direction, layer thickness, internal structure, etc., influence both the formation mechanism and quantitative values of residual stress. The major effect residual stress has on the quality of a printed part is in the distortion of the part. In addition, the dimensional accuracy, surface finish, and fatigue performance of printed parts are influenced by residual stress. This review paper provides a qualitative and quantitative analysis of the formation, distribution, and evolution of residual stress for different metal AM processes. This paper also discusses and analyzes both in situ and ex situ measurement techniques for measuring residual stress. Microstructural evolution and its effect on the formation of residual stress are analyzed. Various pre- and post-processing techniques used to countermeasure residual stress are discussed in detail. Finally, this study aims to present both a qualitative and quantitative analysis of the existing data and techniques in the literature related to residual stress, as well as to provide a critical analysis and guidelines for future research directions, to prevent or overcome residual stress formation in metal AM processes. Full article
(This article belongs to the Special Issue Feature Reviews in Micromachines 2023)
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18 pages, 2803 KiB  
Article
Nmr-VSM: Non-Touch Motion-Robust Vital Sign Monitoring via UWB Radar Based on Deep Learning
Micromachines 2023, 14(7), 1479; https://doi.org/10.3390/mi14071479 - 24 Jul 2023
Viewed by 921
Abstract
In recent years, biometric radar has gained increasing attention in the field of non-touch vital sign monitoring due to its high accuracy and strong ability to detect fine-grained movements. However, most current research on biometric radar can only achieve heart rate or respiration [...] Read more.
In recent years, biometric radar has gained increasing attention in the field of non-touch vital sign monitoring due to its high accuracy and strong ability to detect fine-grained movements. However, most current research on biometric radar can only achieve heart rate or respiration rate monitoring in static environments, which have strict monitoring requirements and single monitoring parameters. Moreover, most studies have not applied the collected data despite their significant potential for applications. In this paper, we introduce a non-touch motion-robust vital sign monitoring system via ultra-wideband (UWB) radar based on deep learning. Nmr-VSM not only enables multi-dimensional vital sign monitoring under human motion environments but also implements cardiac anomaly detection. The design of Nmr-VSM includes three key components. Firstly, we design a UWB radar that can perform multi-dimensional vital sign monitoring, including heart rate, respiratory rate, distance, and motion status. Secondly, we collect real experimental data and analyze the impact of eight factors, such as motion status and distance, on heart rate monitoring. We then propose a deep neural network (DNN)-based heart rate data correction model that achieves high robustness in motion environments. Finally, we model the heart rate variability (HRV) of the human body and propose a convolutional neural network (CNN)-based anomaly detection model that achieves low-latency detection of heart diseases, such as ventricular tachycardia and ventricular fibrillation. Experimental results in a real environment demonstrate that Nmr-VSM can not only accurately monitor heart rate but also achieve anomaly detection with low latency. Full article
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11 pages, 3118 KiB  
Article
Design of Photonic Crystal Biosensors for Cancer Cell Detection
Micromachines 2023, 14(7), 1478; https://doi.org/10.3390/mi14071478 - 23 Jul 2023
Viewed by 1340
Abstract
A photonic crystal biosensor is a compact device fabricated from photonic crystal materials, which enables the detection and monitoring of the presence and concentration changes of biological molecules or chemical substances. In this paper, we propose a biosensor for cancer cell detection based [...] Read more.
A photonic crystal biosensor is a compact device fabricated from photonic crystal materials, which enables the detection and monitoring of the presence and concentration changes of biological molecules or chemical substances. In this paper, we propose a biosensor for cancer cell detection based on a silicon photonic crystal with a hexagonal resonant cavity introduced in a triangular lattice array. One of the bandgap ranges of this structure is 1188 nmλ1968 nm. When the incident light wavelength is within the range of 1188 nmλ1968 nm, the transmission coefficient of this structure at the resonant wavelength of 1469.58 nm is found to reach 99.62% through the finite difference time domain method, with a quality factor of 980. Subsequently, a biosensor is designed from this structure, with its sensing mechanism relying on the change in refractive index leading to a shift in the resonant wavelength. The target sample can be identified by observing the shift in the resonant wavelength. As cancer cells and normal cells possess different refractive indices, this biosensor can be used for their detection. The maximum sensitivity of the sensor is 915.75 nm/RIU and the minimum detection limit is 0.000236 RIU. Full article
(This article belongs to the Special Issue Nanowires for Novel Technological Applications)
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19 pages, 3113 KiB  
Review
MXene-Embedded Electrospun Polymeric Nanofibers for Biomedical Applications: Recent Advances
Micromachines 2023, 14(7), 1477; https://doi.org/10.3390/mi14071477 - 23 Jul 2023
Cited by 1 | Viewed by 1768
Abstract
Recently MXenes has gained immense attention as a new and exciting class of two-dimensional material. Due to their unique layered microstructure, the presence of various functional groups at the surface, earth abundance, and attractive electrical, optical, and thermal properties, MXenes are considered promising [...] Read more.
Recently MXenes has gained immense attention as a new and exciting class of two-dimensional material. Due to their unique layered microstructure, the presence of various functional groups at the surface, earth abundance, and attractive electrical, optical, and thermal properties, MXenes are considered promising candidates for various applications such as energy, environmental, and biomedical. The ease of dispersibility and metallic conductivity of MXene render them promising candidates for use as fillers in polymer nanocomposites. MXene–polymer nanocomposites simultaneously benefit from the attractive properties of MXenes and the flexibility and facile processability of polymers. However, the potentiality of MXene to modify the electrospun nanofibers has been less studied. Understanding the interactions between polymeric nanofibers and MXenes is important to widen their role in biomedical applications. This review explores diverse methods of MXene synthesis, discusses our current knowledge of the various biological characteristics of MXene, and the synthesis of MXene incorporated polymeric nanofibers and their utilization in biomedical applications. The information discussed in this review serves to guide the future development and application of MXene–polymer nanofibers in biomedical fields. Full article
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9 pages, 12190 KiB  
Article
3D Framework Carbon for High-Performance Zinc-Ion Capacitors
Micromachines 2023, 14(7), 1476; https://doi.org/10.3390/mi14071476 - 23 Jul 2023
Viewed by 1126
Abstract
Given the rapid progress and widespread adoption of advanced energy storage devices, there has been a growing interest in aqueous capacitors that offer non-flammable properties and high safety standards. Consequently, extensive research efforts have been dedicated to investigating zinc anodes and low-cost carbonaceous [...] Read more.
Given the rapid progress and widespread adoption of advanced energy storage devices, there has been a growing interest in aqueous capacitors that offer non-flammable properties and high safety standards. Consequently, extensive research efforts have been dedicated to investigating zinc anodes and low-cost carbonaceous cathode materials. Despite these efforts, the development of high-performance zinc-ion capacitors (ZICs) still faces challenges, such as limited cycling stability and low energy densities. In this study, we present a novel approach to address these challenges. We introduce a three-dimensional (3D) conductive porous carbon framework cathode combined with zinc anode cells, which exhibit exceptional stability and durability in ZICs. Our experimental results reveal remarkable cycling performance, with a capacity retention of approximately 97.3% and a coulombic efficiency of nearly 100% even after 10,000 charge–discharge cycles. These findings represent significant progress in improving the performance of ZICs. Full article
(This article belongs to the Special Issue Micro Supercapacitors for Energy Storage and Power Management)
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21 pages, 7881 KiB  
Article
Thermal Management of Microelectronic Devices Using Nanofluid with Metal foam Heat Sink
Micromachines 2023, 14(7), 1475; https://doi.org/10.3390/mi14071475 - 23 Jul 2023
Cited by 2 | Viewed by 1111
Abstract
Microelectronic components are used in a variety of applications that range from processing units to smart devices. These components are prone to malfunctions at high temperatures exceeding 373 K in the form of heat dissipation. To resolve this issue, in microelectronic components, a [...] Read more.
Microelectronic components are used in a variety of applications that range from processing units to smart devices. These components are prone to malfunctions at high temperatures exceeding 373 K in the form of heat dissipation. To resolve this issue, in microelectronic components, a cooling system is required. This issue can be better dealt with by using a combination of metal foam, heat sinks, and nanofluids. This study investigates the effect of using a rectangular-finned heat sink integrated with metal foam between the fins, and different water-based nanofluids as the working fluid for cooling purposes. A 3D numerical model of the metal foam with a BCC-unit cell structure is used. Various parameters are analyzed: temperature, pressure drop, overall heat transfer coefficient, Nusselt number, and flow rate. Fluid flows through the metal foam in a turbulent flow with a Reynold’s number ranging from 2100 to 6500. The optimum fin height, thickness, spacing, and base thickness for the heat sink are analyzed, and for the metal foam, the material, porosity, and pore density are investigated. In addition, the volume fraction, nanoparticle material, and flow rate for the nanofluid is obtained. The results showed that the use of metal foam enhanced the thermal performance of the heat sink, and nanofluids provided better thermal management than pure water. For both cases, a higher Nusselt number, overall heat transfer coefficient, and better temperature reduction is achieved. CuO nanofluid and high-porosity low-pore-density metal foam provided the optimum results, namely a base temperature of 314 K, compared to 341 K, with a pressure drop of 130 Pa. A trade-off was achieved between the temperature reduction and pumping power, as higher concentrations of nanofluid provided better thermal management and resulted in a large pressure drop. Full article
(This article belongs to the Special Issue Nanoscale Thermal Transport and Management)
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13 pages, 3919 KiB  
Article
Experimental Research of Triple Inertial Navigation System Shearer Positioning
Micromachines 2023, 14(7), 1474; https://doi.org/10.3390/mi14071474 - 23 Jul 2023
Viewed by 762
Abstract
In order to improve the positioning accuracy of shearers, the overground experimental device based on the positioning model of TINS (Triple Inertial Navigation System) was built. The influence of TINS installation parameters on positioning accuracy was discussed through two sets of experiments: the [...] Read more.
In order to improve the positioning accuracy of shearers, the overground experimental device based on the positioning model of TINS (Triple Inertial Navigation System) was built. The influence of TINS installation parameters on positioning accuracy was discussed through two sets of experiments: the inter-INS (Inertial Navigation System) distances influence experiments and the tri-INS plane spatial position influence experiments. The results show that the positioning accuracy of the shearer is improved to a different extent under the two sets of experimental conditions. When the inter-INS distances are 0.2 m, the positioning accuracy is the highest and the positioning accuracy improvement effect is also the best. When the negative plane α3 is 45°, the positioning accuracy is the highest, and the positioning accuracy improvement effect is also the best. The analysis shows that the main factor affecting the positioning accuracy is the precision of the evaluated values outputs of TINS from EKF (Extended Kalman Filter). Considering the positioning accuracy, equipment installation convenience and so on, the optimum installation parameters are 90° (horizontal installation) α3 for the positive plane and 0.2 m inter-INS distances. Full article
(This article belongs to the Special Issue MEMS Inertial Device)
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12 pages, 5460 KiB  
Article
Built-In Packaging for Two-Terminal Devices
Micromachines 2023, 14(7), 1473; https://doi.org/10.3390/mi14071473 - 22 Jul 2023
Viewed by 863
Abstract
Conventional packaging and interconnection methods for two-terminal devices, e.g., diodes often involve expensive and bulky equipment, introduce parasitic effects and have reliability issues. In this study, we propose a built-in packaging method and evaluate its performance compared to probing and wire bonding methods. [...] Read more.
Conventional packaging and interconnection methods for two-terminal devices, e.g., diodes often involve expensive and bulky equipment, introduce parasitic effects and have reliability issues. In this study, we propose a built-in packaging method and evaluate its performance compared to probing and wire bonding methods. The built-in packaging approach offers a larger overlap area, improved contact resistance, and direct connection to testing equipment. The experimental results demonstrate a 12% increase in current, an 11% reduction in resistance, and improved performance of the diode. The proposed method is promising for enhancing sensing applications, wireless power transmission, energy harvesting, and solar rectennas. Overall, the built-in packaging method offers a simpler, cheaper, more compact and more reliable packaging solution, paving the way for more efficient and advanced technologies in these domains. Full article
(This article belongs to the Special Issue Advanced Interconnect and Packaging, 2nd Edition)
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29 pages, 12657 KiB  
Review
A Comprehensive Review of In-Body Biomedical Antennas: Design, Challenges and Applications
Micromachines 2023, 14(7), 1472; https://doi.org/10.3390/mi14071472 - 21 Jul 2023
Cited by 3 | Viewed by 2214
Abstract
In-body biomedical devices (IBBDs) are receiving significant attention in the discovery of solutions to complex medical conditions. Biomedical devices, which can be ingested, injected or implanted in the human body, have made it viable to screen the physiological signs of a patient wirelessly, [...] Read more.
In-body biomedical devices (IBBDs) are receiving significant attention in the discovery of solutions to complex medical conditions. Biomedical devices, which can be ingested, injected or implanted in the human body, have made it viable to screen the physiological signs of a patient wirelessly, without regular hospital appointments and routine check-ups, where the antenna is a mandatory element for transferring bio-data from the IBBDs to the external world. However, the design of an in-body antenna is challenging due to the dispersion of the dielectric constant of the tissues and unpredictability of the organ structures of the human body, which can absorb most of the antenna radiation. Therefore, various factors must be considered for an in-body antenna, such as miniaturization, link budget, patient safety, biocompatibility, low power consumption and the ability to work effectively within acceptable medical frequency bands. This paper presents a comprehensive overview of the major facets associated with the design and challenges of in-body antennas. The review comprises surveying the design specifications and implementation methodology, simulation software and testing of in-body biomedical antennas. This work aims to summarize the recent in-body antenna innovations for biomedical applications and indicates the key research challenges. Full article
(This article belongs to the Special Issue Wireless Power Transfer Systems for Biomedical Devices)
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14 pages, 6531 KiB  
Article
Universally Grasping Objects with Granular—Tendon Finger: Principle and Design
Micromachines 2023, 14(7), 1471; https://doi.org/10.3390/mi14071471 - 21 Jul 2023
Cited by 2 | Viewed by 1166
Abstract
Nowadays, achieving the stable grasping of objects in robotics requires an increased emphasis on soft interactions. This research introduces a novel gripper design to achieve a more universal object grasping. The key feature of this gripper design was a hybrid mechanism that leveraged [...] Read more.
Nowadays, achieving the stable grasping of objects in robotics requires an increased emphasis on soft interactions. This research introduces a novel gripper design to achieve a more universal object grasping. The key feature of this gripper design was a hybrid mechanism that leveraged the soft structure provided by multiple granular pouches attached to the finger skeletons. To evaluate the performance of the gripper, a series of experiments were conducted using fifteen distinct types of objects, including cylinders, U-shaped brackets, M3 bolts, tape, pyramids, big pyramids, oranges, cakes, coffee sachets, spheres, drink sachets, shelves, pulley gears, aluminium profiles, and flat brackets. Our experimental results demonstrated that our gripper design achieved high success rates in gripping objects weighing less than 210 g. One notable advantage of the granular-tendon gripper was its ability to generate soft interactions during the grasping process while having a skeleton support to provide strength. This characteristic enabled the gripper to adapt effectively to various objects, regardless of their shape and material properties. Consequently, this work presented a promising solution for manipulating a wide range of objects with both stability and soft interaction capabilities, regardless of their individual characteristics. Full article
(This article belongs to the Special Issue Soft Actuators: Design, Fabrication and Applications)
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13 pages, 1980 KiB  
Article
Spin Hall Effect in Paraxial Vectorial Light Beams with an Infinite Number of Polarization Singularities
Micromachines 2023, 14(7), 1470; https://doi.org/10.3390/mi14071470 - 21 Jul 2023
Cited by 1 | Viewed by 631
Abstract
Elements of micromachines can be driven by light, including structured light with phase and/or polarization singularities. We investigate here a paraxial vector Gaussian beam with an infinite number of polarization singularities residing evenly on a straight line. The intensity distribution is derived analytically [...] Read more.
Elements of micromachines can be driven by light, including structured light with phase and/or polarization singularities. We investigate here a paraxial vector Gaussian beam with an infinite number of polarization singularities residing evenly on a straight line. The intensity distribution is derived analytically and the polarization singularities are shown to exist only in the initial plane and in the far field. The azimuthal angle of the polarization singularities is shown to increase in the far field by π/2. We obtain the longitudinal component of the spin angular momentum (SAM) density and show that it is independent of the azimuthal angle of the polarization singularities. Upon propagation in free space, an infinite number of C-points is generated, where polarization is circular. We show that the SAM density distribution has a shape of four spots, two with left and two with right elliptic polarization. The distance to the transverse plane with the maximal SAM density decreases with decreasing distance between the polarization singularities in the initial plane. Generating such alternating areas with positive and negative SAM density, despite linear polarization in the initial plane, manifests the optical spin Hall effect. Application areas of the obtained results include designing micromachines with optically driven elements. Full article
(This article belongs to the Special Issue Photon-Driven Technologies: Exploring the Latest Advancements)
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13 pages, 10649 KiB  
Article
Investigation of the Degradation Mechanism of SiC MOSFET Subjected to Multiple Stresses
Micromachines 2023, 14(7), 1469; https://doi.org/10.3390/mi14071469 - 21 Jul 2023
Viewed by 944
Abstract
The performance requirements for power devices in airborne equipment are increasingly demanding, while environmental and working stresses are becoming more diverse. The degradation mechanisms of devices subjected to multiple stresses become more complex. Most proposed degradation mechanisms and models in current research only [...] Read more.
The performance requirements for power devices in airborne equipment are increasingly demanding, while environmental and working stresses are becoming more diverse. The degradation mechanisms of devices subjected to multiple stresses become more complex. Most proposed degradation mechanisms and models in current research only consider a single stress, making it difficult to describe the correlation between multiple stresses and the correlation of failures. Then, a multi-physical field coupling model based on COMSOL is proposed. The influence relationship between temperature, moisture, electrical load, and vibration during device operation is considered, and a three-dimensional finite element model is built to investigate the multi-stress degradation mechanism under multi-physical field coupling. The simulation results show that, compared with single-stress models, the proposed multi-stress coupled model can more accurately simulate the degradation process of SiC MOSFET. This provides references for improving the reliability design of power device packaging. Full article
(This article belongs to the Special Issue High-Reliability Semiconductor Devices and Integrated Circuits)
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19 pages, 11671 KiB  
Article
Assessment of Vapor Formation Rate and Phase Shift between Pressure Gradient and Liquid Velocity in Flat Mini Heat Pipes as a Function of Internal Structure
Micromachines 2023, 14(7), 1468; https://doi.org/10.3390/mi14071468 - 21 Jul 2023
Viewed by 636
Abstract
Flat mini heat pipes (FMHPs) are often used in cooling systems for various power electronic components, as they rapidly dissipate high heat flux densities. The main objective of the present work is to experimentally investigate whether differences in the rate of vapor formation [...] Read more.
Flat mini heat pipes (FMHPs) are often used in cooling systems for various power electronic components, as they rapidly dissipate high heat flux densities. The main objective of the present work is to experimentally investigate whether differences in the rate of vapor formation occur on an internal structure containing trapezoidal microchannels and porous sintered copper powder material. Several parameters, such as hydraulic diameter and fluid velocity through the material, as a function of the internal structure porosity, were determined by calculation for a steady state regime. Reynolds number was determined as a function of porosity, according to Darcy’s law, and the Nusselt number was calculated. Since the flow is Darcy-type through the porous medium inside the FMHP, the Darcy friction factor was calculated using five methods: Colebrook, Darcy–Weisbach, Swamee–Jain, Blasius, and Haaland. After experimental tests, it was found that when the porous and trapezoidal microchannel layers are wetted at the same time, the vaporization progresses at a faster rate in the porous material, and the duration of the process is shorter. This recommends the use of such an internal structure in FMHPs since the manufacturing technology is simpler, the materials are cheaper, and the heat flux transport capacity is higher. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Microstructures)
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17 pages, 4140 KiB  
Article
WPD-Enhanced Deep Graph Contrastive Learning Data Fusion for Fault Diagnosis of Rolling Bearing
Micromachines 2023, 14(7), 1467; https://doi.org/10.3390/mi14071467 - 21 Jul 2023
Viewed by 796
Abstract
Rolling bearings are crucial mechanical components in the mechanical industry. Timely intervention and diagnosis of system faults are essential for reducing economic losses and ensuring product productivity. To further enhance the exploration of unlabeled time-series data and conduct a more comprehensive analysis of [...] Read more.
Rolling bearings are crucial mechanical components in the mechanical industry. Timely intervention and diagnosis of system faults are essential for reducing economic losses and ensuring product productivity. To further enhance the exploration of unlabeled time-series data and conduct a more comprehensive analysis of rolling bearing fault information, this paper proposes a fault diagnosis technique for rolling bearings based on graph node-level fault information extracted from 1D vibration signals. In this technique, 10 categories of 1D vibration signals from rolling bearings are sampled using a sliding window approach. The sampled data is then subjected to wavelet packet decomposition (WPD), and the wavelet energy from the final layer of the four-level WPD decomposition in each frequency band is used as the node feature. The weights of edges between nodes are calculated using the Pearson correlation coefficient (PCC) to construct a node graph that describes the feature information of rolling bearings under different health conditions. Data augmentation of the node graph in the dataset is performed by randomly adding nodes and edges. The graph convolutional neural network (GCN) is employed to encode the augmented node graph representation, and deep graph contrastive learning (DGCL) is utilized for the pre-training and classification of the node graph. Experimental results demonstrate that this method outperforms contrastive learning-based fault diagnosis methods for rolling bearings and enables rapid fault diagnosis, thus ensuring the normal operation of mechanical systems. The proposed WPDPCC-DGCL method offers two advantages: (1) the flexibility of wavelet packet decomposition in handling non-smooth vibration signals and combining it with the powerful multi-scale feature encoding capability of GCN for richer characterization of fault information, and (2) the construction of graph node-level fault samples to effectively capture underlying fault information. The experimental results demonstrate the superiority of this method in rolling bearing fault diagnosis over contrastive learning-based approaches, enabling fast and accurate fault diagnoses for rolling bearings and ensuring the normal operation of mechanical systems. Full article
(This article belongs to the Special Issue Machine-Learning-Assisted Sensors)
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11 pages, 3259 KiB  
Article
A Harvester with a Helix S-Type Vertical Axis to Capture Random Breeze Energy Efficiently
Micromachines 2023, 14(7), 1466; https://doi.org/10.3390/mi14071466 - 21 Jul 2023
Cited by 1 | Viewed by 737
Abstract
Breeze energy is a widely distributed renewable energy source in the natural world, but its efficient exploitation is very difficult. The conventional harvester with fixed arm length (HFA) has a relatively high start-up wind speed owing to its high and constant rotational inertia. [...] Read more.
Breeze energy is a widely distributed renewable energy source in the natural world, but its efficient exploitation is very difficult. The conventional harvester with fixed arm length (HFA) has a relatively high start-up wind speed owing to its high and constant rotational inertia. Therefore, this paper proposes a harvester with a helix s-type vertical axis (HSVA) for achieving random energy capture in the natural breeze environment. The HSVA is constructed with two semi-circular buckets driven by the difference of the drag exerted, and the wind energy is transferred into mechanical energy. Firstly, as the wind speed changes, the HSVA harvester can match the random breeze to obtain highly efficient power. Compared with the HFA harvester, the power coefficient is significantly improved from 0.15 to 0.2 without additional equipment. Furthermore, it has more time for energy attenuation as the wind speeds dropped from strong to moderate. Moreover, the starting torque is also better than that of HFA harvester. Experiments showed that the HSVA harvester can improve power performance on the grounds of the wind speed ranging in 0.8–10.1 m/s, and that the star-up wind speed is 0.8 m/s and output peak power can reach 17.1 mW. In comparison with the HFA harvester, the HSVA harvester can obtain higher efficient power, requires lower startup speed and keeps energy longer under the same time. Additionally, as a distributed energy source, the HSVA harvester can provide a self-generating power supply to electronic sensors for monitoring the surrounding environment. Full article
(This article belongs to the Special Issue Energy Conversion and Storage: From Materials to Devices)
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16 pages, 23299 KiB  
Article
Directional and Eye-Tracking Light Field Display with Efficient Rendering and Illumination
Micromachines 2023, 14(7), 1465; https://doi.org/10.3390/mi14071465 - 21 Jul 2023
Viewed by 1026
Abstract
Current efforts with light field displays are mainly concentrated on the widest possible viewing angle, while a single viewer only needs to view the display in a specific viewing direction. To make the light field display a practical practice, a super multi-view light [...] Read more.
Current efforts with light field displays are mainly concentrated on the widest possible viewing angle, while a single viewer only needs to view the display in a specific viewing direction. To make the light field display a practical practice, a super multi-view light field display is proposed to compress the information in the viewing zone of a single user by reducing the redundant viewpoints. A quasi-directional backlight is proposed, and a lenticular lens array is applied to achieve the restricted viewing zone. The eye-tracking technique is applied to extend the viewing area. Experimental results show that the proposed scheme can present a vivid 3D scene with smooth motion parallax. Only 16.7% conventional light field display data are required to achieve 3D display. Furthermore, an illumination power of 3.5 watt is sufficient to lighten a 31.5-inch light field display, which takes up 1.5% of the illumination power required for planar display of similar configuration. Full article
(This article belongs to the Special Issue Three-Dimensional Display Technologies)
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24 pages, 8943 KiB  
Article
Design of a Multi-Mode Hybrid Micro-Gripper for Surface Mount Technology Component Assembly
Micromachines 2023, 14(7), 1464; https://doi.org/10.3390/mi14071464 - 21 Jul 2023
Viewed by 1328
Abstract
In the last few decades, industrial sectors such as smart manufacturing and aerospace have rapidly developed, contributing to the increase in production of more complex electronic boards based on SMT (Surface Mount Technology). The assembly phases in manufacturing these electronic products require the [...] Read more.
In the last few decades, industrial sectors such as smart manufacturing and aerospace have rapidly developed, contributing to the increase in production of more complex electronic boards based on SMT (Surface Mount Technology). The assembly phases in manufacturing these electronic products require the availability of technological solutions able to deal with many heterogeneous products and components. The small batch production and pre-production are often executed manually or with semi-automated stations. The commercial automated machines currently available offer high performance, but they are highly rigid. Therefore, a great effort is needed to obtain machines and devices with improved reconfigurability and flexibility for minimizing the set-up time and processing the high heterogeneity of components. These high-level objectives can be achieved acting in different ways. Indeed, a work station can be seen as a set of devices able to interact and cooperate to perform a specific task. Therefore, the reconfigurability of a work station can be achieved through reconfigurable and flexible devices and their hardware and software integration and control For this reason, significant efforts should be focused on the conception and development of innovative devices to cope with the continuous downscaling and increasing variety of the products in this growing field. In this context, this paper presents the design and development of a multi-mode hybrid micro-gripper devoted to manipulate and assemble a wide range of micro- and meso-SMT components with different dimensions and proprieties. It exploits two different handling technologies: the vacuum and friction. Full article
(This article belongs to the Special Issue Flexible Micromanipulators and Micromanipulation, 2nd Edition)
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16 pages, 6956 KiB  
Article
Effect of Plasma Excitation Power on the SiOxCyHz/TiOx Nanocomposite
Micromachines 2023, 14(7), 1463; https://doi.org/10.3390/mi14071463 - 21 Jul 2023
Viewed by 791
Abstract
Titanium dioxide has attracted a great deal of attention in the field of environmental purification due to its photocatalytic activity under ultraviolet light. Photocatalytic efficiency and the energy required to initiate the process remain the drawbacks that hinder the widespread adoption of the [...] Read more.
Titanium dioxide has attracted a great deal of attention in the field of environmental purification due to its photocatalytic activity under ultraviolet light. Photocatalytic efficiency and the energy required to initiate the process remain the drawbacks that hinder the widespread adoption of the process. Consistently with this, it is proposed here the polymerization of hexamethyldisiloxane fragments simultaneously to TiO2 sputtering for the production of thin films in low-pressure plasma. The effect of plasma excitation power on the molecular structure and chemical composition of the films was evaluated by infrared spectroscopy. Wettability and surface energy were assessed by a sessile drop technique, using deionized water and diiodomethane. The morphology and elemental composition of the films were determined using scanning electron microscopy and energy dispersive spectroscopy, respectively. The thickness and roughness of the resulting films were measured using profilometry. Organosilicon-to-silica films, with different properties, were deposited by combining both deposition processes. Titanium was detected from the structures fabricated by the hybrid method. It has been observed that the proportion of titanium and particles incorporated into silicon-based matrices depends on the plasma excitation power. In general, a decrease in film thickness with increasing power has been observed. The presence of Ti in the plasma atmosphere alters the plasma deposition mechanism, affecting film deposition rate, roughness, and wettability. An interpretation of the excitation power dependence on the plasma activation level and sputtering yield is proposed. The methodology developed here will encourage researchers to create TiO2 films on a range of substrates for their prospective use as sensor electrodes, water and air purification systems, and biocompatible materials. Full article
(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)
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29 pages, 3472 KiB  
Review
Microwave Imaging and Sensing Techniques for Breast Cancer Detection
Micromachines 2023, 14(7), 1462; https://doi.org/10.3390/mi14071462 - 21 Jul 2023
Cited by 5 | Viewed by 3041
Abstract
Medical imaging techniques, including X-ray mammography, ultrasound, and magnetic resonance imaging, play a crucial role in the timely identification and monitoring of breast cancer. However, these conventional imaging modalities have their limitations, and there is a need for a more accurate and sensitive [...] Read more.
Medical imaging techniques, including X-ray mammography, ultrasound, and magnetic resonance imaging, play a crucial role in the timely identification and monitoring of breast cancer. However, these conventional imaging modalities have their limitations, and there is a need for a more accurate and sensitive alternative. Microwave imaging has emerged as a promising technique for breast cancer detection due to its non-ionizing, non-invasive, and cost-effective nature. Recent advancements in microwave imaging and sensing techniques have opened up new possibilities for the early diagnosis and treatment of breast cancer. By combining microwave sensing with machine learning techniques, microwave imaging approaches can rapidly and affordably identify and classify breast tumors. This manuscript provides a comprehensive overview of the latest developments in microwave imaging and sensing techniques for the early detection of breast cancer. It discusses the principles and applications of microwave imaging and highlights its advantages over conventional imaging modalities. The manuscript also delves into integrating machine learning algorithms to enhance the accuracy and efficiency of microwave imaging in breast cancer detection. Full article
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19 pages, 7415 KiB  
Article
Highly Conductive and Reusable Cellulose Hydrogels for Supercapacitor Applications
Micromachines 2023, 14(7), 1461; https://doi.org/10.3390/mi14071461 - 21 Jul 2023
Cited by 2 | Viewed by 1104
Abstract
We report Na-Alginate-based hydrogels with high ionic conductivity and water content fabrication using poly (3,4-ethylene dioxythiophene) (PEDOT): poly (4-styrene sulfonic acid) (PSS) and a hydrogel matrix based on dimethyl sulfoxide (DMSO). DMSO was incorporated within the PEDOT:PSS hydrogel. A hydrogel with higher conductivity [...] Read more.
We report Na-Alginate-based hydrogels with high ionic conductivity and water content fabrication using poly (3,4-ethylene dioxythiophene) (PEDOT): poly (4-styrene sulfonic acid) (PSS) and a hydrogel matrix based on dimethyl sulfoxide (DMSO). DMSO was incorporated within the PEDOT:PSS hydrogel. A hydrogel with higher conductivity was created through the in-situ synthesis of intra-Na-Alginate, which was then improved upon by H2SO4 treatment. Field emission scanning electron microscopy (FESEM) was used to examine the surface morphology of the pure and synthetic hydrogel. Structural analysis was performed using Fourier-transform infrared spectroscopy (FTIR). Thermogravimetric analysis (TGA), which examines thermal properties, was also used. A specific capacitance of 312 F/g at 80 mV/s (energy density of 40.58 W/kg at a power density of 402.20 W/kg) at 100 DC mA/g was achieved by the symmetric Na-Alginate/PEDOT:PSS based flexible supercapacitor. The electrolyte achieved a higher ionic conductivity of 9.82 × 10−2 and 7.6 × 10−2 Scm−1 of Na-Alginate and a composite of Na-Alginate/PEDOT:PSS at 25 °C. Furthermore, the supercapacitor Na-Alginate/PEDOT:PSS//AC had excellent electrochemical stability by showing a capacity retention of 92.5% after 3000 continuous charge–discharge cycles at 10 mA current density. The Na- Alginate/PEDOT:PSS hydrogel displayed excellent flexibility and self-healing after re-contacting the two cut hydrogel samples of electrolyte for 90 min because of the dynamic cross-linking network efficiently dissipated energy. The illumination of a light-emitting diode (LED) verified the hydrogel’s capacity for self-healing. Full article
(This article belongs to the Special Issue Graphene-Nanocomposite-Based Flexible Supercapacitors)
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9 pages, 2627 KiB  
Article
All-Optical Rapid Formation, Transport, and Sustenance of a Sessile Droplet in a Two-Dimensional Slit with Few-Micrometer Separation
Micromachines 2023, 14(7), 1460; https://doi.org/10.3390/mi14071460 - 21 Jul 2023
Viewed by 681
Abstract
We present a sessile droplet manipulation platform that enables the formation and transport of a droplet on a light-absorbing surface via local laser-beam irradiation. The mechanism relies on solutocapillary Marangoni flow arising from a concentration gradient in a binary mixture liquid. Because the [...] Read more.
We present a sessile droplet manipulation platform that enables the formation and transport of a droplet on a light-absorbing surface via local laser-beam irradiation. The mechanism relies on solutocapillary Marangoni flow arising from a concentration gradient in a binary mixture liquid. Because the mixture is strongly confined in a two-dimensional slit with a spacing of a few micrometers, the wetting film is stably sustained, enabling the rapid formation, deformation, and transport of a sessile droplet. In addition, to sustain the droplet in the absence of laser irradiation, we developed a method to bridge the droplet between the top and bottom walls of the slit. The bridge is stably sustained because of the hydrophilicity of the slit wall. Splitting and merging of the droplet bridges are also demonstrated. Full article
(This article belongs to the Special Issue Droplet Microfluidics: Fundamentals and Its Advanced Applications)
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13 pages, 4332 KiB  
Article
Asymmetrically Nanostructured 2D Janus Films Obtained from Pickering Emulsions Polymerized in a Langmuir–Blodgett Trough
Micromachines 2023, 14(7), 1459; https://doi.org/10.3390/mi14071459 - 20 Jul 2023
Cited by 1 | Viewed by 724
Abstract
Low-dimensional structures, such as two-dimensional (2D) Janus films, can be useful in studying fundamental interactions or in applications at the nanoscale. In this work, we report the fabrication of 2D polymer Janus films consisting of one smooth and another nanostructured facet on which [...] Read more.
Low-dimensional structures, such as two-dimensional (2D) Janus films, can be useful in studying fundamental interactions or in applications at the nanoscale. In this work, we report the fabrication of 2D polymer Janus films consisting of one smooth and another nanostructured facet on which silica nanoparticles (NPs) are self-assembled in a compact monolayer shield. The 2D films are made from Pickering emulsions of monomers in water, stabilized by NPs, which are spread over the surface of the water in a Langmuir–Blodgett trough. Following the spreading of the colloidosomes, oil droplets stabilized by NPs collapse, and the interfaces reorganize such that the NP monolayer is found exclusively at the oil/water interface. Upon compression followed by UV polymerization, a 2D solid film is formed, with one smooth and another nanostructured face. The film can be removed from the surface of the water and handled with tweezers. The 2D films exhibit different surface properties on the two sides, such as differences in water wettability. On the nanostructured side, water wettability can be tuned by tuning the surface energy of the nanoparticles, namely by changing their surface functional groups. Upon removal of NPs, the surface can be patterned with an array of circular traces. Full article
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12 pages, 3957 KiB  
Article
Structural Design of Dual-Type Thin-Film Thermopiles and Their Heat Flow Sensitivity Performance
Micromachines 2023, 14(7), 1458; https://doi.org/10.3390/mi14071458 - 20 Jul 2023
Cited by 1 | Viewed by 721
Abstract
Aiming at the shortcomings of the traditional engineering experience in designing thin-film heat flow meters, such as low precision and long iteration time, the finite element analysis model of thin-film heat flow meters is established based on finite element simulation methods, and a [...] Read more.
Aiming at the shortcomings of the traditional engineering experience in designing thin-film heat flow meters, such as low precision and long iteration time, the finite element analysis model of thin-film heat flow meters is established based on finite element simulation methods, and a double-type thin-film heat flow sensor based on a copper/concentrate thermopile is made. The influence of the position of the thermal resistance layer, heat flux density and thickness of the thermal resistance layer on the temperature gradient of the hot and cold ends of the heat flow sensor were comprehensively analyzed by using a simulation method. When the applied heat flux density is 50 kW/m2 and the thermal resistance layer is located above and below the thermopile, respectively, the temperature difference between the hot junction and the cold junction is basically the same, but comparing the two, the thermal resistance layer located above is more suitable for rapid measurements of heat flux at high temperatures. In addition, the temperature difference between the hot and cold contacts of the thin-film heat flux sensor increases linearly with the thickness of the thermal resistance layer. Finally, we experimentally tested the response–recovery characteristics of the sensors, with a noise of 2.1 μV and a maximum voltage output of 15 μV in a room temperature environment, respectively, with a response time of about 2 s and a recovery time of about 3 s. Therefore, the device we designed has the characteristic of double-sided use, which can greatly expand the scope of use and service life of the device and promote the development of a new type of heat flow meter, which will provide a new method for the measurement of heat flow density in the complex environment on the surface of the aero-engine. Full article
(This article belongs to the Special Issue Design and Fabrication of Micro/Nano Sensors and Actuators, Volume II)
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12 pages, 6900 KiB  
Article
Effect of P-Type GaN Buried Layer on the Temperature of AlGaN/GaN HEMTs
Micromachines 2023, 14(7), 1457; https://doi.org/10.3390/mi14071457 - 20 Jul 2023
Viewed by 782
Abstract
In this paper, a P-type GaN buried layer is introduced into the buffer layer of AlGaN/GaN HEMTs, and the effect of the P-type GaN buried layer on the device’s temperature characteristics is studied using Silvaco TCAD software. The results show that, compared to [...] Read more.
In this paper, a P-type GaN buried layer is introduced into the buffer layer of AlGaN/GaN HEMTs, and the effect of the P-type GaN buried layer on the device’s temperature characteristics is studied using Silvaco TCAD software. The results show that, compared to the conventional device structure, the introduction of a P-type GaN buried layer greatly weakens the peak of the channel electric field between the gate and drain of the device. This leads to a more uniform electric field distribution, a substantial reduction in the lattice temperature of the device, and a more uniform temperature distribution. Therefore, the phenomenon of negative resistance caused by self-heating effect is significantly mitigated, while the breakdown performance of the device is also notably enhanced. Full article
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12 pages, 3422 KiB  
Article
Role of Bubble Evolution in the Bubble-Propelled Janus Micromotors
Micromachines 2023, 14(7), 1456; https://doi.org/10.3390/mi14071456 - 20 Jul 2023
Cited by 1 | Viewed by 873
Abstract
Bubble-propelled Janus micromotors have attracted extensive attention in recent years and have been regarded as powerful tools in the environmental and medical fields due to their excellent movement ability. The movement ability can mainly be attributed to the periodic growth, detachment, and/or collapse [...] Read more.
Bubble-propelled Janus micromotors have attracted extensive attention in recent years and have been regarded as powerful tools in the environmental and medical fields due to their excellent movement ability. The movement ability can mainly be attributed to the periodic growth, detachment, and/or collapse of the bubble. However, subjected to the experimental conditions, the mechanism of bubble evolution on the motion of the micromotor could not be elucidated clearly. In this work, a finite element method was employed for exploring the role of bubble evolution in bubble-propelled Janus micromotors, which emphasized the growth and collapse of bubbles. After the proposed model was verified by the scallop theorem, the influence of the growth and rapid collapse of bubbles on micromotors was investigated. Results show that the growth and collapse of a bubble can drive the micromotor to produce a displacement, but the displacement caused by a bubble collapse is significantly greater than that caused by bubble growth. The reasons for this phenomenon are analyzed and explained. In addition to the influence of bubble size, the collapse time of the bubble is also investigated. Full article
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13 pages, 5431 KiB  
Article
Anticancer Activity of Au/CNT Nanocomposite Fabricated by Nanosecond Pulsed Laser Ablation Method on Colon and Cervical Cancer
Micromachines 2023, 14(7), 1455; https://doi.org/10.3390/mi14071455 - 20 Jul 2023
Cited by 2 | Viewed by 1151
Abstract
Gold nanoparticles (AuNPs) and carbon nanotubes (CNTs) are increasingly being investigated for cancer management due to their physicochemical properties, low toxicity, and biocompatibility. This study used an eco-friendly technique (laser synthesis) to fabricate AuNP and Au/CNT nanocomposites. AuNPs, Au/CNTs, and CNTs were tested [...] Read more.
Gold nanoparticles (AuNPs) and carbon nanotubes (CNTs) are increasingly being investigated for cancer management due to their physicochemical properties, low toxicity, and biocompatibility. This study used an eco-friendly technique (laser synthesis) to fabricate AuNP and Au/CNT nanocomposites. AuNPs, Au/CNTs, and CNTs were tested as potential cancer nanotherapeutics on colorectal carcinoma cells (HCT-116) and cervical cancer cells (HeLa) using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. In addition, the non-cancer embryonic kidney cells HEK-293 were taken as a control in the study. The cell viability assay demonstrated a significant reduction in cancer cell population post 48 h treatments of AuNPs, and Au/CNTs. The average cell viabilities of AuNPs, Au/CNTs, and CNTs for HCT-116 cells were 50.62%, 65.88%, 93.55%, and for HeLa cells, the cell viabilities were 50.88%, 66.51%, 91.73%. The cell viabilities for HEK-293 were 50.44%, 65.80%, 93.20%. Both AuNPs and Au/CNTs showed higher cell toxicity and cell death compared with CNT nanomaterials. The treatment of AuNPs and Au/CNTs showed strong inhibitory action on HCT-116 and HeLa cells. However, the treatment of CNTs did not significantly decrease HCT-116 and HeLa cells, and there was only a minor decrease. The treatment of AuNPs, and Au/CNTs, on normal HEK-293 cells also showed a significant decrease in cell viability, but the treatment of CNTs did not produce a significant decrease in the HEK-293 cells. This study shows that a simplified synthesis technique like laser synthesis for the preparation of high-purity nanomaterials has good efficacy for possible future cancer therapy with minimal toxicity. Full article
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13 pages, 19512 KiB  
Article
Highly Efficient Solar-Light-Active Ag-Decorated g-C3N4 Composite Photocatalysts for the Degradation of Methyl Orange Dye
Micromachines 2023, 14(7), 1454; https://doi.org/10.3390/mi14071454 - 20 Jul 2023
Cited by 5 | Viewed by 1066
Abstract
In this study, we utilized calcination and simple impregnation methods to successfully fabricate bare g-C3N4 (GCN) and x% Ag/g-C3N4 (x% AgGCN) composite photocatalysts with various weight percentages (x = 1, 3, 5, and 7 wt.%). The synthesized [...] Read more.
In this study, we utilized calcination and simple impregnation methods to successfully fabricate bare g-C3N4 (GCN) and x% Ag/g-C3N4 (x% AgGCN) composite photocatalysts with various weight percentages (x = 1, 3, 5, and 7 wt.%). The synthesized bare and composite photocatalysts were analyzed to illustrate their phase formation, functional group, morphology, and optical properties utilizing XRD, FT-IR, UV-Vis DRS, PL, FE-SEM, and the EDS. The photodegradation rate of MO under solar light irradiation was measured, and the 5% AgGCN composite photocatalyst showed higher photocatalytic activity (99%), which is very high compared to other bare and composite photocatalysts. The MO dye degradation rate constant with the 5% AgGCN photocatalyst exhibits 14.83 times better photocatalytic activity compared to the bare GCN catalyst. This photocatalyst showed good efficiency in the degradation of MO dye and demonstrated cycling stability even in the 5th successive photocatalytic reaction cycle. The higher photocatalytic activity of the 5% AgGCN composite catalyst for the degradation of MO dye is due to the interaction of Ag with GCN and the localized surface plasmon resonance (SPR) effect of Ag. The scavenger study results indicate that O2●− radicals play a major role in MO dye degradation. A possible charge-transfer mechanism is proposed to explain the solar-light-driven photocatalyst of GCN. Full article
(This article belongs to the Special Issue Sustainable Materials for Energy and Environmental Applications)
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13 pages, 6174 KiB  
Article
Development and Implementation of LED Street Lights with Bright and Extinguishable Controls and Power Converters
Micromachines 2023, 14(7), 1453; https://doi.org/10.3390/mi14071453 - 20 Jul 2023
Cited by 1 | Viewed by 725
Abstract
This study developed and implemented a driving power supply for light-emitting diode (LED) array streetlamps. The power stage was a quasi-resonant (QR)-flyback converter, its input power was the alternating-current power, and the LED array streetlamp was driven by the direct-current output power. The [...] Read more.
This study developed and implemented a driving power supply for light-emitting diode (LED) array streetlamps. The power stage was a quasi-resonant (QR)-flyback converter, its input power was the alternating-current power, and the LED array streetlamp was driven by the direct-current output power. The developed QR-flyback converter was operated in discontinuous conduction mode, and the pulse-width modulation (PWM) control chip was used to switch and conduct at the resonant valley of the drain-source voltage on the metal-oxide-semiconductor field-effect transistor (MOSFET) switch to reduce the switching loss. Moreover, the PWM control chip had a disable function, which was connected with a bright and extinguishable control circuit, and the high/low voltage level signal output by the Arduino development board can be used to control the output power of the QR-flyback converter, achieving bright and extinguishable controls for the LED array streetlamp. Full article
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