Micromachines

22 pages, 6260 KiB

Open AccessArticle

Considerations for the Maximum Heat Load and Its Influence on Temperature Variation of the Evaporator in Flat MHPs in Transient Regimes

by Ioan Mihai, Cornel Suciu and Claudiu Marian Picus

Micromachines 2022, 13(6), 979; https://doi.org/10.3390/mi13060979 - 20 Jun 2022

Cited by 3 | Viewed by 2121

Abstract

The present paper describes a series of considerations for the occurrence of capillary boundaries in flat micro heat pipes (flat MHPs) and the conditions required for their stable operation in relation to the working circumstances and to the type of liquids inside the [...] Read more.

The present paper describes a series of considerations for the occurrence of capillary boundaries in flat micro heat pipes (flat MHPs) and the conditions required for their stable operation in relation to the working circumstances and to the type of liquids inside the pipes. Particularities of heat transfer in a flat MHP are analyzed for situations of either excessive or deficient working liquid. Depending on the physical properties of the working liquids (acetone, methanol and distilled water), the maximum rate of heat flow that can be applied to a flat MHP is determined analytically. The calculus is made with the assumption that constant vaporization of the liquid is ensured in the flat MHP’s evaporator, with no overheating. The considered analytical models allow for the evaluation of the liquid film thickness and the mass flow corresponding to the vaporization region. The temperature difference between the inner and outer walls of a flat MHP is found in the case of a transient regime and a variable thermal flow is applied in the evaporation region. The interior of flat MHPs was modeled in MATLAB using an FTCS (Forward-Time Central-Space) method, which is a finite difference method used for numerically solving the heat equation. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Microchannels)

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18 pages, 4105 KiB

Open AccessArticle

Rational Design of Microfluidic Glaucoma Stent

by Thomas Graf, Gitanas Kancerevycius, Linas Jonušauskas and Patric Eberle

Micromachines 2022, 13(6), 978; https://doi.org/10.3390/mi13060978 - 20 Jun 2022

Cited by 2 | Viewed by 3560

Abstract

Glaucoma is a common, irreparable eye disease associated with high intraocular pressure. One treatment option is implantation of a stent to lower the intraocular pressure. A systematic approach to develop a microchannel stent meshwork that drains aqueous humor from the anterior chamber of [...] Read more.

Glaucoma is a common, irreparable eye disease associated with high intraocular pressure. One treatment option is implantation of a stent to lower the intraocular pressure. A systematic approach to develop a microchannel stent meshwork that drains aqueous humor from the anterior chamber of the eye into the subconjunctival space is presented. The stent has a large number of outlets within its mesh structure that open into the subconjunctiva. The development approach includes a flow resistance model of the stent. Local adaption of the stent’s tubular dimensions allows for adjustment of the flow resistance. In this way, an evenly distributed outflow into the subconjunctiva is achieved. We anticipate that microblebs will form at the stent outlets. Their size is crucial for drainage and control of intraocular pressure. An analytical model for bleb drainage is developed based on the porous properties of the subconjunctival tissue. Both models—the stent flow resistance model and the bleb drainage model—are verified by numerical simulation. The models and numerical simulation are used to predict intraocular pressure after surgery. They allow for a systematic and personalized design of microchannel stents. Stents designed in this way can stabilize the intraocular pressure between an upper and lower limit. Full article

(This article belongs to the Section A：Physics)

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30 pages, 4435 KiB

Open AccessReview

A Comprehensive Review of Micro UAV Charging Techniques

by Syed Agha Hassnain Mohsan, Nawaf Qasem Hamood Othman, Muhammad Asghar Khan, Hussain Amjad and Justyna Żywiołek

Micromachines 2022, 13(6), 977; https://doi.org/10.3390/mi13060977 - 20 Jun 2022

Cited by 74 | Viewed by 8403

Abstract

The groundbreaking Unmanned Aerial Vehicles (UAVs) technology has gained significant attention from both academia and industrial experts due to several applications, such as military missions, power lines inspection, precision agriculture, remote sensing, delivery services, traffic monitoring and many more. UAVs are expected to [...] Read more.

The groundbreaking Unmanned Aerial Vehicles (UAVs) technology has gained significant attention from both academia and industrial experts due to several applications, such as military missions, power lines inspection, precision agriculture, remote sensing, delivery services, traffic monitoring and many more. UAVs are expected to become a mainstream delivery element by 2040 to address the ever-increasing demand for delivery services. Similarly, UAV-assisted monitoring approaches will automate the inspection process, lowering mission costs, increasing access to remote locations and saving time and energy. Despite the fact that unmanned aerial vehicles (UAVs) are gaining popularity in both military and civilian applications, they have a number of limitations and critical problems that must be addressed in order for missions to be effective. One of the most difficult and time-consuming tasks is charging UAVs. UAVs’ mission length and travel distance are constrained by their low battery endurance. There is a need to study multi-UAV charging systems to overcome battery capacity limitations, allowing UAVs to be used for a variety of services while saving time and human resources. Wired and Wireless Power Transfer (WPT) systems have emerged as viable options to successfully solve this difficulty. In the past, several research surveys have focused on crucial aspects of wireless UAV charging. In this review, we have also examined the most emerging charging techniques for UAVs such as laser power transfer (LPT), distributed laser charging (DLC), simultaneous wireless information and power transfer (SWIPT) and simultaneous light wave information and power transfer (SLIPT). The classification and types of UAVs, as well as various battery charging methods, are all discussed in this paper. We’ve also addressed a number of difficulties and solutions for safe operation. In the final section, we have briefly discussed future research directions. Full article

(This article belongs to the Special Issue Micro Air Vehicles)

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22 pages, 15924 KiB

Open AccessReview

Micro/Nano Periodic Surface Structures and Performance of Stainless Steel Machined Using Femtosecond Lasers

by Xiaofeng Xu, Laifei Cheng, Xiaojiao Zhao, Jing Wang and Xinyi Chen

Micromachines 2022, 13(6), 976; https://doi.org/10.3390/mi13060976 - 20 Jun 2022

Cited by 9 | Viewed by 3289

Abstract

The machining of micro/nano periodic surface structures using a femtosecond laser has been an academic frontier and hotspot in recent years. With an ultrahigh laser fluence and an ultrashort pulse duration, femtosecond laser machining shows unique advantages in material processing. It can process [...] Read more.

The machining of micro/nano periodic surface structures using a femtosecond laser has been an academic frontier and hotspot in recent years. With an ultrahigh laser fluence and an ultrashort pulse duration, femtosecond laser machining shows unique advantages in material processing. It can process almost any material and can greatly improve the processing accuracy with a minimum machining size and heat-affected zone. Meanwhile, it can fabricate a variety of micro/nano periodic surface structures and then change a material’s surface performance dramatically, such as the material’s wetting performance, corrosive properties, friction properties, and optical properties, demonstrating great application potential in defense, medical, high-end manufacturing, and many other fields. In recent years, the research is gradually deepening from the basic theory to optimization design, intelligent control, and application technology. Nowadays, while focusing on metal structure materials, especially on stainless steel, research institutions in the field of micro and nano manufacturing have conducted systematic and in-depth experimental research using different experimental environments and laser-processing parameters. They have prepared various surface structures with different morphologies and periods with sound performance, and are one step closer to many civilian engineering applications. This paper reviews the study of micro/nano periodic surface structures and the performance of stainless steel machined using a femtosecond laser, obtains the general evolution law of surface structure and performance with the femtosecond laser parameters, points out several key technical challenges for future study, and provides a useful reference for the engineering research and application of femtosecond laser micro/nano processing technology. Full article

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43 pages, 4253 KiB

Open AccessReview

A Bibliometric Analysis of Low-Cost Piezoelectric Micro-Energy Harvesting Systems from Ambient Energy Sources: Current Trends, Issues and Suggestions

by Mahidur R. Sarker, Mohamad Hanif Md Saad, Amna Riaz, M. S. Hossain Lipu, José Luis Olazagoitia and Haslina Arshad

Micromachines 2022, 13(6), 975; https://doi.org/10.3390/mi13060975 - 20 Jun 2022

Cited by 5 | Viewed by 4114

Abstract

The scientific interest in piezoelectric micro-energy harvesting (PMEH) has been fast-growing, demonstrating that the field has made a major improvement in the long-term evolution of alternative energy sources. Although various research works have been performed and published over the years, only a few [...] Read more.

The scientific interest in piezoelectric micro-energy harvesting (PMEH) has been fast-growing, demonstrating that the field has made a major improvement in the long-term evolution of alternative energy sources. Although various research works have been performed and published over the years, only a few attempts have been made to examine the research’s influence in this field. Therefore, this paper presents a bibliometric study into low-cost PMEH from ambient energy sources within the years 2010–2021, outlining current research trends, analytical assessment, novel insights, impacts, challenges and recommendations. The major goal of this paper is to provide a bibliometric evaluation that is based on the top-cited 100 articles employing the Scopus databases, information and refined keyword searches. This study analyses various key aspects, including PMEH emerging applications, authors’ contributions, collaboration, research classification, keywords analysis, country’s networks and state-of-the-art research areas. Moreover, several issues and concerns regarding PMEH are identified to determine the existing constraints and research gaps, such as technical, modeling, economics, power quality and environment. The paper also provides guidelines and suggestions for the development and enhancement of future PMEH towards improving energy efficiency, topologies, design, operational performance and capabilities. The in-depth information, critical discussion and analysis of this bibliometric study are expected to contribute to the advancement of the sustainable pathway for PMEH research. Full article

(This article belongs to the Special Issue Wearable, Miniaturized, Implantable Energy Harvesters)

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15 pages, 8741 KiB

Open AccessArticle

Investigation of Multiphase Flow in a Trifurcation Microchannel—A Benchmark Problem

by Eugen Chiriac, Marioara Avram and Corneliu Balan

Micromachines 2022, 13(6), 974; https://doi.org/10.3390/mi13060974 - 20 Jun 2022

Cited by 4 | Viewed by 2594

Abstract

The evolution of an interface between two immiscible liquids in a three-branch symmetric microchannel is numerically and experimentally investigated. The main goals of the paper are to correlate the numeric data with the experimental results for the tested flow case and to assess [...] Read more.

The evolution of an interface between two immiscible liquids in a three-branch symmetric microchannel is numerically and experimentally investigated. The main goals of the paper are to correlate the numeric data with the experimental results for the tested flow case and to assess the quality of the VOF procedure to trace the interface using the Fluent commercial code. The focus of the experiments was to characterize the dynamics of the oil–water interface formed in the vicinity of the bifurcation, at the entrance in the main microchannel of 400 microns width and 50 microns height. The oil core surrounded by water is visualized and micro-PIV measurements are performed in water. Experimental results qualitatively and quantitatively confirm the 3D numerical simulations. We propose the present investigated flow as a benchmark case for the study of the interface in a branching microchannel geometry. Full article

(This article belongs to the Special Issue Interfaces in Microfluidics)

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19 pages, 7875 KiB

Open AccessArticle

Design and Development of a Smart IoT-Based Robotic Solution for Wrist Rehabilitation

by Yassine Bouteraa, Ismail Ben Abdallah, Khaled Alnowaiser, Md Rasedul Islam, Atef Ibrahim and Fayez Gebali

Micromachines 2022, 13(6), 973; https://doi.org/10.3390/mi13060973 - 19 Jun 2022

Cited by 13 | Viewed by 2922

Abstract

In this study, we present an IoT-based robot for wrist rehabilitation with a new protocol for determining the state of injured muscles as well as providing dynamic model parameters. In this model, the torque produced by the robot and the torque provided by [...] Read more.

In this study, we present an IoT-based robot for wrist rehabilitation with a new protocol for determining the state of injured muscles as well as providing dynamic model parameters. In this model, the torque produced by the robot and the torque provided by the patient are determined and updated taking into consideration the constraints of fatigue. Indeed, in the proposed control architecture based on the EMG signal extraction, a fuzzy classifier was designed and implemented to estimate muscle fatigue. Based on this estimation, the patient’s torque is updated during the rehabilitation session. The first step of this protocol consists of calculating the subject-related parameters. This concerns axis offset, inertial parameters, passive stiffness, and passive damping. The second step is to determine the remaining component of the wrist model, including the interaction torque. The subject must perform the desired movements providing the torque necessary to move the robot in the desired direction. In this case, the robot applies a resistive torque to calculate the torque produced by the patient. After that, the protocol considers the patient and the robot as active and all exercises are performed accordingly. The developed robotics-based solution, including the proposed protocol, was tested on three subjects and showed promising results. Full article

(This article belongs to the Special Issue Assistive Robots)

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16 pages, 6238 KiB

Open AccessArticle

Study on Solidification Process and Residual Stress of SiCp/Al Composites in EDM

by Wenchao Zhang, Hao Chang and Yu Liu

Micromachines 2022, 13(6), 972; https://doi.org/10.3390/mi13060972 - 19 Jun 2022

Cited by 3 | Viewed by 2288

Abstract

To study the change of residual stress during heating and solidification of SiCp/Al composites, a one-way FSI (Fluid Structure Interaction) model for the solidification process of the molten material is presented. The model used process parameters to obtain the temperature distribution, liquid and [...] Read more.

To study the change of residual stress during heating and solidification of SiCp/Al composites, a one-way FSI (Fluid Structure Interaction) model for the solidification process of the molten material is presented. The model used process parameters to obtain the temperature distribution, liquid and solid-state material transformation, and residual stress. The crack initiated by the thermal stress in the recast layer was investigated, and a mathematical model of crack tip stress was proposed. The results showed a wide range of residual stresses from 44 MPa to 404 MPa. The model is validated using experimental data with three points on the surface layer. Full article

(This article belongs to the Special Issue Micro/Nano Structures and Systems: Analysis, Design, Manufacturing, and Reliability)

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18 pages, 5041 KiB

Open AccessArticle

Deep Q-Learning with Bit-Swapping-Based Linear Feedback Shift Register fostered Built-In Self-Test and Built-In Self-Repair for SRAM

by Mohammed Altaf Ahmed and Suleman Alnatheer

Micromachines 2022, 13(6), 971; https://doi.org/10.3390/mi13060971 - 19 Jun 2022

Cited by 8 | Viewed by 2425

Abstract

Including redundancy is popular and widely used in a fault-tolerant method for memories. Effective fault-tolerant methods are a demand of today’s large-size memories. Recently, system-on-chips (SOCs) have been developed in nanotechnology, with most of the chip area occupied by memories. Generally, memories in [...] Read more.

Including redundancy is popular and widely used in a fault-tolerant method for memories. Effective fault-tolerant methods are a demand of today’s large-size memories. Recently, system-on-chips (SOCs) have been developed in nanotechnology, with most of the chip area occupied by memories. Generally, memories in SOCs contain various sizes with poor accessibility. Thus, it is not easy to repair these memories with the conventional external equipment test method. For this reason, memory designers commonly use the redundancy method for replacing rows–columns with spare ones mainly to improve the yield of the memories. In this manuscript, the Deep Q-learning (DQL) with Bit-Swapping-based linear feedback shift register (BSLFSR) for Fault Detection (DQL-BSLFSR-FD) is proposed for Static Random Access Memory (SRAM). The proposed Deep Q-learning-based memory built-in self-test (MBIST) is used to check the memory array unit for faults. The faults are inserted into the memory using the Deep Q-learning fault injection process. The test patterns and faults injection are controlled during testing using different test cases. Subsequently, fault memory is repaired after inserting faults in the memory cell using the Bit-Swapping-based linear feedback shift register (BSLFSR) based Built-In Self-Repair (BISR) model. The BSLFSR model performs redundancy analysis that detects faulty cells, utilizing spare rows and columns instead of defective cells. The design and implementation of the proposed BIST and Built-In Self-Repair methods are developed on FPGA, and Verilog’s simulation is conducted. Therefore, the proposed DQL-BSLFSR-FD model simulation has attained 23.5%, 29.5% lower maximum operating frequency (minimum clock period), and 34.9%, 26.7% lower total power consumption than the existing approaches. Full article

(This article belongs to the Special Issue Smart Embedded Systems: A Self-Aware System-on-Chip (SoC) and Applications)

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20 pages, 5461 KiB

Open AccessArticle

CFD Analysis and Life Cycle Assessment of Continuous Synthesis of Magnetite Nanoparticles Using 2D and 3D Micromixers

by Sergio Leonardo Florez, Ana Lucia Campaña, M. Juliana Noguera, Valentina Quezada, Olga P. Fuentes, Juan C. Cruz and Johann F. Osma

Micromachines 2022, 13(6), 970; https://doi.org/10.3390/mi13060970 - 19 Jun 2022

Cited by 6 | Viewed by 3695

Abstract

Magnetite nanoparticles (MNPs) have attracted basic and applied research due to their immense potential to enable applications in fields as varied as drug delivery and bioremediation. Conventional synthesis schemes led to wide particle size distributions and inhomogeneous morphologies and crystalline structures. This has [...] Read more.

Magnetite nanoparticles (MNPs) have attracted basic and applied research due to their immense potential to enable applications in fields as varied as drug delivery and bioremediation. Conventional synthesis schemes led to wide particle size distributions and inhomogeneous morphologies and crystalline structures. This has been attributed to the inability to control nucleation and growth processes under the conventional conditions of bulk batch processes. Here, we attempted to address these issues by scaling down the synthesis process aided by microfluidic devices, as they provide highly controlled and stable mixing patterns. Accordingly, we proposed three micromixers with different channel configurations, namely, serpentine, triangular, and a 3D arrangement with abrupt changes in fluid direction. The micromixers were first studied in silico, aided by Comsol Multiphysics^® to investigate the obtained mixing patterns, and consequently, their potential for controlled growth and the nucleation processes required to form MNPs of uniform size and crystalline structure. The devices were then manufactured using a low-cost approach based on polymethyl methacrylate (PMMA) and laser cutting. Testing the micromixers in the synthesis of MNPs revealed homogeneous morphologies and particle size distributions, and the typical crystalline structure reported previously. A life cycle assessment (LCA) analysis for the devices was conducted in comparison with conventional batch co-precipitation synthesis to investigate the potential impacts on water and energy consumption. The obtained results revealed that such consumptions are higher than those of the conventional process. However, they can be reduced by conducting the synthesis with reused micromixers, as new PMMA is not needed for their assembly prior to operation. We are certain that the proposed approach represents an advantageous alternative to co-precipitation synthesis schemes, in terms of continuous production and more homogeneous physicochemical parameters of interest such as size, morphologies, and crystalline structure. Future work should be directed towards improving the sustainability indicators of the micromixers’ manufacturing process. Full article

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10 pages, 4164 KiB

Open AccessArticle

Facile Manufacture of Oxide-Free Cu Particles Coated with Oleic Acid by Electrical Discharge Machining

by Irshad Ahamad Khilji, Siti Nadiah Binti Mohd Safee, Sunil Pathak, Chaitanya Reddy Chilakamarry, Amiril Sahab Bin Abdul Sani and Venugopal Jayarama Reddy

Micromachines 2022, 13(6), 969; https://doi.org/10.3390/mi13060969 - 19 Jun 2022

Cited by 7 | Viewed by 2352

Abstract

Particle synthesis has seen significant advances in current trends. However, the synthesis of metal particles without oxidation is a challenge for researchers. The current study presents a straightforward, convenient, and convincing approach for manufacturing copper (Cu) particles free of surface oxide. The die-sink [...] Read more.

Particle synthesis has seen significant advances in current trends. However, the synthesis of metal particles without oxidation is a challenge for researchers. The current study presents a straightforward, convenient, and convincing approach for manufacturing copper (Cu) particles free of surface oxide. The die-sink Electrical Discharge Machine (EDM) of copper alloys with oleic acid resulted in the formation of Cu particles with diameters between 10 to 20 µm. X-ray diffraction (XRD) was used for particle examination after cleaning and sonication with distilled water. Cu particles with oleic acid coating retained a Cu phase without oxidation after synthesis. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to determine the size and morphology of generated particles. Fourier transforms infrared (FT-IR) analysis revealed the oleic acid-coated Cu surface bonded with an oxygen atom. Also, the agglomeration and change of size involving Cu particles with increasing voltages in the pulse supply in EDM were reported. Full article

(This article belongs to the Special Issue Micromachining Method for Surface Morphology, Volume II)

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42 pages, 8565 KiB

Open AccessReview

A Critical Review on the Sensing, Control, and Manipulation of Single Molecules on Optofluidic Devices

by Mahmudur Rahman, Kazi Rafiqul Islam, Md. Rashedul Islam, Md. Jahirul Islam, Md. Rejvi Kaysir, Masuma Akter, Md. Arifur Rahman and S. M. Mahfuz Alam

Micromachines 2022, 13(6), 968; https://doi.org/10.3390/mi13060968 - 18 Jun 2022

Cited by 5 | Viewed by 7354

Abstract

Single-molecule techniques have shifted the paradigm of biological measurements from ensemble measurements to probing individual molecules and propelled a rapid revolution in related fields. Compared to ensemble measurements of biomolecules, single-molecule techniques provide a breadth of information with a high spatial and temporal [...] Read more.

Single-molecule techniques have shifted the paradigm of biological measurements from ensemble measurements to probing individual molecules and propelled a rapid revolution in related fields. Compared to ensemble measurements of biomolecules, single-molecule techniques provide a breadth of information with a high spatial and temporal resolution at the molecular level. Usually, optical and electrical methods are two commonly employed methods for probing single molecules, and some platforms even offer the integration of these two methods such as optofluidics. The recent spark in technological advancement and the tremendous leap in fabrication techniques, microfluidics, and integrated optofluidics are paving the way toward low cost, chip-scale, portable, and point-of-care diagnostic and single-molecule analysis tools. This review provides the fundamentals and overview of commonly employed single-molecule methods including optical methods, electrical methods, force-based methods, combinatorial integrated methods, etc. In most single-molecule experiments, the ability to manipulate and exercise precise control over individual molecules plays a vital role, which sometimes defines the capabilities and limits of the operation. This review discusses different manipulation techniques including sorting and trapping individual particles. An insight into the control of single molecules is provided that mainly discusses the recent development of electrical control over single molecules. Overall, this review is designed to provide the fundamentals and recent advancements in different single-molecule techniques and their applications, with a special focus on the detection, manipulation, and control of single molecules on chip-scale devices. Full article

(This article belongs to the Special Issue Optofluidic Transducers: Microfluidic Devices Incorporating Optical/Photonic Sensing Capabilities)

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22 pages, 12993 KiB

Open AccessArticle

Temperature Characteristic Analysis of Electromagnetic Piezoelectric Hybrid Drive Motor

by Zheng Li, Xuetong Chen, Hui Zhao, Jinsong Wang, Shenhui Du, Xiaoqiang Guo and Hexu Sun

Micromachines 2022, 13(6), 967; https://doi.org/10.3390/mi13060967 - 18 Jun 2022

Cited by 4 | Viewed by 2079

Abstract

Temperature rise has always been one of the main researchfocusesof the motor. When the temperature is too high, it will have a serious impact on the stability and reliability of motor performance. Due to the special structure of electromagnetic piezoelectric hybrid drive motor [...] Read more.

Temperature rise has always been one of the main researchfocusesof the motor. When the temperature is too high, it will have a serious impact on the stability and reliability of motor performance. Due to the special structure of electromagnetic piezoelectric hybrid drive motor (EPHDM), the loss and temperature distribution of electromagnetic drive part and piezoelectric drive part werestudied. By analyzing the operation principle of the motor, the loss of each part wasresearched. On this basis, the loss of the electromagnetic driving part and piezoelectric driving part werecomputed by using the coupling iterative calculation method. The temperature contour map of the motor wasanalyzed by simulation, and the temperature characteristics of each part of the motor werestudied. Finally, the experimental verification of the prototype, the reliability of the theoretical model, and simulation results wereproved. The results showed that the temperature distribution of the motor is reasonable, the winding temperature is relatively high, and the core temperature and piezoelectric stator temperature are relatively low. The analytical and experimental methods are provided for the further study of heat source optimization. Full article

(This article belongs to the Special Issue Piezoelectric Transducers: Materials, Devices and Applications, Volume III)

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10 pages, 4938 KiB

Open AccessArticle

Diffraction Efficiency of MEMS Phase Light Modulator, TI-PLM, for Quasi-Continuous and Multi-Point Beam Steering

by Xianyue Deng, Chin-I Tang, Chuan Luo and Yuzuru Takashima

Micromachines 2022, 13(6), 966; https://doi.org/10.3390/mi13060966 - 18 Jun 2022

Cited by 6 | Viewed by 3759

Abstract

The recent development of the Micro Electromechanical System (MEMS) Phase Light Modulator (PLM) enables fast laser beam steering for lidar applications by displaying a Computer-Generated Hologram (CGH) without employing an iterative CGH calculation algorithm. We discuss the application of MEMS PLM (Texas Instruments [...] Read more.

The recent development of the Micro Electromechanical System (MEMS) Phase Light Modulator (PLM) enables fast laser beam steering for lidar applications by displaying a Computer-Generated Hologram (CGH) without employing an iterative CGH calculation algorithm. We discuss the application of MEMS PLM (Texas Instruments PLM) for quasi-continuous laser beam steering by deterministically calculated CGHs. The effect on the diffraction efficiency of PLM non-equally spaced phase levels was quantified. We also address the CGH calculation algorithm and an experimental demonstration that steered and scanned the beam into multiple regions of interest points, enabling beam steering for lidar without sequential raster scanning. Full article

(This article belongs to the Special Issue Beam Steering via Arrayed Micromachines)

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13 pages, 4422 KiB

Open AccessArticle

Investigation of Solvent-Assisted In-Mold Bonding of Cyclic Olefin Copolymer (COC) Microfluidic Chips

by Qiang Li, Bingyan Jiang, Xianglin Li and Mingyong Zhou

Micromachines 2022, 13(6), 965; https://doi.org/10.3390/mi13060965 - 18 Jun 2022

Cited by 5 | Viewed by 2480

Abstract

The bonding of microfluidic chips is an essential process to enclose microchannels or microchambers in a lab-on-a-chip. In order to improve the bonding quality while reducing the fabrication time, a solvent-assisted bonding strategy was proposed to seal the microchannels immediately after the cover [...] Read more.

The bonding of microfluidic chips is an essential process to enclose microchannels or microchambers in a lab-on-a-chip. In order to improve the bonding quality while reducing the fabrication time, a solvent-assisted bonding strategy was proposed to seal the microchannels immediately after the cover sheet and substrate chip was injection molded in a single mold. Proper organic solvents were selected and the influences of solvent ratios on the surface roughness, microchannel morphology, and contact angle of microfluidic chips were investigated. When the solvent bonding was integrated in the mold, the influences of solvent volume fraction, solvent dosage, bonding pressure, and bonding time on the bonding quality were analyzed. Results show that the solvent cyclohexane needs to be mixed with isopropanol to reduce the dissolution effect. Solvent treatment is suggested to be performed on the cover sheet with a cyclohexane volume fraction of 70% and a dose of 1.5 mL, a bonding pressure of 2 MPa, and a bonding time of 240 s. The bonding strength reaches 913 kPa with the optimized parameters, while the microchannel deformation was controlled below 8%. Full article

(This article belongs to the Special Issue Feature Papers of Micromachines in "Materials and Processing" 2022)

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14 pages, 7042 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Design and Analysis of a PDLC-Based Reconfigurable Hilbert Fractal Antenna for Large and Fine THz Frequency Tuning

by Prabir Garu and Wei-Chih Wang

Micromachines 2022, 13(6), 964; https://doi.org/10.3390/mi13060964 - 18 Jun 2022

Cited by 5 | Viewed by 2908

Abstract

The proposed reconfigurable radiating antenna design is based on the integration of a reconfigurable fractal antenna and electro-optic substrate material. This antenna can be adjusted to achieve either re-configurability or tunability in the desired frequency range for wireless systems. The electromagnetic characteristics of [...] Read more.

The proposed reconfigurable radiating antenna design is based on the integration of a reconfigurable fractal antenna and electro-optic substrate material. This antenna can be adjusted to achieve either re-configurability or tunability in the desired frequency range for wireless systems. The electromagnetic characteristics of the fractal antenna are manipulated at both the level of fractal geometry, electrical length and dielectric substrate. The designed antenna features multiband responses, in which the geometry and length change create a large frequency shift and the dielectric change using polymer dispersed liquid crystal (PDLC) creates fine and/or continuous tuning. The far field and scattering properties of the antenna are analyzed using the Computer Simulation Technology (CST) Microwave Studio Suite. The proposed approach has successfully demonstrated reconfigurable switching for up to four frequency bands between 0.2 and 0.6 THz. The dielectric constant change in the PDLC substrate shows fine and continuous frequency tuning with an 8% maximum frequency shift when operating around 0.54 THz and a high directivity of 7.35 dBi at 0.54 THz and 8.43 dBi at 0.504 THz. The antenna can also realize a peak gain of 4.29 dBi at 0.504 THz in the extraordinary polarization state of PDLC. The designed antenna can be readily integrated in the current communication devices, such as satellites, smart phones, laptops, and other portable electronic devices, due to its compact geometry and IC compatible design. In satellite applications, the proposed antenna can play a significant role in terms of security. The antenna could be extremely useful for satellites that want to keep their information secret; by constantly switching their operating frequency, spy satellites can evade detection and data collection from enemy ears. Full article

(This article belongs to the Section E：Engineering and Technology)

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16 pages, 3586 KiB

Open AccessArticle

Electro-Sorption of Hydrogen by Platinum, Palladium and Bimetallic Pt-Pd Nanoelectrode Arrays Synthesized by Pulsed Laser Ablation

by Antonino Scandurra, Maria Censabella, Antonino Gulino, Maria Grazia Grimaldi and Francesco Ruffino

Micromachines 2022, 13(6), 963; https://doi.org/10.3390/mi13060963 - 18 Jun 2022

Cited by 4 | Viewed by 2460

Abstract

Sustainable and renewable production of hydrogen by water electrolysers is expected to be one of the most promising methods to satisfy the ever-growing demand for renewable energy production and storage. Hydrogen evolution reaction in alkaline electrolyte is still challenging due to its slow [...] Read more.

Sustainable and renewable production of hydrogen by water electrolysers is expected to be one of the most promising methods to satisfy the ever-growing demand for renewable energy production and storage. Hydrogen evolution reaction in alkaline electrolyte is still challenging due to its slow kinetic properties. This study proposes new nanoelectrode arrays for high Faradaic efficiency of the electro-sorption reaction of hydrogen in an alkaline electrolyte. A comparative study of the nanoelectrode arrays, consisting of platinum or palladium or bimetallic nanoparticles (NPs) Pt₈₀Pd₂₀ (wt.%), obtained by nanosecond pulsed laser ablation in aqueous environment, casted onto graphene paper, is proposed. The effects of thin films of perfluoro-sulfonic ionomer on the material morphology, nanoparticles dispersion, and electrochemical performance have been investigated. The NPs-GP systems have been characterized by field emission scanning electron microscopy, Rutherford backscattering spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge cycles. Faradaic efficiency up to 86.6% and hydrogen storage capacity up to 6 wt.% have been obtained by the Pt-ionomer and Pd/Pt₈₀Pd₂₀ systems, respectively. Full article

(This article belongs to the Special Issue Metal Nanostructures and Devices)

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18 pages, 2218 KiB

Open AccessArticle

Efficient Modeling and Simulation of PMUT Arrays in Various Ambients

by Omer M. O. Abdalla, Gianluca Massimino, Alessandro Stuart Savoia, Fabio Quaglia and Alberto Corigliano

Micromachines 2022, 13(6), 962; https://doi.org/10.3390/mi13060962 - 18 Jun 2022

Cited by 9 | Viewed by 3945

Abstract

This paper presents a numerical reduced-order modeling (ROM) approach for complex multi-layered arrays of piezoelectric micromachined ultrasonic transducers (PMUTs). The numerical modeling technique adopted to generate an array of PMUTs consisting of a considerable number of transducers allows for a large reduction in [...] Read more.

This paper presents a numerical reduced-order modeling (ROM) approach for complex multi-layered arrays of piezoelectric micromachined ultrasonic transducers (PMUTs). The numerical modeling technique adopted to generate an array of PMUTs consisting of a considerable number of transducers allows for a large reduction in computational cost without reducing accuracy. The modeling idea is based on coupling shell elements applied to the PMUT structural layers with 3D-solid elements applied to the piezoelectric layer. A set of eigenfrequency and frequency domain analyses are presented considering a single ROM of a PMUT performing in different ambients and the performing central frequencies are obtained for every considered scenario. A unique arrangement of 228 PMUTs is presented and tested for its ability to transmit and receive acoustic waves. The operating frequency band of the array and the level of interference and cross-talk among different PMUTs in the near field are estimated. Finally, the results from a preliminary experimental test performed to analyze the acoustic abilities of an 8 × 8 array of PMUTs are presented. A corresponding numerical model is created and the obtained results matched the experimental data, leading to a validation of the modeling technique proposed in this work. Full article

(This article belongs to the Special Issue Micro and Smart Devices and Systems)

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13 pages, 5145 KiB

Open AccessArticle

Average Power Handling Capability of Corrugated Slow-Wave Transmission Lines

by Zehao Zheng, Min Tang, Haochi Zhang and Junfa Mao

Micromachines 2022, 13(6), 961; https://doi.org/10.3390/mi13060961 - 17 Jun 2022

Cited by 1 | Viewed by 2020

Abstract

In this article, the average power handling capability (APHC) of corrugated slow-wave transmission lines (SWTLs) is investigated. Firstly, the attenuation constants of conductor and dielectric are extracted by the multiline method. Secondly, the thermal resistance of corrugated SWTLs is analyzed based on the [...] Read more.

In this article, the average power handling capability (APHC) of corrugated slow-wave transmission lines (SWTLs) is investigated. Firstly, the attenuation constants of conductor and dielectric are extracted by the multiline method. Secondly, the thermal resistance of corrugated SWTLs is analyzed based on the constant-angle model. To deal with the non-uniform corrugated structure of SWTLs, the concept of average heat-spreading width (AHSW) is introduced. Finally, the APHC of the corrugated SWTL is calculated using the attenuation constant and the thermal resistance. In addition, the APHC considering the temperature-dependent resistivity of metal conductor is also presented. For validation, the APHCs of SWTLs with different geometric parameters are evaluated. The results agree well with those obtained by the commercial software. Full article

(This article belongs to the Special Issue Advanced Interconnect and Packaging)

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19 pages, 4278 KiB

Open AccessArticle

Preparation and Characterization of Eco-Friendly Transparent Antibacterial Starch/Polyvinyl Alcohol Materials for Use as Wound-Dressing

by Mohammad Mohsen Delavari and Ion Stiharu

Micromachines 2022, 13(6), 960; https://doi.org/10.3390/mi13060960 - 17 Jun 2022

Cited by 10 | Viewed by 3252

Abstract

In this study, eco-friendly and transparent starch-based/polyvinyl alcohol/citric acid composite films are evaluated for their efficacy as wound dressing materials. The starch/polyvinyl alcohol (PVA) materials with added citric acid (0.46–1.83 wt%) and glycerol were made and handled based on the modified casting method. [...] Read more.

In this study, eco-friendly and transparent starch-based/polyvinyl alcohol/citric acid composite films are evaluated for their efficacy as wound dressing materials. The starch/polyvinyl alcohol (PVA) materials with added citric acid (0.46–1.83 wt%) and glycerol were made and handled based on the modified casting method. This new formulation decreases the amount of PVA used in the conventional preparation method. Citric acid ensures an appropriate antibacterial environment for wound-dressing materials. The mechanical, chemical, and surface morphological properties of such films were assessed and analyzed by tensile strength tests, UV–Vis spectrometry, swelling index, and scanning electron microscopy (SEM). Furthermore, the water vapor transmission (WVT) quantity was measured for an ideal wound-healing process to investigate an optimal moisture environment around the wound bed. Moreover, the pH level of the dressings was measured to examine the possibility of bacterial growth around these starch-based films. Additionally, the films’ in-vitro antibacterial activities were studied against the two most common Gram-positive and Gram-negative bacteria (Escherichia coli and Staphylococcus aureus). The new starch-based dressings demonstrated suitable degradation, antibacterial activity, fluid absorption, and adequate mechanical strength, representing wound-dressing materials’ vital features. Full article

(This article belongs to the Special Issue Selected Papers from ICMA2021)

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15 pages, 8048 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

High Performance Eight-Port Dual-Band MIMO Antenna System for 5G Devices

by Saad Hassan Kiani, Muhammad Abbas Khan, Umair Rafique, Mohamed Marey, Abdullah G. Alharbi, Hala Mostafa, Muhammad Amir Khan and Syed Muzahir Abbas

Micromachines 2022, 13(6), 959; https://doi.org/10.3390/mi13060959 - 17 Jun 2022

Cited by 10 | Viewed by 3930

Abstract

This study provides an eight-component multiple-input multiple-output (MIMO) antenna architecture for fifth-generation (5G) mobile communication systems. The single antenna element is comprised of an L-shaped radiating component, an L-shaped parasitic element, and a ground plane with a rectangular slot. The main element with [...] Read more.

This study provides an eight-component multiple-input multiple-output (MIMO) antenna architecture for fifth-generation (5G) mobile communication systems. The single antenna element is comprised of an L-shaped radiating component, an L-shaped parasitic element, and a ground plane with a rectangular slot. The main element with a slot-loaded ground plane helps to draw current from a coaxial feed from the other side of the board, while the parasitic element helps to elongate the current path and improve the impedance of the system. This enables the system to radiate at two different frequency ranges: 3.34–3.7 GHz and 4.67–5.08 GHz, with 360 MHz and 410 MHz bandwidths, respectively. For MIMO configuration, the radiating elements are designed on either side of a 0.8 mm thick FR-4 substrate, allowing space to accommodate a battery, radio frequency (RF) systems and subsystems, and camera and sensor modules. The corner and the middle elements are arranged in such a manner so that they can provide spatial and pattern diversity. Furthermore, at least 12 dB of isolation is established between any two radiating elements. Various MIMO performance parameters were evaluated, e.g., mean effective gain (MEG), channel capacity (CC), envelope correlation coefficient (ECC), realized gain, far-field characteristics, and efficiency. Single- and double-hand mode evaluations were performed to further demonstrate the capability of the proposed MIMO antenna. A prototype of the proposed MIMO antenna was manufactured and assessed to verify the simulated data. The measured and simulated results were found to be in good agreement. On the basis of its performance characteristics, the designed MIMO system could be used in 5G communication systems. Full article

(This article belongs to the Special Issue Microwave Antennas: From Fundamental Research to Applications)

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10 pages, 3685 KiB

Open AccessArticle

Effects of Bonding Materials on Optical–Thermal Performances and High-Temperature Reliability of High-Power LED

by Jiaxin Liu, Yun Mou, Yueming Huang, Jiuzhou Zhao, Yang Peng and Mingxiang Chen

Micromachines 2022, 13(6), 958; https://doi.org/10.3390/mi13060958 - 17 Jun 2022

Cited by 10 | Viewed by 2583

Abstract

The die-bonding layer between chips and substrate determinates the heat conduction efficiency of high-power LED. Sn-based solder, AuSn20 eutectic, and nano-Ag paste were widely applied to LED interconnection. In this paper, the optical–thermal performances and high-temperature reliability of LED with these bonding materials [...] Read more.

The die-bonding layer between chips and substrate determinates the heat conduction efficiency of high-power LED. Sn-based solder, AuSn20 eutectic, and nano-Ag paste were widely applied to LED interconnection. In this paper, the optical–thermal performances and high-temperature reliability of LED with these bonding materials have systematically compared and studied. The thermal conductivity, electrical resistivity, and mechanical property of these bonding materials were characterized. The LED module packaged with nano-Ag has a minimum working temperature of 21.5 °C. The total thermal resistance of LED packaged with nano-Ag, Au80Sn20, and SAC305 is 4.82, 7.84, and 8.75 K/W, respectively, which is 4.72, 6.14, and 7.84 K/W higher after aging for 500 h. Meanwhile, the junction temperature change of these LEDs increases from 2.33, 3.76, and 4.25 °C to 4.34, 4.81, and 6.41 °C after aging, respectively. The thermal resistance of the nano-Ag, Au80Sn20 and SAC305 layer after aging is 1.5%, 65.7%, and 151.5% higher than before aging, respectively. After aging, the LED bonded with nano-Ag has the better optical performances in spectral intensity and light output power, which indicates its excellent heat dissipation can improve the light efficiency. These results demonstrate the nano-Ag bonding material could enhance the optical-thermal performances and high-temperature reliability of high-power LED. Full article

(This article belongs to the Special Issue Advanced Technologies in Electronic Packaging)

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21 pages, 2008 KiB

Open AccessArticle

Dynamic Model of a Conjugate-Surface Flexure Hinge Considering Impacts between Cylinders

by Alessandro Cammarata, Pietro Davide Maddìo, Rosario Sinatra, Andrea Rossi and Nicola Pio Belfiore

Micromachines 2022, 13(6), 957; https://doi.org/10.3390/mi13060957 - 16 Jun 2022

Cited by 3 | Viewed by 2147

Abstract

A dynamic model of a Conjugate-Surface Flexure Hinge (CSFH) has been proposed as a component for MEMS/NEMS Technology-based devices with lumped compliance. However, impacts between the conjugate surfaces have not been studied yet and, therefore, this paper attempts to fill this gap by [...] Read more.

A dynamic model of a Conjugate-Surface Flexure Hinge (CSFH) has been proposed as a component for MEMS/NEMS Technology-based devices with lumped compliance. However, impacts between the conjugate surfaces have not been studied yet and, therefore, this paper attempts to fill this gap by proposing a detailed multibody system (MBS) model that includes not only rigid-body dynamics but also elastic forces, friction, and impacts. Two models based on the Lankarani-Nikravesh constitutive law are first recalled and a new model based on the contact of cylinders is proposed. All three models are complemented by the friction model proposed by Ambrosìo. Then, the non-smooth Moreau time-stepping scheme with Coulomb friction is described. The four models are compared in different scenarios and the results confirm that the proposed model outcomes comply with the most reliable models. Full article

(This article belongs to the Special Issue Flexible Micromanipulators and Micromanipulation)

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10 pages, 23185 KiB

Open AccessArticle

Thin-Film Transistors from Electrochemically Exfoliated In₂Se₃ Nanosheets

by Xiangxiang Gao, Hai-Yang Liu, Jincheng Zhang, Jian Zhu, Jingjing Chang and Yue Hao

Micromachines 2022, 13(6), 956; https://doi.org/10.3390/mi13060956 - 16 Jun 2022

Cited by 10 | Viewed by 4106

Abstract

The wafer-scale fabrication of two-dimensional (2D) semiconductor thin films is the key to the preparation of large-area electronic devices. Although chemical vapor deposition (CVD) solves this problem to a certain extent, complex processes are required to realize the transfer of thin films from [...] Read more.

The wafer-scale fabrication of two-dimensional (2D) semiconductor thin films is the key to the preparation of large-area electronic devices. Although chemical vapor deposition (CVD) solves this problem to a certain extent, complex processes are required to realize the transfer of thin films from the growth substrate to the device substrate, not to mention its harsh reaction conditions. The solution-based synthesis and assembly of 2D semiconductors could realize the large-scale preparation of 2D semiconductor thin films economically. In this work, indium selenide (In₂Se₃) nanosheets with uniform sizes and thicknesses were prepared by the electrochemical intercalation of quaternary ammonium ions into bulk crystals. Layer-by-layer (LbL) assembly was used to fabricate scalable and uniform In₂Se₃ thin films by coordinating In₂Se₃ with poly(diallyldimethylammonium chloride) (PDDA). Field-effect transistors (FETs) made from a single In₂Se₃ flake and In₂Se₃ thin films showed mobilities of 12.8 cm²·V⁻¹·s⁻¹ and 0.4 cm²·V⁻¹·s⁻¹, respectively, and on/off ratios of >10³. The solution self-assembled In₂Se₃ thin films enriches the research on wafer-scale 2D semiconductor thin films for electronics and optoelectronics and has broad prospects in high-performance and large-area flexible electronics. Full article

(This article belongs to the Special Issue 2D Semiconductor Materials and Devices)

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17 pages, 6669 KiB

Open AccessArticle

Structural Design and Analysis of Hybrid Drive Multi-Degree-of-Freedom Motor

by Zheng Li, Hui Zhao, Xuetong Chen, Shenhui Du, Xiaoqiang Guo and Hexu Sun

Micromachines 2022, 13(6), 955; https://doi.org/10.3390/mi13060955 - 16 Jun 2022

Cited by 2 | Viewed by 2168

Abstract

Piezoelectric-driven multi-degree-of-freedom motors can turn off self-lock, withstand high and low temperatures, are small in size and compact in structure, and can easily achieve miniaturization. However, they have a short life cycle and limited applications. In addition, high-intensity operation will result in a [...] Read more.

Piezoelectric-driven multi-degree-of-freedom motors can turn off self-lock, withstand high and low temperatures, are small in size and compact in structure, and can easily achieve miniaturization. However, they have a short life cycle and limited applications. In addition, high-intensity operation will result in a decrease in their stability. Electromagnetic-driven multi-degree-of-freedom motors, on the other hand, are simple and highly integrated, but they are large in volume and lack positioning accuracy. Therefore, combining the two drive modes can achieve complementary advantages, such as improving the motor’s torque, accuracy, and output performance. Firstly, the structure of the hybrid drive motor is introduced and its working principle is analyzed. The motor can achieve single and hybrid drive control, which is beneficial to improving the performance of the motor. Secondly, the influence of magnetization mode, permanent magnet thickness, slot torque, and stator mode on the motor is analyzed. Thirdly, the structure of the motor is determined to be 6 poles and 15 slots, the thickness of the permanent magnet is 12 mm, and the radial magnetization mode is used. Finally, the mixed torque and speed of the motor in the multi-degree-of-freedom direction are tested by experiments, which indirectly verifies the rationality of the structure design. Full article

(This article belongs to the Special Issue Piezoelectric Transducers: Materials, Devices and Applications, Volume III)

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11 pages, 4602 KiB

Open AccessArticle

Thermo-Hydraulic Performance of Pin-Fins in Wavy and Straight Configurations

by Mohamad Ziad Saghir and Mohammad Mansur Rahman

Micromachines 2022, 13(6), 954; https://doi.org/10.3390/mi13060954 - 16 Jun 2022

Cited by 4 | Viewed by 2069

Abstract

Pin-fins configurations have been investigated recently for different engineering applications and, in particular, for a cooling turbine. In the present study, we investigated the performance of three different pin-fins configurations: pin-fins forming a wavy mini-channel, pin-fins forming a straight mini-channel, and a mini-channel [...] Read more.

Pin-fins configurations have been investigated recently for different engineering applications and, in particular, for a cooling turbine. In the present study, we investigated the performance of three different pin-fins configurations: pin-fins forming a wavy mini-channel, pin-fins forming a straight mini-channel, and a mini-channel without pin-fins considering water as the working fluid. The full Navier–Stokes equations and the energy equation are solved numerically using the finite element technique. Different flow rates are studied, represented by the Reynolds number in the laminar flow regime. The thermo-hydraulic performance of the three configurations is determined by examining the Nusselt number, the pressure drop, and the performance evaluation criterion. Results revealed that pin-fins forming a wavy mini-channel exhibited the highest Nusselt number, the lowest pressure drop, and the highest performance evaluation criterion. This finding is valid for any Reynolds number under investigation. Full article

(This article belongs to the Special Issue Advances in Heat and Mass Transfer in Micro/Nano Systems)

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8 pages, 2690 KiB

Open AccessArticle

Effect of Grain Structure and Ni/Au-UBM Layer on Electromigration-Induced Failure Mechanism in Sn-3.0Ag-0.5Cu Solder Joints

by Yuanxiang Zhang, Jicheng Zhang, Yong Wang and Yike Fang

Micromachines 2022, 13(6), 953; https://doi.org/10.3390/mi13060953 - 16 Jun 2022

Cited by 4 | Viewed by 2815

Abstract

The development of advanced electronic devices leads to highly miniaturized interconnect circuits (ICs), which significantly increases the electromigration (EM) phenomenon of solder and circuits due to higher current density. The electromigration of solder joints under high current density has become a severe reliability [...] Read more.

The development of advanced electronic devices leads to highly miniaturized interconnect circuits (ICs), which significantly increases the electromigration (EM) phenomenon of solder and circuits due to higher current density. The electromigration of solder joints under high current density has become a severe reliability concern in terms of microelectronic product reliability. The microstructure of the solder plays an important role in the electromigration induced degradation. In this study, Sn-3.0Ag-0.5Cu solder bumps with Ni/Au under bump metallization (UBM) layer were fabricated and electromigration acceleration tests were conducted under current density of 1.4 × 10⁴ A/cm² and 120 °C to investigate the effect of grain structure and Ni/Au-UBM layer on EM-induced failure. Grain structures of solder bumps were determined by utilizing the Electron Backscatter Diffraction (EBSD) technique, and single-crystal solder, single-crystal dominated solder, and polycrystalline solder are observed in different test samples. According to the Scanning Electron Microscope (SEM) images, it is observed that the Ni/Au-UBM layer of the Cu pad can inhibit atom diffusion between solder bump and Cu pad, which reduces the consumption of Cu pad but causes a large void and crack at the interface. The EM lifetime of single crystal solder bumps is lower than that of polycrystalline solder bumps when the c-axis of single crystal solder bumps is perpendicular to the electron flow direction. Additionally, the single crystal structure will increase the brittleness of the solder bump, and cracks are easily generated and expanded under the stress caused by the mismatch of thermal expansion coefficients between the solder bump and Ni/Au-UBM layer near Cu pad. Polycrystalline solder bumps with a higher misorientation angle (15–55°) have a higher atom diffusion rate, which will result in the acceleration of the EM-induced failure. Full article

(This article belongs to the Special Issue Advanced Packaging for Microsystem Applications)

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13 pages, 3842 KiB

Open AccessArticle

A Precise Closed-Loop Controlled ZnO Nanowire Resonator Operating at Room Temperature

by Xianfa Cai and Lizhong Xu

Micromachines 2022, 13(6), 952; https://doi.org/10.3390/mi13060952 - 16 Jun 2022

Cited by 2 | Viewed by 2070

Abstract

To realize the real-time measurement of masses of nanoparticles, virus molecules, organic macromolecules, and gas molecules, and to analyze their physical and chemical properties, a ZnO nanowire (NW) resonator operating at room temperature with an ultrahigh resonant frequency, real-time detection, and high precision [...] Read more.

To realize the real-time measurement of masses of nanoparticles, virus molecules, organic macromolecules, and gas molecules, and to analyze their physical and chemical properties, a ZnO nanowire (NW) resonator operating at room temperature with an ultrahigh resonant frequency, real-time detection, and high precision was designed and developed in this study. The machining method is simple and easy to integrate into an integrated circuit. A closed-loop detection system based on a phase-locked loop (PLL) and frequency modulation technology (FM) was used to perform closed-loop testing of electromagnetically excited ZnO NW. The first-order resonance frequency of the resonator was 10.358 MHz, the quality factor Q value was about 600, the frequency fluctuation value f_RMS was about 300 Hz, and the FM range could reach 200 kHz. The equivalent circuit model of the resonator was established, the parasitic parameters during the test were obtained, and the frequency accuracy and phase noise of the resonator were analyzed and tested. The experimental results show that the closed-loop system can automatically control the resonator in a wide range of frequency bands, with good tracking performance of the resonant frequency, small frequency fluctuation, and low phase noise level. Full article

(This article belongs to the Section B1: Biosensors)

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15 pages, 11130 KiB

Open AccessArticle

Finite Element Modeling and Test of Piezo Disk with Local Ring Electrodes for Micro Displacement

by Yonggang Liu, Shuliang Zhang, Pengfei Yan and Hiji Li

Micromachines 2022, 13(6), 951; https://doi.org/10.3390/mi13060951 - 16 Jun 2022

Cited by 6 | Viewed by 2362

Abstract

A new piezoelectric actuator combining interdigitated ring electrodes and a PZT-52(Lead Zirconate Titanate) disk was investigated for the large displacement requirements of piezoelectric actuators. Finite element models were established according to the structural characteristics of the actuator and static analysis was carried out [...] Read more.

A new piezoelectric actuator combining interdigitated ring electrodes and a PZT-52(Lead Zirconate Titanate) disk was investigated for the large displacement requirements of piezoelectric actuators. Finite element models were established according to the structural characteristics of the actuator and static analysis was carried out based on ANSYS software. Then Ø25 mm × 2 mm samples were prepared. The displacement detection system was established, and the influence of electrode structure on radial displacement was studied experimentally. A comparison between the experimental results and the finite element analysis confirmed that the finite element model was correct. The results showed that the effect of electrode width on displacement was small. With decrease in electrode center distance and increase in the number of electrodes pairs, the radial displacement increased correspondingly. The peak of radial displacement was 1.63 μm under a 200 V voltage excitation voltage of 0.2 Hz. This was 2.5 times that for a conventional electrode piezo disk with the same structure. The actuator demonstrated better displacement properties. The piezoelectric disk could be valuable in applications involving micro-nano devices. Full article

(This article belongs to the Special Issue Piezoelectric MEMS/NEMS—Materials, Devices, and Applications)

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15 pages, 9672 KiB

Open AccessArticle

Design and Experimental Research of 3-RRS Parallel Ankle Rehabilitation Robot

by Yupeng Zou, Andong Zhang, Qiang Zhang, Baolong Zhang, Xiangshu Wu and Tao Qin

Micromachines 2022, 13(6), 950; https://doi.org/10.3390/mi13060950 - 16 Jun 2022

Cited by 22 | Viewed by 3341

Abstract

The ankle is a crucial joint that supports the human body weight. An ankle sprain will adversely affect the patient’s daily life, so it is of great significance to ensure its strength. To help patients with ankle dysfunction to carry out effective rehabilitation [...] Read more.

The ankle is a crucial joint that supports the human body weight. An ankle sprain will adversely affect the patient’s daily life, so it is of great significance to ensure its strength. To help patients with ankle dysfunction to carry out effective rehabilitation training, the bone structure and motion mechanism of the ankle were analyzed in this paper. Referring to the configuration of the lower-mobility parallel mechanism, a 3-RRS (R and S denote revolute and spherical joint respectively) parallel ankle rehabilitation robot (PARR) was proposed. The robot can realize both single and compound ankle rehabilitation training. The structure of the robot was introduced, and the kinematics model was established. The freedom of movement of the robot was analyzed using the screw theory, and the robot kinematics were analyzed using spherical analytics theory. A circular composite rehabilitation trajectory was planned, and the accuracy of the kinematics model was verified by virtual prototype simulation. The Multibody simulation results show that the trajectory of the target point is basically the same as the expected trajectory. The maximum trajectory error is about 2.5 mm in the simulation process, which is within the controllable range. The experimental results of the virtual prototype simulation show that the maximum angular deflection error of the three motors is 2° when running a circular trajectory, which meets the experimental requirements. Finally, a control strategy for passive rehabilitation training was designed, and the effectiveness of this control strategy was verified by a prototype experiment. Full article

(This article belongs to the Special Issue Intelligent Human-Assisted Robotic Systems: From Microrobots to Wearable Robots)

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