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Editorial

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5 pages, 190 KiB

Open AccessEditorial

Editorial for the Special Issue on Micro/Nano Structures and Systems: Analysis, Design, Manufacturing, and Reliability

by Stelios K. Georgantzinos

Micromachines 2023, 14(2), 253; https://doi.org/10.3390/mi14020253 - 19 Jan 2023

Viewed by 1360

Abstract

The advancement of fundamental sciences in recent decades has led to an increased focus on the prediction of phenomena occurring at the micro and nano scales. Micro- and nanostructures have a wide range of applications in various fields, such as aerospace and automobiles, [...] Read more.

The advancement of fundamental sciences in recent decades has led to an increased focus on the prediction of phenomena occurring at the micro and nano scales. Micro- and nanostructures have a wide range of applications in various fields, such as aerospace and automobiles, and are widely used in nano- and micro-sized systems and devices, such as biosensors, nanoactuators, and nanoprobes. The design of these structures relies on a complete understanding of their physical and mechanical behaviors. Mechanics plays a crucial role at the micro- and nanoscales, from the generation of nanostructures to the properties of nanocomposite materials and the manufacturing and design of machines, structures, sensors, actuators, fluidics, and more. This Special Issue aims to bring together high-quality papers that advance the field of micro- and nanostructures and systems through the use of modern computational and analytical methods, in conjunction with experimental techniques, for their analysis, design, manufacture, maintenance, quality, and reliability. Full article

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

Research

Jump to: Editorial, Review

15 pages, 2659 KiB

Open AccessArticle

Optimization of Quality, Reliability, and Warranty Policies for Micromachines under Wear Degradation

by Alexandra D. Tseni, Panagiotis Sotiropoulos and Stelios K. Georgantzinos

Micromachines 2022, 13(11), 1899; https://doi.org/10.3390/mi13111899 - 2 Nov 2022

Cited by 5 | Viewed by 1494

Abstract

This work presents an optimization technique to determine the inspection, warranty period, and preventive maintenance policies for micromachines suffering from degradation. Specifically, wear degradation is considered, which is a common failure process for many Micro-Electro-Mechanical Systems (MEMS). The proposed mathematical model examines the [...] Read more.

This work presents an optimization technique to determine the inspection, warranty period, and preventive maintenance policies for micromachines suffering from degradation. Specifically, wear degradation is considered, which is a common failure process for many Micro-Electro-Mechanical Systems (MEMS). The proposed mathematical model examines the impact of quality control on reliability and the duration of the warranty period given by the manufacturer or the supplier to the customer. Each of the above processes creates implementation costs. All the individual costs are integrated into a single measure, which is used to build the model and derive the optimal parameters of the quality and maintenance policies. The implementation of various levels of the quality, warranty, and maintenance policies are compared with their optimum level options to highlight their contribution to the assurance and improving product quality. To the authors’ best knowledge, the introduction of a warranty period is implemented for the first time in the open literature concerning this type of optimization model for MEMs and surely can bring additional advantages to their quality promotion strategy. The proposed optimization tool provides a comprehensive simultaneous answer to the optimal selection of all the values of the design variables determining the overall maintenance and quality management approach. Full article

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

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12 pages, 6146 KiB

Open AccessArticle

An Annular Fresnel Zone Plate without Central Spots Fabricated by Femtosecond Laser Direct Writing

by Xiaoyan Sun, Fang Zhou and Lian Duan

Micromachines 2022, 13(8), 1285; https://doi.org/10.3390/mi13081285 - 10 Aug 2022

Cited by 2 | Viewed by 2554

Abstract

In recent years, micro-annular beams have been widely used, which has expanded the possibilities for laser processing. However, the current method of generating an annular beam still has shortcomings, such as spot energy at the center of the produced beam. In this study, [...] Read more.

In recent years, micro-annular beams have been widely used, which has expanded the possibilities for laser processing. However, the current method of generating an annular beam still has shortcomings, such as spot energy at the center of the produced beam. In this study, a Fresnel zone plate with an annular structure was machined using a femtosecond laser. After focusing, an annular laser beam without a spot in the center was obtained, and the radius and focal length of the annular beam could be easily adjusted. In addition, two annular Fresnel zone plates were concentrically connected to obtain a concentric double-ring beam in the same focal plane. The simulation and experimental results were consistent, providing effective potential for applications related to nontraditionally shaped laser beams. Full article

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

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19 pages, 7302 KiB

Open AccessArticle

Performance Evaluation of Different Coating Materials in Delamination for Micro-Milling Applications on High-Speed Steel Substrate

by Sandeep Bhoi, Ashwani Kumar, Arbind Prasad, Chandan Swaroop Meena, Rudra Bubai Sarkar, Bidyanand Mahto and Aritra Ghosh

Micromachines 2022, 13(8), 1277; https://doi.org/10.3390/mi13081277 - 8 Aug 2022

Cited by 24 | Viewed by 2460

Abstract

The objective of the present work is to carry out analytical and finite element analysis for commonly used coating materials for micro-milling applications on high-speed steel substrate and evaluate the effects of different parameters. Four different coating materials were selected for micro-milling applications: [...] Read more.

The objective of the present work is to carry out analytical and finite element analysis for commonly used coating materials for micro-milling applications on high-speed steel substrate and evaluate the effects of different parameters. Four different coating materials were selected for micro-milling applications: titanium nitride (TiN), diamond-like carbon (DLC), aluminium titanium nitride (AlTiN) and titanium silicon nitride (TiSiN). A 3D finite element model of coating and substrate assembly was developed in Abaqus to find the Hertzian normal stress when subjected to normal load of 4 N, applied with the help of a rigid ball. The radius of the rigid ball was 200 µm. For all the coating materials, the length was 3 mm, the width was 1 mm, and the thickness was 3 µm. For the high-speed steel substrate, the length was 3 mm, the width was 1 mm, and the thickness was 50 µm. Along the length and width, coating and substrate both were divided into 26 equal parts. The deformation behaviour of all the coating materials was considered as linear–elastic and that of the substrate was characterized as elastic–plastic. The maximum normal stress developed in the FEA model was 12,109 MPa. The variation of the FEA result from the analytical result (i.e., 12,435.97 MPa is 2.63%) which is acceptable. This confirms that the FEA model of coating–substrate assembly is acceptable. The results shows that the TiSiN coating shows least plastic equivalent strain in the substrate, which serves the purpose of protecting the substrate from plastic deformation and the TiSiN of 3 micron thickness is the most optimum coating thickness for micro-milling applications. Full article

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

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13 pages, 17058 KiB

Open AccessArticle

Design of a Cylindrical Compliant Linear Guide with Decoupling Parallelogram Mechanisms

by Tinghao Liu and Guangbo Hao

Micromachines 2022, 13(8), 1275; https://doi.org/10.3390/mi13081275 - 8 Aug 2022

Cited by 9 | Viewed by 3349

Abstract

A conventional linear guiding mechanism refers to the slide rail guides composed of multiple assemble parts. These guiding mechanisms suffer from many adverse effects, including lubrication, wear and assembly issues. A novel compliant guiding mechanism is proposed in this paper to address these [...] Read more.

A conventional linear guiding mechanism refers to the slide rail guides composed of multiple assemble parts. These guiding mechanisms suffer from many adverse effects, including lubrication, wear and assembly issues. A novel compliant guiding mechanism is proposed in this paper to address these common problems, and this mechanism transfers or transforms motion, force and energy via the deformation of flexible members. This linear guide is designed in a cylindrical shape, and the centre platform moves along its axis (i.e., the motion direction). The proposed linear guide consists of several in-parallel curved compound double parallelogram mechanisms (CDPMs) connected by the same number of decoupling parallelogram mechanisms. Nonlinear finite element analysis (FEA) is used for stiffness analysis and shows that applying the decoupling mechanisms to the detached linear guide (the in-parallel curved CDPMs only) can dramatically improve the stiffness in undesired movement (bearing) directions while keeping its original stiffness along its axis. The nonlinear FEA can capture the stiffness variation by considering all the structural deformation. The issue of bearing-direction stiffness degradation of the detached linear guide is dealt with by applying decoupling mechanisms. The static experimental test is conducted on a 3D printed prototype and shows that the stiffness in the motion direction is nearly constant (linear). The results obtained from the experimental test show good agreement with those obtained from the nonlinear FEA with a maximum error of 9.76%. Full article

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

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13 pages, 6466 KiB

Open AccessArticle

Implementation of Flip-Chip Microbump Bonding between InP and SiC Substrates for Millimeter-Wave Applications

by Jongwon Lee, Jae Yong Lee, Jonghyun Song, Gapseop Sim, Hyoungho Ko and Seong Ho Kong

Micromachines 2022, 13(7), 1072; https://doi.org/10.3390/mi13071072 - 5 Jul 2022

Cited by 2 | Viewed by 4928

Abstract

Flip-chip microbump (μ-bump) bonding technology between indium phosphide (InP) and silicon carbide (SiC) substrates for a millimeter-wave (mmW) wireless communication application is demonstrated. The proposed process of flip-chip μ-bump bonding to achieve high-yield performance utilizes a SiO₂-based dielectric passivation process, a [...] Read more.

Flip-chip microbump (μ-bump) bonding technology between indium phosphide (InP) and silicon carbide (SiC) substrates for a millimeter-wave (mmW) wireless communication application is demonstrated. The proposed process of flip-chip μ-bump bonding to achieve high-yield performance utilizes a SiO₂-based dielectric passivation process, a sputtering-based pad metallization process, an electroplating (EP) bump process enabling a flat-top μ-bump shape, a dicing process without the peeling of the dielectric layer, and a SnAg-to-Au solder bonding process. By using the bonding process, 10 mm long InP-to-SiC coplanar waveguide (CPW) lines with 10 daisy chains interconnected with a hundred μ-bumps are fabricated. All twelve InP-to-SiC CPW lines placed on two samples, one of which has an area of approximately 11 × 10 mm², show uniform performance with insertion loss deviation within ±10% along with an average insertion loss of 0.25 dB/mm, while achieving return losses of more than 15 dB at a frequency of 30 GHz, which are comparable to insertion loss values of previously reported conventional CPW lines. In addition, an InP-to-SiC resonant tunneling diode device is fabricated for the first time and its DC and RF characteristics are investigated. Full article

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

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17 pages, 6289 KiB

Open AccessArticle

Numerical Study on the Cavitation Characteristics of Micro Automotive Electronic Pumps under Thermodynamic Effect

by Kaipeng Wu, Asad Ali, Changhong Feng, Qiaorui Si, Qian Chen and Chunhao Shen

Micromachines 2022, 13(7), 1063; https://doi.org/10.3390/mi13071063 - 1 Jul 2022

Cited by 5 | Viewed by 1644

Abstract

In order to study the influence of thermodynamic effects on the cavitation performance of hydromechanics, the Singhal cavitation model was modified considering the influence of the thermo-dynamic effects, and the modified cavitation model was written into CFX using the CEL language. Numerical simulation [...] Read more.

In order to study the influence of thermodynamic effects on the cavitation performance of hydromechanics, the Singhal cavitation model was modified considering the influence of the thermo-dynamic effects, and the modified cavitation model was written into CFX using the CEL language. Numerical simulation of the cavitation full flow field at different temperatures (25 °C, 50 °C and 70 °C) was carried out with the automotive electronic water pump as the research object. The results show that the variation trend of the external characteristic simulation and experimental values is the same at all flow rates, and the calculation accuracy meets the subsequent cavitation demand. With the increase in temperature, the low-pressure area inside the automotive electronic pump’s impeller decreases. NPSHr decreases and the cavitation resistance is enhanced. During the process of no cavitation to cavitation, the maximum pressure pulsation amplitude in the impeller channel gradually increases. The generation and collapse of cavitations cause the change of pressure pulsation in the internal flow field, causing pump vibration. Full article

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

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16 pages, 7219 KiB

Open AccessArticle

Electrochemical Milling of Deep-Narrow Grooves on GH4169 Alloy Using Tube Electrode with Wedged End Face

by Zhisen Ye, Guilin Qiu and Xiaolei Chen

Micromachines 2022, 13(7), 1051; https://doi.org/10.3390/mi13071051 - 30 Jun 2022

Cited by 7 | Viewed by 1730

Abstract

Deep-narrow grooves (DNGs) of nickel-based alloy GH4169 are extensively used in aerospace industry. Electrochemical milling (EC-milling) can manufacture special structures including DNGs by controlling the moving path of simple tool, showing a flexible process with the advantages of high machining efficiency, regardless of [...] Read more.

Deep-narrow grooves (DNGs) of nickel-based alloy GH4169 are extensively used in aerospace industry. Electrochemical milling (EC-milling) can manufacture special structures including DNGs by controlling the moving path of simple tool, showing a flexible process with the advantages of high machining efficiency, regardless of material hardness, no residual stresses, burrs, and tool wear. However, due to the inefficient removal of electrolytic by-products in the inter-electrode gap (IEG), the machining accuracy and surface quality are always unsatisfactory. In this paper, a novel tube tool with wedged end face is designed to generate pulsating flow field in IEG, which can enhance the removal of electrolytic by-products as well as improve the machining quality of DNG. The flow field simulation results show that the electrolyte velocity in the IEG is changed periodically along with the rotation of the tube tool. The pulsating amplitude of electrolyte is changed by adjusting the wedged angle in the end face of the tube tool, which could affect the EC-milling process. Experimental results suggest that the machining quality of DNG, including the average width, taper of sidewall, and surface roughness, is significantly improved by using the tube tool with wedged end face. Compared with other wedged angles, the end face with the wedged angle of 40° is more suitable for the EC-milling process. DNG with the width of 1.49 mm ± 0.04 mm, taper of 1.53° ± 0.46°, and surface roughness (Ra) of 1.04 μm is well manufactured with the milling rate of 0.42 mm/min. Moreover, increasing the spindle speed and feed rate can further improve the machining quality of DNG. Finally, a complex DNG structure with the depth of 5 mm is well manufactured with the spindle speed of 4000 rpm and feed rate of 0.48 mm/min. Full article

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

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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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19 pages, 8638 KiB

Open AccessArticle

A Comparative Evaluation of Magnetorheological Micropump Designs

by Sevki Cesmeci, Rubayet Hassan and Mahmoud Baniasadi

Micromachines 2022, 13(5), 764; https://doi.org/10.3390/mi13050764 - 12 May 2022

Cited by 3 | Viewed by 2414

Abstract

In this study, we assessed the performance characteristics of five different magnetorheological micropump designs, two of which were our proposed designs, while others were from the existing designs in the literature. Comparisons have been performed based on physics-based simulations, and the fully coupled [...] Read more.

In this study, we assessed the performance characteristics of five different magnetorheological micropump designs, two of which were our proposed designs, while others were from the existing designs in the literature. Comparisons have been performed based on physics-based simulations, and the fully coupled magneto-solid-fluid interaction simulations were carried out in COMSOL Multiphysics software. For a fair and meaningful comparison, both the material and geometric properties were kept the same, and the simulations were run for one complete pumping cycle. The results showed that the proposed flap and duckbill valve models could pump 1.09 µL and 1.16 µL respectively in 1 s, which was more than the rest of the existing micropump models. Moreover, at 0.5 s, when the magnetic flux density was maximum, the flap and duckbill valve models could pump almost twice as fluid as some of the existing valve models did. The results also demonstrated that the flap and duckbill valve models were nearly five times faster than some of existing models. In conclusion, the proposed two micropump models could propel more net fluid volume than the existing micropump designs, experienced low leakage during the contraction and expansion phase, and had faster response times. We believe that the present study provides valuable insights for future micropump designs, which have an extensive range of application areas, ranging from insulin dosing systems for T1D patients to artificial organs to transport blood and from organ-on-chip applications to micro-cooling systems. Full article

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

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10 pages, 3752 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Refractive Index Sensor Based on a Metal-Insulator-Metal Bus Waveguide Coupled with a U-Shaped Ring Resonator

by Xiaoyu Zhang, Shubin Yan, Jilai Liu, Yifeng Ren, Yi Zhang and Lifang Shen

Micromachines 2022, 13(5), 750; https://doi.org/10.3390/mi13050750 - 9 May 2022

Cited by 7 | Viewed by 1980

Abstract

In this study, a novel refractive index sensor structure was designed consisting of a metal-insulator-metal (MIM) waveguide with two rectangular baffles and a U-Shaped Ring Resonator (USRR). The finite element method was used to theoretically investigate the sensor’s transmission characteristics. The simulation results [...] Read more.

In this study, a novel refractive index sensor structure was designed consisting of a metal-insulator-metal (MIM) waveguide with two rectangular baffles and a U-Shaped Ring Resonator (USRR). The finite element method was used to theoretically investigate the sensor’s transmission characteristics. The simulation results show that Fano resonance is a sharp asymmetric resonance generated by the interaction between the discrete narrow-band mode and the successive wide-band mode. Next, the formation of broadband and narrowband is further studied, and finally the key factors affecting the performance of the sensor are obtained. The best sensitivity of this refractive-index sensor is 2020 nm/RIU and the figure of merit (FOM) is 53.16. The presented sensor has the potential to be useful in nanophotonic sensing applications. Full article

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

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16 pages, 7984 KiB

Open AccessArticle

Design of Deployable Structures by Using Bistable Compliant Mechanisms

by Tinghao Liu and Guangbo Hao

Micromachines 2022, 13(5), 651; https://doi.org/10.3390/mi13050651 - 19 Apr 2022

Cited by 17 | Viewed by 7576

Abstract

A deployable structure can significantly change its geometric shape by switching lattice configurations. Using compliant mechanisms as the lattice units can prevent wear and friction among multi-part mechanisms. This work presents two distinctive deployable structures based on a programmable compliant bistable lattice. Several [...] Read more.

A deployable structure can significantly change its geometric shape by switching lattice configurations. Using compliant mechanisms as the lattice units can prevent wear and friction among multi-part mechanisms. This work presents two distinctive deployable structures based on a programmable compliant bistable lattice. Several novel parameters are introduced into the bistable mechanism to better control the behaviour of bistable mechanisms. By adjusting the defined geometry parameters, the programmable bistable lattices can be optimized for specific targets such as a larger deformation range or higher stability. The first structure is designed to perform 1D deployable movement. This structure consists of multi-series-connected bistable lattices. In order to explore the 3D bistable characteristic, a cylindrical deployable mechanism is designed based on the curved double tensural bistable lattice. The investigation of bistable lattices mainly involves four types of bistable mechanisms. These bistable mechanisms are obtained by dividing the long segment of traditional compliant bistable mechanisms into two equal parts and setting a series of angle data to them, respectively. The experiment and FEA simulation results confirm the feasibility of the compliant deployable structures. Full article

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

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Review

Jump to: Editorial, Research

56 pages, 7964 KiB

Open AccessReview

Review Paper: Residual Stresses in Deposited Thin-Film Material Layers for Micro- and Nano-Systems Manufacturing

by Michael Huff

Micromachines 2022, 13(12), 2084; https://doi.org/10.3390/mi13122084 - 26 Nov 2022

Cited by 31 | Viewed by 12903

Abstract

This review paper covers a topic of significant importance in micro- and nano-systems development and manufacturing, specifically the residual stresses in deposited thin-film material layers and methods to control or mitigate their impact on device behavior. A residual stress is defined as the [...] Read more.

This review paper covers a topic of significant importance in micro- and nano-systems development and manufacturing, specifically the residual stresses in deposited thin-film material layers and methods to control or mitigate their impact on device behavior. A residual stress is defined as the presence of a state of stress in a thin-film material layer without any externally applied forces wherein the residual stress can be compressive or tensile. While many material properties of deposited thin-film layers are dependent on the specific processing conditions, the residual stress often exhibits the most variability. It is not uncommon for residual stresses in deposited thin-film layers to vary over extremely large ranges of values (100% percent or more) and even exhibit changes in the sign of the stress state. Residual stresses in deposited layers are known to be highly dependent on a number of factors including: processing conditions used during the deposition; type of material system (thin-films and substrate materials); and other processing steps performed after the thin-film layer has been deposited, particularly those involving exposure to elevated temperatures. The origins of residual stress can involve a number of complex and interrelated factors. As a consequence, there is still no generally applicable theory to predict residual stresses in thin-films. Hence, device designers usually do not have sufficient information about the residual stresses values when they perform the device design. Obviously, this is a far less than ideal situation. The impact of this is micro- and nano-systems device development takes longer, is considerably more expensive, and presents higher risk levels. The outline of this paper is as follows: a discussion of the origins of residual stresses in deposited thin-film layers is given, followed by an example demonstrating the impact on device behavior. This is followed by a review of thin-film deposition methods outlining the process parameters known to affect the resultant residual stress in the deposited layers. Then, a review of the reported methods used to measure residual stresses in thin-films are described. A review of some of the literature to illustrate the level of variations in residual stresses depending on processing conditions is then provided. Methods which can be used to control the stresses and mitigate the impact of residual stresses in micro- and nano-systems device design and fabrication are then covered, followed by some recent development of interest. Full article

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

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24 pages, 4537 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Atomic Layer Assembly Based on Sacrificial Templates for 3D Nanofabrication

by Guangzhou Geng, Zhongshan Zhang, Chensheng Li, Ruhao Pan, Yunlong Li, Haifang Yang and Junjie Li

Micromachines 2022, 13(6), 856; https://doi.org/10.3390/mi13060856 - 30 May 2022

Cited by 5 | Viewed by 2664

Abstract

Three-dimensional (3D) nanostructures have attracted widespread attention in physics, chemistry, engineering sciences, and biology devices due to excellent functionalities which planar nanostructures cannot achieve. However, the fabrication of 3D nanostructures is still challenging at present. Reliable fabrication, improved controllability, and multifunction integration are [...] Read more.

Three-dimensional (3D) nanostructures have attracted widespread attention in physics, chemistry, engineering sciences, and biology devices due to excellent functionalities which planar nanostructures cannot achieve. However, the fabrication of 3D nanostructures is still challenging at present. Reliable fabrication, improved controllability, and multifunction integration are desired for further applications in commercial devices. In this review, a powerful fabrication method to realize 3D nanostructures is introduced and reviewed thoroughly, which is based on atomic layer deposition assisted 3D assembly through various sacrificial templates. The aim of this review is to provide a comprehensive overview of 3D nanofabrication based on atomic layer assembly (ALA) in multifarious sacrificial templates for 3D nanostructures and to present recent advancements, with the ultimate aim to further unlock more potential of this method for nanodevice applications. Full article

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

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23 pages, 4735 KiB

Open AccessReview

Design Aspects of Additive Manufacturing at Microscale: A Review

by Nikolaos Rogkas, Christos Vakouftsis, Vasilios Spitas, Nikos D. Lagaros and Stelios K. Georgantzinos

Micromachines 2022, 13(5), 775; https://doi.org/10.3390/mi13050775 - 15 May 2022

Cited by 15 | Viewed by 4258

Abstract

Additive manufacturing (AM) technology has been researched and developed for almost three decades. Microscale AM is one of the fastest-growing fields of research within the AM area. Considerable progress has been made in the development and commercialization of new and innovative microscale AM [...] Read more.

Additive manufacturing (AM) technology has been researched and developed for almost three decades. Microscale AM is one of the fastest-growing fields of research within the AM area. Considerable progress has been made in the development and commercialization of new and innovative microscale AM processes, as well as several practical applications in a variety of fields. However, there are still significant challenges that exist in terms of design, available materials, processes, and the ability to fabricate true three-dimensional structures and systems at a microscale. For instance, microscale AM fabrication technologies are associated with certain limitations and constraints due to the scale aspect, which may require the establishment and use of specialized design methodologies in order to overcome them. The aim of this paper is to review the main processes, materials, and applications of the current microscale AM technology, to present future research needs for this technology, and to discuss the need for the introduction of a design methodology. Thus, one of the primary concerns of the current paper is to present the design aspects describing the comparative advantages and AM limitations at the microscale, as well as the selection of processes and materials. Full article

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

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28 pages, 9219 KiB

Open AccessReview

Latest Performance Improvement Strategies and Techniques Used in 5G Antenna Designing Technology, a Comprehensive Study

by Iftikhar Ahmad, Wenhao Tan, Qasim Ali and Houjun Sun

Micromachines 2022, 13(5), 717; https://doi.org/10.3390/mi13050717 - 30 Apr 2022

Cited by 20 | Viewed by 3951

Abstract

In the recent era, fifth-generation technology (5G) has not been fully implemented in the realm of wireless communication. To have excellent accessible bandwidth feasibility, and in order to achieve the aims of 5G standards, such as higher data rates and ultrahigh-definition video streaming, [...] Read more.

In the recent era, fifth-generation technology (5G) has not been fully implemented in the realm of wireless communication. To have excellent accessible bandwidth feasibility, and in order to achieve the aims of 5G standards, such as higher data rates and ultrahigh-definition video streaming, the millimeter wave (mmWave) band must be employed. Services with minimal latency and many other features are feasible only in the mmWave spectrum. To avoid numerous communication complexities such as high connection losses, short wavelength, and restricted bandwidth, as well as path-loss challenges in the mmWave range, an antenna with wide bandwidth, high gain, narrow steerable beam, high isolation, low side-lobe levels, and multiband features is required to alleviate these difficulties and meet 5G communication standards. To overcome these challenges, specific strategies and techniques should be employed in the traditional antenna designing procedure to excellently improve the performance of the antenna in terms of bandwidth, gain, and efficiency and to reduce the mutual coupling effect between the closely colocated antenna elements in MIMOs and arrays. The researchers reported on a variety of bandwidth and gain improvement approaches. To gain broader coverage, traditional antenna design techniques must be modified. In this study, the latest state-of-the-art work is reviewed, such as the role of the metamaterials (MMTs), parasitic patches, hybrid feeding, EBG structure, impact of the slots with different geometrical shapes in the radiator to achieve the goal of wide bandwidth, boosted gain, reduced side-lobes level, as well as stable radiation properties. Mutual coupling reduction techniques are also briefly reported. The role of reconfigurability is focused on in this study, and at the end, the future challenges in the field of antenna design and possible remedies to such issues are reviewed. Full article

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

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