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Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary

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A special issue of Micromachines (ISSN 2072-666X).

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 17947

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Prof. Dr. Xiuqing Hao

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Guest Editor

College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Interests: micromachining processes; functional micro-textured surfaces and applications
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Hu Qiu

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Guest Editor

State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Interests: micro and nanoscale mechanics; nanomaterials and devices; nanosensors

Dr. Cheng Shen

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Guest Editor

College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Interests: vibration and acoustic of lightweight structures; acoustic metamaterials; dynamics analysis and control of rotor systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nanjing University of Aeronautics and Astronautics (NUAA) is a leading research oriented comprehensive university, which enjoys multiple disciplines in engineering technology, natural sciences, business and management and social sciences. Established in 1952, NUAA strives to conduct world-level research and education with an emphasis on aerospace technology, astronautics and civil aviation. NUAA is among the first batch of national universities entitled to award doctoral degrees. Enlisted as a “National Project 211” and a “Project 985 Innovative platform for Engineering discipline” university, it is one of the 55 universities in China with a graduate school. NUAA now has 4 campuses, 18 colleges, and more than 190 research institutions, including 5 national key laboratories and research centers.

To celebrate the 70th anniversary of NUAA, Micromachines will publish this Special Issue entitled “Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary”. This Special Issue will collect high-quality full research articles or comprehensive literature reviews in the broad scope of micro- and nanoscale structures, materials, devices, systems as well as micromachining processes.

We look forward to receiving your contributions.

Prof. Dr. Xiuqing Hao
Prof. Dr. Hu Qiu
Dr. Cheng Shen
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Advanced micro- and nanoscale materials
Micromachining processes and high energy beam machining technology
Smart materials and engineering
Micro- and nanoscale intelligent systems
Functional surfaces
Sensors and actuators
Precision measurement technology
Precision manufacturing science
Advanced manufacturing engineering
Additive manufacturing
Vibration and noise control
Engine manufacturing
Advanced energy storage technology
Micro- and nanoscale energy harvesting
Micro- and nanoscale mechanics
Micro- and nanodevices and systems
Micro- and nanoscale mass and heat transport
Micro- and nanoscale liquid-solid interface
Dynamics analysis and control of rotor systems
Metamaterial
Impact, blast and high-rate loading techniques

Published Papers (12 papers)

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Research

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13 pages, 9055 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Investigation on Wire Electrochemical Discharge Micro-Machining

by Weijing Kong, Ziyu Liu, Rudong Zhang and Yongbin Zeng

Micromachines 2023, 14(8), 1505; https://doi.org/10.3390/mi14081505 - 27 Jul 2023

Cited by 1 | Viewed by 1016

Abstract

With the development of MEMS, the machining demand and requirements for difficult-to-machine metal micro parts are getting higher. Microelectric discharge machining is an effective method to process difficult-to-machine metals. However, the recast layer caused by high temperatures in microelectric discharge machining affects the properties of machined materials. Here, we propose the wire electrochemical discharge micro-machining (WECDMM) and develop a new electrolyte system, which removes the recast layer. In this study, the mechanism of WECDMM was elucidated. The electrolyte was optimized through a comparison experiment, and NaNO₃-glycol solution was determined as the best electrolyte. The influences of key process parameters including the conductivity of the electrolyte, pulse voltage, pulse-on time and wire feed rate were analyzed on the slit width, standard deviation, the radius of fillet at the entrance of the slit and roughness. Typical microstructures were machined, which verified the machining ability of WECDMM. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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16 pages, 25374 KiB

Open AccessArticle

Numerical and Experimental Investigation on a “Tai Chi”-Shaped Planar Passive Micromixer

by Annan Xia, Cheng Shen, Chengfeng Wei, Lingchen Meng, Zhiwen Hu, Luming Zhang, Mengyue Chen, Liang Li, Ning He and Xiuqing Hao

Micromachines 2023, 14(7), 1414; https://doi.org/10.3390/mi14071414 - 13 Jul 2023

Cited by 1 | Viewed by 939

Abstract

(1) Background: Microfluidic chips have found extensive applications in multiple fields due to their excellent analytical performance. As an important platform for micro-mixing, the performance of micromixers has a significant impact on analysis accuracy and rate. However, existing micromixers with high mixing efficiency are accompanied by high pressure drop, which is not conducive to the integration of micro-reaction systems; (2) Methods: This paper proposed a novel “Tai Chi”-shaped planar passive micromixer with high efficiency and low pressure drop. The effect of different structural parameters was investigated, and an optimal structure was obtained. Simulations on the proposed micromixer and two other micromixers were carried out while mixing experiments on the proposed micromixer were performed. The experimental and simulation results were compared; (3) Results: The optimized values of the parameters were that the straight channel width w, ratio K of the outer and inner walls of the circular cavity, width ratio w₁/w₂ of the arc channel, and number N of mixing units were 200 μm, 2.9, 1/2, and 6, respectively. Moreover, the excellent performance of the proposed micromixer was verified when compared with the other two micromixers; (4) Conclusions: The mixing efficiency M at all Re studied was more than 50%, and at most Re, the M was nearly 100%. Moreover, the pressure drop was less than 18,000 Pa. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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13 pages, 6730 KiB

Open AccessArticle

Improving Thermal Conductivity and Tribological Performance of Polyimide by Filling Cu, CNT, and Graphene

by Chen Liu, Jingfu Song, Gai Zhao, Yuhang Yin and Qingjun Ding

Micromachines 2023, 14(3), 616; https://doi.org/10.3390/mi14030616 - 07 Mar 2023

Cited by 7 | Viewed by 1672

Abstract

The thermal conductivity, mechanical, and tribological properties of polyimide (PI) composites filled by copper (Cu), carbon nanotube (CNT), graphene nanosheet (GNS), or combination were investigated by molecular dynamics simulation (MD). The simulated results suggested that Cu can improve thermal stability and thermal conductivity, but it reduces mechanical properties and tribological properties. CNT and GNS significantly improved the thermal and tribological properties at low content, but they decreased the properties at high content. In this study, the modification mechanism, friction, and wear mechanism of different fillers on polyimide were revealed by observing the frictional interface evolution process from the atomic scale, extracting the atomic relative concentration, the temperature and velocity distribution at the friction interface, and other microscopic information. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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19 pages, 8537 KiB

Open AccessArticle

Effects of Ti Containing Cu-Based Alloy on Sintering Mechanism, Element Diffusion Behavior and Physical Properties of Glass-Ceramic Bond for Cubic Boron Nitride Abrasive Tool Materials

by Xianglong Meng, Bing Xiao and Hengheng Wu

Micromachines 2023, 14(2), 303; https://doi.org/10.3390/mi14020303 - 24 Jan 2023

Cited by 1 | Viewed by 1041

Abstract

Ti containing Cu-based (TC) alloy reinforced glass-ceramic bond was fabricated for cubic boron nitride (CBN) abrasive tool materials, and its crystal composition, phase transformation, sintering activation energy, microstructure, element diffusion mathematical model, physical properties, and the bonding mechanism between the TC alloy reinforced glass-ceramic bond and the CBN grains were systematically investigated. The results showed that the structure, composition and sintering behavior of glass-ceramic were influenced by TC alloy adding. The generated TiO₂ affected obviously the precipitation of β-quartz solid solution Li₂Al₂Si₃O₁₀, thus improving the relative crystallinity, mechanical strength and thermal properties. By establishing the mathematical model for element diffusion, the element diffusion coefficients of Ti and Cu were 7.82 and 6.98 × 10⁻¹¹ cm²/s, respectively, which indicated that Ti diffused better than Cu in glass-ceramic. Thus, Ti⁴⁺ formed a strong Ti–N chemical bond on the CBN surface, which contributed to improving the wettability and bonding strength between CBN and glass-ceramic bond. After adding TC alloy, the physical properties of the composite were optimized. The porosity, bulk density, flexural strength, Rockwell hardness, CTE, and thermal conductivity of the composites were 5.8%, 3.16 g/cm³, 175 MPa, 90.5 HRC, 3.74 × 10⁻⁶ °C⁻¹, and 5.84 W/(m·k), respectively. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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17 pages, 10597 KiB

Open AccessArticle

Simulation and Experimental Analysis of Surface Defects in Turning of TiC_p/TC4 Composites

by Haixiang Huan, Chilei Zhu, Biao Zhao, Wenqiang Xu and Ke Zhang

Micromachines 2023, 14(1), 69; https://doi.org/10.3390/mi14010069 - 27 Dec 2022

Viewed by 1229

Abstract

Processing TiCp/TC4 composites has always been difficult due to the mismatch between the mechanical and thermal properties of the matrix and the reinforced particles, which results in a variety of machined surface defects. To expose the mechanism of defect generated on the cutting surface of TiCp/TC4 composites and improve their cutting surface quality, a 3D finite element orthogonal turning simulation model of TiCp/TC4 composites is developed. The failure at the matrix-particle interface and the fracture and removal mechanism of the reinforcing phase particles are analyzed from a microscopic perspective using a single particle cutting simulation model. In addition, a three-dimensional cutting simulation model with randomly dispersed TiC particles and a volume fraction of 5% is developed, and various forms of cutting surface defects of TiCp/TC4 composites are examined. To verify the validity of the finite element simulation model, TiCp/TC4 composites with a volume fraction of 5% are selected for turning tests. For various cutting tools and particle relative positions, the simulation and test results show that the removal of particles takes the following forms: debonding, crushing, brittle fracture, and slight fracture at the top, leading to a shallow cavity, microcracks, residual TiC particles embedded in the cavity, and surface defects with severe plastic deformation of the matrix surrounding the cavity on the machined surface. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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12 pages, 6514 KiB

Open AccessArticle

Study on Preparation and Grinding Performance of Vitrified Bond CBN Grinding Wheel with Controllable Porosity

by Qiao Xu, Honggen Zhou, Hengheng Wu, Li Sun, Xiaona Shi and Guochao Li

Micromachines 2023, 14(1), 21; https://doi.org/10.3390/mi14010021 - 22 Dec 2022

Viewed by 1349

Abstract

Vitrified bond cubic boron nitride (CBN) grinding wheel specimens with controllable porosity were prepared by regulating the pore former dextrin content and varying the forming pressure, and the performance of the grinding camshaft was studied. The porosity of the specimens increases with the increase in dextrin content, and decreases first and then increases with the increase in the forming pressure. The grinding experiments show that the dextrin content is negatively correlated with the grinding force and grinding temperature, while the grinding force and grinding temperature of the specimens increase and then decrease with the increase in the forming pressure. When we observe and measure the grinding surface of the specimen and workpiece, we see that the surface roughness of the specimen after grinding is smaller than that before grinding. In addition, the greater the porosity of the specimen, the rougher the surface of the workpiece after grinding. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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11 pages, 5145 KiB

Open AccessArticle

Study of Copper Electrodeposition at a Very Low Temperature near the Freezing Point of Electrolyte

by Yu Mo, Chunjian Shen and Di Zhu

Micromachines 2022, 13(12), 2225; https://doi.org/10.3390/mi13122225 - 15 Dec 2022

Viewed by 1707

Abstract

At or above room temperature, metal electrodeposits often feature coarse grains, uneven microstructure and high roughness with abnormal bulges. In this study, copper electrodeposits with abnormal properties were prepared in a sulfate bath at a low temperature near the freezing point of the electrolyte. The results showed that the average grain size of the copper featured an “increase-decrease” trend while decreasing the temperature form 5 °C to −5 °C, yielding a trend from 0.25 μm to 1 μm and then to 0.6 μm. In the early stage, the temperature does not change the three-dimensional continuous nucleation mode of deposited copper. When the nucleus density reaches saturation, the polarization caused by overpotential will act on the respective nucleation and crystal growth process twice, and finally exhibit a completely different trend than that at room temperature. This study may provide insights for breakthroughs in material properties from a temperature perspective. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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14 pages, 4618 KiB

Open AccessArticle

Experimental Investigation: Vibration Measurement of a Rotating Blade with Digital Image Correlation and Blade Tip-Timing

by Zhonghan Liang, Yuxiang Zhang and Lin Yue

Micromachines 2022, 13(12), 2156; https://doi.org/10.3390/mi13122156 - 06 Dec 2022

Cited by 1 | Viewed by 1398

Abstract

High cycle fatigue has been known as an important form of aeroengine blade failure. This study aims to achieve a method of investigation for a rotating blade vibration measurement, combining the two non-contact optical techniques of digital image correlation (DIC) and blade tip-timing (BTT). Dynamic parameters of a thin-blade were obtained on a stationary vibration platform with stereo-DIC system. Meanwhile, the finite element analysis (FEA) of this thin-blade was performed within different rotating speeds. Then, the set of thin-blades was mounted in a simulated compressor test rig equipped with BTT and a wireless strain gauge (SG) system. A rotor speed sweep experiment was carried out and the blade synchronous resonance parameters were extracted. Results show that the displacement mode shapes match well between DIC and FEA, and that MAC values of the first six order modes are over than 0.88. The predicting strain from the FE model and SG agreed to within 32.41% in the worst case, and the predicting strain from the DIC model corresponds to 28.53% in the worst case. This is an effective non-contact, high-precision full-field deformation measurement method that is worth exploring for structural design and dynamic strain assessment of vibrating components. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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14 pages, 3994 KiB

Open AccessArticle

Study on the Control Method of Sidewall Taper in Electrolytic Broaching of Micro Multi-Grooves

by Jia Liu, Hao Wu and Feng Gao

Micromachines 2022, 13(12), 2062; https://doi.org/10.3390/mi13122062 - 24 Nov 2022

Cited by 1 | Viewed by 901

Abstract

Micro multi-grooves are important functional structures widely used in new heat exchanger types, chemical reactors, and other applications. Electrolytic broaching is an efficient and low-cost technology for processing micro multi-grooves. In the conventional electrolytic broaching of multi-grooves, the cathode tools are usually designed as a wedge-shaped tooth structure array with a constant tooth width, and the sidewalls are covered with insulating layers. The machined groove sidewall is always tapered because of stray current corrosion, which strongly affects the groove contour accuracy. Cathode tools with variable tooth width structures are proposed to solve this problem. Based on the simulation results of the electrolytic broaching anode forming process, the optimal front tooth width is obtained through the golden section optimization method, and comparative tests of the conventional and optimized cathode tools were carried out. At an electrochemical broaching feed rate of 120 mm/min, array microgrooves with widths of about 550 μm and depths of about 520 μm were processed. With the optimized variable tooth width tool, the sidewall tapers of the grooves were reduced from 7.254° to 0.268°. The experimental results verify the effectiveness of the simulation and cathode structure optimization. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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22 pages, 7296 KiB

Open AccessArticle

Study of Surface Integrity of Titanium Alloy (TC4) by Belt Grinding to Achieve the Same Surface Roughness Range

by Guiyun Jiang, Zeyong Zhao, Guijian Xiao, Shaochuan Li, Benqiang Chen, Xiaoqin Zhuo and Jie Zhang

Micromachines 2022, 13(11), 1950; https://doi.org/10.3390/mi13111950 - 11 Nov 2022

Cited by 5 | Viewed by 1442

Abstract

Titanium alloy materials are used in a variety of engineering applications in the aerospace, aircraft, electronics, and shipbuilding industries, and due to the continuous improvement of the contemporary age, surface integrity needs to be improved for engineering applications. Belt grinding parameters and levels directly affect the surface integrity of titanium alloys (TC4), which further affects the fatigue life of the titanium alloys during service. In order to investigate the surface integrity of titanium alloys at different roughness levels, the surfaces were repeatedly ground with the same type and different models of abrasive belts. The results showed that at roughness Ra levels of 0.4 μm to 0.2 μm, the compressive residual stresses decreased with increasing linear velocity and there were problems with large surface morphological defects. At the roughness Ra of 0.2 μm or less, grinding improves the surface morphology, the compressive residual stress increases with increasing feed rate, and the surface hardness decreases with increasing linear velocity. In addition, the research facilitates the engineering of grinding parameters and levels that affect surface integrity under different roughness conditions, providing a theoretical basis and practical reference. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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11 pages, 4520 KiB

Open AccessArticle

A Fast-Responding Electro-Activated Shape Memory Polymer Composite with Embedded 3D Interconnected Graphene Foam

by Yucheng Zhou, Jianxin Zhou, Jiasheng Rong and Cong Hu

Micromachines 2022, 13(10), 1589; https://doi.org/10.3390/mi13101589 - 24 Sep 2022

Cited by 2 | Viewed by 1436

Abstract

Shape memory polymers (SMPs) have gained increasing attention as intelligent morphing materials. However, due to the inherent electrical insulation and poor thermal conductivity of polymers, deformation and temperature control of SMPs usually require external heating devices, bringing about design inconveniences and fragility of interfaces. Herein, we report a shape memory composite that integrates reliable temperature and shape control functions into the interior. The composite is comprised of resin-based SMP and three-dimensional interconnected graphene foam (3DGF), exhibiting a high recovery rate and thermal/electrical conductivity. With only 0.26 wt% of graphene foam, the composite can improve electrical conductivity by 15 orders of magnitude, thermal conductivity by 180%, tensile strength by 64.8%, and shape recovery speed by 154%. Using a very simple Joule heating scheme, decimeter-sized samples of the composite deformed to their preset shapes in less than 10 s. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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Review

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19 pages, 1821 KiB

Open AccessReview

Application of 3D Bioprinting in Liver Diseases

by Wenhui Li, Zhaoyue Liu, Fengwei Tang, Hao Jiang, Zhengyuan Zhou, Xiuqing Hao and Jia Ming Zhang

Micromachines 2023, 14(8), 1648; https://doi.org/10.3390/mi14081648 - 21 Aug 2023

Cited by 4 | Viewed by 2579

Abstract

Liver diseases are the primary reason for morbidity and mortality in the world. Owing to a shortage of organ donors and postoperative immune rejection, patients routinely suffer from liver failure. Unlike 2D cell models, animal models, and organoids, 3D bioprinting can be successfully employed to print living tissues and organs that contain blood vessels, bone, and kidney, heart, and liver tissues and so on. 3D bioprinting is mainly classified into four types: inkjet 3D bioprinting, extrusion-based 3D bioprinting, laser-assisted bioprinting (LAB), and vat photopolymerization. Bioinks for 3D bioprinting are composed of hydrogels and cells. For liver 3D bioprinting, hepatic parenchymal cells (hepatocytes) and liver nonparenchymal cells (hepatic stellate cells, hepatic sinusoidal endothelial cells, and Kupffer cells) are commonly used. Compared to conventional scaffold-based approaches, marked by limited functionality and complexity, 3D bioprinting can achieve accurate cell settlement, a high resolution, and more efficient usage of biomaterials, better mimicking the complex microstructures of native tissues. This method will make contributions to disease modeling, drug discovery, and even regenerative medicine. However, the limitations and challenges of this method cannot be ignored. Limitation include the requirement of diverse fabrication technologies, observation of drug dynamic response under perfusion culture, the resolution to reproduce complex hepatic microenvironment, and so on. Despite this, 3D bioprinting is still a promising and innovative biofabrication strategy for the creation of artificial multi-cellular tissues/organs. Full article

(This article belongs to the Special Issue Micro- and Nanoscale Science, Technology and Engineering in Nanjing University of Aeronautics and Astronautics: Celebrating 70th Anniversary)

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