Micro-Manufacturing and Applications, Volume III: Advanced Hybrid Processes in Micro-Manufacturing

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E:Engineering and Technology".

Deadline for manuscript submissions: closed (1 August 2022) | Viewed by 28132

Special Issue Editor


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Guest Editor
Department MAE, College CDEPS, Brunel University, London UB8 3PH, UK
Interests: micro nano manufacturing; non-traditional manufacturing technologies; micro milling; micro EDM; nicro ECM; lazer machining; micro abrasive machining
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Following the success of the two previous special issues dedicated to machines and equipment and technologies for micro, nano manufacturing, it was decided to open third special issue, specially dedicated to hybrid technologies and equipment. In this case we will be happy to accept papers which are not treating a specific product or production but are still the area of the lab development. Such ‘blue sky research’ will become a triggering point for further developments and applications and may give new scope to design new micro parts and equipment.

Again, all types of micro technologies will be accepted. Hybrid technologies will be considered in a broader term and will not involve only simultaneously applied processes but sequential and combined. New innovative and improved metrology and methods for analysing the structure and topography of micro parts are also welcome.

The approach to the technologies must be presented with deep understanding of the physics and chemistry of the processes and this will be of high importance. Process limitations and advantages must be discussed in order the readers to find the right processing window for the specific technology.

Dr. Atanas Ivanov
Guest Editor

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

  • micro manufacturing
  • micro technologies
  • micro parts
  • nontraditional micro technologies

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Published Papers (14 papers)

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Research

Jump to: Review

9 pages, 2382 KiB  
Article
Removal Modeling and Experimental Verification of Magnetorheological Polishing Fused Silica Glass
by Limin Zhang, Weixing Li, Jiakang Zhou, Mingming Lu, Qiang Liu, Yongsheng Du and Yakun Yang
Micromachines 2023, 14(1), 54; https://doi.org/10.3390/mi14010054 - 25 Dec 2022
Cited by 2 | Viewed by 1419
Abstract
Compared to conventional polishing methods, magnetorheological polishing has no subsurface damage and a has good polishing effect, which is suitable for fused silica glass surface processing. However, the existing magnetorheological polishing material removal model has low processing efficiency and uneven removal, which cannot [...] Read more.
Compared to conventional polishing methods, magnetorheological polishing has no subsurface damage and a has good polishing effect, which is suitable for fused silica glass surface processing. However, the existing magnetorheological polishing material removal model has low processing efficiency and uneven removal, which cannot realize the deterministic processing of parts. The material removal (MR) model of fused silica glass is established by convolving the dwell time with the material removal function. The residence time is Fourier transformed. The consequence of process variable such as machining time, workpiece rotational frequency, machining gap and X-direction deflection on the MR of workpiece interface are analyzed. Experiments verify the validity of the material removal model. The surface precision PV value of the workpiece surface under the optimal process parameters was decreased from 7.959 nm to 0.609 nm for machining. The experiment results indicate that the established MR model can be implemented as the deterministic MR of the optical surface and ameliorate the surface accuracy of the workpiece surface. Full article
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13 pages, 10691 KiB  
Article
Flexible Heater Fabrication Using Amino Acid-Based Ink and Laser-Direct Writing
by Sangmo Koo
Micromachines 2022, 13(12), 2209; https://doi.org/10.3390/mi13122209 - 13 Dec 2022
Viewed by 1501
Abstract
Nature’s systems have evolved over a long period to operate efficiently, and this provides hints for metal nanoparticle synthesis, including the enhancement, efficient generation, and transport of electrons toward metal ions for nanoparticle synthesis. The organic material-based ink composed of the natural materials [...] Read more.
Nature’s systems have evolved over a long period to operate efficiently, and this provides hints for metal nanoparticle synthesis, including the enhancement, efficient generation, and transport of electrons toward metal ions for nanoparticle synthesis. The organic material-based ink composed of the natural materials used in this study requires low laser power for sintering compared to conventional nanoparticle ink sintering. This suggests applicability in various and sophisticated pattern fabrication applications without incurring substrate damage. An efficient electron transfer mechanism between amino acids (e.g., tryptophan) enables silver patterning on flexible polymer substrates (e.g., PET) by laser-direct writing. The reduction of silver ions to nanoparticles was induced and sintered by simultaneous photo/thermalchemical reactions on substrates. Furthermore, it was possible to fabricate a stable, transparent, and flexible heater that operates under mechanical deformation. Full article
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13 pages, 1659 KiB  
Article
Glass-to-Glass Fusion Bonding Quality and Strength Evaluation with Time, Applied Force, and Heat
by Nhi N. Trinh, Leslie A. Simms, Bradley S. Chew, Alexander Weinstein, Valeria La Saponara, Mitchell M. McCartney, Nicholas J. Kenyon and Cristina E. Davis
Micromachines 2022, 13(11), 1892; https://doi.org/10.3390/mi13111892 - 2 Nov 2022
Cited by 3 | Viewed by 4054
Abstract
A bonding process was developed for glass-to-glass fusion bonding using Borofloat 33 wafers, resulting in high bonding yield and high flexural strength. The Borofloat 33 wafers went through a two-step process with a pre-bond and high-temperature bond in a furnace. The pre-bond process [...] Read more.
A bonding process was developed for glass-to-glass fusion bonding using Borofloat 33 wafers, resulting in high bonding yield and high flexural strength. The Borofloat 33 wafers went through a two-step process with a pre-bond and high-temperature bond in a furnace. The pre-bond process included surface activation bonding using O2 plasma and N2 microwave (MW) radical activation, where the glass wafers were brought into contact in a vacuum environment in an EVG 501 Wafer Bonder. The optimal hold time in the EVG 501 Wafer bonder was investigated and concluded to be a 3 h hold time. The bonding parameters in the furnace were investigated for hold time, applied force, and high bonding temperature. It was concluded that the optimal parameters for glass-to-glass Borofloat 33 wafer bonding were at 550 °C with a hold time of 1 h with 550 N of applied force. Full article
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15 pages, 4138 KiB  
Article
Simulation of a Hemispherical Chamber for Thermal Inkjet Printing
by Xishun Peng, Anjiang Lu, Pangyue Li, Zhongpeng Chen, Ziran Yu, Jianwu Lin, Yi Wang, Yibo Zhao, Jiao Yang and Jin Cheng
Micromachines 2022, 13(11), 1843; https://doi.org/10.3390/mi13111843 - 28 Oct 2022
Cited by 1 | Viewed by 1642
Abstract
It is crucial to improve printing frequency and ink droplet quality in thermal inkjet printing. This paper proposed a hemispherical chamber, and we used the CFD (computational fluid dynamics model) to simulate the inkjet process. During the whole simulation process, we first researched [...] Read more.
It is crucial to improve printing frequency and ink droplet quality in thermal inkjet printing. This paper proposed a hemispherical chamber, and we used the CFD (computational fluid dynamics model) to simulate the inkjet process. During the whole simulation process, we first researched the hemispherical chamber’s inkjet state equipped with straight, conical shrinkage, and conical diffusion nozzles. Based on the broken time and volume of the liquid column, the nozzle geometry of the hemispherical chamber was determined to be a conical shrinkage nozzle with a specific size of 15 µm in height and 15 µm in diameter at the top, and 20 µm in diameter at the bottom. Next, we researched the inkjet performance of the square chamber, the round chamber, and the trapezoidal chamber. The round chamber showed the best inkjet performance using 1.8 µs as the driving time and 10 MPa as the maximum bubble pressure. After that, we compared the existing thermal inkjet printing heads. The results showed that the hemispherical chamber inkjet head had the best performance, achieving 30 KHz high-frequency printing and having the most significant volume ratio of droplet to the chamber, reaching 14.9%. As opposed to the current 15 KHz printing frequency of the thermal inkjet heads, the hemispherical chamber inkjet head has higher inkjet performance, and the volume ratio between the droplet and the chamber meets the range standard of 10–15%. The hemispherical chamber structure can be applied to thermal inkjet printing, office printing, 3D printing, and bio-printing. Full article
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19 pages, 6099 KiB  
Article
The Effect of Holding Time on Dissimilar Transient Liquid-Phase-Bonded Properties of Super-Ferritic Stainless Steel 446 to Martensitic Stainless Steel 410 Using a Nickel-Based Interlayer
by Majid Hafizi, Masoud Kasiri-Asgarani, Mojtaba Naalchian, Hamid Reza Bakhsheshi-Rad and Filippo Berto
Micromachines 2022, 13(11), 1801; https://doi.org/10.3390/mi13111801 - 22 Oct 2022
Cited by 3 | Viewed by 1495
Abstract
The dissimilar joining of martensitic and ferritic stainless steels have been developed that needs corrosion resistance and enhanced mechanical properties. In this study, the transient liquid-phase bonding of martensitic stainless steel 410 and super-ferritic stainless steel 446 was conducted with a nickel-based amorphous [...] Read more.
The dissimilar joining of martensitic and ferritic stainless steels have been developed that needs corrosion resistance and enhanced mechanical properties. In this study, the transient liquid-phase bonding of martensitic stainless steel 410 and super-ferritic stainless steel 446 was conducted with a nickel-based amorphous interlayer (BNi-2) at constant temperature (1050 °C) and increasing times of 1, 15, 30, 45, and 60 min. For characterization of the TLP-bonded samples, optical microscopy and scanning emission microscopy equipped with energy-dispersive X-ray spectroscopy were used. To investigate the mechanical properties of TLP-bonded samples, the shear strength test method was used. Finally, the X-ray diffraction method was used for microstructural investigation and phase identification. The microstructural study showed that the microstructure of base metals changed: the martensitic structure transited to tempered martensite, including ferrite + cementite colonies, and the delta phase in super-ferritic stainless steel dissolved in the matrix. During the transient liquid-phase bonding, the aggregation of boron due to its diffusion to base metals resulted in the precipitation of a secondary phase, including iron–chromium-rich borides with blocky and needle-like morphologies at the interface of the molten interlayer and base metals. On the other hand, the segregation of boron in the bonding zone resulted from a low solubility limit, and the distribution coefficient has induced some destructive and brittle phases, such as nickel-rich (Ni3B) and chromium-rich boride (CrB/Cr2B). By increasing the time, significant amounts of boron have been diffused to a base metal, and diffusion-induced isothermal solidification has happened, such that the isothermal solidification of the assembly has been completed under the 1050 °C/60 min condition. The distribution of the hardness profile is relatively uniform at the bonding zone after completing isothermal solidification, except the diffusion-affected zone, which has a higher hardness. The shear strength test showed that increasing the holding time was effective in achieving the strength near the base metals such that the maximum shear strength of about 472 MPa was achieved. Full article
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18 pages, 10051 KiB  
Article
Effects of Multi-Pass Turning on Stress Corrosion Cracking of AISI 304 Austenitic Stainless Steel
by Yansong Zhang, Huan Xue, Yongchun Li, Xuelin Wang, Xinli Jiang, Chongwen Yang, Kewei Fang, Wenqian Zhang and Hui Jiang
Micromachines 2022, 13(10), 1745; https://doi.org/10.3390/mi13101745 - 15 Oct 2022
Cited by 2 | Viewed by 1348
Abstract
Austenitic stainless steels are extensively used in mechanical engineering. The machined surface integrity has an essential influence on the stress corrosion cracking (SCC) performance of stainless steels. In this paper, the effects of multi-pass turning on the SCC susceptibility of AISI 304 austenitic [...] Read more.
Austenitic stainless steels are extensively used in mechanical engineering. The machined surface integrity has an essential influence on the stress corrosion cracking (SCC) performance of stainless steels. In this paper, the effects of multi-pass turning on the SCC susceptibility of AISI 304 austenitic stainless steel were investigated by correlating the SCC crack density to the machining-induced surface characteristics in terms of roughness, micro-hardness, and residual stress. In the multi-pass turning, the surface roughness and residual stress were the least after the double pass turning, and the surface micro-hardness was the maximum after the triple-pass turning. The SCC susceptibility was evaluated after SCC tests in boiling MgCl2 solution. The results showed that the weakest SCC sensitivity was observed in double-pass turning 304 stainless steel, while the most susceptible SCC was found in triple-pass turning. Compared with the double-pass turning, the increase in SCC sensitivity of triple-pass turning was attributed to the larger roughness, higher micro-hardness and greater residual tensile stresses. Full article
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16 pages, 6154 KiB  
Article
Optomechanical Performances of Advanced Lightweight Mirrors Based on Additive Manufacturing
by Kai Zhang, Xiaolin Xie, Chao Wang, Ha Wang, Fang Xu, He Wang, Xin Zhang, Haijun Guan, Hemeng Qu and Jizhen Zhang
Micromachines 2022, 13(8), 1334; https://doi.org/10.3390/mi13081334 - 17 Aug 2022
Cited by 9 | Viewed by 1785
Abstract
Additive manufacturing (AM)—layer-by-layer printing—completely changes the conventional manufacturing method. The design freedom for mirrors is increased without the limits of the manufacturing process. Advanced lightweight mirrors (ALM), new-type mirrors designed using the generative method and lattice technologies, have emerged as the times require. [...] Read more.
Additive manufacturing (AM)—layer-by-layer printing—completely changes the conventional manufacturing method. The design freedom for mirrors is increased without the limits of the manufacturing process. Advanced lightweight mirrors (ALM), new-type mirrors designed using the generative method and lattice technologies, have emerged as the times require. Contrasting with conventional lightweight mirrors (CLM), the performances of ALM are drastically improved. This paper took the Voronoi mirrors as an ALM case study and introduced a design flow. In addition, a conventional honeycomb mirror was designed using the analytical method as the control. The optomechanical performances of the two were further compared through finite element analysis (FEA). Finally, ALM’s optomechanical performances outperformed CLM’s, including the area density, structural stiffness, surface stability, and quilting deflection. Full article
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14 pages, 8470 KiB  
Article
Preparation of Micro-Pit-Textured PCD Tools and Micro-Turning Experiment on SiCp/Al Composites
by Xu Wang, Valentin L. Popov, Zhanjiang Yu, Yiquan Li, Jinkai Xu, Qiang Li and Huadong Yu
Micromachines 2022, 13(7), 1141; https://doi.org/10.3390/mi13071141 - 19 Jul 2022
Cited by 6 | Viewed by 1620
Abstract
Serious tool wear occurs very often during machining due to the reinforcing phases in the workpiece. In this study, micro-pit-textures were prepared on the surfaces of PCD tools with a nanosecond laser to improve their cutting performance on SiCp/Al composites. The micro-pits were [...] Read more.
Serious tool wear occurs very often during machining due to the reinforcing phases in the workpiece. In this study, micro-pit-textures were prepared on the surfaces of PCD tools with a nanosecond laser to improve their cutting performance on SiCp/Al composites. The micro-pits were designed with rounded corners to improve the chip flow. The location and size of the texture were determined by analyzing the tool-chip contact area of the non-textured tool. The cutting performance of these textured PCD tools was investigated through orthogonal cutting experiments. It was found that the optimal cutting performance of the textured tools was achieved with the proper distance of the texture from the main cutting edge (35 μm) and the pit spacing (60 μm), aa a result of which the main cutting force reduced by about 14%, and the tool wear and surface adhesion significantly reduced. This texture was then applied in the micro-turning experiments of the PCD tool on the SiCp/Al composites. The cutting force in this experiment reduced by 22%, and the textured tool provided better chip transfer and tool anti-tipping. In this study, the role of SiC particles as a third body between the tool and the chip surface is discussed. Full article
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11 pages, 5793 KiB  
Article
Ti6Al4V Alloy Remelting by Modulation Laser: Deep Penetration, High Compactness and Metallurgical Bonding with Matrix
by Longzhang Shen, Yong Chen, Hongmei Zhu, Yuantao Lei and Chanjun Qiu
Micromachines 2022, 13(7), 1107; https://doi.org/10.3390/mi13071107 - 14 Jul 2022
Cited by 6 | Viewed by 1284
Abstract
Titanium alloys are famous for their light weight, high strength, and heat- and corrosion-resistant properties. However, the excellent mechanical properties are closely related to its microstructure. Innovative machining operations are required for the welding, surface strengthening, and repairs to ensure the refining of [...] Read more.
Titanium alloys are famous for their light weight, high strength, and heat- and corrosion-resistant properties. However, the excellent mechanical properties are closely related to its microstructure. Innovative machining operations are required for the welding, surface strengthening, and repairs to ensure the refining of the crystalline structure for improved strength requirements, enhanced mechanical properties, and integrating strength. By direct laser melting on the surface of Ti-6Al-4V alloy, the differences of molten pools under continuous and modulated laser mode were compared in the article. Under the same power, the heat influence zone of the laser pool could be reduced to 1/3 of that of the continuous laser. The deep molten pool could be obtained by a continuous laser by the action of high energy density. The tensile property changed a lot between different depths of melt penetration. A high-density, fine-grain molten pool could be obtained under the action of a high-frequency (20 kHz) modulation laser. The mechanical properties of the tensile sample between different depths of melt penetration, which contained the remelting zone, were close to the substrate. The research conclusions can provide technical support for the development of laser remelting processing technology. Full article
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10 pages, 2661 KiB  
Article
Tetracycline Adsorption on Magnetic Sludge Biochar: Effects of pH, Humic Acid (HA), and Fulvic Acid (FA)
by Yuanhui Wu, Meizhi Yang, Dan Long, Fanian Yang and Suxing Luo
Micromachines 2022, 13(7), 1057; https://doi.org/10.3390/mi13071057 - 30 Jun 2022
Cited by 6 | Viewed by 1863
Abstract
Natural organic matters (NOMs) are ubiquitous in the environment, but few systematic studies have examined the influence of NOMs on the sorption ability of magnetic sludge biochar. In this study, magnetic sludge biochar was synthesized, characterized, and used as a sorbent to remove [...] Read more.
Natural organic matters (NOMs) are ubiquitous in the environment, but few systematic studies have examined the influence of NOMs on the sorption ability of magnetic sludge biochar. In this study, magnetic sludge biochar was synthesized, characterized, and used as a sorbent to remove tetracycline (TC) from aqueous solutions. The effects of pH, humic acid (HA), and fulvic acid (FA) on TC adsorption by magnetic sludge biochar were studied using batch experiments. Adding HA and FA can alter the adsorption behavior of TC, except for its pH dependency. The results of this study show that relatively low concentrations of dissolved HA (≤8 ppm) and FA (≤5 ppm) promote the adsorption capacity of TC, but higher concentrations compete against TC for sorption sites on the surface of magnetic sludge biochar. The results of this study promote a better understanding of the application of magnetic sludge biochar in real antibiotic wastewater. Full article
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9 pages, 4345 KiB  
Article
Surface Roughening of Pt-Polystyrene Spherical Janus Micromotors for Enhanced Motion Speed
by Le Zhou, Yi Wei, Hongwen Zhang, Zhulin Huang, Shuyi Zhu, Zhipeng Zhao, Yujing Guo, Hao Fu, Qian Zhao and Weiping Cai
Micromachines 2022, 13(4), 555; https://doi.org/10.3390/mi13040555 - 31 Mar 2022
Cited by 5 | Viewed by 2005
Abstract
Spherical Janus micromotors (SJMs) have attracted much attention, and their high-speed motion is highly desired due to their various potential applications. However, the conventional template-deposition method often leads to an active Pt coating with a smooth surface, which is unbeneficial to speed enhancement [...] Read more.
Spherical Janus micromotors (SJMs) have attracted much attention, and their high-speed motion is highly desired due to their various potential applications. However, the conventional template-deposition method often leads to an active Pt coating with a smooth surface, which is unbeneficial to speed enhancement in terms of catalytic reaction. Here, a facile surface roughening method is presented to fabricate the Pt-polystyrene (PS) SJMs with rough Pt surface (or Ptr-PS SJMs) by plasma-etching the PS colloidal monolayer and then depositing Pt. The Ptr-PS SJMs can exhibit directional motion pushed by the Pt in the various H2O2 solutions, and they show much higher motion speeds than the Pt-PS SJMs with smooth Pt surfaces at the same H2O2 concentration. The Pt-pushed motion is related to the locally asymmetric catalytic reaction of the Pt coating on PS. The speed is also associated with the surface roughness of the Pt coating. The Pt film with a rough surface causes enhanced motion speed due to the improvement of reaction catalytic activity. This work presents a new route to enhancing the motor motion speed, which is of significance in designing micromotors with high-speed motion. Full article
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9 pages, 21368 KiB  
Article
Miniaturized Sulfite-Based Gold Bath for Controlled Electroplating of Zone Plate Nanostructures
by Hanna Ohlin, Thomas Frisk, Mattias Åstrand and Ulrich Vogt
Micromachines 2022, 13(3), 452; https://doi.org/10.3390/mi13030452 - 17 Mar 2022
Cited by 4 | Viewed by 2869
Abstract
X-ray zone plates made from gold are common optical components used in X-ray imaging experiments. These nanostructures are normally fabricated using a combination of electron-beam lithography and gold electroplating with cyanide gold baths. In this study, we present a gold electroplating process in [...] Read more.
X-ray zone plates made from gold are common optical components used in X-ray imaging experiments. These nanostructures are normally fabricated using a combination of electron-beam lithography and gold electroplating with cyanide gold baths. In this study, we present a gold electroplating process in a miniaturized gold-suplphite bath. The miniaturization is enabled by on-chip reference plating areas with well defined sizes, offering a reliable way to control the height of the structures by carefully choosing the plating time at a given current density in accordance with a calibration curve. Fabricated gold zone plates were successfully used in X-ray imaging experiments with synchrotron radiation. Although gold electroplating of nanostructures is a well-established method, details about the actual process are often missing in the literature. Therefore, we think that our detailed descriptions and explanations will be helpful for other researchers that would like to fabricate similar structures. Full article
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20 pages, 9242 KiB  
Article
Surface Quality Optimization in Micromachining with Cutting Tool Having Regular Constructive Geometry
by Catalin Gabriel Dumitras, Dragos Florin Chitariu, Florin Chifan, Cristina Georgiana Lates and Mihaita Horodinca
Micromachines 2022, 13(3), 422; https://doi.org/10.3390/mi13030422 - 8 Mar 2022
Cited by 3 | Viewed by 1970
Abstract
In this paper we studied the influence of micromachining parameters on processed surface quality. Usually in discussions about micro-cutting or micromachining, the grinding or diamond turning processes are considered. Cutting tools used in the mentioned processes do not have regular constructive geometry and, [...] Read more.
In this paper we studied the influence of micromachining parameters on processed surface quality. Usually in discussions about micro-cutting or micromachining, the grinding or diamond turning processes are considered. Cutting tools used in the mentioned processes do not have regular constructive geometry and, in this case, it is difficult to use constructive geometric parameters such as clearance angle α or rake angle γ to optimize the quality of the machined surface. In order to determine the influence of the cutting tool’s constructive geometry on the hardness of the machined material, we used a fractional factorial design of a centered and rotatable type 26−1. A mathematical model based on five independent cutting parameters was created that allowed optimization of surface quality based on obtained roughness. The results can be applied in micromilling or microturning. Full article
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Review

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18 pages, 6544 KiB  
Review
Controllable Shrinking Fabrication of Solid-State Nanopores
by Xin Lei, Jiayan Zhang, Hao Hong, Zhishan Yuan and Zewen Liu
Micromachines 2022, 13(6), 923; https://doi.org/10.3390/mi13060923 - 10 Jun 2022
Cited by 3 | Viewed by 2385
Abstract
Nanopores have attracted widespread attention in DNA sequencing and protein or biomarker detection, owning to the single-molecule-scale detection accuracy. Despite the most use of naturally biological nanopores before, solid-state nanopores are widely developed with strong robustness, controllable sizes and geometries, a wide range [...] Read more.
Nanopores have attracted widespread attention in DNA sequencing and protein or biomarker detection, owning to the single-molecule-scale detection accuracy. Despite the most use of naturally biological nanopores before, solid-state nanopores are widely developed with strong robustness, controllable sizes and geometries, a wide range of materials available, as well as flexible manufacturing. Therefore, various techniques typically based on focused ion beam or electron beam have been explored to drill nanopores directly on free-standing nanofilms. To further reduce and sculpt the pore size and shape for nano or sub-nano space-time sensing precision, various controllable shrinking technologies have been employed. Correspondingly, high-energy-beam-induced contraction with direct visual feedback represents the most widely used. The ability to change the pore diameter was attributed to surface tension induced original material migration into the nanopore center or new material deposition on the nanopore surface. This paper reviews typical solid-state nanopore shrinkage technologies, based on the careful summary of their principles and characteristics in particularly size and morphology changes. Furthermore, the advantages and disadvantages of different methods have also been compared completely. Finally, this review concludes with an optimistic outlook on the future of solid-state nanopores. Full article
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