Selected Papers from the 13th Symposium on Micro-Nano Science and Technology on Micromachines

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

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 10159

Special Issue Editors

Special Issue Information

Dear Colleagues,

This Special Issue will publish selected papers from the 13th Symposium on Micro-Nano Science and Technology on Micromachines in Tokushima, Japan, 14–16 November 2022.

We encourage contributions on significant and original works in order to understand physical, chemical, and biological phenomena at the micro/nano scales and to develop applied technologies. The conference will cover the following main topics:

1: Precision machinery, lubrication, and design;
2: Material mechanics;
3: Fluid mechanics;
4: Thermal science and engineering;
5: Production processing and mechanical materials;
6: Robotics and mechatronics;
7: Medical biotechnology;
8: Micro/nano system.

Papers attracting the most interest at the conference, or that provide novel contributions, will be selected for publication in Micromachines. These papers will be peer-reviewed for validation of research results, developments, and applications.

Prof. Dr. Tetsuo Kan
Prof. Dr. Masahiro Motosuke
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.

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Published Papers (6 papers)

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Research

13 pages, 4412 KiB  
Article
Pneumatic Microballoons for Active Control of the Vibration-Induced Flow
by Taku Sato, Kanji Kaneko, Takeshi Hayakawa and Hiroaki Suzuki
Micromachines 2023, 14(11), 2010; https://doi.org/10.3390/mi14112010 - 29 Oct 2023
Viewed by 933
Abstract
Vibration-induced flow (VIF), in which a mean flow is induced around a microstructure by applying periodic vibrations, is increasingly used as an active flow-control technique at the microscale. In this study, we have developed a microdevice that actively controls the VIF patterns using [...] Read more.
Vibration-induced flow (VIF), in which a mean flow is induced around a microstructure by applying periodic vibrations, is increasingly used as an active flow-control technique at the microscale. In this study, we have developed a microdevice that actively controls the VIF patterns using elastic membrane protrusions (microballoons) actuated by pneumatic pressure. This device enables on-demand spatial and temporal fluid manipulation using a single device that cannot be achieved using a conventional fixed-structure arrangement. We successfully demonstrated that the device achieved displacements of up to 38 µm using the device within a pressure range of 0 to 30 kPa, indicating the suitability of the device for microfluidic applications. Using this active microballoon array, we demonstrated that the device can actively manipulate the flow field and induce swirling flows. Furthermore, we achieved selective actuation of the microballoon using this system. By applying air pressure from a multi-input channel system through a connection tube, the microballoons corresponding to each air channel can be selectively actuated. This enabled precise control of the flow field and periodic switching of the flow patterns using a single chip. In summary, the proposed microdevice provides active control of VIF patterns and has potential applications in advanced microfluidics, such as fluid mixing and particle manipulation. Full article
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14 pages, 5790 KiB  
Article
Spiral Chiral Metamaterial Structure Shape for Optical Activity Improvements
by Kohei Maruyama, Miyako Mizuna, Takuya Kosuge, Yuki Takeda, Eiji Iwase and Tetsuo Kan
Micromachines 2023, 14(6), 1156; https://doi.org/10.3390/mi14061156 - 30 May 2023
Cited by 1 | Viewed by 1430
Abstract
We report on a spiral structure suitable for obtaining a large optical response. We constructed a structural mechanics model of the shape of the planar spiral structure when deformed and verified the effectiveness of the model. As a verification structure, we fabricated a [...] Read more.
We report on a spiral structure suitable for obtaining a large optical response. We constructed a structural mechanics model of the shape of the planar spiral structure when deformed and verified the effectiveness of the model. As a verification structure, we fabricated a large-scale spiral structure that operates in the GHz band by laser processing. Based on the GHz radio wave experiments, a more uniform deformation structure exhibited a higher cross-polarization component. This result suggests that uniform deformation structures can improve circular dichroism. Since large-scale devices enable speedy prototype verification, the obtained knowledge can be exported to miniaturized-scale devices, such as MEMS terahertz metamaterials. Full article
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12 pages, 8914 KiB  
Article
Thin Glass Micro Force Plate Supported by Planar Spiral Springs for Measuring Minute Forces
by Taisei Kiriyama, Kenichiro Shimazaki, Rihachiro Nakashima and Hidetoshi Takahashi
Micromachines 2023, 14(5), 1056; https://doi.org/10.3390/mi14051056 - 16 May 2023
Cited by 1 | Viewed by 1233
Abstract
Microforce plates are indispensable tools for quantitatively evaluating the behavior of small objects such as tiny insects or microdroplets. The two main measurement principles for microforce plates are: the formation of strain gauges on the beam that supports the plate and the measurement [...] Read more.
Microforce plates are indispensable tools for quantitatively evaluating the behavior of small objects such as tiny insects or microdroplets. The two main measurement principles for microforce plates are: the formation of strain gauges on the beam that supports the plate and the measurement of the deformation of the plate using an external displacement meter. The latter method is characterized by its ease of fabrication and durability as strain concentration is not required. To enhance the sensitivity of the latter type of force plates with a planar structure, thinner plates are generally desired. However, brittle material force plates that are both thin and large and can be fabricated easily have not yet been developed. In this study, a force plate consisting of a thin glass plate with a planar spiral spring structure and a laser displacement meter placed under the plate center is proposed. The plate deforms downward when a force is exerted vertically on its surface, resulting in the determination of the applied force using Hooke’s law. The force plate structure is easily fabricated by laser processing combined with the microelectromechanical system (MEMS) process. The fabricated force plate has a radius and thickness of 10 mm and 25 µm, respectively, with four supporting spiral beams of sub-millimeter width. A fabricated force plate featuring a sub-N/m spring constant achieves a resolution of approximately 0.01 µN. Full article
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14 pages, 4806 KiB  
Article
Single-Cell Microarray Chip with Inverse-Tapered Wells to Maintain High Ratio of Cell Trapping
by Ryota Sano, Kentaro Koyama, Narumi Fukuoka, Hidetaka Ueno, Shohei Yamamura and Takaaki Suzuki
Micromachines 2023, 14(2), 492; https://doi.org/10.3390/mi14020492 - 20 Feb 2023
Cited by 1 | Viewed by 1636
Abstract
A single-cell microarray (SCM) influenced by gravitational force is expected to be one of the simple methods in various fields such as DNA analysis and antibody production. After trapping the cells in the SCM chip, it is necessary to remove the liquid from [...] Read more.
A single-cell microarray (SCM) influenced by gravitational force is expected to be one of the simple methods in various fields such as DNA analysis and antibody production. After trapping the cells in the SCM chip, it is necessary to remove the liquid from the SCM to wash away the un-trapped cells on the chip and treat the reagents for analysis. The flow generated during this liquid exchange causes the trapped cells to drop out of conventional vertical wells. In this study, we propose an inverse-tapered well to keep trapped cells from escaping from the SCM. The wells with tapered side walls have a reduced force of flow toward the opening, which prevents trapped cells from escaping. The proposed SCM chip was fabricated using 3D photolithography and polydimethylsiloxane molding techniques. In the trapping experiment using HeLa cells, the cell residual rate increased more than two-fold for the SCM chip with the inverse-tapered well with a taper angle of 30° compared to that for the conventional vertical SCM chip after multiple rounds of liquid exchanges. The proposed well structure increases the number of trapped cells and decreases the cell dropout rate to improve the efficiency of cellular analysis. Full article
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9 pages, 2407 KiB  
Article
Conduction Conditions for Self-Healing of Metal Interconnect Using Copper Microparticles Dispersed with Silicone Oil
by Naoki Suetsugu and Eiji Iwase
Micromachines 2023, 14(2), 475; https://doi.org/10.3390/mi14020475 - 18 Feb 2023
Viewed by 1324
Abstract
This study clarifies the conditions for the bridging and conduction of a gap on a metal interconnect using copper microparticles dispersed with silicon oil. An AC voltage applied to a metal interconnect with a gap covered by a dispersion of metal microparticles traps [...] Read more.
This study clarifies the conditions for the bridging and conduction of a gap on a metal interconnect using copper microparticles dispersed with silicon oil. An AC voltage applied to a metal interconnect with a gap covered by a dispersion of metal microparticles traps the metal microparticles in the gap owing to the influence of a dielectrophoretic force on the interconnect, thus forming a metal microparticle chain. The current was tuned independently of the applied voltage by changing the external resistance. An AC voltage of 32 kHz was applied to a 10 µm wide gap on a metal interconnect covered with 3 µm diameter copper microparticles dispersed with silicone oil. Consequently, the copper microparticle chains physically bridged the interconnect and exhibited electrical conductivity at an applied voltage of 14 Vrms or higher and a post-bridging current of 350 mArms or lower. It was shown that the copper microparticle chains did not exhibit electrical conductivity at low applied voltages, even if the microparticle chains bridged the gap. A voltage higher than a certain value was required to achieve electrical conductivity, whereas an excessive voltage caused bubble formation and destroyed the bridges. These phenomena were explained based on the applied voltage and reference value of the current after bridging. Full article
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8 pages, 2907 KiB  
Article
Origami-Type Flexible Thermoelectric Generator Fabricated by Self-Folding
by Yusuke Sato, Shingo Terashima and Eiji Iwase
Micromachines 2023, 14(1), 218; https://doi.org/10.3390/mi14010218 - 15 Jan 2023
Cited by 2 | Viewed by 2653
Abstract
The flexibility of thermoelectric generators (TEGs) is important for low-contact thermal resistance to curved heat sources. However, approaches that depend on soft materials, which are used in most existing studies, have the problem of low performance in terms of the substrate’s thermal conductivity [...] Read more.
The flexibility of thermoelectric generators (TEGs) is important for low-contact thermal resistance to curved heat sources. However, approaches that depend on soft materials, which are used in most existing studies, have the problem of low performance in terms of the substrate’s thermal conductivity and the thermoelectric conversion efficiency of the thermoelectric (TE) elements. In this study, we propose a method to fabricate “Origami-TEG”, a TEG with an origami structure that enables both flexibility and the usage of high-performance rigid materials by self-folding. By applying the principle of the linkage mechanism to self-folding, we realized a fabrication process in which the TE element-mounting process and the active-material-addition process were separated in time. The fabricated origami-TEG showed similar internal resistance and maximum output power when attached to heat sources with flat and curved surfaces. Furthermore, it exhibited high-performance stability against both stretching and bending deformations. Full article
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