論文 - 三木　則尚

Synthesis of sub-micrometer biphasic Au-AuGa<inf>2</inf>/liquid metal frameworks

David R., Miki N.

Nanoscale （Nanoscale）  11 （ 44 ） 21419 - 21432 2019年11月

ISSN  20403364

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© 2019 The Royal Society of Chemistry. A novel biphasic sub-micrometer Au-AuGa2/liquid metal framework, consisting of solid nanoparticles encapsulating liquid metal (LM) droplets, is introduced. By utilizing oxide-free galvanic replacement of a Ga-alloy LM with alkaline KAuBr4, the controllable process of gold-based encapsulation of individual sub-micrometer LM droplets capped with polyvinylpyrrolidone, lysozyme or sodium alginate is demonstrated. The morphology, structure and composition of the encapsulated droplets are characterized in-depth via scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. For the first time, the existence of two kinetic regimes leading to the controllable synthesis of either intermetallic AuGa2 or Au nanoparticles to encapsulate LM droplets is highlighted via the study of the evolution of the pH of the reaction medium. The as-formed biphasic sub-micrometer Au-LM frameworks demonstrate moderate stability in an aqueous environment and formidable structural and chemical stability in ambient air at room temperature. The encapsulation process can be adapted to the micro-patterning of LM droplet surfaces to produce conductive Au-encapsulated LM droplets then sintered to recover LM lines, while the sub-micrometer Au-LM droplets can be reintegrated onto larger LM surfaces and volumes to create multi-metallic and multi-scale biphasic structures with controllable electrical properties. The adaptability of the encapsulation process to the macro-, micro- and nanoscale of liquid metal features with a wide range of surfactants could in principle allow its use in various systems and applications.

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EEG-Hat with Candle-like Microneedle Electrode

Kawana T., Yoshida Y., Kudo Y., Miki N.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS （Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS）     1111 - 1114 2019年07月

ISSN  9781538613115

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© 2019 IEEE. This paper reports the EEG-Hat, the hat-type EEG device with candle-like dry microneedle electrodes. Current wearable EEG devices have two major problems; 1) no adjustability to every participant and 2) no ability to measure EEG at hairy part. If these problems are solved, health care technologies in daily life will be developed drastically. The EEG-Hat potentially solves these problems. This device can adjust the electrodes to different size and shape of human head. This device has shutter-like structures to separate hair, so using this device, it is possible to measure EEG without separating hair by hand. First, we quantified the force to press the electrodes and the amount of separating hair. Then, the EEG-Hat fabricated based on the findings successfully measured EEG from 3 hairy parts without manual separation.

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Thermal Sensation Display with Controllable Thermal Conductivity

Hirai S., Miki N.

2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII （2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII）     1659 - 1661 2019年06月

ISSN  9781728120072

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© 2019 IEEE. We demonstrate a thermal sensation display that can present various thermal sensation by varying the thermal conductivity of the display. Thermal sensation, i.e., cold/cool/warm/hot, is one of the major tactile sensations and needs to be further investigated to advanced VR/AR systems. Although many reports on the tactile displays present hot/cold surfaces by changing the surface temperature, the proposed display is the first one that can control thermal conductivity. The device contains liquid metal, whose contact to the top titanium plate determines the thermal conductivity of the device and thus, the thermal sensation presented to the users. This device can be a good platform for the study of thermal sensation.

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Quad Lipid Bilayer Module with 1-Gω Series Resistors Toward Quantitative Stochastic-Biosensors

Ito Y., Osaki T., Kamiya K., Yamada T., Miki N., Takeuchi S.

2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII （2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII）     6 - 8 2019年06月

ISSN  9781728120072

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© 2019 IEEE. This work designs and demonstrates the lipid bilayer-based ultra-sensitive biosensor capable of short-time detection in a quantitative manner, which is achieved by connecting multiple sensor elements in parallel.Artificial cell membranes with functional membrane proteins can form sensitive/selective biosensors. But the sensors suffer lengthy detection time at low concentration of analytes because the sensing mechanism relies on stochastic phenomena.In this work, we connected independent membrane sensors in parallel, where the ionic current through the multiple membranes was monitored by a single detector. With this format, the detection time is shortened based on the number of the array and the sensing can be quantitative. We developed a quad sensor assembling four membranes in parallel, and examined detection time of a single membrane sensor, the quad sensor, and four parallel quad-sensors. 1-Gω resistor was installed in series with each membrane to avoid overload current caused by membrane rupture. The results showed significant improvement in the detection time and deviation by the parallelization, which promises quantitative monitoring with the stochastic sensor.

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A Flexible Tactile Sensor to Detect Stiffness Distribution Without Measuring Displacement

Nagatom T., Miki N.

2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII （2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII）     551 - 553 2019年06月

ISSN  9781728120072

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© 2019 IEEE. In this study, we developed a flexible tactile sensor that scans the surface to detect the stiffness distribution. Note that the sensor does not need to know the displacement or strain of the target surface.Endoscopic palpation is a promising technology to detect tumors that have larger stiffness than normal tissues. The stiffness can be deduced by acquiring the load applied and the displacement, whereas the displacement or strain of the tissue is difficult to obtain given that endoscope has an arbitrary shape when in use and the tissue surface is not flat. In this study, we propose a new stiffness sensor composed of four strain gauges with different Young's modulus to detect the target without measuring the strain. The developed flexible sensor uses encapsulated liquid metal as the electrodes and can scan the surface.

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Electroencephalogram Measurement in Adapting Process to Inverse Vision

Onomoto T., Yoshida Y., Miki N.

2019 International Conference on Electronics Packaging, ICEP 2019 （2019 International Conference on Electronics Packaging, ICEP 2019）     134 - 137 2019年04月

ISSN  9784990218867

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© 2019 Japan Institute of Electronics Packaging. This paper describes investigation of the brain activity in an adapting process to inversion vision through electroencephalogram (EEG). In particular, we used Candle-like microneedle electrodes, which does not require any preparation for measuring high-quality EEG. Note that conventional wet electrodes require abrasion of stratum corneum and application of electrolyte paste as preparation for measurement of EEG and they give discomfort to subjects and take time for experimenters. In our previous study, the eye movement during the adapting process was measured and the progress of the process was successfully captured. In this study, we measured EEG during the pointing task under an inverse vision state to correlate the perceptual learning with EEG. We discovered that High β wave, Low γ wave and Mid γ wave had strong correlation with the process of adapting to inversed vision.

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Long-Term in vivo Experiment Protocol Using SD Rats

Ito T., Koya Y., Miki N.

2019 International Conference on Electronics Packaging, ICEP 2019 （2019 International Conference on Electronics Packaging, ICEP 2019）     144 - 148 2019年04月

ISSN  9784990218867

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© 2019 Japan Institute of Electronics Packaging. Our group has been developing implantable artificial dialysis system to decrease burden of chronic kidney disease patients. To evaluate the device, long-Term in vivo experiments are mandatory. However, we need to complete the detailed design of the devices prior to the long-Term tests, which range from the temporal change of the device performance to time to surgical procedures. To do so, we need to conduct mid-and long-Term in vivo experiments for multiple times to acquire sufficient information. It is useful to use small animals, such as rats, for in vivo experiment. However, there is no prior work that discusses mid-and long-Term coagulation ability control in small animals. In this study, we investigated the heparin administration to manage the coagulability. A simplified device was connected to SD rats under coagulability control and the blood coagulation in the device was characterized. And succeeded in blood clotting inhibition for 48 hours

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Tuneable Microparticle Filters

Iseri E., Kaya K., Di Dio G., Yasuga H., Miki N., Van Der Wijngaart W.

Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) （Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)）  2019-January   290 - 291 2019年01月

ISSN  9781728116105

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© 2019 IEEE. We introduce microparticle filters with temperature tuneable size cut-off and surface energy. At room temperature, the filter cut-off is 164 \pm 23\ \mu \mathrm{m}, and the filter is water-absorbing/oil-repelling (hydrophilic). At 50 °C, the filter cut-off is 695\pm 31\ \mu \mathrm{m}, and the filter is oil-absorbing/water-repelling (hydrophobic).

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Stacking 2D Droplet Arrays for 3D Configurable Droplet Network

Yasuga H., Osaki T., Kamiya K., Iseri E., Van Der Wijngaart W., Takeuchi S., Miki N.

Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) （Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)）  2019-January   387 - 388 2019年01月

ISSN  9781728116105

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© 2019 IEEE. Droplet interface bilayer (DIB) networks are expected to lead to tissue-like materials that can be designed from single droplets. Although various functions, such as sensors or computing, have been implemented into DIB networks, there remains a challenge in terms of configurability of constituent droplets in three-dimensional (3D). In this paper, we construct 3D DIB networks with defined droplet positions. We prepared 2D droplet arrays in paper-like substrates based on a method that we previously reported. Vertical stacking of the 2D arrays resulted in DIB formation between layers, i.e., a 3D DIB network.

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A Precise Sampling Strip with Microstructures

Kamiya H., Ota T., Yasuga H., Miki N.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS （Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS）  2018-July   3837 - 3840 2018年10月

ISSN  9781538636466

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© 2018 IEEE. This paper presents a precise sampling microstructure formed as a paper strip. We have been developing dialysis system that can be implanted into a human body as an artificial kidney. For the safe use of our artificial kidney, the patients' urine needs to be constantly monitored to detect the abnormal value of ion concentration essential for human life. We are conceiving the monitoring system based on sampling by a paper strip. In this study, we fabricated the strip consisting of slanted and interlocked micropillars for the sampling, known as synthetic microfluidic paper. The paper-like substrate can be fabricated with a well-controlled geometry and subsequently enables precise sampling. Through the conducted experiments, it was shown that synthetic microfluidic paper had better mechanical properties, showed more precision in sampling than paper filter as well as corresponding liquid holding capability to the paper filter. Our proposed paper-based sampling system is expected to lead to the development of minimally invasive ion monitoring system with quantitative sampling strip.

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Enfold-type connecting system of artificial blood vessels for micro implantable dialysis device

Watanabe A., Ota T., Kanno Y., Miki N.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS （Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS）  2018-July   5810 - 5813 2018年10月

ISSN  9781538636466

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© 2018 IEEE. This paper reports the connecting mechanism for the artificial blood vessels along with the recent development of the micro implantable dialysis device. Our group has been studying the micro implantable dialysis device, which will drastically improve the quality of life of dialysis patients. We expect to replace the device every couple of years, which will involve surgery. In order to simplify the surgery to reduce the load to the patients, we develop a connector for the artificial vessels, which allows the exchange of the device by low invasive surgery. The connector needs to be designed not to induce blood coagulation. We designed a connecting mechanism that enfolds the artificial vessels to allow blood to contact only to the surface of the artificial vessels. In order to verify effectiveness of the proposed connecting mechanism, we investigated the connector surfaces with SEM after blood circulation tests. Then, we evaluated blood coagulation capacity of the connecting system as well as the set of the connecting system and the micro dialysis device with respect to the activated partial thromboplastin time (APTT). No remarkable increase of blood coagulation at the connecting point was observed after 72 hours of blood circulation tests. Short-term experiments for 120 minutes to evaluate APTT showed a small decrease of APTT, which needs to be further investigated in a longer-term experiments.

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Automatic Planar Asymmetric Lipid Bilayer Membrane Formation toward Biological High-Throughput Assay

Gotanda M., Kamiya K., Osaki T., Fujii S., Misawa N., Miki N., Takeuchi S.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS （Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS）  2018-July   4496 - 4499 2018年10月

ISSN  9781538636466

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© 2018 IEEE. This paper describes automation of planar lipid bilayer formation by introducing a stepping motor to a microfluidic device. Planar lipid bilayers or lipid vesicles are useful to understand biological reactions and to investigate the interaction between lipids and proteins. Therefore, to acquire large amount of the information, high-throughput production of planar lipid bilayers or giant vesicles (GVs) is necessary. The droplet split-and-contact method, which enhances the efficiencies of both planar lipid bilayer formation and GV generation, needs to be automated for increasing the throughput. Previous droplet split-and-contact devices were manipulated manually; hence, the influence of manipulation on planar lipid bilayer formation was not evaluated quantitatively. First, to develop an automated system for generating asymmetric planar lipid bilayers, a stepping motor, which allows to control the angular speed of the rotor, is integrated into the droplet split- and-contact device (Fig. 1({b)). Next, we assessed planar lipid bilayer generation at various angular speeds and found the speed limit for bilayer formation. Finally, we generated asymmetric planar lipid bilayers that have different lipid composition on outer and inner leaflets using this automated device and confirmed the asymmetry of the planar lipid bilayers by generating GVs.

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Blood-Separating Device Without Energy Source for Implantable Medical Devices

Otsuki H., Ota T., Miki N.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS （Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS）  2018-July   4661 - 4664 2018年10月

ISSN  9781538636466

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© 2018 IEEE. Coagulation of blood inside the implanted medical device is quite a critical problem to limit the lifetime. In this paper, we propose a microfluidic blood separating device using curved and branched channels. It utilizes centrifugal force on curved flow and separates blood flow into blood cell rich and blood cell poor ones at the bifurcation. Though it cannot separate the plasma from blood cells completely, the blood with small concentrations of blood cells will have low coagulatibity and extend the lifetime of the implant medical device. The device does not require any external pumps or valves, i.e., the system does not need any power sources but the blood pressure. We conducted experiments with a titanium foil which contacted to human whole blood with different hematocrit values for 7 days. The device was experimentally characterized with respect to the channel design. The former experiments suggested that lower concentration of blood cells helps avoiding blood coagulations, and the latter showed that the separation by our device is mainly affected by the flow rate and channel curvature.

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Preparation-Free Measurement of Event-Related Potential in Oddball Tasks from Hairy Parts Using Candle-Like Dry Microneedle Electrodes

Yoshida Y., Kudo Y., Hoshino E., Minagawa Y., Miki N.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS （Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS）  2018-July   4685 - 4688 2018年10月

ISSN  9781538636466

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© 2018 IEEE. This paper reports successful measurement of even-related potential (ERP) using candle-like dry microneedle electrodes, which can acquire high-quality electroencephalogram (EEG) from hairy parts without any pretreatment. In our previous work, we successfully measured spontaneous EEG activity and its application to assess the stress state of the subjects. ERPs originate from electrophysiological response to stimulus and are one of the most important indices to capture the cognitive and sensory activities. In this work, using the candle-like dry microelectrodes, we demonstrate successful measurement of ERPs elicited by oddball tasks. Two oddball tasks using pure tone stimuli and speech stimuli were assigned to the subjects, where EEG was acquired from the parietal region (Cz in international 10-20 system). Note that no pretreatment, such as removal of hairs and abrasion of the scalp, was applied. As a result, P300 and mismatch negativity (MMN) were successfully measured in the both oddball tasks from the averaged EEG after the stimuli. Based on these results and given the attractive natures of the candle-like dry microneedle electrodes; they do not need any skin treatment and conductive gels and they can measure EEG from the hairy parts, the developed electrodes will accelerate cognitive neuroscience research using ERPs.

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Development of an automatic urine monitoring device using cross-selectivity sensing principle

Ioller B., Miki N.

2018 International Conference on Electronics Packaging and iMAPS All Asia Conference, ICEP-IAAC 2018 （2018 International Conference on Electronics Packaging and iMAPS All Asia Conference, ICEP-IAAC 2018）     324 - 327 2018年06月

ISSN  9784990218850

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© 2018 Japan Institute of Electronics Packaging. Despite today's race for IoT application dedicated to home care, and healthcare service, remote analysis of urine, one of the best bio-marker, remains quite challenging and can be improved. This paper demonstrates an automatic urine monitoring device using the capillarity effect inside a channel and cross-selectivity principle to create a modular and daily analysis solution. The developed device was tested on simulated urine and successfully determined its basic composition (ionic concentration and color). We finally proposed a realistic use-case for heatwave prevention in Japan by connecting our device with a ESP32 module to bring the daily result to a healthcare application.

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Reduction of parasitic capacitance of flexible tactile sensors

Nagatomo T., Miki N.

2018 International Conference on Electronics Packaging and iMAPS All Asia Conference, ICEP-IAAC 2018 （2018 International Conference on Electronics Packaging and iMAPS All Asia Conference, ICEP-IAAC 2018）     562 - 565 2018年06月

ISSN  9784990218850

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© 2018 Japan Institute of Electronics Packaging. In this study, we successfully reduced the parasitic capacitance of PDMS-based flexible tactile sensors by decreasing the dielectric constant of PDMS. UV exposure changes Si-CH3 bonds in PDMS to Si-O, which leads to the low dielectric constant. This simple but effective method can be readily applicable to improve signal-To-noise ratio of PDMS-based flexible sensors.

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Practical realization of enfold connecting system of artificial blood vessel for simplifying maintenance surgery evaluation of thrombus formation and blood coagulation capasity

Watanabe A., Ota T., Kanno Y., Miki N.

2018 International Conference on Electronics Packaging and iMAPS All Asia Conference, ICEP-IAAC 2018 （2018 International Conference on Electronics Packaging and iMAPS All Asia Conference, ICEP-IAAC 2018）     141 - 144 2018年06月

ISSN  9784990218850

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© 2018 Japan Institute of Electronics Packaging. Evaluations for the enfold connecting system of system is developed to reduce and simplify the maintenance surgery of the artificial organ.The connector is designed not to contact the blood directly and the artificial blood vessel enfolds metal pipe in connector. Thanks to this design, the biocompatibility of the connector is comparable with an artificial vessel. We confirmed the blood coagulate protein which form a thrombus at the joint point of the connector with SEM. And we also measured a potential of blood coagulation by activated partial thromboplastin time (APTT). We didn't find the remarkable increase of blood coagulation on the connecting point for 72 hours. And APTT decreased a little in the experiment of a blood circulation system with the connector but we can't conclude that the connector causes a blood coagulation from results for 120 minutes. Additionally, we measured a potential of blood coagulation by APTT about the micro dialysis device which is developed in our group. We conducted the micro dialysis device experiments as with the same method of the connector experiments of APTT. We did not observe the remarkable disease of APTT for 120 minutes about the micro dialysis device as well. However, we found that the hemolysis was possible to be occurred in the micro dialysis device.

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Droplet microfluidics inside paper

Yasuga H., Guo W., Hansson J., Haraldsson T., Miki N., Van Der Wijngaart W.

Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) （Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)）  2018-January   269 - 271 2018年04月

ISSN  9781538647820

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© 2018 IEEE. Here, we demonstrate, for the first time: the self-digitization, i.e. spontaneous formation, of microdroplets during the imbibition of paper; the on-demand merging of individual microdroplets in paper; and the on-demand ejection of individual microdroplets from the paper. Two technical novelties underlie these novel functions: the formation of free-standing synthetic microfluidic paper, i.e. a porous matrix of slanted and interconnected micropillars without bottom layer; and the hydrophobic surface modification of the paper. The ease of manipulation and the direct access to the microdroplets from the environment makes this an extremely versatile tool, with potential applications in liquid sample digitisation and microparticle generation.

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Triple-coaxial flow for continuous production of microtubes containing microbes for bioremediation

Fujimoto K., Higashi K., Onoe H., Miki N.

Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) （Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)）  2018-January   1269 - 1271 2018年04月

ISSN  9781538647820

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© 2018 IEEE. This paper describes a microfluidic device to continuously produce a hydrogel microtube using triple-coaxial flow. In our prior work, double-coaxial flow was used to produce hydrogel microtubes, though continuous and mass production was a challenge. In this work, we also demonstrate bioremediation using the microtubes that encapsulate microbial suspension. The microenvironment created by the microtubes enabled efficient purification of aqueous sample solution and in addition, the microbes are maintained inside the microtube and are easily collected without contaminating the solution. The proposed technology can be applied to any types of microbes and can be of great benefit for various microbial processes.

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Liquid metal electrodes micro-array for electrical stimulation via direct contact

David R., Miki N.

Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) （Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)）  2018-January   373 - 375 2018年04月

ISSN  9781538647820

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© 2018 IEEE. We have developed a novel liquid metal based electrodes micro-array for the electrical stimulation of biological tissues with a direct liquid metal - biological tissue contact surface. This work presents for the first time an effort to introduce Gallium based liquid metal components to the field of implantable electrical stimulation systems. The electrical performance and overall integrity of the liquid metal open micro-channel electrodes were fully characterized and analyzed in regard of the properties of the liquid metal used, the surrounding environment, and the stimulation signal. Stable direct contact stimulation electrodes down to a width of 50 μm were successfully produced and tested in-vitro.

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