論文 - 三木　則尚

Impact of polyimide on the recycling of waste expanded polystyrene into flat‑sheet filtration membrane

Tutik Sriani, Muslim Mahardika, Norihisa Miki, Chandrawati Putri Wulandari, Gunawan Setia Prihandana

（Journal of Material Cycles and Waste Management）  2024年09月

研究論文（学術雑誌）, 査読有り

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Relationship Between Interoceptive Accuracy and Tactile Exploration Behavior

H. Aso, H. Ishizuka, T. Hiraki, Y. Minagawa, N. MIki

IEEE Access 12   93145 - 93151 2024年

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

　概要を見る

This paper presents a novel finding suggesting that tactile exploration behaviors, with a focus on finger scanning motion, are influenced by interoception. Initially, we investigated finger motion for surface scanning across various precisely controlled surface patterns using microfabrication techniques. Participants were then categorized into two distinct groups based on whether their finger scanning speed depended on surface patterns. Subsequently, we assessed participants' interoception through a heart rate counting task. The identified groups correlated with levels of interoceptive accuracy, indicating a significant relationship between interoception and tactile-related behaviors. This discovery could have a profound impact on tactile research, as it suggests the need to consider interoception properties alongside conventional participant demographics such as age and gender in experimental design.

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Microfabricated Nitinol Stent Retrievers with a Micro-Patterned Surface

Kato S., Ban Y., Ota T., Miki N.

Micromachines （Micromachines）  15 （ 2 ）  2024年02月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

　概要を見る

Stent retrievers are medical devices that are designed to physically remove blood clots from within the blood vessels of the brain. This paper focuses on microfabricated nitinol (nickel–titanium alloy) stent retrievers, which feature micro-patterns on their surface to enhance the effectiveness of mechanical thrombectomy. A thick film of nitinol, which was 20 µm in thickness, was sputtered onto a substrate with a micro-patterned surface, using electroplated copper as the sacrificial layer. The nitinol film was released from the substrate and then thermally treated while folded into a cylindrical shape. In vitro experiments with pig blood clots demonstrated that the micro-patterns on the surface improved the efficacy of blood clot retrieval.

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Reproducible reformation of a bilayer lipid membrane using microair bubbles

Hashimoto I., Osaki T., Sugiura H., Mimura H., Takamori S., Miki N., Takeuchi S.

Droplet （Droplet）  2 （ 3 ）  2023年07月

研究論文（学術雑誌）,  ISSN  27692159

　概要を見る

Planar bilayer lipid membranes (BLMs) are widely used as models for cell membranes in various applications, including drug discovery and biosensors. However, the nanometer-thick bilayer structure, assembled through hydrophobic interactions of amphiphilic lipid molecules, makes such BLM systems mechanically and electrically unstable. In this study, we developed a device to reform BLMs using a microair bubble. The device consists of a double well divided by a separator with a microaperture, where a BLM was formed by infusing a lipid-dispersed solvent and an aqueous droplet into each well in series. When the BLM ruptured, a microair bubble was injected from the bottom of the well to split the merged aqueous droplet at the microaperture, which resulted in the reformation of two lipid monolayers on the split droplets. By bringing the two droplets into contact, a new BLM was formed. An angled step design was introduced in the BLM device to guide the bubble and ensure the splitting of the merged droplet. We also elucidated the optimal bubble inflow rate for the reproducible BLM reformation. Using a 4-channel parallel device, we demonstrated the individual and repeatable reformation of BLMs. Our approach will aid the development of automated and arrayed BLM systems.

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Real-time quantitative characterization of ion channel activities for automated control of a lipid bilayer system

Ogishi K., Osaki T., Mimura H., Hashimoto I., Morimoto Y., Miki N., Takeuchi S.

Biosensors and Bioelectronics （Biosensors and Bioelectronics）  237 2023年10月

研究論文（学術雑誌）, 査読有り,  ISSN  09565663

　概要を見る

This paper describes a novel signal processing method to characterize the activity of ion channels on a lipid bilayer system in a real-time and quantitative manner. Lipid bilayer systems, which enable single-channel level recordings of ion channel activities against physiological stimuli in vitro, are gaining attention in various research fields. However, the characterization of ion channel activities has heavily relied on time-consuming analyses after recording, and the inability to return the quantitative results in real time has long been a bottleneck to incorporating the system into practical products. Herein, we report a lipid bilayer system that integrates real-time characterization of ion channel activities and real-time response based on the characterization result. Unlike conventional batch processing, an ion channel signal is divided into short segments and processed during the recording. After optimizing the system to maintain the same characterization accuracy as conventional operation, we demonstrated the usability of the system with two applications. One is quantitative control of a robot based on ion channel signals. The velocity of the robot was controlled every second, which was around tens of times faster than the conventional operation, in proportion to the stimulus intensity estimated from changes in ion channel activities. The other is the automation of data collection and characterization of ion channels. By constantly monitoring and maintaining the functionality of a lipid bilayer, our system enabled continuous recording of ion channels over 2 h without human intervention, and the time of manual labor has been reduced from conventional 3 h to 1 min at a minimum. We believe the accelerated characterization and response in the lipid bilayer systems presented in this work will facilitate the transformation of lipid bilayer technology toward a practical level, finally leading to its industrialization.

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ProtoHand: Solderless Prototyping of Electrical Circuits on a Soft Artificial Hand with Liquid Metal

Yamaguchi S., Nakano N., Hiraki T., Ishizuka H., Miki N.

IEEE Sensors Letters （IEEE Sensors Letters）  7 （ 3 ）  2023年03月

研究論文（学術雑誌）, 最終著者, 責任著者, 査読有り

　概要を見る

In this letter, we propose and demonstrate ProtoHand, which is a soft artificial hand that can work as a universal platform for prototyping electrical circuits similar to a breadboard. ProtoHand is made of flexible and transparent polydimethyl siloxane. ProtoHand has multiple channels filled with liquid metal beneath the surface, like the blood vessels of a hand. Electric components, such as resistors and capacitors, can be inserted by piercing into ProtoHand and electrically connected via the conductive liquid metal. Soldering is unnecessary, and the parts can be removed without leakage of the liquid metal; therefore, prototyping of electric circuits can be performed on this soft hand in a reusable manner. ProtoHand will help the design of multifunctional robot hands and could also be an excellent educational tool.

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Easily Attach/Detach Reattachable EEG Headset with Candle-like Microneedle Electrodes

Kawana T., Zemba Y., Ichikawa R., Miki N.

Micromachines （Micromachines）  14 （ 2 ）  2023年02月

研究論文（学術雑誌）, 最終著者, 責任著者, 査読有り

　概要を見る

To expand the applications of the electroencephalogram (EEG), long-term measurement, a short installation time, and little stress on the participants are needed. In this study, we designed, fabricated, and evaluated an EEG headset with three candle-like microneedle electrodes (CMEs). The user is able to detach and reattach the electrodes, enabling long-term measurement with little stress. The design of the CMEs was experimentally determined by considering the skin-to-electrode impedance and user comfort. An EEG was successfully measured from areas with a high hair density without any preparation. The installation time was shorter than 60 s and the electrodes could be detached and reattached. The headset was designed such that the discomfort caused by its ear pads was higher than that caused by the electrodes. In 1 h experiments, the participants did not feel pain and the detachment of the CMEs was found to improve the comfort level of the participants in most cases. A successful demonstration of the long-term measurement of EEGs while watching a whole movie verified that the developed EEG headset with CMEs is applicable for EEG measurement in a variety of applications.

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Stretchable Strain Sensor with Small but Sufficient Adhesion to Skin

Nishikawa T., Yamane H., Matsuhisa N., Miki N.

Sensors （Sensors）  23 （ 4 ）  2023年02月

研究論文（学術雑誌）, 最終著者, 責任著者, 査読有り,  ISSN  14248220

　概要を見る

Stretchable strain sensors that use a liquid metal (eutectic gallium–indium alloy; E-GaIn) and flexible silicone rubber (Ecoflex) as the support and adhesive layers, respectively, are demonstrated. The flexibility of Ecoflex and the deformability of E-GaIn enable the sensors to be stretched by 100%. Ecoflex gel has sufficiently large adhesion force to skin, even though the adhesion force is smaller than that for commercially available adhesives. This enables the sensor to be used for non-invasive monitoring of human motion. The mechanical and electrical properties of the sensor are experimentally evaluated. The effectiveness of the proposed sensors is demonstrated by monitoring joint movements, facial expressions, and respiration.

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Handshake Feedback in a Haptic Glove Using Pouch Actuators

Yamaguchi S., Hiraki T., Ishizuka H., Miki N.

Actuators （Actuators）  12 （ 2 ）  2023年02月

研究論文（学術雑誌）, 最終著者, 責任著者, 査読有り

　概要を見る

In this paper, we propose and demonstrate a haptic device with liquid-pouch motors that can simulate a handshake. Because handshakes involve contact of the palms or soft skin, handshake simulation requires the haptic device to provide pressure onto specific areas of the palm with soft contact. This can be achieved with thermally driven liquid-pouch motors, which inflate and deflate when a low-boiling-point liquid, here Novec™ 7000, evaporates and condenses, respectively. Due to the simplicity of the soft actuator system, this haptic glove is lightweight and conformable. To design the haptic glove, we experimentally investigated the contact region and strength in handshakes, which led to an optimal number, size and position for the liquid-pouch motors. Sensory experiments with human subjects verified that the designed haptic glove successfully simulated handshakes.

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Micromanufactured Tactile Samples for Characterization of Rough and Dry Tactile Perception

Yanagibashi K., Miki N.

Micromachines （Micromachines）  13 （ 10 ）  2022年10月

　概要を見る

The quantitative characterization of tactile perception, which is crucial in the design of tactile devices, requires the tested samples to have individually and precisely controlled properties associated with the senses. In this work, we microfabricated such tactile samples and then quantitatively characterized tactile perception with a focus on roughness and dryness. In the roughness perception experiments, the tactile samples had a stripe pattern with ridge and groove widths that were individually controlled. The experimental results revealed that the feeling of roughness was more dominated by the width of the groove than that of the ridge and that conventionally used roughness parameters such as (Formula presented.) and (Formula presented.) were not sufficient for predicting roughness perception. In the dryness perception experiments, the tactile samples had a micropattern formed by dry etching and an array of squares. The experimental results revealed that dry perception had different properties when the feature sizes were below and above 30 µm, which may have been due to the effect of adhesion on friction. The proposed tactile samples were suitable for the quantitative and precise characterization of tactile perception.

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Machine-Learning-Based Fine Tuning of Input Signals for Mechano-Tactile Display

Yamanaka S., Nagatomo T., Hiraki T., Ishizuka H., Miki N.

Sensors （Sensors）  22 （ 14 ） 5299 2022年07月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  14248220

　概要を見る

Deducing the input signal for a tactile display to present the target surface (i.e., solving the inverse problem for tactile displays) is challenging. We proposed the encoding and presentation (EP) method in our prior work, where we encoded the target surface by scanning it using an array of piezoelectric devices (encoding) and then drove the piezoelectric devices using the obtained signals to display the surface (presentation). The EP method reproduced the target texture with an accuracy of over 80% for the five samples tested, which we refer to as replicability. Machine learning is a promising method for solving inverse problems. In this study, we designed a neural network to connect the subjective evaluation of tactile sensation and the input signals to a display; these signals are described as time-domain waveforms. First, participants were asked to touch the surface presented by the mechano-tactile display based on the encoded data from the EP method. Then, the participants recorded the similarity of the surface compared to five material samples, which were used as the input. The encoded data for the material samples were used as the output to create a dataset of 500 vectors. By training a multilayer perceptron with the dataset, we deduced new inputs for the display. The results indicate that using machine learning for fine tuning leads to significantly better accuracy in deducing the input compared to that achieved using the EP method alone. The proposed method is therefore considered a good solution for the inverse problem for tactile displays.

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Pressure-controlled ultrasound probe for reliable imaging in breast cancer diagnosis

Matsumoto Y., Katsumura A., Miki N.

Japanese Journal of Applied Physics （Japanese Journal of Applied Physics）  61 （ SD ） SD1035 2022年05月

研究論文（学術雑誌）, 共著, 最終著者, 査読有り,  ISSN  00214922

　概要を見る

Breast cancer is the most common cancer among women worldwide, with over 2 million new cases diagnosed each year. Early detection can be achieved by screening examinations such as mammography and ultrasonography. The latter has demonstrated advantages such as safety and sensitivity to dense breasts, but is often performed as a follow-up test after abnormal findings at mammography or on palpation. Indeed, the technique shows limitations of operator-dependence and non-reproducibility, since the quality of imaging is highly dependent on the skill of the technologist performing the examination. We therefore designed a diagnosis-assisting device comprising piezoresistive sensors of microscale thickness that can be attached to the ultrasound transducer. The operator is informed when excessive pressure is detected, allowing correction of the transducer position. Finally, we fabricated a breast phantom including tumors from agar and collagen to assess the effectiveness of the device.

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Study Effect of nAg Particle Size on the Properties and Antibacterial Characteristics of Polysulfone Membranes

Prihandana G.S., Sriani T., Muthi’ah A.D., Machmudah A., Mahardika M., Miki N.

Nanomaterials （MDPI）  12 （ 3 ） 388 2022年01月

研究論文（国際会議プロシーディングス）, 共著, 最終著者, 査読有り

　概要を見る

Polysulfone ultrafiltration membranes were fabricated using various sizes (20, 40, and 90–210 nm) of silver nanoparticles (nAg) blended in a dope solution. To characterize the performance and properties of the prepared membranes, scanning electron microscopy (SEM), water contact angle, protein separation, water flux, and antibacterial tests were conducted. The characterization results revealed that when nAg particles (20 nm) were blended into the base polymer PSF, the PSF/nAg blended membrane had the lowest contact angle (58.5◦ ) and surface energy (110.7 mN/m). When experimenting with ultrafiltration using protein solutions, bare PSF and PSF/nAg-20 blended membranes gave similar values of protein rejection: 93% of bovine serum albumin (BSA) and 70% of lysozyme rejection. Furthermore, SEM studies showed that the surface pore size was reduced by adding 20 nm nAg particles in the casting solution. Most importantly, the introduction of 40 nm nAg particles reduced the growth of bacterial colonies on the membrane surface by up to 72%. These findings revealed that nAg particles are expected to be a potential modifier for the fabrication of an ultrafiltration membrane.

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Direct Wiring of Liquid Metal on an Ultrasoft Substrate Using a Polyvinyl Alcohol Lift-off Method

Murakami K., Tochinai R., Tachibana D., Isano Y., Matsuda R., Nakamura F., Kurotaki Y., Isoda Y., Yamane M., Sugita Y., Fukuda J., Ueno K., Miki N., Fuchiwaki O., Ota H.

ACS Applied Materials and Interfaces （ACS Applied Materials and Interfaces）  14 （ 5 ） 7241 - 7251 2022年02月

研究論文（学術雑誌）, 査読有り,  ISSN  19448244

　概要を見る

In recent years, wiring and system construction on ultrasoft materials such as biological tissues and hydrogels have been proposed for advanced wearable devices, implantable devices, and soft robotics. Among the soft conductive materials, Ga-based liquid metals (LMs) are both biocompatible and ultrasoft, making them a good match for electrodes on the ultrasoft substrates. However, gels and tissues are softer and less wettable to the LMs than conventional soft substrates such as Ecoflex and polydimethylsiloxane. In this study, we demonstrated the transfer of LM paste composed of Ga-based LM and Ni nanoparticles onto ultrasoft substrates such as biological tissue and gels using sacrificial polyvinyl alcohol (PVA) films. The LM paste pattern fabricated on the PVA film adhered to the ultrasoft substrate along surface irregularities and was transferred without being destroyed by the PVA film before the PVA's dissolution in water. The minimum line width that could be wired was approximately 165 μm. Three-dimensional wiring, such as the helical structure on the gel fiber surface, is also possible. Application of this transfer method to tissues using LM paste wiring allowed the successful stimulation of the vagus nerve in rats. In addition, we succeeded in transferring a temperature measurement system fabricated on a PVA film onto the gel. The connection between the solid-state electrical element and the LM paste was stable and maintained the functionality of the temperature-sensing system. This fundamental study of wiring fabrication and system integration can contribute to the development of advanced electric devices based on ultrasoft substrates.

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Unsupervised Learning Enables Extraction of Tactile Information from Text Database

T. Nagatomo, T. Hiraki, H. Ishizuka, N. Miki

IEEE Access （IEEE）  11   101155 - 101166 2021年11月

研究論文（学術雑誌）, 最終著者, 責任著者, 査読有り

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Pump‐free microfluidic hemofiltration device

Ito T., Ota T., Kono R., Miyaoka Y., Ishibashi H., Komori M., Yasukawa A., Kanno Y., Miki N.

Micromachines （Micromachines）  12 （ 8 ） 992 2021年08月

研究論文（学術雑誌）, 共著, 査読有り

　概要を見る

Hemofiltration removes water and small molecules from the blood via nanoporous filtering membranes. This paper discusses a pump‐free hemofiltration device driven by the pressure dif-ference between the artery and the vein. In the design of the filtering device, oncotic pressure needs to be taken into consideration. Transmembrane pressure (TMP) determines the amount and direc-tion of hemofiltration, which is calculated by subtracting the oncotic pressure from the blood pres-sure. Blood pressure decreases as the channels progress from the inlet to the outlet, while oncotic pressure increases slightly since no protein is removed from the blood to the filtrate in hemofiltra-tion. When TMP is negative, the filtrate returns to the blood, i.e., backfiltration takes place. A small region of the device with negative TMP would thus result in a small amount of or even zero filtrates. First, we investigated this phenomenon using in vitro experiments. We then designed a hemofiltra-tion system taking backfiltration into consideration. We divided the device into two parts. In the first part, the device has channels for the blood and filtrate with a nanoporous membrane. In the second part, the device does not have channels for filtration. This design ensures TMP is always positive in the first part and prevents backfiltration. The concept was verified using in vitro experiments and ex vivo experiments in beagle dogs. Given the simplicity of the device without pumps or electrical components, the proposed pump‐free hemofiltration device may prove useful for either implantable or wearable hemofiltration.

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The effect of haptic stimulation simulating heartbeats on the regulation of physiological responses and prosocial behavior under stress: The influence of interoceptive accuracy

Xu M., Tachibana T., Suzuki N., Hoshino E., Terasawa Y., Miki N., Minagawa Y.

Biological Psychology （Biological Psychology）  164   108172 2021年08月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  03010511

　概要を見る

Research has discovered the modulatory effect of peripheral stimulation simulating altered bodily signals on emotion. Whether such an effect varies depending on one's interoceptive accuracy (IAc) remains unclear. Therefore, we provided haptic stimulation simulating participants’ slowed-down heartbeats or no stimulation while they engaged in socially stressful tasks to examine whether participants reacted differently depending on their IAc. Results showed that haptic stimulation exhibited the opposite effect on participants with different levels of IAc for both heart rate and heart rate variability (HRV). When receiving the stimulation, participants with higher IAc showed less increased heart rate and more elevated HF than participants with lower IAc. In contrast, in the absence of stimulation, an opposite pattern of response depending on participants’ IAc was observed. The modulatory effect of stimuli and IAc on prosocial behavior was not significant. Individual differences in IAc were shown to affect how one perceives/responds to altered bodily signals.

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Precision electropolishing on fabricating ss 316l microchannel – a taguchi approach

Setyawan M.A., Mahardika M., Sriani T., Miki N., Prihandana G.S.

International Journal on Engineering Applications （International Journal on Engineering Applications）  9 （ 4 ） 209 - 216 2021年

研究論文（学術雑誌）, 共著,  ISSN  22812881

　概要を見る

This paper presents the fabrication of a microchannel on stainless steel 316L (SS 316L) by electropolishing method. Machining parameters such as applied voltage, concentration of NaCl in the electrolyte solution and machining gap between tool and workpiece have been optimized in this electropolishing process. The Taguchi method is adopted to ascertain the optimum process parameters in order to increase maximum material removal rate using L9 orthogonal array. Pareto analysis of variance is employed in order to analyze the machining process parameters to the material removal rate. The result shows that the optimal parameters to achieve the maximum material removal rate is by using a combination of 10 V as applied voltage, NaCl concentration of 15 wt.%, and setting 1 cm as the machining gap. It has been also found out that in order to have relatively high material removal without sacrificing the surface quality and the geometrical accuracy of the microchannel produced, applied voltage at 7 V, NaCl concentration of 7 wt.% and machining gap of 3 cm is the best combination of the electropolishing parameters. Copyright © 2021 Praise Worthy Prize S.r.l.-All rights reserved.

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Fluid interfacial energy drives the emergence of three-dimensional periodic structures in micropillar scaffolds

Yasuga H., Iseri E., Wei X., Kaya K., Di Dio G., Osaki T., Kamiya K., Nikolakopoulou P., Buchmann S., Sundin J., Bagheri S., Takeuchi S., Herland A., Miki N., van der Wijngaart W.

Nature Physics （Nature Physics）  17 （ 7 ） 794 - 800 2021年03月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  17452473

　概要を見る

Structures that are periodic on a microscale in three dimensions are abundant in nature, for example, in the cellular arrays that make up living tissue. Such structures can also be engineered, appearing in smart materials1–4, photonic crystals5, chemical reactors6, and medical7 and biomimetic8 technologies. Here we report that fluid–fluid interfacial energy drives three-dimensional (3D) structure emergence in a micropillar scaffold. This finding offers a rapid and scalable way of transforming a simple pillar scaffold into an intricate 3D structure that is periodic on a microscale, comprising a solid microscaffold, a dispersed fluid and a continuous fluid. Structures generated with this technique exhibit a set of unique features, including a stationary internal liquid–liquid interface. Using this approach, we create structures with an internal liquid surface in a regime of interest for liquid–liquid catalysis. We also synthesize soft composites in solid, liquid and gas combinations that have previously not been shown, including actuator materials with temperature-tunable microscale pores. We further demonstrate the potential of this method for constructing 3D materials that mimic tissue with an unprecedented level of control, and for microencapsulating human cells at densities that address an unresolved challenge in cell therapy.

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Artificial Cell Membrane Sensors with Membrane Proteins

Y. Ito, T. Osaki, N. Miki, S. Takeuchi

表面と真空 2021年04月

研究論文（学術雑誌）, 共著, 査読有り