Published papers

Neuromuscular choristoma (NMC) is an extremely rare, benign nerve tumor composed of intermingled mature skeletal muscle fibers and nerve bundles. Most cases arise in childhood from major nerves such as the sciatic or brachial plexus. Surgical manipulation, including biopsy or partial excision, has been reported to induce desmoid-type fibromatosis (DTF); therefore, invasive procedures should be avoided. Here, the authors report a case of NMC arising from the mental nerve in a 24-year-old man who presented with a gradually enlarging, soft, and poorly mobile subcutaneous mass with indistinct borders. Magnetic resonance imaging (MRI) revealed findings characteristic of NMC, and en bloc resection, including the overlying skin, was performed. Histopathologic examination revealed mature skeletal muscle fibers intermingled with nerve fascicles, confirming the diagnosis of NMC. No neurological deficits or recurrences occurred during a several-month follow-up. This is the first reported case of adult-onset NMC arising from a peripheral branch and the only second peripheral nerve case worldwide. NMC may mimic lipoma or schwannoma in the craniofacial region, and a biopsy can trigger DTF formation; therefore, noninvasive MRI-based diagnosis and cautious surgical planning are essential.

Simultaneous detection of multiple odorants is a major challenge in the development of portable, cell-based biohybrid sensors, primarily due to the difficulty of distinguishing between different sensor cell types. Here, a strategy that encodes odorant sensor cell types using the shape of hydrogel particles, enabling shape-based identification through deep learning is reported. Each particle shape corresponds to a unique sensor cell type expressing a distinct odorant receptor (OR). A convolutional neural network is trained to classify these shapes with high accuracy, and the resulting shape identification scheme is applied to time-lapse fluorescence images of mixed particles exposed to single odorants. This enabled reliable assignment of particle identity and extraction of shape-specific fluorescence signals. Distinct odorant-dependent responses are observed, consistent with the known ligand specificities of the corresponding ORs. While this study focuses on individual odorants, the shape-based approach provides a position-independent, scalable method for multiplexed odorant detection. This framework supports the development of compact, high-throughput biohybrid sensors for safety, environmental monitoring, and diagnostic applications.

Multilayered hemodialysis devices enable blood flow without the need for an external pump, whereas hollow fiber-type devices require a pump due to significant pressure loss across the fibers. This highlights a key advantage of multilayered devices for implantable applications, where a simpler and lighter system reduces the burden on patients. This study investigates the mechanical strength and dialysis efficiency of polyether sulfone (PES) flat-sheet membranes for multilayered devices. PES membranes, with thicknesses ranging from 40 to 160 µm, were prepared using the liquid inversion method, with thickness controlled via spin coating. The mechanical strength of the membranes was tested following the ISO 8637–1:2017 protocol, and membranes thicker than 80 µm were experimentally verified to withstand pressures of up to 500 mmHg, making them suitable for dialysis applications. Furthermore, the study demonstrates the successful use of 80 µm membranes in both in vitro and ex vivo experiments with rats, identifying this thickness as optimal for multilayered dialysis devices.

Olfactory receptors are known for their high specificity, sensitivity, and nanometer-sized sensing element, making them ideal for in situ odorant sensor applications. However, one of the major limitations of these sensors is the requirement for an aqueous environment to maintain their function, while most odorants are poorly soluble in water. To address this issue, a microfluidic device consisting of a gas-flow channel and a microwell is proposed that enables the effective dissolution of a gaseous odorant in an aqueous solution. Computational simulations are used to design the gas-flow channel and the well, and the performance of the odorant dissolution is verified using the fabricated device. This study considers that convection in water induced by the gas flow enhances the dissolution of a gaseous odorant. The feasibility of the device is demonstrated for on-site detection of a gaseous odorant. This approach facilitates the development of highly responsive and portable sensors utilizing olfactory receptors, offering a promising solution to the limitations of current odorant sensors.

Expanded polystyrene (EPS) is one of major plastic pollutants which toxicity increased when exposed to UV irradiation. In this study, the feasibility of upcycling waste EPS (WEPS), which originates from food packaging, into a flat-sheet filtration membrane was explored. The membrane was fabricated using the wet-phase inversion method, with polyimide serving as a blending additive varied from 2 to 8 wt.%. Characterization was carried out using water contact angle measurements, SEM, and UV–Vis spectrophotometry. The experimental results indicated that all WEPS/PI membranes demonstrated microplastic rejection rates exceeding 80%, and they exhibited greater uniformity compared to the pristine WEPS membrane. Furthermore, protein rejection improved with the concentration of PI. The addition of 8 wt.% polyimide led to a 240% increase in protein rejection, with all membranes having hydrophilic surface. The SEM images revealed that the introduction of polyimide altered the membrane’s structure, enhancing its filtration properties by modifying the finger-like structure of the membrane. The addition of 8% polyimide to the WEPS dope solution decreased both pore size and porosity to the least value observed, while also enhancing the antifouling property by 67%. The experimental findings indicate that the WEPS/PI membrane holds significant promise to solve challenges of waste EPS accumulation, as well as offering sustainable solutions for addressing microplastic pollution by recycling the waste EPS into high-end filtration membrane.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.