We developed a technology for reduction of fluid resistance in nanochannel by incorporating a superhydrophobic structure on the wall. Superhydrophobic structure was fabricated by nanopillar and hydrophobic modification. For the superhydrophobic structure, nanopillars with a diameter of 300 nm were fabricated by electron beam lithography, and the pillar surface was hydrophobically modified with a silane agent. As a result, water-repellent surface with a contact angle of 136° was realized. The water-repellent surface was incorporated into the nanochannel by top-down glass fabrication. The results of mass flowmetry suggested that the fluid resistance was reduced by about 40%. Therefore, reduction of fluid resistance in the nanochannel was verified for the first time. This study will contribute to miniaturization and energy saving in nanofluidic devices by reduction of fluid resistance.

The present study theoretically deals with two types of weakly nonlinear (i.e., finite but small amplitude) propagations of pressure waves in water flows containing many spherical microbubbles, especially focusing on the effect of a nonuniform distribution of flow velocity. By using the method of multiple scales with appropriate choices of the set of scaling relations composed of three nondimensional ratios, the Korteweg-de Vries-Burgers equation for a low frequency long wave and the nonlinear Schrödinger equation for a high frequency short wave can be derived as nonlinear wave equations with variable coefficients. Hence, we succeeded the extension of our previous result for quiescent bubbly liquids into the case of bubbly flows with nonuniform flow velocities.

Comb-tooth electrodes type MEMS capacitance sensor and two-electrode resistance sensor have been studied for detection of fuel liquid film on an engine intake pipe. The capacitance sensor showed little response to the gasoline and its main component liquid. In an engine test, the capacitance sensor showed obvious response to a cyclic injection of E20 gasoline. With the resistance sensor and a giga-ohm measurement circuit, it was confirmed that nonconductive gasoline becomes detectable conductive liquid with ethanol mixing. Also, it was found that static electricity in the fuel under a friction can be detected by the resistance measurement system.

This study investigated the force acting on a nanoparticle in a solidification process by conducting non-equilibrium molecular dynamics simulation, to elucidate interactions between a nanoparticle and a solidification interface, which are related to particle pushing and engulfment phenomena. The simulation system consisted of a Pt nanoparticle and Ar molecules, and the 12-6 Lennard-Jones potential was adopted for all the interaction functions. Controlling the temperature at a solid Ar region, a solidification process was simulated in a solid-liquid system with a nanoparticle, and we investigated effects of the interaction strengths between the nanoparticle and Ar molecules on the interactions between the solidification interface and nanoparticle. The microscopic picture of the force acting on a nanoparticle in a solidification process was revealed showing the instantaneous and averaged values of the force, and the relationship between the force and the nanoparticle-pushing/engulfment phenomena was discussed.

The charge trapping depth of negatively-charged CYTOP polymer electret is evaluated by density function theory, with polarizable continuum model incorporated. The computed solid-state electron affinity is in accordance with the experiment data and the MD/DFT results, while requiring 31 times smaller computational cost.

In this study, we developed a spread-gel-type sensor that can measure the surface temperature of objects and human body. Water solution of hydroxyethyl cellulose and sucrose was used as the gel. Fluorescent molecules were mixed in the gel as probes, and the fluorescence polarization, which shows a correlation with temperature due to the rotational Brownian motion of the molecules, was measured to obtain the temperature. In order to increase the accuracy of temperature measurement, models that take into account the heat transfer problem of the gel and the water evaporation effects on the sucrose concentration were discussed. We applied these models to the time distributions of the degree of polarization to first evaluate the gel thickness and evaporation rate, and then derive the temperature of the surface on which the gel was spreaded.

This paper presents a nonlinear circuit for rotational electret energy harvester for the first time. When rotating at 1 rps, 400 μW is obtained at a 5V load with a SECE prototype, which is twice of that with a conventional buck converter.

In this study, we introduce a novel micro-sampling device based on a micro-needle structure (diameter: 500 μm) aimed at extracting sample from the plant’s stem in a minimum invasive way. The micro-sampling device contains an inner needle, an outer tube, shape memory alloy actuator, and a 3D-printed platform. The design of the 3D-printed platform is introduced, which is crucial for control the movement of the micro-needle precisely. An experiment was designed to evaluate the sampling performance of the micro sampling device and experiment results indicate the great sampling performance of the micro-sampling device and its potential for being applied to extract sap sample from crops in a continuous basis.

In this paper, We report a method to minimize the anchor-loss in novel design of a ring resonator is reported. The effects of anchor size as well as stress cancellation mechanism were studied by numerical experiments. Resonators made of single crystal silicon were made by SOI process. The fabricated device could be electromagnetically driven and the motion was detected by laser Doppler velocimetry. The frequency mismatch was as small as 3%. Fabricated device provides very low mismatch between antinodes amplitude.

Dynamics in friction is studied from an atomistic point of view. Friction is formulated as a problem of whether or not a given kinetic energy for the translational motion dissipates into the kinetic energies for the internal motions during sliding. From the study of the Frenkel-Kontorova model with kinetic energy terms，it is found that two different regimes appear in a parameter space specifying the model: the superlubricity and the friction regimes. We have also found the peculiar frictional behavior in the specific frictional parameters， showing the abrupt decrease in the translational kinetic energy of a sliding body. Vibration analysis is performed using FFT to clarify factors leading to friction regimes.

The liquid metal is in a liquid state at room temperature and compatible with easily printing process. In this study, liquid metal composite composed of liquid metal, lithium titanate (LTO), and nickel powder was utilized as a conductive agent and binder for the printing process of lithium-ion batteries. Liquid metal electrodes were prepared by mixing the liquid metal with LTO and nickel powder as the anode. The composite was coated on copper foil to form an anode. Using the anode and counter electrode made by carbon coated LFP, coin cell was assembled and the functionality was evaluated. The results showed that the electrode could be used as the anode of the lithium-ion battery. This electrode is expected to be used for printed batteries, which lead easy integration and mechanical flexibility.

Until now, a lot of wearable devices which have stretchability have been developed. However, the devices have stretchability only in a sensor part, not circuit part or entire device. In this study, stretchable system which is composed of hard and soft hetero-polymer substrate and liquid metal electrodes was developed. The substrate consists of three layers, epoxy, PDMS and Eco-Flex. The electric components were mounted on the epoxy substrate, which prevent the deformation of a circuit. The circuit based on liquid metal electrodes was constructed on the PDMS and Eco-Flex parts. We succeeded in the development of the system and demonstrated the functionality of the system in this study.

To improve the accuracy of PCR (Polymerase Chain Reaction) tests, RNA molecules of viruses have to be collected from a small amount of specimen. For this reason, filter materials that have strong adhesion to RNAs are needed for the accuracy improvement. So, the author developed a materials informatics (MI) technology for selecting the best filter materials with strong adhesion to RNA molecules. In this study, the author has applied this technology to design the best ceramics with strong adhesion to RNAs that are contained in RNA viruses such as COVID-19 and SARS. Here, results of molecular dynamics simulations were used as the input data for the MI technology. As results of MI design, the best ceramics with strong adhesion to RNAs, whose interbase spacing is 0.338 nm, was found to be CaO-5%MgO, whose lattice constants were a=0.338 nm and b=0.585 nm, because coherent interfaces were obtained in these cases. It was confirmed that MI technology is effective for designing strong interfaces because the results was confirmed by scratch tests.

Body on a chip (BOC) replicate human physiological conditions by co-culturing human cell lines interconnected via a medium re-circulation. In this paper, we design and fabricate an integrated Heart-Liver on a chip with a microelectrode array (MEA) since a major challenge in BOC remains to monitor electrophysiological activities of cardiomyocytes in real-time upon the treatment of drug candidates. The MEA encapsulated by parylene-C films was patterned on polydimethylsiloxane (PDMS), that had enabled to seamlessly integrate into BOC having a pneumatic pump. The impedance magnitude of MEA measured under the condition of medium re-circulation shows a potential for recording field potential of cardiac electrical activities.

In this study, we propose a closed microfluidic chip for cell trapping, chromosome stretching, and fluorescence observation on a single chip in a quick and simple operation using centrifugal force. The proposed chip was fabricated using a mold fabricated in batches by 3D lithography with multiple masks. In cell experiments, more cells were trapped compared to the conventional open chip. Since the closed chip did not allow cells to drop out of the structure for rinsing to remove excess cells remaining on the chip, the rinse process improved the trapping rate in the case of the closed chip. In addition, a large number of chromosome stretching was observed on the closed chip.

We evaluated the effect of non-deformation regions that occur in the regions at both ends connected to the uncut regions when the kirigami structure is stretched. In addition, the purpose is to reduce the ratio of non-uniform deformed regions by non-deformation regions by devising a part of the structure at both ends. First, in order to evaluate the effect of the non-deformation regions, we measured the width length and the deformed amount in the longitudinal direction when the kirigami structure is stretched. As a result, it was shown that the effect of the non-uniform deformed regions equal to the number of cycles in the width direction. Second, in order to reduce the non-uniform deformed regions, we proposed a kirigami structure in which the width directions are separated by making cuts at both ends. Finally, when the proposed kirigami structure is stretched, the non-uniform deformed regions are reduced by 80%.

This study evaluated the characterization of vertical deformation on planar spiral structure composed by multiple beams. Planar spiral structures composed by one, two and three beams were fabricated by laser processing of PET film. The vertical deformation due to torsional deformation of the beam and the inclined deformation of the entire planar spiral structure due to bending deformation of the beam are evaluated theoretically and experimentally by measuring the vertical deformation along the beam when displacement is applied to the tip of each spiral structure. As a result, it is confirmed that the planar spiral structure composed by multiple beams have less inclined deformation than the structure composed by a single beam.

This paper presents the first compact MEMS rate integrating gyroscope (RIG) module for direct angle measurement and its experimental demonstration of position estimation. The 5-cm prototype module vertically integrates a vacuum-sealed MEMS RIG device, an analog front-end PCB, and a digital microcontroller PCB. Continuous angle measurement is confirmed with an angular random walk of 0.6 deg/rt-h and a bias instability of 4.3 deg/h, proving comparable noise performances with previous FPGA-based large RIG systems. The RIG module provides direct information of rotation angle, which eliminates the integration error of offset and noise occurred in the conventional rate-gyroscope based systems. In position tracking experiments of model train running (560-cm distance) and indoor pedestrian walking (88-m distance), the maximum position errors are 3 cm (0.5%) and 1.6 m (1.8%), respectively.

Blood plasma contains lots of biomarkers such as proteins and nucleic acids. However, preparation of the plasma is commonly operated in large research facilities by centrifugation. This research aids to develop a blood cell separation method on a paper microchip alongside the development of Point-of-Care Testing. In this study, the method of building a deposition barrier of micro-magnetic beads for solid and liquid separation inside a paper chip by magnetic force is investigated. The microscale thickness of a paper chip allows to effectively create and utilize the magnetic force to control micro-magnetic beads in a microfluidic flow.

The number of patients with chronic kidney disease is increasing worldwide and they have to undergo dialysis treatment three times a week for four hours. Therefore, we are developing an implantable dialysis device using MEMS technology to reduce the patient's burden. The device consists of acrylic microchannels and PES-PEG membranes. However, there is a problem of performance degradation of the dialysis membrane due to blood coagulation in the device. In this study, we coated the dialysis membranes with MPC polymer, an antithrombotic material, and observed changes of contact angles, changes of protein absorption by SEM, and measured the amount of filtrate before and after coating. We confirmed that MPC polymer could be coated on PES-PEG membranes and that the higher the concentration of MPC polymer, the better the hemocompatibility.

Plant roots receive the mechanical impedance from the soil during the growth process, thus the roots need sufficient strength to grow in the soil continuously. However, it is difficult to analyze the mechanical properties of growing roots quantitatively because the soil is naturally opaque. In this paper, we describe an on-chip analytical method using micropillar which is applicable to estimation of the mechanical properties of growing roots. We calculated the displacement of the micropillar during contacting with the root based on the finite element method and derived the equation to estimate Young’s modulus of roots. By using this method, we obtained the averaged values of estimated Young’s modulus of the roots in plant Arabidopsis thaliana: 1.0 MPa at 1/2MS medium and 0.39 MPa at 1/1000MS medium.

Monodispersity of giant vesicles (GV) is considered as an essential property for engineering cell-mimicking microreactors and drug delivery capsules. Here, we report a facile and highly reproducible microfluidics-based method to generate monodisperse water-in-oil-in-water (W/O/W) double emulsion with a thin oil layer as a template of monodisperse GV. A lipid monolayer is formed at the interface of the monodisperse W/O droplets generated by hydrodynamic flow focusing and the W-O laminar flow. When the W/O droplet and the W-O laminar flow interface come in contact, a lipid bilayer is formed, and the W/O droplet passes across the W-O laminar flow interface to form thin-shelled double emulsion droplets. Here we conducted the parametric study of the liquid and membrane compositions which produce stable droplet transfer.

We have developed a microdevice to investigate the relationship between cell behavior and gene expression in parallel at the single cell level. In this paper, we have developed a device combining a surface tension valve and a vacuum-driven pump to realize a heterogeneous introduction of solution into single chambers that contains cells. The surface tension valve was used as a passive valve to stop the flow of the solution without external control. A vacuum-driven pump was used to introduce the liquid into the multiple channels in parallel, and the device integrated with the two elements performed the two operations in sequence.

Geckos have a large number of fine hairs on their feet. The fine hair structure enables it to walk on the wall. Since this principle is easy to attach and detach and does not stain the bonded surface, research has been carried out to replicate this principle on an industrial scale. In this study, we adopted a method of reproducing the hairs by fabricating a matrix model using a three-dimensional optical lithography system and transferring them by UV nanoimprinting. The conventional UV nanoimprinting method has the problem of insufficient transfer to the tips of fine hairs. Therefore, in this paper, we performed UV nanoimprinting under a cohesive gas atmosphere to improve the transferability of fine hairs.

In this paper, we propose a low-frequency diaphragm vibration energy harvester with a 2D mechanical metamaterial structure in the elastic layer. In general, diaphragm-type devices have a higher resonance frequency than cantilever-type devices. However, the metamaterial structure of the elastic layer is used to reduce the bending rigidity of the diaphragm-type devices to achieve a low resonance frequency approaching that of environmental vibrations. After investigating the device shape by FEM analysis, a diaphragm-type device was fabricated by combining the organic sacrificial layer etching method with a multilayer deposition method of piezoelectric polymer film, which can be deposited on a relatively large area with high yield, and its vibration and power generation characteristics were evaluated.

In this study, we propose an interposer with frequency conversion function using bistable structure for a vibration energy harvester (VEH). The bistable structure consists of a buckling beam having a two dimensional structure. Therefore, the proposed device has high compatibility with the micro electro mechanical systems (MEMS) process and it is easily miniaturized, integrated, and mass-produced. Vibration analysis using the finite element method (FEM) and vibration tests using prototype device were performed to evaluate the vibration behavior and the frequency conversion characteristics. As a result of the experiments and calculations, it is possible to generate an acceleration higher than the input acceleration, which suggested a design guideline for interposer of the VEH.

In recent, nanoparticle identification technologies have attracted much attention in various research fields, where further high throughput and high accuracy of measurements are required. Herein, we propose a novel method to analyze single nanoparticles using a double-slit structure embedded in a nanochannel and an optical vortex. Single gold particles with a diameter of 200 nm are captured and manipulated by an optical vortex. Under an ionic current condition, the orbital motion of a particle around a double-slit structure is recognized by electrical spike signals, which achieves a sampling frequency over 30 Hz and works well to improve the measurement accuracy. It is suggested that the amplitude of the current pulse depends on the salt concentration and particle trajectory in liquids. Taking account of these factors, a relationship between the electrical signals and particle behavior is discussed.

In this paper, we report a method for achieving thin, single-layer, selective circularly polarized light absorption operating in the visible light region using spiral shaped Au nanochiral structures. The results of finite element simulations show that the Au nanochiral structures exhibited very strong selective circularly polarized light absorption in the visible light rigion. In addition, the operating wavelength is found to be highly dependent on the number of turns of the Au nanochiral structures. The Au nanochiral structure was fabricated to achieve the selective circularly polarized light absorption. Using vacuum evaporation, we fabricated an Au nanochiral structures with a cryogenic glancing angle deposition, which showed selective circularly polarized light absorption in visible light in simulations.

A novel integrated sensor has been fabricated for use in greenhouse facilities for monitoring environmental conditions, thus enabling a further understanding of their impact on plant growth. The device has been designed to measure the following parameters: light intensity, air temperature/ pressure/ humidity in addition to wind speed. The sensing units have been integrated onto a printed circuit board enclosed within a 3D printed case designed to enable each measurement through specific channels and openings. A radio model was placed on the board to enable the wireless transmission of data to a receiver gateway, while a solar panel and supercapacitor enabled the sensor to self-sufficiently power itself.

The development of nanotechnology has created huge potential to build highly sensitive, low cost, portable sensors with low power consumption. The extremely high surface-to-volume ratio and hollow structure of nanomaterials is ideal for the adsorption of gas molecules. In this study, we developed multi-walled carbon nanotube (MWCNT) paper-based gas sensor which is a low-cost solution and investigate the response of MWCNT gas sensors at room temperature. The multi-walled carbon nanotubes paper was prepared by filtration method. We measured resistance at 5 points for each CNT papers by four probes method to check uniformity. We suppose response fit to the Langmuir isotherm. The results show us: (1) The MWCNT paper gotten by this method has good homogeneity. (2) Sensor response is fitting to the Langmuir isotherm and we certified stable repeatability of this sensor by Langmuir isotherm.

In order to develop high performance hydrogen censor we fabricated the composite film made of carbon nanotube and palladium. Carbon nanotubes were spin-coated on a glass substrate and palladium and particles were sputtered on this film. The response to hydrogen was measure using vacuum chamber and introducing hydrogen/argon mixture. There was a clear difference in the sensor response even in the temperature difference between summer and winter. In addition, since a clean chamber was used, the number of water molecules used as a dopant yesterday was small, and the behavior that CNT changed from p-type to n-type due to dissociative adsorption of hydrogen was confirmed. This phenomenon was clearly observed as Seebeck effect.

All solid-state lithium ion battery is important for many technological applications. We focus on ion transport in the electrolyte. The purpose of our research is to understand the relationship between structural and ionic transport properties in two types of polymers, PEO and P(2EO-MO), with lithium salts LiTFSI by using molecular dynamics simulations. We calculated diffusion coefficients of Li and TFSI and their dependence on salt concentration ratio. Li ions are found to exist mainly as the dissociated state and the clustering state with multiple salts. The change in the Li diffusion coefficients is found to be attributed to the variations in the hopping times and distance for intra/inter hopping and cluster sizes.

In this study, we conducted non-equilibrium molecular dynamics simulation to elucidate the energy transport properties of the adsorbed layer of liquid (Ar) molecules in contact with the solid (Pt) wall, for a liquid-solid interfacial system. We focused on the energy transport at each adsorption site, and found that the heat transport through solid-liquid interface was enhanced due to the high density of liquid molecules at the hollow site for a strong liquid-solid interaction. On the other hand, the energy transports at top and hollow sites were almost the same for a weak liquid-solid interaction. The results also showed that the transport efficiency was higher around the top site than around the hollow.

Weakly nonlinear pressure waves in bubbly liquids were theoretically studied by deriving the KdVB (Korteweg–de Vries–Burgers) equation. Particularly, the energy equation at the bubble-liquid interface (Prosperetti, J. Fluid Mech., 222, 587, 1991) and the effective polytropic exponent were newly introduced into our model (Kanagawa et al., J. Fluid Sci. Technol., 6, 838, 2011) to clarify thermal effect inside bubbles mainly on wave dissipation. Thermal conduction was investigated in detail by using some temperature-gradient models. The main results are summarized as follows: (i) Two types of dissipation term appeared: one was a second-order derivative and the other was a term without differentiation. (ii) The thermal effect contributed to not only the dissipation effect but the nonlinear effect. (iii) The thermal dissipation effect in this study was comparable with that in a KdVB equation derived by Prosperetti (1991) although forms of dissipation terms describing the effect of thermal conduction differed.

We analyzed the transport properties of cerium ions, which were added to improve the chemical durability of a polymer electrolyte membrane (PEM), using molecular dynamics simulations. A system of the PEM, in which cerium ions were incorporated and the water flow was set, was constructed to investigate the convective ion transport properties. At a low water content, cerium ion diffusions are hardly affected by water flow because cerium ions are trapped by sulfonate groups of the Nafion polymer and the connectivity of water cluster is low. As the water contents increase, the water clusters are connected and the cluster size increases, leading to the increase in the free cerium ions that are moved away from the sulfonate groups. Hence, cerium ion diffusions are strongly affected by the water convection at high water contents.

A multi-material microstereolithography system in which multiple photocurable resins are stored on a single glass palette was developed to produce multicolor three-dimensional (3D) models. Multiple photocurable resins with different colors are replaced by moving a linear translational X-stage that supports the glass palette. A Z-stage moves radially to remove the air bubbles that adhere around the 3D model when replacing the resins. The uncurable resin was washed out by sequentially immersing the 3D structure in two tanks containing a cleaning solvent. This makes it possible to produce multicolor 3D models without contamination of resins and air bubbles.

Nowadays, social networks services have made it possible for us to talk each other without seeing in person. And the sense of each other’s presence is becoming less and less. One of the examples of touching is handshake. Handshake is the basis of communication. To reproduce the behavior of handshake, we made tactile gloves. we used pouches inside of the glove to apply pressure. To do so, we made a pouch with a liquid called NOVEC, whose boiling point is 34°C. Firstly, we measured the pressure distribution of the handshake. Next, we adjusted the size and placement of the pouch. Lastly, I adjusted the amount of NOVEC in the pouch. As a result, artificial pressure could be measured from the pouch with NOVEC. This approach is expected to be applied to other chances besides handshake.

Capillary force is attracting two objects while a liquid bridge is generated between them. By using the capillary force, it is possible to pick and place small objects having various shapes. In previous study, we have developed a mechanism for discharging a droplet. The mechanism is composed of a piston for pushing a liquid and a valve for preventing a back flow. However, it is difficult to discharge the droplet with a diameter of less than 1mm because the seal of the piston is not sufficient. In this study, we have improved the mechanism by replacing the piston pump to a diaphragm pump. In experiments, we have succeeded to discharge a droplet with a diameter of 0.5mm, half diameter of the previous mechanism. In pick-and-place experiments, we have evaluated the positioning errors of 1mm³ acrylic cubes and 0603 chip capacitors.

This paper describes a system that amplifies a change in structural color by integrating structures with negative Poisson's ratio and structural color gels. We built a theory of displacement in structures with negative Poisson's ratio. We measured the change of the structural color when acrylamide (AAM) hydrogel with colloidal crystals was pressed, and measured shrinkage ratio of a temperature-responsive poly N-isopropylacrylamide (PNIPAM) hydrogel. From above results, we fabricated the structure with negative Poisson's ratio and checked its motion. We believe that this system is an effective approach for the practical application of structural color gel sensors with high measurement sensitivity.

Flexible and soft actuators composed of gels do not damage the human body or delicate objects. That is why there is high potential demand for the gel-based actuators. Most of conventional soft actuators are driven by air pressure and heat shrinkage of gel, but their response speed is too slow to satisfy their demand for their potential bio-medical applications. In this study, we propose a soft actuator that enables high-speed response by using electromagnetic force. It is composed of liquid metal for electric wires and gel for its substrate, and by changing the direction of the electric currents flowing in the liquid metal in magnetic field, various movements such as expansion and contraction, and omnidirectional translation can be realized in water.

Copper wiring on nonplanar surfaces of PDMS substrates was demonstrated by using near-infrared femtosecond laser pulse induced thermochemical reduction of glyoxylic acid copper complex. First, the nonlinear optical absorption characteristics of glyoxylic acid copper complex were investigated by an open aperture z-scan method. The z-scan curves indicated that GACu complex exhibited the nonlinear optical absorption at around the focal spot. When femtosecond laser pulses were focused and irradiated into GACu complex films on glass and PDMS nonplanar substrates, a copper wire was successfully formed on the both substrates without significant oxidation in the atmosphere. The minimum line width on glass and PDMS were 24.01 μm and 10.8 μm, respectively. Electrical conductive Cu wires were formed on the PDMS nonplanar substrates. This technique enables us to fabricate Cu wires on various substrates.

In recent years, the demand for minimally invasive needles for diabetic patients has increased. In this study, we developed a method for manufacturing a resin hollow needle with a small diameter and a high aspect ratio by the nanoimprint method. In this method, a mother made using a high-precision 3D printer. A mold for nanoimprint was prepared by transferring the mold to PDMS. We succeeded in forming a mold at a lower cost and at a higher speed than the molding by the electroforming method used in the conventional method. In addition, by optimizing the molding conditions. We have also succeeded in producing a hollow structure with an outer diameter of 100 μm and a total length of 1 mm using polylactic acid, which is a biodegradable resin, as a raw material.

Heterogeneous device integration by 3D stacking of microfabricated devices is a promising approach to improve the functionalities of microdevices when miniaturization is approaching its limit. In this study, a novel wafer-level thermocompression bonding technique for heterogeneous device integration using electroplated Al thin film is reported. The Al bonding frames were fabricated by electroplating from a chloroaluminate ionic liquid. The bonding process was achieved using the cold welding technique at a temperature as low as 250°C. The electroplated Al bonding frame was mechanically deformed by the groove structures on the counter wafer, thus releasing a fresh Al surface which enables thermocompression bonding at such a low temperature.

To provide tactile feedback to human’s palm, the palm-based devices has been developed, which is equipped with tactile sensors. Currently, soft actuators are used to drive the artificial muscles in this device, but the presence of electrical wiring makes it difficult to achieve complex motions and make the device wearable. However, it is difficult to make the device wearable. Thus, we aimed to invent a palm-type device that does not require wiring by mounting an actuator and a tactile sensor in a palm-type device using liquid metal as the working fluid. As a first step, we have developed a palm-type device with a tactile sensor in the palm of hand.

With the increasing use of Internet of Things in various domains, which has led to an increase in the number of sensors being installed, it is indispensable to develop environment friendly sensor modules. Correspondingly, we investigated the formation of BiFeO₃ films as a lead-free ferroelectric material on DyScO₃ substrate. Experiments were performed to analyze the film formation process via the sputtering method, followed by heat treatment. Consequently, a BiFeO₃ film was formed with a single (110) orientation, and two types of bonds (FeO and Fe₂O₃) were observed. Additionally, no issues related to adhesion or peeling were found. Thus, the developed BiFeO₃ film can be potentially used as a ferroelectric material in various devices.

We have proposed and experimentally demonstrated an electrostatic operation to make one-dimensional stream of bacteria by dielectrophoresis for future bacteria counter detecting at single-cell level continuously. The key to the new design is the separation of the collection part and alignment part in a single stream of flow path. We investigated the concept by both the simulation using finite element method and experiment. As a result, we could improve the collection ratio up to 93% within 0.13s.

We have been developing an on-site water monitoring system available for continuous monitoring of residual chlorine in environmental water. It is required that this system has high robustness to realize stable monitoring under severe environment during years. However, mineral precipitates and biofilm are formed in a microchannel and deteriorate absorbance measurement. In previous studies, we have proposed and fabricated a Diamond like carbon (DLC) coated microchannel. DLC coating can prevent mineral precipitate, but cannot prevent biofilm forming(1). Then we proposed to overlay the biocompatible 2-Methacryloxyethylphosphorylcholine (MPC) based copolymer on the DLC coating(2). (This is abbreviated MPC/DLC/glass) Mineral precipitates on the MPC/DLC/glass were more suppressed than those on the glass. In the case of Staphylococcus aureus(S. aureus), which is known to form biofilm, the bacteria adhesion on the MPC/DLC/glass was 20 % or more lower than that on the glass.

Piezoelectret is a group of perforated space-charged polymer structures, and recently attract much attention due to their softness and high piezoelectric coefficients. Prototypes for tactile sensing and vibrational/kinetic energy harvesting are proposed. However, discharge of piezoelectrets during operation limits the output power. In this study, electret discharge mechanisms both in air and solid are investigated from breakdown perspectives, and an optimal design method is proposed. The design based on the present method is validated through discharge experiments as well as power generation experiments. With the optimized device, it is expected to generate 130 μJ energy per pushing cycle, which is 8 times higher than our previous one.

This paper describes the motion change of ethanol driven micro-robots by the stimuli-responsive hydrogel. The main components of micro-robot are thermal responsive hydrogel, silicone tube, and PDMS. The micro-robots are soaked in the ethanol solution, then the ethanol is filled in the hydrogel. The micro-robots can propel by the Marangoni effect caused by ethanol diffusion. The motion of the micro-robot is depending on the diffusion speed of ethanol. The diffusion speed of ethanol increase by shrinking of the stimuli-responsive hydrogel, thus the micro-robots can change the motion responding to the surrounding environment. At room temperature (25°C), the micro-robots exhibit the pulsatile motion. On the other hand, the micro-robots continuously propel at high temperatures (50°C). We believe that our proposed ethanol driven micro-robot could be applied to mimicking the behavior of micro-organism, elucidation of the principle of ordered motion, and self-organization.

Nanopore sensor attracts attention as a highly sensitive and selective detection mechanism of analytes at single molecule level. In previous studies, nanopore sensors were applied for detection of nucleic acids, organic molecules, and metal ions. However, the detection time of the nanopore sensors could take long at low analyte concentrations because the detection principle depends on stochastic phenomena. In this work, we studied the detection time of the nanopore sensor under stirring of solution containing the analyte. Stirring of solution was implemented by using gas flow at the surface of the solution. We observed and analyzed the influence of the stirring state on the detection time of methyl-β-cyclodextrin, which is a known nanopore blocker.