前中 一介

© MYU K.K. I have reviewed bulk micromachining and surface micromachining as techniques for the fabrication of MEMS sensors. These techniques are used differently depending on their purposes, and both are considered to be the main techniques for fabricating various sensors. I have introduced monolithic integration of sensors and circuits as an elegant technique in this session. Although the current mainstream is that sensors and integrated circuits are fabricated on different chips and are connected in a package, I suggest that monolithic integration is ultimately preferable, and await future solutions to the technical problems.

© MYU K.K. I have outlined the advancement of sensors and network sensing systems. It is said that in the future we will enter the Trillion Sensors Universe, a society in which trillions of sensors are required per year. The "trillion" is not an overestimation. Sensor networks are a composite technology involving information processing, wireless systems, circuits, energy, sensors, and related materials. I expect that Sensors and Materials will contribute to the above society in the field of sensors and materials.

© MYU K.K. Through the five sessions of this series with the theme of Sensors in Network, I have explained the developmental history, current status, and future prospects of sensors and their applications and technologies by focusing on sensors that will be used in the future IoT and Trillion Sensor Universe society. Although the concept of the sensor network itself was proposed previously, sensors, processors, RF technologies, power sources, and network infrastructures have made progress and enabled everyone to construct sensor networks easily. As mobile phones were evolved into new devices (beyond telephones) by becoming equipped with a camera function, sensor networks still have a room to receive novel ideas and greatly change to new ones. I expect the future progress of sensor networks.

© 2016 The Institute of Electrical Engineers of Japan. This paper demonstrates an improvement in the generated power of a NdFeB electromagnetic vibration energy harvester by optimizing the device dimensions considering a mass-damper-spring system and the Lorentz force. The electromagnetic harvester follows a velocity-damped-resonant-generator (VDRG) model. When the electrical and mechanical attenuation coefficients are equivalent and the device is operated at a resonant state, the maximum power will be obtained. In this paper, we simulated and optimized the power generation considering a mass-damper-spring structure and the Lorentz force. From our simulation results, we determined an optimal design for 100 Hz and 3 μmp-p of sinusoidal external vibration to generate 0.42 μW of power from the device with a 10 × 10 × 0.5 mm3 active harvesting area and 50 of Q-factor. This exhibits power that is 43 times larger than the previous design.

© MYU K.K. I have described the features of combo sensors as sensor devices that are used in sensor nodes to efficiently collect multiple types of data. In addition, I have discussed the transmission of data to networks and its frequency, and also mentioned network topology. In the next session, I will explain the system for monitoring biological activities as a concrete application example of sensor nodes.

Multimorph structure of Pb(Zr,Ti)O-3 (PZT) thin films by using sputtering deposition, which is compatible with batch-fabrication, was realized for the applications of low voltage driving and large generative force actuators. Test microcantilevers with four layers of PZT thin film were fabricated by dry etching of PZT with metal thin films on a four inch wafer, without deterioration of piezoelectric performance. All PZT layers worked well as piezoelectric material and an actuation test revealed a four-fold displacement per voltage compared with single layer actuations. In addition, a limit of the number of laminated layer for PZT multimorph was also evaluated from point of the view of total stress index.

In a bay and harbor, a coastal radio station (port radio) supports a safe navigation of vessels supplying useful information, and a port coordinator who is an operator of the port radio serves the works. The navigator recognizes the navigational situation from own ship centered relation among other vessels, and the port coordinator does from the whole situation. These good relations keep safe navigation in the bay and harbor. The mental workload using a physiological index is useful to read the performance of ship bridge teammates. Moreover, the index is useful for the port coordinator. In this study, we aim the port coordinator's mental workload, and propose that a physiological index and body acceleration read their mental workload and performance for real situations. We think the monitoring of mental workload links the bay and harbor conditions. The result shows the heart rate and body accelerations read their mental workload and performance well.

In this study, we propose a novel fishing support system using millimeter size acceleration sensors for detecting fish bite. On the base of field test, rod top acceleration of vibration with fish bite and its human cognition were investigated by sensor measurement and verbal communication, respectively. As a result, it was shown that an experimental participant could not cognize all of fish bites that were detected by the sensor. Thus, the validity of the fishing support system with the acceleration sensor mounted on a rod top was confirmed.

In this paper, we present a SPICE equivalent circuit model of an electrostatic vibration energy harvester. The SPICE model consists of a generation part and a mass-spring system part considering electrostatic force. The change in capacitance between electrodes with the position of the mass is analyzed by FEM analysis and is applied for the generation part. For investigating the characteristics of the actual harvester, the harvester was fabricated and charged by a -200 V monopolar potential. The maximum output power of the monopolar-charged harvester is 1.1 µW with applied vibration amplitude of 350 µm_pp at 323.3 Hz with 0.8 MΩ optimum load resistance. We confirmed that the examined and analyzed results indicate high correspondence.

© Published under licence by IOP Publishing Ltd. In this study, we report an improvement of output power from an electret type vibration energy harvester. Typical crossing-area change harvester has a stripe-shaped electret and counter electrode for making the capacitance change. In order to improve space efficiency, the counter electrodes are divided and arraignment with the same pitch of the electret. We investigate that adjoining the counter electrodes, the fringing effect is decreased and the capacitance change between the electrodes is larger than the conventional design from FEM analysis. The output power of 2.5 μW and 5.3 μW are obtained in each kind of counter electrode with the applied acceleration of 3 G at 350 Hz, which is about 2 or 4 times as high as our previous work.

© Published under licence by IOP Publishing Ltd. The narrowing air-gap between coil and magnet of electromagnetic energy harvester is one of the most important parameter to improve the generated power. Because of the sputtering 15 pm thickness NdFeB/Ta multilayer film with high temperature annealing, the large curvature distortion is occurred on Si substrate. In this paper we demonstrate a compensation method for residual stress on the sputtered NdFeB magnetic film on Si wafer. By using both-side sputtering method, we reduced the residual stress, which reduces the reliability of MEMS fabrication and performance of harvesters, from 144 MPa to 9.4 MPa. The electromagnetic type energy harvester with narrow gap of 20 μm was successfully fabricated and evaluated.

© 2015 The Japan Society of Applied Physics. Multimorph structures composed of multiple thin-film piezoelectric layers and electrode layers were realized by sputtering deposition. Cantilevers with four layers of Pb(Zr,Ti)O3 (PZT) thin film are fabricated and evaluated. The electrical and piezoelectric characteristics of each PZT layer are very similar and are comparable to those of conventional single-layer PZT thin film. The piezoelectric constant d31 is estimated to be %38.3pm/V from the relationship between tip displacement and applied voltage under the condition of driving four all piezoelectric layers. The generative force is also estimated from the tip displacement. It is confirmed that multimorph cantilevers have larger generative force than those of conventional unimorph and bimorph cantilevers for identical driving voltage.

Multimorph structures composed of multiple thin-film piezoelectric layers and electrode layers were realized by sputtering deposition. Cantilevers with four layers of Pb(Zr,Ti)O-3 (PZT) thin film are fabricated and evaluated. The electrical and piezoelectric characteristics of each PZT layer are very similar and are comparable to those of conventional single-layer PZT thin film. The piezoelectric constant d(31) is estimated to be -38.3pm/V from the relationship between tip displacement and applied voltage under the condition of driving four all piezoelectric layers. The generative force is also estimated from the tip displacement. It is confirmed that multimorph cantilevers have larger generative force than those of conventional unimorph and bimorph cantilevers for identical driving voltage. (C) 2015 The Japan Society of Applied Physics

We studied the effects of increasing the thickness of bimorph structures containing double layers of Pb(Zr,Ti)O-3 (PZT) thin films. Thick PZT films allow high-voltage application (e.g. in terms of coercive electric field and breakdown voltage) and large generative force, which are effective in microelectromechanical systems (MEMS) applications. Improvement of the deposition conditions and electrode structures facilitates the fabrication of the thin-film PZT/PZT bimorph structure. The PZT/PZT bimorph with a total thickness of 5.8 mu m, deposited using a radio-frequency (RF) magnetron sputtering system is much thicker than conventional bimorph structures. The characteristics of the two piezoelectric layers were similar to each other and revealed good electric and ferroelectric characteristics with a remanent polarization of 20 mu C cm(-2) and a coercive electric field of 50 kV cm(-1). PZT/PZT bimorph cantilevers were fabricated in order to evaluate their characteristics for actuator applications. The residual stress of the bimorph cantilever was reduced by an annealing process. The vibration test on the fabricated bimorph cantilevers during electrical voltage application revealed a twice as large displacement as compared with a single layer actuation, and the piezoelectric coefficient value d(31) was estimated to be -61 pm V-1, which is better than the value of conventional PZT/PZT bimorph cantilevers (-13 pm V-1). It was also shown that the influence of the temperature change is much less than that in unimorph structures with similar dimensions. The evaluated results demonstrate that the PZT/PZT bimorph structures are effective as MEMS devices.

This paper reports a batch fabrication process combining piezoelectric Pb(Zr, Ti)O-3 (PZT) thin films with photosensitive polymer SU-8. Fabricated PZT/SU-8 structure shows small stiffness and less brittleness. In addition, the piezoelectric characteristics are equivalent to conventional PZT thin films on Si substrates. From the result of actuation experiments of cantilevers, the PZT/SU-8 structures show excellent flexibility. This allows 1-mm long cantilever to actuate at bending angle over 90 degrees without breaking.

In this paper, a design improvement of combination spring that consists of linear resonator and curved beam for nonlinear vibration energy harvesting is described. The intrinsic curved beam for snap-through buckling acts as mechanical frequency converter (MFC) that applies high frequency acceleration to the linear resonator. We newly designed the parallel curved beams to reduce the force required for snap-through and maximum stress during snap-through behavior. From FEM analyses, the force and the stress are reduced from 35.4 mN to 10 mN and from 350 MPa to 200 MPa, respectively. (C) 2015 The Authors. Published by Elsevier Ltd.

The evaluation of mental workload using a pysiological index is useful to read the performance of ship bridge teammates: a captain, a duty officer, a helmsman, and a pilot. The physiological indices, heart rate variability (R-R interval), salivary amylase and nitrate, and facial (nasal) temperature, are fine indices for picking up during their ship handling. It usual evaluates for veteran-seafarers on both of simulator and real ship by subjective evaluations; however, we think it is not enough, and need to utilize the numerical values for mental and performance evaluation. This paper proposes that physiological index and body acceleration do well for evaluating navigator's mental workload and performance for real ship and simulator-based ship handling. The result shows the heart rate variability and body accelerations read their mental workload and performance well.

Recently, given Japan's aging society background, wearable healthcare devices have increasingly attracted attention. Many devices have been developed, but most devices have only a sensing function. To expand the application area of wearable healthcare devices, an interactive communication function with the human body is required using an actuator. For example, a device must be useful for medication assistance, predictive alerts of a disease such as arrhythmia, and exercise. In this work, a haptic stimulus actuator using a piezoelectric pump is proposed to realize a large displacement in wearable devices. The proposed actuator drives tactile sensation of the human body. The measurement results obtained using a sensory examination demonstrate that the proposed actuator can generate sufficient stimuli even if adhered to the chest, which has fewer tactile receptors than either the fingertip or wrist.

This paper describes flexible and stretchable wiring for human monitoring systems by using magnetic powder conductor buried in the hollow tube of the silicone rubber substrate. The conductor powder was coated with Au sputtering and Cu plating for improving conductivity. From preliminary results of fabrication and measurements, the wiring shows resistance of few k Omega for over 40% stretch ratio.

The evaluation of mental workload using a pysiological index is useful to read the performance and the stress of ship bridge teammates: a captain, a duty officer, a helmsman, and a pilot. The heart rate variability (HRV) and facial temperature are fine indices for picking up during their ship handling. Moreover, in recently, the Micro Electro Mechanical Systems (MEMS) is popular worldwide, we can get a sensor by moderate price, and we are easy to compose some sensors freely-air temperature, humidity, air pressure, acceleration, and so on. We are able to evaluate the mental workload and the performance together without the stress of wearing the sensor, and it will lead to develop a healthcare monitoring system for navigators. We think we can prevent the human error by the monitoring system. In this study, we measure the HRV and body accerelations using a large model sensor, and show the results of pilot as a first step of the research.

We developed MEMS bi-stable spring for vibration energy harvester (VEH), which consists of intrinsically curved shape spring and gravitational acceleration. By applying the gravitational acceleration, the curved beam is offset to the gravity direction. It will make more symmetrical bi-stable motion and the symmetry is improved from 3.3 to 65.4%. We proposed that the combination between curved beam and gravity acceleration for decreasing snap-through acceleration. From the analytical result, we investigate the combination can effective to use for decreasing of snap-through force. We also fabricated the prototype device by using MEMS fabrication process. The frequency response for horizontal direction and the acceleration response for vertical direction are measured. The acceleration response shows that the gravitational acceleration improves the symmetry of snap-through force.

For the continuous and long term healthcare monitoring of human, low power ASICs (Application Specific Integrated Circuits) are designed. The ECG (Electrocardiogram) signal is acquired and amplified by the ECG head amplifier. The analog ECG signal is converted into digital one by using the ADC (Analog to Digital Converter). The digital ASIC converts the raw ECG signal into heart rate. The characteristics extraction can reduce the total power consumption of the system. To realize low power consumption of the ASIC, an algorithm based on fuzzy logic, which is very simple and light processing, is employed. The novel system with these circuits cuts down 80 % power consumption compared with the conventional prototype system.

In this paper, we present a design approach for electrostatic energy harvester under low acceleration. In electrostatic energy harvester, the electrostatic force that prevents mass movement or causes pull-in is occurred due to the charged electret. We propose a dual-phase electrode arrangement and bipolar charged electret to reduce the electrostatic force. Utilizing dual-phase electrode arrangement or bipolar charged electret, the electrostatic energy harvester can reduce electrostatic force both vertical and horizon directions in a static condition from FEM analysis. It is found that the approached electrostatic energy harvester can generate more power than conventional structure in a low acceleration from SPICE equivalent circuit model. In addition, the air-gap can be smaller and the limited output power can be higher by reducing vertical electrostatic force.

This paper presents an equivalent circuit model of an electrostatic energy harvester for a SPICE circuit simulator. The output power and impedance of the proposed model are approximated by using a simplified model of a voltage-controlled capacitor. The relationship between the capacitance and the electrode position is calculated by FEM analysis by taking the fringing effect into account; this relationship is applied to a sub-circuit model for the SPICE simulator. Further, the results of this study show that the output waveform and the optimal resistance obtained using the SPICE simulator correspond with the measurement results. In addition, the operation of a harvesting system connected with a commercially available power management IC is demonstrated.

This paper presents an electrostatic vibration energy harvester with a bipolar-charged electret for high output power and for low electrostatic force. In conventional electrostatic energy harvesters, electrets are charged by monopolar charge (mainly by negative) with a high potential for large power harvesting. We propose a bipolar charging method in order to form an electret, which not only has negative charge but also positive charge. The electrostatic energy harvester, with a size of 13×12×1.2 mm³, was fabricated and charged by a -250-V monopolar potential and by a ±250-V bipolar potential. The maximum output power of the monopolar- and bipolar-charged harvester is 3.1 µW and 9.8 µW, respectively with an applied acceleration of 7 g at 352 Hz with a 0.9-MΩ load resistance. The output power is 9 µW at 1.4 g and the maximum effectiveness against the velocity-damped resonant-generator (VDRG) limit is 2.5%. By using the bipolar-charged electret, the high output power obtained from the high charging potential was compared to a conventional harvester charged by the monopolar method. Further, using the finite element method (FEM) analysis, we determined that the electrostatic force that prevents harvesting mass movement is significantly reduced on the bipolar-charged electret. The electrostatic forces under static conditions along the vertical and horizontal directions obtained through the FEM analysis were reduced to 15% and 20%, respectively, from those of the monopolar-charged electret.

In order to establish a novel healthcare monitoring system for elderly people, this paper investigated temporal change of intraoral temperature during drinking cold/hot water and breathing. The temperatures were measured by four sensors located extensively on the palate. As a result, it was shown that from the temperature changes during drinking and breathing, there exist the possibility of these feeding behavior detection.

We designed and evaluated low power ASIC (Application Specific Integrated Circuits) for the human activity and health monitoring systems to reduce the total power consumption. The ASIC extracts walking and running steps and holds the maximum and minimum values from raw data of acceleration sensor. To realize ultra-low power consumption, the algorithm is designed to reduce the amount of the data calculation for pedometer. Power consumption was reduced to 15% from previous prototype system by using the designed ASIC.

This paper presents an electrostatic vibration energy harvester with a conventional monopolar-charged and a novel bipolar-charged electret. The maximum output power of the -200 V monopolar-charged and ±100 V bipolar-charged harvester were 1.1 µW and 0.9 µW, respectively with a vibration amplitude of 350 µm_pp at 323 Hz with a 0.8 MΩ load resistance. The bipolar-charged harvester generates higher output power than the monopolar-charged harvester with an applied acceleration from 0 g to 0.7 g, because electrostatic force of the monopolar-chaged electret along the vibration direction prevents harvesting mass movement compared to the bipolar-charged electret. Further, we analyzed a SPICE model with electrostatic force and confirmed that the characteristics were according to the experiment results.

In this paper we describe a small-sized and extremely low-power consumption transceiver module for a wireless sensor network, especially suitable for biosignal transmission. Currently, many types of transceiver modules such as Bluetooth, ZigBee, and low-power radio modules for 315 MHz are available on the market. However, when we consider an extremely small and light system including a battery and transceiver module for a wireless sensor network mounted on the human body, almost all the transceiver modules on the market consume too much power and are too large for assembly. In this study we concentrated on creating an extremely low-power consumption and small/lightweight transceiver module for the 315 MHz radio band. As a result, we successfully designed and fabricated a transceiver module with a size of 11 x 11 x 1.5 mm(3) including a bipolar ASIC for the radio circuit and an eight-bit microcontroller. The operation currents of the receiver and transmitter are 2 mA and 1 mA, respectively, for a supply voltage of 2.5 V. These results are generally sufficient for many uses for wireless sensor network systems, and not only for biosignal applications.

© 2014 TSI Press. For maintaining our daily healthcare, we need to understand our own physical condition. In understanding such data, additional information such as what the subject is doing at that time is needed. For example, let us assume that we have a record of a certain heart rate 90. If such value is observed when the subject person was sleeping, that value is high and the subject may have some trouble on his/her health. On the other hand, when the subject was running, the subject has no problem on his/her health. In this paper, we propose a combined system for maintaining our healthcare. Our proposed system consists of both systems; (1) a fuzzified neural network based unusual condition detection and (2) a standard neural network based action estimation. The proposed system can handle multiple kinds of sensors' data. In this paper, the following three kinds of sensors were handled; (1) three-axis acceleration data, (2) heart rate, and (3) breathing rate. From experimental results, the effectiveness of our proposed system is shown for understanding our conditions.

体に貼り付けることのできる小型バイタルセンシングノードについて、我々の研究成果を述べる。我々は、将来的にはディスポーザブルとなるようなバイタルセンシングノードについての研究を行ってきた。研究分野は、MEMS技術を核に、小型センシングノード実現に有効な基礎材料・加工技術、センサ、発電、柔軟基板、低消費電力集積回路、市販部品を用いたデモモデル、などである。本稿では、成果をようやくしたうえで、バイタル量としてもっとも基本的な心電波形取得についての具体的な回路例とその特徴を述べる。

エレクトレットを用いた静電型エナジーハーベスタは,振動マスにエレクトレットを成膜・荷電し対向電極との静電誘導で発電するデバイスである.そのため,発電電力や電力が最大になる最適負荷はマスの振動周波数や振幅によって大きく変化する.電気回路シミュレータ(SPICE)では可変容量のモデルを作成することで,時間変化に対する電極間の容量変化を表すことができる.そこで,本研究では有限要素法を用いてフリンジ効果を考慮した電極間の静電容量を解析し,その結果を等価回路モデルに利用することで,SPICEシミュレータ上でマスの動きに対するハーベスタの発電波形や最適負荷を解析した.その結果と実デバイスとの比較を行うことで,SPICEの等価回路モデルが発電量や最適負荷の見積もりに有用であることを確認した.

世界的な少子高齢化、社会の複雑化によるストレスやそれに起因する大きな事故などをうけ、各個人で実行可能な(病院へ行かなくても状態把握ができるという意味で)分散的健康管理が注目を浴びている。身体に装着するタイプの生体モニタリングシステムは、継続的モニタリングや強制的モニタリングが可能で、特に直接皮膚に貼り付ける絆創膏のようなデバイスでは、心電や筋電、体表温、発汗などのバイタルサインを直接精度良くモニタリングできるというメリットを持つ。本稿では、このようなウエアラブル・ヘルスケアシステムについて述べる。

世界的な少子高齢化、社会の複雑化によるストレスやそれに起因する大きな事故などをうけ、各個人で実行可能な(病院へ行かなくても状態把握ができるという意味で)分散的健康管理が注目を浴びている。身体に装着するタイプの生体モニタリングシステムは、継続的モニタリングや強制的モニタリングが可能で、特に直接皮膚に貼り付ける絆創膏のようなデバイスでは、心電や筋電、体表温、発汗などのバイタルサインを直接精度良くモニタリングできるというメリットを持つ。本稿では、このようなウエアラブル・ヘルスケアシステムについて述べる。

世界的な少子高齢化、社会の複雑化によるストレスやそれに起因する大きな事故などをうけ、各個人で実行可能な(病院へ行かなくても状態把握ができるという意味で)分散的健康管理が注目を浴びている。身体に装着するタイプの生体モニタリングシステムは、継続的モニタリングや強制的モニタリングが可能で、特に直接皮膚に貼り付ける絆創膏のようなデバイスでは、心電や筋電、体表温、発汗などのバイタルサインを直接精度良くモニタリングできるというメリットを持つ。本稿では、このようなウエアラブル・ヘルスケアシステムについて述べる。

世界的な少子高齢化、社会の複雑化によるストレスやそれに起因する大きな事故などをうけ、各個人で実行可能な(病院へ行かなくても状態把握ができるという意味で)分散的健康管理が注目を浴びている。身体に装着するタイプの生体モニタリングシステムは、継続的モニタリングや強制的モニタリングが可能で、特に直接皮膚に貼り付ける絆創膏のようなデバイスでは、心電や筋電、体表温、発汗などのバイタルサインを直接精度良くモニタリングできるというメリットを持つ。本稿では、このようなウエアラブル・ヘルスケアシステムについて述べる。