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In the field of silicon on nothing (SON) structure [1], micrometer-thick monocrystalline layers suspended over their parent wafer were produced by high-temperature annealing of specific arrays of trenches. Those trenches reorganize into one single void and leave a thin overlayer on top. Since this method may be an easy way of synchronous fabricating high-quality silicon films and vacuum void, this paper investigates its potential applications for a pressure sensor. A capacitive absolute pressure sensor whose pressure sensitive membrane is formed by the SON structure was fabricated and evaluated. The radius and thickness of the sensitive membrane are 100 and 1.7-mu m, respectively. The average sensitivity of the sensor array with 15 diaphragms is 2.88 fF/kPa. This novel fabrication process enables to easily form a high vacuum cavity without hermetical sealing process such as anodic bonding technology, to achieve an excellent long-term stability and reliability, in particular, and to easily integrate detection circuits with the sensor.

© Published under licence by IOP Publishing Ltd. This article introduces a MEMS batch fabrication process of micro magnet array with bipolar magnetic pole for an electromagnetic vibration energy harvester. In order to obtain the large electromotive force from large magnetic flux density change, we established the fine patterned alternating magnetized bipolar magnetic structure. The batch fabrication process of bipolar magnet array is composed of two wafers processing with S-pole and N-pole magnetization and bonding process. By the prototype fabrication of bipolar magnet with the 200 μm SN-interval, we showed the usability of the batch fabrication process of the bipolar magnet array. In addition, we estimated the generated power of energy harvester with a bipolar magnet array. Compared to a harvester with monopolar magnet array, we showed the good result for bipolar one.

© Published under licence by IOP Publishing Ltd. This paper shows a design optimization of MEMS (Microelectromechanical Systems) electromagnetic energy harvester by using finite element method (FEM) analysis to obtain a maximum generated power. The electromagnetic energy harvester consists of the sputtered NdFeB magnet film on a high-aspect-ratio corrugated Si structure and a counter Au serpentine coil. The each dimension of the device is optimally designed by using FEM simulation. After the prototyping with MEMS fabrication process, the measurement results of the power generation are 2.65 mV of the induced electromotive force and 7.60 nW of the output power with optimum load resistance of 231 Ω at the vibration condition of 100 Hz, 294 μmp-p.

© Published under licence by IOP Publishing Ltd. In this study, the improvement of energy harvesting from wideband vibration with random change by using a combination of linear and nonlinear spring system is investigated. The system consists of curved beam spring for non-linear buckling, which supports the linear mass-spring resonator. Applying shock acceleration generates a snap through action to the buckling spring. From the FEM analysis, we showed that the snap through acceleration from the buckling action has no relationship with the applied shock amplitude and duration. We use this uniform acceleration as an impulse shock source for the linear resonator. It is easy to obtain the maximum shock response from the uniform snap through acceleration by using a shock response spectrum (SRS) analysis method. At first we investigated the relationship between the snap-through behaviour and an initial curved deflection. Then a time response result for non-linear springs with snap through and minimum force that makes a buckling behaviour were obtained by FEM analysis. By obtaining the optimum SRS frequency for linear resonator, we decided its resonant frequency with the MATLAB simulator.

A coupled thermal-structural model of a gas-sealed capacitive pressure sensor is presented. The gas-sealed capacitive pressure sensor is used specifically for human activity monitoring, to measure atmospheric pressure in our research. A mechanical temperature compensation structure is utilized to reduce the thermal drift of the gas-sealed pressure sensor. In order to determine the compensation results of the temperature compensation structure, a thermal-structural model is presented. Classical laminated plate theory is used to derive the equations of equilibrium for clamped circular laminated plates containing one or more layers. Methods to estimate the model parameters and types of compensation structures are discussed, and model verification via experimentation is presented. The findings indicate that the resultant model is relevant, thus enabling the design of a mechanical compensation structure for a gas-sealed capacitive pressure sensor, to reduce thermal drift. (C) 2013 Elsevier B.V. All rights reserved.

© Published under licence by IOP Publishing Ltd. This paper presents an evaluation of an electrostatic vibration energy harvester with the bipolar charged electret. The energy harvester with the size of 13 × 12 × 1.2 mm3 was fabricated. The output power of the bipolar charged with ±250 V harvester was 9 μW when the acceleration was 1.4 g at 352 Hz with 0.9 MΩ load resistance. The effectiveness against the velocity-damped resonant-generator (VDRG) limit was 2.5%. The electrostatic forces of the actual device with DC bias, which simulates charged electret with monopolar and bipolar were experimentally and numerically verified. We estimated the electrostatic force by measuring the vibration amplitude versus applied acceleration of the electret mass. As a result, we investigated the bipolar charged device can reduce the effect of electrostatic force as low as no bias condition. The numerical model of the energy harvester considering the electrostatic force by FEM static analysis was also established. The comparison between the numerical model and the measurement results showed a similar inclination.

© Published under licence by IOP Publishing Ltd. In this study, we report an equivalent circuit model of an electrostatic energy harvester for a SPICE circuit simulator. In order to simulate a harvesting system, the output power of the device is calculated in the simulator. The capacitance between the electrodes is obtained by FEM analysis by taking the fringing effect into account and the result is applied to a sub-circuit model for the simulator. Mechanical vibrations are converted into electricity by an equivalent circuit model of a mass-spring structure and an electrostatic energy harvester. The simulated output power and output waveform correspond with the measurement results of our electrostatic energy harvester. We also simulate the operation of a harvesting system connected with a power management IC.

This paper demonstrates successful deposition and etching of Pb[Zr,Ti]O₃ (PZT) thin films on pre-etched Si substrate with pits having depths of several hundred micrometers. Conventionally, for fabrication of microelectromechanical systems, PZT films are deposited onto a flat substrate because of inherent difficulties associated with stable deposition and processing. We successfully established the fabrication of PZT thin films and electrodes on non-flat and pre-etched substrate by using sputtering deposition and projection exposure techniques. The evaluation results reveal that the PZT thin film deposited onto the pre-etched substrate has good ferroelectric characteristics, including piezoelectric d₃₃ constant of 80 pm/V.

The objective of this paper is to evaluate pilots' body and physiological performance during their works using a large model sensor (tri-axial accelerometer and atmospheric pressure sensor) and a heart rate monitor toward safe harbors. The dis/embarkation experiment is carried out for the real pilotage. The results show that the largest acceleration 1.5-2.0 G appears during transfer from a pilot ladder to a pilot boat, and the sensor read their behavior at the ladder. The atmospheric pressure detected a height change. The heart rate read his mental workload for the decision-making for ship handling.

We proposed a standard three-layer feedforward neural network based human activity estimation method. The purpose of the proposed method is to record the subject activity automatically. Here, the recorded activity includes not only actual accelerometer data but also rough description of his/her activity. In order to train the neural networks, we needed to prepare numerical datasets of accelerometer which are measured for every subject person. In this paper, we propose a fuzzy neural network based method for recording the subject activity. The proposed fuzzy neural network can handle both real and fuzzy numbers as inputs and outputs. Since the proposed method can handle fuzzy numbers, the training dataset can contain some general rules, for example, "If x and y axis accelerometer outputs are almost zero and z axis accelerometer output is equal to acceleration of gravity then the subject person is standing."

This paper shows the fabrication of the prototype of electromagnetic MEMS energy harvester and the power generation experiment al results. The electromagnetic energy harvester consists of the sputtered NdFeB magnet film on high aspect ratio corrugated Si trench and the Au serpentine coil. The each structure of the device is fabricated with the optimum geometry designed by the FEM simulation. In the result, we obtained 2.65 mV of the induced electromotive force and 7.60 nW of the output power. The experimental results agreed well with simulation results, and we confirmed the usefulness of the analytical method for the estimation of the power generation.

This paper demonstrates successful deposition and etching of Pb[Zr,Ti]O3 (PZT) thin films on pre-etched Si substrate with pits having depths of several hundred micrometers. Conventionally, for fabrication of microelectromechanical systems, PZT films are deposited onto a flat substrate because of inherent difficulties associated with stable deposition and processing. We successfully established the fabrication of PZT thin films and electrodes on non-flat and pre-etched substrate by using sputtering deposition and projection exposure techniques. The evaluation results reveal that the PZT thin film deposited onto the pre-etched substrate has good ferroelectric characteristics, including piezoelectric d33 constant of 80 pm/V. © 2014 The Institute of Electrical Engineers of Japan.

We designed and evaluated ASICs (Application Specific Integrated Circuits) for the human activity monitoring systems to reduce the total power consumption. The ASIC extracts the heart rate from measured ECG (Electrocardiogram) raw signal. To realize the ASIC with ultra-low power consumption, we used novel algorithm based on fuzzy logic which is very simple and light processing. The fabricated ASIC shows sufficient function and low power as low as 2 µW.85% of the power consumption for MPU (Micro-Processing Unit) processing was cut by using the heart rate extraction ASIC.

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Previously, we have developed a human monitoring system, which used 8051 microcontroller. The system has a 3-axis acceleration sensor, a pressure sensor, a humidity sensor, and an electrocardiogram (ECG) circuit. This paper reports the newly developed system by using PSoC (Programmable System-on-Chip), which is a microcontroller with some analog blocks in a single chip. The ECG and the acceleration are sampled at 125 Hz, the others are at 1 Hz by the PSoC. The sampled data are stored on the micro SD card or Static RAM (SRAM), transmitted by a Bluetooth module or USB interface to a PC. The multipurpose I/O pins for addition of some sensors are designed in the system. The multipurpose I/O pins are utilized to control and communicate with an infrared temperature sensor. The system was designed and fabricated by 4-layer printed circuit board (PCB). In comparison with the previous work, the system size was reduced from 85×48×15 mm³ to 50×50×15 mm³, the power consumption without Bluetooth communication was reduced from 45.0 mA to 24.6 mA when the power supply voltage is 3.3 V and the master clock is 48 MHz.

This paper describes a human activity monitoring system including various MEMS sensors. Currently, health care devices are in the limelight because aging of society has been progressing and it is required that we should take care our health by ourselves without the help of younger people. For health care, a continuous monitoring system for human activity is effective. The patch type devices, which are installed directly on the body, are one of the candidates for suitable human monitoring system that watches over the daily activity and physical and mental conditions. In this paper, background of the work, current status, requests to the devices and example devices will be shown as well as the example data for activity monitoring. Finally, future demands for the monitoring system are discussed.

For elderly people, we imagined an eating monitoring system, that detects electromyogram (EMG) signals by tiny electrodes mounted on artificial teeth. Thus, by placing the electrodes on gums of participants, we investigated the relationship between EMG signals and tongue motions, and evaluated the possibility of the eating detection. Concretely, the EMG signals were measured by two pairs of silver balls (ϕ1mm) used as the electrodes, and the balls were located on participants' gums at neighborhoods of right-and-left canine and molar teeth. It was found that EMG signals could be detected by using only the one pair of the tiny silver ball electrodes located on the gum at the neighborhoods of the canine or molar teeth. Moreover, it was also found that two tongue motions of sticking out and pressing to palate could be recognized by using the two pairs of the electrodes located on the gum at the neighborhoods of the canine and molar teeth. From the facts, eating motions may be detected by analyzing the EMG signals.

This article is dealing with current status and trend of acceleration sensors and angular rate sensors (gyroscopes). Recently, MEMS acceleration sensors and gyroscopes are widely used for consumer electronics, such as cellular phones and digital cameras, as well as equipment in plants and automobiles. In the devices, the cost and size are constantly reduced whereas their performances are increased. In this paper, basics of an acceleration sensor and gyroscope and example structures of them are shown and some trends of the devices are discussed.

本研究では、小型で省電力なMEMSデバイスによる身体状態モニタリングシステムを提案する。提案手法ではMEMSデバイスから収集される3軸加速度とECGのそれぞれのデータを利用して、対象人物が何をしているときにどのような状態であるかを推定し、それが対象の普段の状態であるのか、異なるのかを判断する。

Continuous human monitoring will be substantially useful to realize a high quality of life society. In the previous work, we fabricated a prototype system for monitoring an electrocardiograph, heart rate (HR), 3 axes human body acceleration and temperature for human body and human circumstances, simultaneously. These data are transmitted to the host PC and analyzed for the human activities or conditions recognitions. Above all a heart rate variability (HRV) that calculated from HR is extremely valuable for recognizing a mental or physical stress of human subjects. In this study, we demonstrate a fuzzy logic HR extraction algorithm on the daisy chain shaped wearable prototype device to realize an autonomous HRV monitoring system. On-board fuzzy logic algorithm not only reduces the communication traffic but also improves an accuracy of the HR extraction comparing to the simple threshold methods. © 2013, TSI® Press.

A novel fabrication method for nanoscale tubular structures is presented in this paper. The tubular structures can be obtained by heating single-crystal silicon trenches or pillars formed by the inductively coupled plasma reactive-ion etching (ICP-RIE) Bosch process in hydrogen ambient. The importance of initial vacuum in the reaction chamber for tube formation and the tube formation mechanism were discussed. The components and sidewall size of the tubular structure were also studied to verify that the tube is made of the fluorocarbon (CF) passivation layer deposited by the Bosch process. The CF tubular structure would be a promising structure for BioMEMS. (C) 2013 The Japan Society of Applied Physics

This paper presents a wearable PPG (photoplethysmographic) sensor system with a PSoC microcontroller unit. The PSoC includes a CPU, analog and digital blocks to configure mixed-signal circuits, and an internal oscillator in a single IC package. The PSoC allows designers to reduce the number of external discrete devices and the system size. The novel PPG sensor system consists of a photo interrupter, the PSoC, and the Bluetooth module, which are on PCBs (Printed Circuit Boards) of 18, 13, and 10 mm in diameter, respectively. The photo interrupter detects the pulse wave due to the change in volume of blood vessels. The PSoC also includes an analog filter, amplifiers, and digital circuits to calculate HR (heart rate) from the pulse wave of human body. The system could detect the pulse wave and transmit the HR data to a host PC wirelessly. The supply voltage is 3.3 V, and the total current consumption is about 51 mA. In comparison with our previous work, the area of discrete RCL (resistor, capacitor, and inductor) devices was reduced from 1230 mm2 to 466 mm2, the number of those devices was reduced from 26 pieces to 6 pcs, and the weight of the system was reduced from 13 g to 7 g. We also investigated a pulse voltage driving method for the LED of the photo interrupter to reduce the current consumption of the LED. And we describe an energy harvester for autonomous power source for the monitoring system. © 2013 Copyright TSI® Press.

We have investigated annealing conditions for producing silicon-on-nothing (SON) structures with extremely flat surfaces by high temperature annealing of high-aspect-ratio hole arrays fabricated on Si(001) surfaces. In the phase immediately after SON structures are formed through the surface-diffusion driven evolution induced by high temperature annealing, the SON surfaces are rough. We show that additional annealing after the SON structure formation at high temperatures, where preferential sublimation from step edges occurs, effectively removes the surface roughness to yield SON structures with extremely flat (001) surfaces with fairly low step densities. (C) 2013 The Japan Society of Applied Physics

A microfabrication process for poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) based flexible piezoelectric devices is proposed using heat controlled spin coating and reactive ion etching (RIE) techniques. Dry etching of P(VDF-TrFE) in CF4+O-2 plasma is found to be more effective than that using SF6+O-2 or Ar+O-2 feed gas with the same radiofrequency power and pressure conditions. A maximum etching rate of 400 nm/min is obtained using the CF4+O-2 plasma with an oxygen concentration of 60% at an antenna power of 200 W and a platen power of 20 W. The oxygen atoms and fluorine atoms are found to be responsible for the chemical etching process. Microstructuring of P(VDF-TrFE) with a feature size of 10 mu m is achieved and the patterned films show a high remanent polarization of 63.6 mC/m(2).

Vertical Si nanowires with ultra-high-aspect-ratio were fabricated using a combined process of deep reactive ion etching and sacrificial oxidation. The combined process starts with etching the Si substrates by the Bosch process to form micrometer-scale structures. The etched micrometer-scale structures are shrunk to nanometer-scale by sacrificial oxidation. The fabricated Si nanowires that were aligned vertically to the substrate had a diameter of less than 200 nm and a length greater than 10 mu m. One of the fabricated Si nanowires had a diameter of 110 nm and a length of 11 mu m. The resulting aspect-ratio reached 100, which is a value that is significantly high for vertical Si nanowires fabricated by using a top-down approach.

We have investigated annealing conditions for producing silicon-on-nothing (SON) structures with extremely flat surfaces by high temperature annealing of high-aspect-ratio hole arrays fabricated on Si(001) surfaces. In the phase immediately after SON structures are formed through the surface-diffusion driven evolution induced by high temperature annealing, the SON surfaces are rough. We show that additional annealing after the SON structure formation at high temperatures, where preferential sublimation from step edges occurs, effectively removes the surface roughness to yield SON structures with extremely flat (001) surfaces with fairly low step densities. © 2013 The Japan Society of Applied Physics.

This study addresses the design optimization of the electromagnetic energy harvester consisting of the sputtered NdFeB film on a high aspect ratio corrugated Si structure and Au electroplated serpentine coil. The high-aspect-ratio Si structure has advantages that the magnetic flux density change is caused by distance change between the coil and magnet film on the fine-patterned corrugated Si, and it is easier to fabricate with high yield than previous study. We also optimized design parameters such as width and depth of the trench, coil size by using FEM analysis and theoretical calculations. Assuming the mass size of 10×10 mm2, the trench depth of the 400 μm, the vibration amplitude of 40 μm p-p and the vibration frequency of 100 Hz, the maximum output power of 12 nW and the maximum electromotive force of 4 mV are obtained for 60 μm and 80 μm magnet widths, respectively. © Published under licence by IOP Publishing Ltd.

Monolithic fabrication of lead zirconate titanate [Pb(Zr,Ti)O-3 or PZT] based thin film resonant devices such as microcantilevers, Lamb wave and bulk acoustic wave resonators are demonstrated. High-performance PZT thin films with a thickness of 2.6 mu m are prepared on a silicon on insulator wafer by a sputtering deposition process. A highly selective reactive ion etching process is employed for micro-patterning of PZT, platinum electrodes, and SiO2 insulation layer. Self-actuation of the PZT microcantilevers is demonstrated and the frequency response is characterized using a laser Doppler vibrometer. The frequency response of the Lamb wave resonator is evaluated by measuring its transmission characteristic using a network analyzer. For a Lamb wave resonator with a length of 240 mu m and an interdigital period of 80 mu m, the 1st order and 2nd resonance frequencies are 15.3 and 41.8 MHz, respectively.

This paper reports depositions of double layers of thick Pb(Zr, Ti)O-3 films in order to realize piezoelectric bimorph structures for MEMS(micro electro-mechanical systems) applications. The PZT/PZT bimorph with the total thickness of 5.4 mu m, deposited by magnetron sputtering system, is much thicker than conventionally reported ones. The optimization of the sputtering conditions and electrode structures results in preferable electric and ferroelectric characteristics for both top and bottom PZT layers. In addition, the characteristics of the two layers are consistent with each other.

For monitoring and estimating our daily activity, some kinds of devices are available. One of such kinds of monitoring devices is a MEMS based prototype which is developed by the Maenaka Human Sensing Fusion Project. We have developed a estimation method of human activity from three-axis acceleration data using the above-mentioned prototype. This method can estimate our unit activities, such as (1) walking, (2) running, (3) sitting, (4) lying, and (5) standing. In this paper, we propose a system that can find unusual situation from ECG data. Our proposed system is based on the fuzzified neural networks. The fuzzified neural network is trained by using sensing data with reliability grade. Since the fuzzified neural network learns normal state of the subject person, we can understand the ECG state of the subject when we analyze fuzzy outputs from the trained fuzzified neural network. This paper shows estimation results by using actual monitoring data which contains normal state, and artificial unusual data. From the results for the actual monitoring data, we can see that our proposed system was able to estimate the testing data as normal. From the results of estimating artificial unusual data, our proposed system can find the subject person's unusual situation. (C) 2013 The Authors. Published by Elsevier B.V.

The proposed time-to-digital converter is based on a Schmitt trigger monostable multivibrator and an external thermistor with a negative temperature coefficient. It is used to implement an ultra-low-power (105 pJ/conversion measured) temperature sensor. The sensor has significantly lower power (1/250) than state of the art diode/ADC temperature sensors. The proposed temperature sensor also dissipates 1/3 of the power of state of the art frequency-to-digital converter (ring oscillator) based temperature sensors. Furthermore, the proposed circuit is robust to process and power supply variation due to the ratiometric nature of the Schmitt trigger threshold levels. Two precision analog components, an on-chip MIM capacitor and an external thermistor, are used to set the gain of the sensor. All other circuitry in the proposed temperature sensor is digital, and the output is the measured temperature in a 2's complement, 8-bit digital code with the LSB representing 0.5°C. © 2013 IEEE.

In this paper, a bipolar charging method for electrostatic vibratory energy harvester and its analysis result of electrostatic force are described. To improve the harvesting power, higher voltage charged electret with large capacitance change structures are extensively studied. However, the higher voltage also shows a higher electrostatic force, which prevents the device movement for harvesting and causes pull-in behavior. From the result of FEM analysis on bipolar charged electret, the electrostatic force for vertical and horizontal directions were reduced by 15% and 10% from negative only charged device, respectively. © Published under licence by IOP Publishing Ltd.

A sea pilot supports a captain to steer the huge vessel in a harbor and a bay where has a special geographical feature. The pilotage is one of important factors in order to keep a safety and a security of main harbors worldwide. In their works, the marine accident sometime happens, and it always did for the transfer from a vessel to a pilot boat in the sea. The pilots and pilot's associations do their best for reducing the accidents under International Maritime Organization (IMO) convention. The purpose of this paper is to evaluate a pilot's performance while their work using large model sensors (acceleration and atmospheric pressure sensors), and we read characteristics of performance for their work. This research is first challenge to evaluate the real pilots' performance.

This paper presents a SPICE modeling of piezoelectric energy harvesting (PEH) device. We developed a wireless sensor system with the PEH device as an application. The PEH device is composed of a stainless cantilever, which has a piezoelectric film on the both side surface. The PEH device oscillates at resonance frequency when the tip of the cantilever is plucked. In SPICE simulator, an equation of motion of the cantilever is described to express a mass-spring-damper system by behavioral source. The stress of the piezoelectric film is computed by theoretical calculation and FEM analysis. Then, the stress, the piezoelectric coefficient d31, and the area of the film surface formulate the electrical charge. The output voltage is given by the charge varying and an inherent capacitance. The comparison between an analysis and an experiment is represented. The output power of theoretical calculation and measurement are 310 μJ and 920 μJ respectively has occurred by plucking once. We also developed a prototype system of WSN node utilizing the PEH device. The system transmits the temperature data a few times by plucking once. © 2013 IEEE.

This paper presents a design optimization of a novel electromagnetic MEMS energy harvester by using a fine patterned NdFeB array with a serpentine shaped coil for gathering electromotive force. The serpentine coil can be easy to be fabricated in comparison with a spiral coil that fabricated in the previous work. The magnetic flux density is calculated by FEM analysis. The various line-and-space parameters of the magnet and the coil are investigated for the optimization of the output power. The electromotive force and the output power are calculated by a theoretical equation. As a result of optimization, the electromotive force of 31.3 mV and the output power of 0.722 μW are obtained when an applied vibration amplitude is ±200 um at 595 Hz with magnet line and space of 70 μm. © 2013 IEEE.

This paper reports fabrication and evaluation of reflectance type pulse oximeter with ring-shaped photodiode. The pulse oximeter can measure a blood oxygen saturation (SpO(2)). SpO(2) is used as an index of respiratory diseases. Therefore measurements of SpO(2) prevent apnea syndrome and asthma. We have developed a system for measuring SpO(2) in daily life. A small and stably measurable sensor is required for the system. Because of realization of the sensor, LEDs are located in the center of a ring-shaped photodiode. This structure collects lights from all directions for reducing noises of body motion. In a previous study, a pulse wave sensor using the ring-shaped photodiode was fabricated, and could measure the pulse wave. In this paper, the improved sensor to measure SpO(2) is shown. Photodiodes is evaluated on current-voltage characteristics.

This study shows a development of an ultra low power application specific integrated circuit (ASIC) that extracts R-R intervals from electrocardiogram (ECG) data on a human monitoring system. The continuous human monitoring is substantially useful to realize a high quality of life human society especially for elderly people who live alone. However, it is difficult to realize such a system that can operate longtime without maintenances because of its battery limitation. A micro controller unit (MCU) has to be continuously operated to samples the ECG waveform, which is known as one of a power hungry device in the system. In order to reduce the power consumption of the MCU, an ultra low power ASIC for ECG feature extraction is developed for replace a role of MCU to extract the R-R intervals of ECG feature values.

In this study, we report the optimization of electrode design for increasing output power of the vibration electrostatic energy harvesters. The output power depends on the capacitance change and its frequency. Without consideration for fringe effect of a parallel-plate capacitance, the narrower electrode pitch L is, the larger output power. However, under actual conditions, power output is limited by fringe effect. To consider fringe effect, the optimum electrode dimension changes due to the distance between the electret and counter electrode. By using FEM analysis with fringe effect, we find the characteristic of fringe effect at parallel-plate capacitor, and then the optimum width of counter electrode fFand electrode pitch L are obtained.

This paper shows the optimization of the structure of the electromagnetic energy harvester consisting of the sputtered NdFeB film on high aspect ratio Si trench and the Au serpentine coil. The magnetic flux density change is caused by distance change between coil and magnet film on the corrugated Si. In order to maximize the harvesting energy, the optimum parameters such as width, depth of Si trench, and coil size are investigated by FEM analysis and theoretical calculation. Assuming the trench depth of 400 μm the vibration amplitude of 400 μm_<p-p> and the frequency of 100 Hz the maximum output power of 12 nW and the maximum electromotive force of 4 mV are obtained by 60 μm and 80 μm, respectively.