藤田 孝之

The size of conventional Geiger counters is large because the detector (GM tubes: Geiger muller tubes) is fabricated by mechanical processing. In this paper, an MEMS (micro electro mechanical systems) GM tube using a wafer level packaging is proposed. The MEMS-GM tube with glass/Si/glass stacked structure was fabricated by using anodic bonding and polymer bonding. With the supplied voltage of 2.6 kV to the MEMS-GM tube, pulse waves were observed when a radioactive material approached to the fabricated device.

To realize extremely low-power consuming sensor systems, a SOHI (Silicon on Honeycomb Insulator) wafer, which has ultra-small parasitic capacitance, is proposed and an accelerometer is fabricated to demonstrate use of the technique. In case of using a low-power-consumption switched capacitor measurement circuit, parasitic capacitance decreases sensor sensitivity dramatically. The concept of the SOHI wafer is a special SOI (Silicon on Insulator) wafer with the buried SiO2 layer replaced with a honeycomb-shaped SiO2 thick layer (20 mu m thick) to reduce the parasitic capacitance. In this paper, two types of SOHI wafer, which could reduce the parasitic capacitance to about 21% and 2% of typical SOI wafers, respectively are proposed. On a trial production, the structure of a prototype three-dimensional accelerometer is fabricated. By demonstrating the application of sensor fabrication, the SOHI wafer is shown as a useable material as the base substrate. Also, the ability to realize the accelerometer with low parasitic capacitance by using the SOHI wafer is demonstrated.

Continuous monitoring of human physical and mental conditions are heavily required solving issues to realize a high quality of life society. The human condition data especially; heartbeat, ECG (electrocardiogram), respiration and blood pressure are very important vital signs to prevent a human sudden disease, such as a heart attack. In this study, we fabricated a novel sensor to monitor the heartbeat and respiration, which is made on a flexible thin film of P(VDF/TrFE) as a sensing material and PDMS (poly dimethyl siloxane) as a substrate material. The PDVF (poly vinylidene fluoride) that is thin, flexible and piezoelectric material can be used for the flexible force sensor. The fabrication steps and some experimental results for human monitoring system are described.

Surface MEMS (microelectromechanical systems), which is fabricated by the microprocessing techniques based on thin film deposition and processing, are incorporated into consumer electronics and automobiles. The structures of the surface MEMS having thin shape with small aspect ratio are difficult to drive to the lateral direction. The conventional electrostatic actuators have comb electrodes, resulting in a complex structure. This research addresses on the actuators available to move in a lateral direction by using thin-film Pb(Zr,i)O-3. Test cantilevers with two segmented top electrodes on the piezoelectric film are fabricated and the driving characteristics are evaluated. Applications of electrical voltages with reversed phases to the segmented top electrodes at the resonant frequency with lateral oscillation mode moved the cantilever with large displacement of 7 mu m. A non-linear effect in the frequency response was also observed for the large applied voltages.

The efficiency of transportation system depends on many factors, such as traffic congestion, vehicle accidents and road conditions. To improve the reliability, productivity and safety of the system, many researchers propose to use a wireless sensor network (WSN) as a solution. A WSN usually consists of many tiny sensor nodes for sensing, data processing and communication. In this study, we present the development of a small-sized, low-power and lightweight wireless sensor node. It is equipped with a 3-axes accelerometer, an altimeter sensor, humidity sensor, temperature sensor, 315 MHz RF transceiver module and a typical coin-sized lithium battery (3.0 V, 220 mAh). The entire sensor node fits within a 28 x 20 x 8 mm(3) volume and is only 7 grams (not including the antenna). An 8-bit MCU is included in the RF transceiver module to control sensor node operation. It collects and transmits sensors data in real time to the RF repeater with bit rate 24 kbps. During continuous operation, the sensor node consumes less than 3 mA current. Thus for a 220 mAh battery, the wireless sensor node can continue operating for more than 75 hours.

This paper reports a fabrication process of pulse wave sensor and detection result of pulse wave using the ring-shaped sensor, which has ring-shaped photodiode. An LED is located at the center of a photodiode. This structure achieved noninvasive detection of the pulse wave and does not have the directivity. Therefore, the ring-shaped sensor is expected to reduce noises of body motion (motion artifacts). We evaluated the characteristics of the photodiode and detected the pulse wave using the fabricated sensor. As a result, the ring-shaped sensor can detect the pulse wave. Furthermore, detection of the pulse wave can be applied to measure the pulse wave velocity (PWV).

In this paper, fabrication method of acceleration sensor with low parasitic capacitance is descried. By using Silicon on Honeycomb Insulator (SOHI) wafer as a base material instead of Silicon on insulator (SOI) wafer, parasitic capacitance has reduced to 20%. The sensitivity of the acceleration sensor measured from differential capacitance change revealed 1.5 fF/G. The linear relationship between gravity acceleration and detection capacitance is measured by using commercial C/V converting circuit. By combining the SOHI acceleration sensor and specially designed C/V converting circuit with ultra-low power consumption, the sensitivity of the acceleration sensor can be expected to increase in 22 times than that for SOI wafer. The C/V converter circuit with ultra low power consumption of 1.13-mu W will realize long term and continuous monitoring of human activities by assembled with capacitive-type sensors based on SOHI wafer.

Electro-magnetically actuated Vibratory Beam Actuator (VBA) with high resolution and stability has been reported. The VBA senses acceleration from the frequency changes of the beams supporting a proof-mass. In this paper, piezoelectric PZT (Pb[Zr, Ti]O-3) thin films are employed to actuate the beam and to sense the vibration frequency for miniaturizing the VBA. Well-established fabrication processes including dry-etching PZT are applied to the VBA fabrications. For the acceleration sensing by using VBA, a self-oscillation system, which includes phase-lock-loop (PLL) to maintain resonant oscillations of the beams is constructed. Gravity sensing test, i.e. inclining the sensor, demonstrates a good linearity between applied acceleration and sensing signal. The VBA, promising as a next generation accelerometer, is miniaturized to the area of 4 mm(2). (C) 2012 Elsevier Ltd .... Selection and/or peer-review under responsibility of the Symposium Cracoviense Sp. z.o.o.

This study presents a wafer-level batch fabrication technique of NdFeB film for MEMS (Micro Electromechanical Systems) based electromagnetic type energy harvester. By using 20 mu m thickness NdFeB sputtered magnetic film on a trench-etched Si microstructure, fine patterned magnet structures for energy harvester had been realized. However the size of the sputtered sample was limited to the slightly small size. In this study, we improve the sputtering equipment to apply the NdFeB film process on a four-inch Si wafer. The film characteristics, estimation of the compatibility with the MEMS process and also energy harvesting result are presented. (C) 2012 Elsevier Ltd....Selection and/or peer-review under responsibility of the Symposium Cracoviense Sp. z.o.o.

In this study, an electret charging method for fabricating energy harvester with SiN/SiO_2 film that is selectively charged by using biased electrodes is demonstrated. Inorganic material of SiN and SiO_2 have high thermal robustness to endure the soldering temperature and the electret charging method by using the biased electrode doesn't require physical patterning of the electret film. Our charging method to SiN/SiO_2 film, a fine patterned electret with highly thermal robustness is obtained.

In this paper, we presented a measurement of power output versus acceleration with a data logger. The vibration energy harvester consists of a Si grid, a vibration mass, which has a charged electret film, and a cover glass. The data logger can measure voltage outputs, acceleration, temperature, humidity, and electrocardiogram (ECG). Accelerations and output voltages from the harvester were measured by 10 bit ADC (analog-to-digital converter) and the sampling frequency was 125 Hz. The power output at different accelerations on modal thruster is calculated by the output voltage from the harvester and the 20 MΩ load resistance. The power output was proportional to acceleration and the maximum generated power was 17.3 nW. The generated power worn on ankle while walking was 2.1 nW.

This study demonstrates the electret type inertial energy harvester for low-frequency vibrations such as human movements. Because a moving mass of the harvester is supported by the very soft spring, the mass collides easily with the frame structure. This collision induces the higher natural frequency vibration to the mass even at the applied vibration frequencies below the natural resonant frequency, which improves the efficiency of the power generation. The fabricated device generated the power of 1.8 nW(rms) for applied vibration of 20 Hz and 200 mu m(p-p) with the optimal load resistance of 32 MO. The packaged device size is 0.23 cm(3) and the weight of the moving mass is 122 mg. (C) 2011 Published by Elsevier Ltd.

A pilotage is one of important factors in order to keep a safety and a security of main harbors in Japan; however, pilots' marine accidents sometime happen while they work. The pilots' accidents happen well for the transfer from vessel to pilot boat on the sea, and pilots and pilots' associations do their best for reducing the accidents under International Maritime Organization (IMO) convention. In other word, a safety measure for the transfer is the important subject for pilots. The purpose of this paper is to evaluate a pilot's physical performance while their work using large model sensors (acceleration sensors), and we read characteristics of performance for the transfer. This research is first challenge to evaluate the pilots' performance in real situation.

Continuous observation of human activities and circumstances are quite important to improve the QoL (Quality of Life). A small device that can collect a lot of data of the human conditions and circumstances by suing various MEMS (Micro Electro Mechanical Systems) sensors is very useful device to prevent the human accidents or troubles. The accidents especially happen to the professional driver or pilot e. g. the operator of the human centered transportation systems cause a serious accident. This study demonstrates a prototype development of an autonomous multi-environmental sensing device for human applications that can measure various time-based data, simultaneously. The measured data are stored in a micro SD card memory via an onboard microcontroller, which will be help for data analysis and preventing the accidents. The detailed configurations of the prototype device and some experimental results are also shown.

Thick silicon dioxide with good heat insulation properties can reduce the parasitic capacitance and heat conductivity in sensors and actuators. This research focuses on the evaluation of the mechanical properties of the silicon dioxide microstructure fabricated by using trench etching and oxidation process in order to use it for movable elements. in MEMS devices. The elastic modulus is estimated from the resonant frequency of fabricated cantilevers. It revealed comparable values to that of bulk SiO2. Non-linear characteristics such as hardening and softening spring effects are observed dependent on the patterning direction of trench etching. (C) 2011 Published by Elsevier Ltd.

水先業務において、海上における水先要請船舶と水先艇間における移乗による乗下船は、水先人にとって身体的危険を伴う労働環境の一つである。そして、死亡事故に至ることが全国発生件数から見れば3年に1人の頻度で生じている。本研究では、伊勢三河湾水先区の三級水先修業生を対象に、乗下船時の身体運動を小型加速度センサーにより測定し、得られた身体運動の知見から乗下船時における安心・安全について検討、考察する。

This study describes fabrication and measurement of an electromagnetic type energy harvester by using buried NdFeB Film. The energy harvester is fabricated by bonding a vibrator with buried micro-magnets and a stator with integrated microcoils. Performance of the micro-magnet is enhanced by improved methods of mechanical polishing of buried NdFeB. It is expected that the power output of the energy harvester with the improved micro-magnet will be enhanced to about 50 times as much as the previous work.

In this study, an electret based energy harvester with a single silicon structure that shares harvesting counter electrodes and charging grid is demonstrated. The shared electrode achieves the batch fabrication process that can avoid the charge leakage from the charged electret. The mass structure supported by the thin Si spring has resonant frequency of 40Hz. The harvesting demonstration showed the 0.23μW at 10Hz, 0.1G with load resistance of 1MΩ.

It reports on the exploratory experiment of a hybrid wafer with two or more die wired for each other in this thesis. The cavity is formed to the wafer, and individual die is arranged there (die is MEMS device and LSIs, etc.). The surface of the wafer and the surface of the dies are made smooth with the resin, and flat wiring is done to the electrode pads of individual die by the photolithography technology. The accumulating mounting to which other wafers are sticked together in using the flip-chip technology and the TSV technology on the wafer can be done. As a result, it becomes possible to raise the package density from a past wafer-level packaging technology further. © 2010 TSI Press.