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The physical sensors have been playing an essential role in realizing various electronic control systems. This paper describes the basics of these physical sensors including their classification, operation principals and the relevant MEMS sensors, followed by the history of their developments.

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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.

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Currently, pressure sensors are used in various fields such as industrial process applications, automotive applications, the portable information equipment. Sensor detection method suitable for the environment and the measurement range of the fluid used has been developed. In this paper, the author describes the applications and the basic structure of a MEMS pressure sensor that contributed to the development. And describes the history technical challenges of the development, as well as the expected future technology.

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More than 24 billion high-sensitivity InSb thin-film Hall elements with the ferrite sandwich structure have been fabricated and applied over the last 30 years. The technologies and application of the high-sensitivity thin-film Hall elements or Hall sensors are discussed in conjunction with present and historical status. They have been used to develop many kinds of very small DC brushless, or Hall motors and also have been applied to many key devices such as contactless sensors, switches, current sensors and many kinds of home-use electrical systems and car sensors. More than 90% Hall elements were used to fabricate Hall motors which were strongly required from electronic and information systems developed mainly at the final 20 years term of last twenty century.

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Thermal infrared focal plane arrays and small-format infrared array sensors are attracting much attention for extending our sense of sight. These infrared sensors are manufactured with the MEMS (Microelectromechanical Systems) technology, which is a powerful method to fabricate high thermal isolation structures. This paper reviews basics and state-of-the-art of MEMS-based infrared sensors. Business trends in the low-end infrared sensor market are also discussed.

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The article reviews recent progress of CMOS image sensor technology. The fundamental performance of CMOS image sensors has been steadily improved in the past 20 years by the introduction of pinned photodiode active pixels, amplifier sharing techniques, column A/D converters (ADCs), back-side illumination and 3D stacking. The new function and new applications of imaging technology are opened up with low-noise global shutters, wide dynamic range pixels, high-performance column ADCs, on-chip analog frame memories, and lock-in pixel technologies.

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In this paper, we investigated influence on plant bioelectric potential by basic human behaviors. We analyzed four basic human behaviors such as touching the plant, opening the door, approaching the plant and turning on the lighting. As a result, the special response of bioelectric potential were influenced by each behavior. Bioelectric potential shows the impulse responses due to the behavior. Therefore we tried to learn and recognize human behaviors by extracting a characteristic from plant bioelectric potential. The method to recognize basic human behaviors that we propose uses a low level ingredient of cepstrum of plant bioelectric potential. Some data didn't recognize correctly because of individual difference of human behaviors, however, F-measure became an average of 0.76. It shows that the proposal method may be effective way to recognize basic human behaviors from plant bioelectric potential.

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Acoustic emission (AE) sensor is attractive to detect machine fracture in real-time. We fabricated AE sensors using MEMS technology. The AE sensors consist of silicon cantilevers resonating at the frequencies of 50kHz, 100kHz, and 150kHz. Silicon piezoresistors are installed close to the cantilevers. In order to obtain the ambient pressure appropriate for the operation of cantilevers, the Q factor of cantilever is calculated by the analytical models as a function of pressure. The properties of fabricated sensors were measured in vacuum chamber. We also tentatively packaged the AE sensor and an amplifier in vacuum to decrease the influences of air damping and noise.

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A high output voltage micro thermoelectric generator (µTEG) has been developed by fabricating thermocouples having a high aspect ratio with a high integration density. They have been made by a novel and simple fabrication method, in which thermoelectric nanopowders are filled in a photosensitive glass mold by using aerosol deposition (ASD). This method has a possibility to increase the aspect ratio of thermocouples drastically while increasing their toughness and increasing their thermal resistance. We have fabricated thermocouples with an aspect ratio of 3.3 and a high integration density of 620 TCs/cm². Their Seebeck coefficient and electrical resistivity are 290 µV/K and 1.5 mΩcm, respectively. The µTEG reaches a thermal resistance of 3.6 K/W·cm², output voltage efficiency of 0.18 V/K/cm², and output power efficiency of 18 µW/K²/cm². These HAR thermocouples have an advantage for energy harvesting from a human body because they can result in a high temperature difference because of their high thermal resistance.

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In this paper, we report the numerical calculation and experimental verification of a quartz-crystal-resonator-based methanol concentration sensor for fuel cell applications. This sensor is composed of a quartz crystal resonator (QCR) and an interdigital capacitor (IDC). Our sensor can detect a very small capacitance change with a resolution of sub fF. The fabricated sensor can measure a methanol concentration with a resolution of 0.008 wt%. In the present study, we found out optimized sensor design (QCR and IDC) for the substrate thickness and the range of the methanol concentration. By the use of this study, the capacitive sensor with higher resolution can be realized, and it can be expected to apply to various types of capacitive sensors.

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A novel method has been proposed to detect proximity and tactile information using a single MEMS sensor. Tactile information is obtained from DC resistance change of NiCr strain gauge film. In contrast, proximity information is obtained from AC impedance change, which is caused by photo-absorption of Si wafer irradiated by a neighboring LED. Therefore, selection of the information to be acquired is performed by switching the DC and AC measurement system. Experimental results show almost linear tactile output to indentation of 0 to 0.5mm and non-linear proximity output to distance of 0 to 50mm, respectively. Moreover, the sensor is able to acquire rough shape of a toroidal object by proximity measurement.

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For strict application of food hygiene regulation such as hazard analysis - critical control point system, the development of rapid and simple measurement scheme for biological particles is essential. Recently, a hybrid method using dielectrophoretic manipulation and micro fluidic operation has attracted attention for the bioparticle detection. However, the influence of electrode structure on the dielctrophoretic force has not been fully understood. For effective design of dielectrophoretic devices, it is important to investigate quantitatively the capture characteristics. In the present work, we numerically simulated the particle dynamics in the capture region of a dielectrophoretic micro device with interdigitated electrodes. The dependence of dielctrophoretic force on the electrode width and gap length showed that there was the maximum of capture height of particles for adequate electrode structure. Furthermore, the number of captured particles was accurately evaluated in consideration of the effective region ratio. Under typical condition, the number of captured particles almost agreed with the experimental result.

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The Science-day is a event that provides people of all ages with hands-on workshops under the concept of “Feel the process of Science”. For the next generation , we would like to develop a community in which people can become close to science as part of their culture, by modeling “local production for local consumption” of Science and Technology.

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[in Japanese]

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