The gas monitoring system for elders' apartment using QCM sensors was newly developed. The QCM sensors for sulfide gas and ammonia gas were used for this system. The system for bodily wastes was fabricated and applied to nursing care system in elders' apartment. This system is composed by the sensor unit, communication unit and data server. Care person can see whether the linen should be changed or not without seeing over each room. The QCM sensors have some problems such as the interference of humidity and temperature, therefore these influences were dissolved using humidity sensor and temperature sensor as feedback source. The sensors were placed in several points of elders' apartment for 2 weeks. This system can be used in elders' apartment successfully.

View full abstract

A micro capacitive inclination sensor was developed by using micro machining techniques. Electrodes of the sensor are 40 μm in a gap and 12 mm² in area. The sensor detects difference of capacitance, which varies with movement of silicone oil accompanying with inclination of the sensor, but there is a problem of surface tension caused by the narrow gap of the electrodes. In order to solve the problem, novel structures of the sensor for injection of the oil into micro channels and retaining a horizontal plane of the oil were devised. As a result, downsizing of the sensor was realized.

View full abstract

In order to develop a high temperature (200°C∼400°C) and high sensitive NO_x gas sensor, we developed a new structure of SiC-based hetero-junction device Pt/SnO₂/SiC/Ni, Pt/In₂O₃/SiC/Ni and Pt/WO₃/SiC/Ni using a laser ablation method for the preparation of both metal (Pt) electrode and metal-oxide film. It was found that Pt/In₂O₃/SiC/Ni sensor shows higher sensitivity to NO₂ gas compared with the Pt/SnO₂/SiC/Ni and Pt/WO₃/SiC/Ni sensor, whereas the Pt/WO₃/SiC/Ni sensor had better sensitivity to NO gas. These results suggest that selective detection of NO and NO₂ gases may be obtained by choosing different metal oxide films.

View full abstract

Silicon through-hole interconnections filled with Au-Sn solder by Molten Metal Suction Method (MMSM) have been developed. They are expected to realize wafer-level package of various devices such as Micro Electro-Mechanical Systems (MEMS), RF devices and some sensors. In this paper, RF characteristics of the through-hole interconnections were examined. Co-planar type circuits including one signal line and two grand lines were used for the measurement. Each line has two through-hole interconnections connected electrically by Cu wiring. The diameter of the through-holes was 80 μm and the thickness of the substrate was 200 μm, respectively. S-parameter S₂₁ was measured from 0.1 GHz to 8 GHz. The thickness of SiO₂ insulation and the resistivity of the Si substrate were especially focused on. Transmission loss of 1.2 μm SiO₂ sample at 1 GHz was 0.86 dB and that of 0.1 μm SiO₂ sample was 3.7 dB, respectively. On the other hand, the transmission loss of 10 Ωcm sample at 1 GHz was 0.86 dB and that of 1000 Ωcm sample was 0.01 dB, respectively. From these results, it was appeared that RF transmission performance of the Si through-hole interconnections becomes superior as the thickness of SiO₂ was thicker and as the resistivity of the Si substrate becomes higher.

View full abstract

In this report, the ITO-ZnSe-CdTe-ZnTe cell was used for a photo sensor. ITO(Indium Tin Oxide) was used on the glass substrates as the transparent electrode, and ZnSe and CdTe layer were prepared by the vacuum deposition on this ITO, and were treated with heat at 560°C. The ZnSe-CdTe sample that CdTe layer was prepared on ITO-ZnSe(0.1μm) substrate has not high-density level at the junction surface, and the CdTe layer with little lattice imperfection can be prepared. In spite of improvement in the crystalline form, this ZnSe-CdTe sample cell has not sufficient electric current response for the light absorption of CdTe layer. In order to increase the electric current response for the light, ZnTe layer was prepared by the vacuum deposition on the ZnSe-CdTe layer, and were treated with heat at 560°C. This ITO-ZnSe-CdTe-ZnTe photo sensor cell has sufficient electric current response for the visible light and near infrared light. It is presumed that the electric filed in the CdTe layer is enough to drive the cell.

View full abstract

This paper proposes an abnormality detection system for bather sitting in bathtub. Increasing number of in-bathtub drowning accidents in Japan draws attention. Behind this large number of bathing accidents, Japan's unique social and cultural background come surface. For majority of people in Japan, bathing serves purpose in deep warming up of body, relax and enjoyable time. Therefore it is the custom for the Japanese to soak in bathtub. However overexposure to hot water may cause dizziness or fainting, which is possible to cause in-bathtub drowning. For drowning prevention, the system detects bather's abnormal state using an ultrasonic sensor array. The array, which has many ultrasonic sensors, is installed on the ceiling of bathroom above bathtub. The abnormality detection system uses the following two methods: posture detection and behavior detection. The function of posture detection is to estimate the risk of drowning by monitoring bather's posture. Meanwhile, the function of behavior detection is to estimate the risk of drowning by monitoring bather's behavior. By using these methods, the system detects bathers' different state from normal. As a result of experiment with a subject in the bathtub, the system was possible to detect abnormal state using subject's posture and behavior. Therefore the system is useful for monitoring bather to prevent drowning in bathtub.

View full abstract