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.

View full abstract

Electrostatic field distribution measurement using a silicon micro-mirror array fabricated by Micro-Electro-Mechanical Systems (MEMS) process has been presented. The deflection angle of each micro-mirror, which is placed on a spherical surface and is deflected by electrostatic field, was measured optically using a two-dimensional optical scanner and a position sensitive detector (PSD). The obtained electrostatic data showed good agreement with Coulomb's law and the system was applied to measure the electrostatic field distribution of charged substance.

View full abstract

The preparation of nitrogen added chromium thin films and their electrical properties were investigated. We found out that the N added Cr thin films indicated negative temperature coefficient of resistivity (TCR). Furthermore, the TCR changed from negative to positive values by annealing and became zero in a middle step of the change. The observed behavior was considered to be related to the structural transformation between δ-Cr and α-Cr by the addition of nitrogen or the annealing. The strain gauge factors (Gf) of the specimens with nearly zero TCR showed huge values of about 9 in maximum, which was verified to exceed those of conventional strain gauge metallic materials by a factor of about 4.5. These Cr-N thin films should be noteworthy as the new type high sensitive strain gauge materials. In this paper, the fundamental experimental results will be described, as well as some demonstrations on the high sensitive pressure detection using the Cr-N films formed on a metal diaphragm.

View full abstract

Vibration coupling in out-of-plane resonators was investigated to design low acceleration sensitivity tuning fork gyroscopes (TFGs) of out-of-plane sensing axis type. Numerical and theoretical analysis was carried out on a spring-coupled translational x-axis TFG. The vibration coupling was controlled by separating the in-phase mode (f_in) from anti-phase mode (f_anti). The theoretical and numerical analysis showed that the acceleration sensitivity is inversely proportional to decoupling ratio, whereas the angular rate sensitivity does not change by keeping the f_anti constant. For experimental verification, we designed four types of coupled resonators and fabricated them from SOI wafer: two of them are frame-coupled and the other two are spring-coupled. In each coupling type, one adopted a translational resonator and the other adopted a torsional resonator. The measured anti-phase vibration amplitude against in-phase oscillation decreased by weakening coupling which agreed with the numerical analysis. As decoupling ratio (=(f_in-f_anti)/f_anti) of the spring-coupled translational resonator increased from 0.09 to 0.29, the anti-phase vibration amplitude in the analysis and measurement decreased to 28% and 51%, respectively.

View full abstract

We propose a proximity and tactile sensor using self-capacitance measurement. The proposed sensor consists of the two electrodes (E₁ and E₂), GND and elastic body. The capacitance between E₁ or E₂ and GND is measured by switching between E₁ and E₂. The capacitance between E₂ and GND is used to detect the object before contact (proximity range) and to discriminate the material on contact. In addition, the capacitance between E₁ and GND is used to detect the indentation on contact. In the experiment, detection of the object before and after contact, and identification of materials on contact were demonstrated. In addition, the object is grasped by the proposed sensor which detects the object at proximity and contact range. This technique may be applicable to proximity and tactile sensor for robot.

View full abstract