In this paper, we propose a new use of an electrostatic MEMS cantilever structure as a voltage-controlled oscillator (VCO). A cantilever made of plated gold is accompanied with a drive electrode to turn on the contact switch upon voltage application. The electrical interconnection is arranged to discharge the cantilever when it is brought into contact with the switch, thereby promptly losing the electrostatic force and opening the contact switch again. As a result, the electrostatic cantilever spontaneously repeats the electrostatic pull-in and release at a frequency determined by the DC level of the applied voltage. A metallic cantilever of 500 μm long, 8 μm wide, and 12 μm thick is experimentally confirmed to work as an VCO in the frequency range between 8.4 kHz and 10.7 kHz controlled by the DC voltage between 160V and 180V.

The purpose of this study is to reproduce tastes expect the five basic tastes with a multichannel taste sensor. The sensor can isolate and detect five tastes. The basic taste evaluation is expressed in terms of the concentration of typical tasting substances. For example, if the taste is salty, the sensor output for sodium chloride is obtained data and converted to an equivalent sodium chloride concentration from the sensor output of the unknown taste solution. In the case of rice taste, we found it difficult to describe it in terms of a combination of the five basic tastes. In the existing sensory test of rice, there are no items defined that correspond to taste in the narrow sense. We estimated that rice tastes other than the five basic tastes. Therefore, we first analyzed to find out what the taste substances were in the rice. The response characteristics of a multichannel taste sensor for rice were determined. The inorganic ionic components in rice were analyzed, and a mixed solution containing the obtained taste substances, NaH₂PO₄ and CaCl₂, was prepared, and it was shown to have the same sensor output as that of the rice extract. The results of this study suggest that as the mixture is made from two substances, a quantitative evaluation of rice taste can be made on two axes: the taste sensor output corresponding to the concentration of each substance.

In this study, we focused on acoustic emission (AE) as a method for quantitative evaluation of fermentation. Since bubbling in the culture medium and detachment of the medium during fermentation are considered to be phenomena similar to corrosion, AE could be expected to be detected. Therefore, we conducted AE measurements using ECS during fermentation of yeast in sucrose solution, fermentation of yeast during sake brewing, and fermentation of sawdust in a hot bath facility, and investigated the possibility of evaluation of fermentation process using electret sensor (ECS). AE was detected during the fermentation of yeast. The peak frequency of AE detected during yeast fermentation was widely distributed. Cumulative number of AE, however, showed a strong correlation with the decrease in sugar content during fermentation, indicating the possibility of quantitative evaluation of the fermentation state by AE measurement if a time lag is considered. In the measurement of AE from the fermentation of sake malt, a large amount of AE was detected from the lower part of the tank immediately after brewing, and the number of AE gradually increased in the upper part of the tank. These AE measurements suggested that even in top fermentation, the initial fermentation may occur in the lower part of the tank. In the fermentation and warm bath facility, AE during fermentation could be detected even in powdered media. Although the durability of the ECS needs to be improved under high temperature and high humidity conditions, it is expected to be able to monitor the fermentation process better than temperature measurements.