Vol.3 No.3 2010
Research paper : Development of a sensor system for animal watching to keep human health and food safety (T. Itoh et al.)−233−Synthesiology - English edition Vol.3 No.3 (2010) 3 Advantage of using the MEMS technologyQuestion (Jun Hama, Evaluation Department, AIST)You explain that power consumpution of animal sensor can be extremely reduced by using MEMS technology,which allows creating an all-in-one structure, in addition to simiplifying the animal sensor. Can you specifically tell us the advantages of the manufacturing process for sensors?Answer (Toshihiro Itoh)A three-dimensional mechanical structure is necessary to achieve the switch sensor. The MEMS technology is good at creating the three-dimensional microstructure and the protective packaging structure all at once on the silicon wafer. It can be considered the only technology to realize such devices including small and low-cost three-dimensional mechanical structure. Specifically, the MEMS technology is mandatory for creating the oscillator with piezoelectric thin film and the encapsulation structure for the accelerometer, and for creating the bimetal cantilever array, contact, and encapsulation structures for the thermosensor.4 Setting of the thresholdQuestion (Jun Hama)How did you actually set the threshold to determine the abnormal activities? Please explain the decision process within the range you may disclose.Answer (Toshihiro Itoh)We conducted several experiments using dozens of chickens at NIAH using the wireless sensor nodes. Basically, we set the thresholds for temperature and acceleration by comparing the temperature and acceleration data of the chickens inoculated with the virus (with several virus strains) and the non-inoculated chickens.5 Cost reductionQuestion (Jun Hama)To reduce the cost of the health monitoring system, I am sure you’ve done lots of devising, such as minimizing the sample number of chickens to which the nodes are attached in the technological development of an inexpensive sensor system. Is there any statistical difference in the total sample number of animals depending on the characteristic of the animals?Answer (Toshihiro Itoh)I am not sure there is any difference according to the character of the animals, but I’ve heard from the expert at NIAH that 0.3~1 % is probably sufficient as the number of samples to watch the health of the chicken population at a poultry farm. Also, by simulating the relationship between the sensor concentration and detection time (the time required from the first infection of the chicken to the determination of abnormality and reporting) using the experimental data, we think about 5 % is the minimum number needed.6 Realization of the MEMS technologyQuestion (Jun Hama)You are attempting the product realization and diffusion of the chicken health monitoring as one of the ways to pioneer the use of the MEMS technology. Please explain specifically the prospect for an outlet that emphasizes the superiority of the MEMS technology. Answer (Toshihiro Itoh)In general, I think the MEMS technology is a core manufacturing technology for all kinds of sensors that demand downsizing and cost reduction. Therefore, various sensor interface devices in an ambient societyNote) will be realized by the MEMS technology. A system with a similar concept will be applicable to the health behavior monitoring of animals other than chickens. For other use such as monitoring the environment of some facility, it must be reconsidered from step 1 (including whether MEMS is necessary). However, the concept of making the nodes as “light” as possible so it can be spread widely and profusely while making the receiver system advanced, is effective for the application to environmental monitoring including agriculture and disaster prevention.Note) Ambient society: While the “ubiquitous society” is a world where the necessary information can be retrieved “anytime, anywhere, by anyone”, the “ambient society” is a world where the necessary information is provided by the environment that surrounds the person as it senses the person’s situation.