Masashi Miura

There is presently much interest in tunable, flexible, or reconfigurable metamaterial structures that work in the terahertz frequency range. They can be useful for a range of applications, including spectroscopy, sensing, imaging, and communications. Various methods based on microelectromechanical systems have been used for fabricating terahertz metamaterials, but they typically require high-cost facilities and involve a number of time-consuming and intricate processes. Here, we demonstrate a simple, robust, and cost-effective method for fabricating flexible and stackable multiresonant terahertz metamaterials, using silver nanoparticle inkjet printing. Using this method, we designed and fabricated two arrays of split-ring resonators (SRRs) having different resonant frequencies on separate sheets of paper and then combined the two arrays by stacking. Through terahertz time-domain spectroscopy, we observed resonances at the frequencies expected for the individual SRR arrays as well as at a new frequency due to coupling between the two SRR arrays.

We are developing a wireless sensor network system to monitor natural water quality. Our wireless sensor network system consists of sensors for detecting water quality and systems for transferring detected data and handling power modules. Previously, we proposed a low cost buoy type sensor node to monitor lake water quality. We prototyped a single sensor node and evaluated it in the lake. However, to obtain extensive field data for large-area lake water, multiple sensor nodes are necessary. In this paper, we report the improvement results of the previous sensor node, which is performed to achieve multiple sensor nodes as elements of the wireless sensor network system. The improved sensor node has compact size and the communication system of it is optimized. We fabricated the improved sensor nodes and evaluated them in the lake. As a result, we could confirm that the wireless sensor network system consisted of improved sensor nodes was successfully functioned in real time and real environment.