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In Japan, a huge portion of the population is aged people, who are prone to various diseases and injuries on a regular basis. Injuries due to falls are one of the biggest risk factors. Consequently, the demand for fall detection sensors, especially the ones that used a triboelectric nanogenerator (TENG) has recently increased. In a previous study, our group reported the development of a wearable sensor for fall detection with privacy protection using the principle of TENG. Conventional TENGs use polymer films as friction material. However, it is difficult for film-based TENGs to harvest output from various angles of contact separation, as the films have two-dimension structures. Consequently, our previous study focused on developing brush-based TENG (B-TENG), and B-TENG harvested output from various angles of contact-separation. However, the B-TENGs we developed were not sensitive enough to detect signals of lower contact force, and thereby could not be used in fall detection sensors. In this study, we focused on improving the performance of B-TENG by investigating the properties of the brushes and the effect of various external parameters on the harvested output voltage of B-TENGs. Consequently, we have constructed an optimized B-TENG, which harvests almost 18 times higher output voltage than the previous one developed by our group. Thus, this optimized B-TENG has the potential for practical use in fall detection sensors. [ABSTRACT FROM AUTHOR]

Japanese lacquer artwork is one of the most famous cultural heritages in Japan. The main component of the Japanese lacquer is urushiol, which consists of phenol derivatives. The dimerization process of urushiol has been investigated in detail, but the structure of urushiol polymer has not. In this study, the structure was investigated by using thermogravimetry (TG)-linked scan mass spectrometry (MS). Linked scan MS is effective in detecting the thermal degradation products of urushiol polymer as the evolved gas. As a result, it is concluded that 3-pentadecylcatechol and 3-pentadecenylcatechol are the main components of the terminal groups of the urushiol polymer, and 3-pentadecatrienylcatechol is a main component of the polymer skeleton. [ABSTRACT FROM AUTHOR]