“…The triboelectric nanogenerator (TENG) [5]- [7] and the piezoelectric nanogenerator (PENG) [8]- [10], for example, could exploit random mechanical energy into the powering source. Recent works have shown the promising concept in the potential applications of wireless or flexible electronic devices [11]- [15], internet of things (IoTs) [16]- [18], healthcare and medical areas [19]- [22]. Besides nanogenerators, there are other self-powered sensing concepts based on various mechanisms like the photovoltaic (PV) [15], [23]- [25], thermoelectric/pyroelectric [23], [26]- [29], electromagnetic [30], [31], and electrochemical effects [32], [33].…”