“…[1][2][3][4][5][6] It has been a challenge to continuously power those individual wireless sensors and the related electronic components in WSNs, because conventional batteries have their shortcoming of the finite lifetime. [7] Therefore, it becomes a promising and feasible approach to harvest energy from environmental energy source, including vibrational energy, [8,9] wave energy, [10] stray magnetic energy, [11,12] solar energy, [13] etc., to power these individual wireless sensor (as self-powered sensors). [7] The low-amplitude, low frequency stray magnetic field is widely surrounding in or around the modern building, generated by power supply cables and air conditioning machines et al; [5,7,14] while the vibrational energy coming from vehicle motions, human walking, and machines are also widespread in the environment.…”