Triboelectric Nanogenerators for Battery‐Free Wireless Sensor System Using Multi‐Degree of Freedom Vibration

Abstract In a daily environment, several vibration energies have low amplitude and broad range of frequencies, and it is crucial to harvest them efficiently in a single triboelectric nanogenerator (TENG). Here, a multi‐degree of freedom (DOF) vibration system is coupled with TENG to make several resonant frequencies in a single device. When the number of DOF increases in the system, the number of resonant frequencies also increases. These resonant frequencies are calculated by MATLAB software using the masses and spring constant of DOF vibration system. With the masses of 20 g and the spring constant of 82.712 N m −1 , it is found that 1‐DOF has one resonant frequency (20.47 Hz), 2‐DOF has two resonant frequencies (12.63 and 33.17 Hz), and 3‐DOF has three resonant frequencies (9.12, 25.55, and 36.87 Hz). At each resonant frequency, the displacement of all weight layers increases due to the constructive interference of resonance, resulting in higher output than other frequencies at the frequency sweep experiment. In addition, the magnitude and phase of output signals obtained in friction regions are evaluated through COMSOL simulation. A self‐powered wireless sensor module with 3‐DOF TENGs to detect the humidity/temperature and transmit the data every 30 min by harvesting vibration energy is demonstrated.