Levitating oscillator-based triboelectric nanogenerator for harvesting from rotational motion and sensing seismic oscillation

Ever-rising skyscrapers and the growing number of densely populated large cities face an increased danger from earthquakes. To lessen the risk of this natural disaster, critical facilities must be equipped by a reliable warning system. However, conventional sensors which detect the velocity and acceleration of the seismic vibrations, consumes an external power, which cannot be placed in many buildings due to limitations in electricity supply. In this work, a self-powered seismic sensor is fabricated using the three-dimensional printing technology. The proposed device can be operated based on the triboelectricity, which converts an external mechanical energy into an electrical energy. The proposed device exhibits an exceptional behavior of a friction-free due to its sophisticated designed structure with a levitating oscillator. The fundamental parameters representing the device performance are systematically analyzed with various operation mode. Water-assisted oxidized Al electrodes allow full-contact with the polytetrafluoroethylene triboelectric oscillator film, subsequently, produce the highest values of output parameter as follows; an open-circuit voltage of 29.44 V, a short-circuit current of 204 nA, and a peak power density of 2.501 mW/m² at a load resistance of 50 MΩ. Frequency reversibility is also demonstrated from the frequency response of the short-circuit current during the operation in lateral-contact mode. Because of inherently friction-free characteristics of the proposed device, this device shows high sensitivity, low sensing limit, and long residual signal, which is experimentally verified. In order to test the sensing ability of the device, artificial seismic vibrations are applied with vertical forces of 4 N and 2.4 N. An alert software program displays the sensing ability of the device with the signals over 1 V, which is the threshold voltage. The stability of the device in humid conditions and its durability for 3100 s in the output voltage measurement represent the possibility of this device as a reliable sensor. Due to the simple three-dimensional printing technology and its inherently friction-free characteristics, the proposed device can be employed as a self-powered sensor capable of warning about dangerous earthquake disasters.