Theoretical study of nanogenerator with resistive load and its sensing performance as a motion sensor

Nanogenerators have shown their promising potential in energy harvesting and self-powered sensing. There are numerous working configurations and several output modes for nanogenerators. In this paper, a theoretical study is conducted analytically and numerically on electret-based nanogenerators as a dynamic motion sensor working in the contact-separation mode with resistive load. The analytical solution is derived as the asymptote for the output voltage across the load resistor under sinusoidal input movement. The effectiveness and the prerequisite condition of the deduced analytical solution is validated by numerical calculation. The influence of initial conditions on transient process is investigated. It is derived and demonstrated that certain amount of initial charges on electrodes will shorten or even eliminate the transient process. Making an analogy with a typical first-order resistor-capacitor high pass filter, the magnitude and cut-off frequency of the nanogenerator are extracted from the analytical solution. The impact on the output performance of parameters related to the device, the input motion and the measurement circuit are explored in detail. A design and optimization flow is proposed for the nanogenerator-based motion sensor, which will serve as a guidance and a powerful tool that can be referred to in practical applications.