An elastic-spring-substrated nanogenerator as an active sensor for self-powered balance

We report on a novel design of a piezoelectric nanogenerator that is monolithically integrated onto an elastic spring by growing ZnO nanowire arrays on the surface of the spring. Under a cyclic compressive force applied to the spring, the nanogenerator produced a stable AC output voltage and current, which are linearly responding to the applied weight on the spring. By conjunction of the experimental data with finite element simulation, we show that the output open-circuit voltage of the nanogenerator can serve as an active sensor for a self-powered weight measurement system. By active sensor we mean that the sensor automatically gives an electric output signal without applying an external power source, which can be used to directly quantify the mechanical triggering applied onto the nanogenerator.