Piezoelectric nanostructures: From growth phenomena to electric nanogenerators

Zinc oxide is a unique material that exhibits semiconducting, piezoelectric, and pyroelectric multifunctionalities. By controlling the size and orientation of the polar surfaces of ZnO nanobelts, single-crystal nanocombs, nanorings, nanohelices, nanosprings, and nanobows of ZnO have been synthesized. This article centers on the fundamental growth mechanism and fabrication of electromechanical devices based on piezoelectric ZnO nanostructures, including a nanogenerator using aligned ZnO nanowires for converting nanoscale mechanical energy into electric energy. The mechanism of the electric nanogenerator relies on the unique coupling of the piezoelectric and semiconducting properties of ZnO, which is the fundamental principle of nano-piezotronics, a new field using the piezoelectric effect for fabricating electronic devices and components. The approach has the potential of converting biological mechanical energy, acoustic/ultrasonic vibration energy, and biofluid hydraulic energy into electricity, demonstrating a new pathway for self-powering of wireless nanodevices and nanosystems.