Nanogenerators and Nanopiezotronics

Developing novel technologies for wireless nanodevices and nanosystems is of critical importance for in-situ, realtime and implantable biosensing, biomedical monitoring and biodetection. It is highly desired for wireless devices and even required for implanted biomedical devices to be self-powered without the use of a battery. Therefore, it is essential to explore innovative nanotechnologies for converting mechanical energy (such as body movement, muscle stretching), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as body fluid and blood flow) into electrical energy that can be used to power nanodevices. We have demonstrated an innovative approach for converting nano-scale mechanical energy into electrical energy using piezoelectric zinc oxide nanowire (NW) arrays. We have recently developed a DC nanogenerator driven by an ultrasonic wave. This represents a tremendous step towards realization of practical piezoelectric based nanogenerators. The mechanism of operation of the electric generator relies on the unique coupling of piezoelectric and semiconducting properties of ZnO as well as the elegant rectifying function of the Schottky barrier formed between a metal tip and the NW. Based on this principle, piezoelectric-field effect transistors, gated diodes, sensors and resonators have been fabricated. These form the fundamental components of nano-piezotronics. Piezotronics is the field of using coupled piezoelectric-semiconducting properties for fabricating novel and unique electronic devices and components.