"We are interested in very small devices that can be used in applications such as health care, environmental monitoring and personal electronics," said Wang. "How to power these devices is a critical issue."
The earliest zinc oxide nanogenerators used arrays of nanowires grown on a rigid substrate and topped with a metal electrode. Later versions embedded both ends of the nanowires in polymer and produced power by simple flexing. Regardless of the configuration, the devices required careful growth of the nanowire arrays and painstaking assembly.
In the latest paper, Wang and his group members Youfan Hu, Yan Zhang, Chen Xu, Guang Zhu and Zetang Li reported on much simpler fabrication techniques. First, they grew arrays of a new type of nanowire that has a conical shape. These wires were cut from their growth substrate and placed into an alcohol solution.
The solution containing the nanowires was then dripped onto a thin metal electrode and a sheet of flexible polymer film. After the alcohol was allowed to dry, another layer was created. Multiple nanowire/polymer layers were built up into a kind of composite, using a process that Wang believes could be scaled up to industrial production.
When flexed, these nanowire sandwiches which are about two centimeters by 1.5 centimeters generated enough power to drive a commercial display borrowed from a pocket calculator.
Wang says the nanogenerators are now close to producing enough current for a self-powered system that might monitor the environment for a toxic gas, for instance, then broadcast a warning. The system would include capacitors able to store up the small charges until enough power was available to send
|Contact: John Toon|
Georgia Institute of Technology Research News