Washington, Nov 10 : Researchers have developed a new type of small-scale electric power generator able to produce alternating current by the stretching and releasing of zinc oxide wires.
These zinc oxide wires are encapsulated in a flexible plastic substrate with two ends bonded.
The new "flexible charge pump" generator is the fourth generation of devices designed to produce electrical current by using the piezoelectric properties of zinc oxide structures to harvest mechanical energy from the environment.
The new generator can produce an oscillating output voltage of up to 45 millivolts, converting nearly seven percent of the mechanical energy applied directly to the zinc oxide wires into electricity.
"The flexible charge pump offers yet another option for converting mechanical energy into electrical energy," said Zhong Lin Wang, director of the Center for Nanostructure Characterization at the Georgia Institute of Technology.
"This adds to our family of very small-scale generators able to power devices used in medical sensing, environmental monitoring, defense technology and personal electronics," he added.
Earlier, nanowire nanogenerators and microfiber nanogenerators developed by Wang and his research team depended on intermittent contact between vertically-grown zinc oxide nanowires and an electrode, or the mechanical scrubbing of nanowire-covered fibers.
These devices were difficult to construct, and the mechanical contact required caused wear that limited how long they could operate.
Also, because zinc oxide is soluble in water, they had to be protected from moisture.
"Our new flexible charge pump resolves several key issues with our previous generators," Wang said.
"The new design would be more robust, eliminating the problem of moisture infiltration and the wearing of the structures. From a practical standpoint, this would be a major advantage," he added.
To boost the current produced, arrays of the flexible charge pumps could be constructed and connected in series.
Multiple layers of the generators could also be built up, forming modules that could then be embedded into clothing, flags, building decorations, shoes, or even implanted in the body to power blood pressure or other sensors.
When the modules are mechanically stretched and then released, because of the piezoelectric properties, the zinc oxide material generates a piezoelectric potential that alternately builds up and then is released.
For the future, Wang sees the family of small-scale generators enabling development of a new class self-powered wireless sensing systems.
The devices could gather information, store it and transmit the data - all without an external power source.
"Self-powered nanotechnology could be the basis for a new industry," he said. "That's really the only way to build independent systems," he added.