Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have created a new piezoelectric nanogenerator that promises to overcome the restrictions found in previous attempts to build a simple, low-cost, large scale self-powered energy system.
Piezoelectric materials can convert vibrational and mechanical forces from, for example, wind and waves, into an electric current. This property has been harnessed to create better microphone transducers and, in more recent years, to harvest energy from clothing, shoes, and even traffic.
Last year, a team led by Dr. Zhong Lin Wang announced it had created the world's first piezoelectric nanogenerator and, shortly after, also announced the first self-powered nanodevice complete with a wireless transmitter. Now Wang and his team have announced further progress in creating a low-cost, large-scale nanogenerator which is also simple to manufacture.
The team produced a composite by mixing piezoelectric nanoparticles, carbon nanotubes and reduced graphene oxide in a matrix of polydimethylsiloxane (PDMS). The nanogenerator was then fabricated by process of spin-casting.
"The generator is mainly made of plastics and zinc oxide, so the materials are environmentally friendly," says Wang.
Bending the nanogenerator produces a difference of potential between the two electrodes (Image: KAIST)
Despite its relative simplicity, the composite generates a much higher power density than other devices with a similar structure and has an energy conversion efficiency of seven percent. Wang told us that if the nanogenerator were to be embedded in a pair of shoes, an average-build person could generate around 3W just by walking. For reference, that would be roughly enough to power an iPad 2 (if you wanted to power the new iPad, however, you'd have to either pick up your pace or put on a few pounds).
Preliminary durability studies have confirmed that, even after thousands of cycles in which the material was repeatedly bent and released, the nanogenerator consistently produced the same amount of electric current, with no noticeable degradation in performance.
As Wang points out, the applications of such a technology are very broad and could include biosensing, medical devices, environmental and health monitoring, defense technology, and - why not - the Internet of Things.