A small metallic tab that, when attached to the body, is capable of generating electricity from bending a finger and other simple movements could one day power our electronic devices.
“No one likes being tethered to a power outlet or lugging around a portable charger. The human body is an abundant source of energy. We thought: ‘Why not harness it to produce our own power?’” says Qiaoqiang Gan, associate professor of electrical engineering in the School of Engineering and Applied Sciences at the University at Buffalo and lead author of a paper describing the tab in the journal Nano Energy.
The tab is a triboelectric nanogenerator. Triboelectric charging occurs when certain materials become electrically charged after coming into contact with a different material. Most everyday static electricity is triboelectric.
Researchers have proposed numerous nanogenerators that utilize the triboelectric effect, but most are difficult to manufacture (requiring complex lithography) or are not cost effective. The tab that the team is developing addresses both of those concerns.
It consists of two thin layers of gold, with polydimethylsiloxane (also called PDMS, a silicon-based polymer used in contact lenses, Silly Putty, and other products) sandwiched in between.
Key to the device is that one layer of gold is stretched, causing it to crumple upon release and create what looks like a miniature mountain range. When that force is reapplied, for example from a finger bending, the motion leads to friction between the gold layers and PDMS.
“This causes electrons to flow back and forth between the gold layers. The more friction, the greater the amount of power is produced,” says c0-lead author Yun Xu, a professor at the Institute of Semiconductors (IoP) at the Chinese Academy of Science.
The study, describes a small tab (1.5 centimeters long, by 1 centimeter wide). It delivered a maximum voltage of 124 volts, a maximum current of 10 microamps and a maximum power density of 0.22 millwatts per square centimeter. That’s not enough to quickly charge a smartphone; however it lit 48 red LED lights simultaneously.
Because the tab is easily fabricated, Zhang is leading a team of undergraduates tasked with improving the tab’s performance. The team plans to use larger pieces of gold, which they expect to deliver even more electricity when stretched and folded together.
Researchers are also working on developing a portable battery to store energy produced by the tab. They envision the system serving as a power source for various wearable and self-powered electronic devices.
The US National Science Foundation, the National Basic Research Program of China, National Natural Science Foundation of China, Beijing Science and Technology Projects, Key Research Projects of the Frontier Science of the Chinese Academy of Sciences and National Key Research and Development Plan support the work.
Source: University at Buffalo