New research from the University at Buffalo and the Chinese Academy of Sciences could one day let you leave the charger at home and top up your phone battery using body movements. The team has developed a triboelectric nanogenerator in the form of a small metallic tab that can generate electricity from simple body movements, such as the bending of a finger.

The tab utilizes the triboelectric effect, which sees some materials produce an electric charge through friction with another material – most everyday static electricity falls under the tribolelectric banner. In the case of the tab, the two materials are gold and polydimethylsiloxane (PDMS), with thin layers of the former surrounding a layer of the latter.

When one of the gold layers of gold is stretched and then released, it crumples, creating what looks like a miniature mountain range. Then, when the device is bent again, friction is created between the gold and PDMS layers, producing an electric charge.

"This causes electrons to flow back and forth between the gold layers," says co-lead author Yun Xu from the Chinese Academy of Sciences. "The more friction, the greater the amount of power is produced."

The device measures just 1.5 cm (0.6 in) long and 1 cm (0.4 in) wide and successfully delivered a maximum voltage of 124 volts, a maximum current of 10 microamps and a maximum power density of 0.22 millwatts per sq cm. That's a long way from enough to charge a smartphone, yet, but was enough for the team to light up 48 red LED lights simultaneously.

Unlike various other triboelectric nanogenerators proposed by scientists, the team says their device is cost effective and simple to manufacture.

"No one likes being tethered to a power outlet or lugging around a portable charger," says another co-lead author of the study, Qiaoqiang Gan. "The human body is an abundant source of energy. We thought: 'Why not harness it to produce our own power?'"

With that goal in mind, the team is already looking to improve the performance of the tab by using larger pieces of gold. They are also working on a portable battery that could store energy produced by the tab.

The team's study was published in Nano Energy.

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