It happens to nearly everyone with a smartphone: they're out in public and suddenly notice their phone's battery percent is dangerously low. If they don't have a portable charging device, they're often stuck next to the nearest outlet while their phone charges to a reasonable percentage. A team of electrical engineers and nanotechnicians want to change that scenario by making sure it never happens again.
"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?'" said lead author Qiaoqiang Gan, PhD, associate professor of electrical engineering in University of Buffalo's School of Engineering and Applied Sciences.
The team harnessed an effect known as the triboelectric effect. Triboelectric charging happens after one material comes into contact with a different material. This causes a loss and exchange of electrons. Most everyone has experienced trioboelectric charge in their life -- static electricity being the most common example.
In order to capture and harness the triboelectric effect, however, the engineers from the University of Buffalo and Institute of Semiconductors (IoP) at Chinese Academy of Science (CAS) looked to the nano-scale rather than capture large quantities of the triboelectric power. The device looks like an oddly thick Band-Aid placed on the knuckle. It has two thin layers of gold wiht a silcon-based polymer caleld polydimethylsiloxane (PDMS). PDMS is also found in contact lenses, Silly Putty, and other squishy common products.
Whenever a wearer bends their finger while wearing the nanogenerator, one layer of the gold stretches and then crumples after being released in what the researchers describe as a mini mountain range. Force gets reapplied to the "mountain range" and that creates 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 another lead author, Yun Xu, PhD, professor of IoP at CAS.
The tab is incredibly small according to the study. It's only about 1.5 cm long and 1 cm wide. At its maximum, it generated 124 volts and a maximum current of 10 microamps. Its maximum power density according to the study was 0.22 milliwatts per square cm. While it's not quite to cell-phone charging capacity, it could safely charge 48 LED lights simultaneously as it did for the researchers.
The biggets problem with the nanogenerator the teams produced? It's incredibly difficult to manufacture at its current state, and most are not cost effective. So don't plan on being able to charge your phone with finger calisthenics just yet. The team hasn't given up, however. They're currently working on an additional portable battery to store energy produced by the triboelectric tab. They're also looking into how larger pieces of gold affect how much electricity is generated, and they expect that the larger the peice the more electricity they can harness. They hope that if they can create an entire system and then figure out how to reduce the cost, they can then look to potentially upscaling the project.
Via: Science Daily