Along with piezoelectricity (i.e. production of electricity as a result of mechanical pressure), now scientists have started worked on triboelectricity (i.e. production of electricity as a result of friction) to charge “portable electronics” such as cell phones with friction.
This research has been published online in the journal Nano Letters.
Scientists in this research have developed a nanogenerator from inexpensive materials that can produce mechanical energy from static electricity and friction that is sufficient to charge personal electronics. With this device, the energy production will be as simple as the slight movement of phone in pockets during motion.
This device that takes the advantage of static charge phenomenon, referred to as the triboelectric effect, showed remarkable power outputs as compared to the piezoelectric devices. Interestingly, this device has been made from inexpensive usual-day materials including a type of plastic, polyethylene terephthalate, and a metal. These materials become charged when thin films of these materials come into direct contact with each other and upon flexing of the two films, current start flowing that can be used to charge the battery. The surface area can be increased, when the two surfaces are patterned with nanoscale structures resulting in more friction and more power.
This device is able to convert 10-15% of mechanical energy into electricity while the thinner materials could convert even 40% as Zhong Lin Wang, a professor of materials science at Georgia Tech, said. You can imagine the power produced by considering that a fingernail-sized square of the triboelectric nanodevice could produce eight milliwatts of energy that can run a pacemaker and a 5x5cm can light up 600 LEDs at once, or charge a lithium-ion battery to power up a commercial cell phone.
The working mechanism of the TENG was studied by finite element simulation. The output voltage, current density, and energy volume density reached 230 V, 15.5 μA/cm2, and 128 mW/cm3, respectively, and an energy conversion efficiency as high as 10–39% has been demonstrated.
“The choice of materials is wide, and fabricating the device is easy,” said Wang. This device is so simple that nearly 50 types of common plastics, metals and other materials could be harmonized to develop the nanogenerator.
Sihong Wang, Long Lin, and Zhong Lin Wang, (2012). Nanoscale Triboelectric-Effect-Enabled Energy Conversion for Sustainably Powering Portable Electronics. Nano Letters. DOI: 10.1021/nl303573d