Wear backpack, walk and charge mobile phone!

To address growing demands to recharge electrical devices in a world that is constantly facing power outages, researchers developing a new, portable charging source that relies on human walk.

To address growing demands to recharge electrical devices in a world that is constantly facing power outages, researchers developing a new, portable charging source that relies on human walk.

Led by material scientist Zhong Lin Wang, the team of US researchers at Georgia Institute of Technology has created a backpack that captures mechanical energy from the natural vibration of human walking and converts it into electrical energy.

This technology could revolutionise the way we charge small electronic devices.

The backpack contains a device made from thin, lightweight plastic sheets, interlocked in a rhombic grid.

As we walk, the rhythmic movement that occurs as weight shifts from side to side causes the inside surfaces of the plastic sheets to touch and then separate, touch and then separate.

The periodic contact and separation drives electrons back and forth, producing an alternating electric current.

This process, known as the triboelectrification effect, also underlies static electricity.

Wang added highly-charged nanomaterials that maximise the contact between the two surfaces - pumping up the energy output of what Wang called the triboelectric nanogenerator (TENG).

"The TENG is as efficient as the best electromagnetic generator and is lighter and smaller than any other electric generators for mechanical energy conversion," explained Wang.

In the lab, the team showed that natural human walking with a two-kg load generated enough power to simultaneously light more than 40 commercial LEDs.

"The backpack would be able to generate between 2 and 5 watts of energy as the wearer walks - enough to charge a cell phone," noted researchers in a study published in the journal ACS Nano.