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Charging mobile phones with noise

Everyday noise could present a cheap and omnipresent source of energy for charging mobile phones, British researchers have proved.

A prototype device built by scientists from the Queen Mary University of London (QMUL) in cooperation with Nokia generates enough power to charge a smartphone just by being exposed to sounds generally considered a nuisance such as traffic noise, unwanted music or even chants from a football ground.

The device, about the size of a Nokia Lumia phone, consists of energy-harvesting nanogenerators capable of turning vibrations generated by sound waves or movement into electricity.

The team previously demonstrated that a similar concept could improve the performance of solar cells, enhancing their energy production by playing loud music. The current innovation promises that mobile phone users would never run out of battery or be forced to look for a socket to plug in their devices.

"Being able to keep mobile devices working for longer, or do away with batteries completely by tapping into the stray energy that is all around us is an exciting concept,” said Joe Briscoe, a researcher at QMUL’s School of Engineering and Materials Science, who developed the concept together with his colleague Steve Dunn.

“This collaboration was an excellent opportunity to develop alternative device designs using cheap and scalable methods. We hope that we have brought this technology closer to viability," he said about the work with Nokia.

The nanogenerators contain zinc oxide, a material capable of creating voltage when squashed or stretched. The material is formed into nanorods, which can be coated onto various surfaces in different locations making the energy harvesting quite versatile. When such a surface is squashed or stretched, the nanorods generate a high voltage.

The nanorods respond to vibration and movement created by everyday sounds, including people’s voices. Electrical contacts on both sides of the rods are then used to harvest the voltage to charge a phone.

In order to make it possible to produce these nanogenerators at scale, the scientists found innovative ways to cut costs in the production process.

Firstly, they developed a process whereby they could spray on the nanorod chemicals – almost like nanorod graffiti – to cover a plastic sheet in a layer of zinc oxide. When put into a mixture of chemicals and heated to just 90°C, the nanorods grew all over the surface of the sheet.

Secondly, gold is traditionally used as an electrical contact but the team were able to produce a method of using cheaper aluminium foil instead.

The prototype device is capable of generating five volts, which is enough to charge a phone.

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