A team of scientists from the Queen Mary University of London has teamed up with Nokia to create a sound-powered smartphone. About the size of a Nokia Lumia 925 phone, the device is filled with energy-harveting ‘nanogenerators’ that can react to sound vibrations and create electricity.
The technology is based on a concept proposed by Korean scientists four years ago called the piezoelectric effect, which describes how nanowires made from zinc oxide produce an electrical current when they’re subjected to some kind of mechanical stress, such as being squashed, stretched or bent. The Korean researchers discovered that these tiny nanowires were so sensitive, they’d bend in response to the pressure of sound waves.
With this in mind, the UK team started off by spraying a coating of liquid zinc oxide onto a plastic sheet, says Ben Coxworth at Gizmag, which they placed into a mixture of chemicals and heated to 90ºC (194ºF). This made the liquid zinc oxide grow into tiny nanorods that spread all over the sheet.
"In order to harvest the voltage generated, the nanorod sheet was sandwiched between two electrical contact sheets,” Coxworth adds. "Whereas these contacts would typically be made from gold, the researchers developed a cost-cutting technique that allowed them to use ordinary aluminium foil instead."
The team found that when they installed this device in their smartphone prototype, and exposed it to sounds like traffic, human voices, and music, it was able to generate five volts, which is enough to charge a mobile phone.
"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 one of the team, engineer Joe Briscoe, in a press release. "We hope that we have brought this technology closer to viability."