Imagine if the chants at a football game, or the noise of an excited festival crowd could serve a useful purpose by actually charging your phone.
Following the success of the last charging project, where we harnessed the power of lightning to charge a Lumia device, we were keen to experiment further.
We teamed up with Dr Joe Briscoe and Dr Steve Dunn of Queen Mary University of London (QMUL) to see if we could create an energy-harvesting prototype (a nanogenerator) that could be used to charge a mobile phone using everyday background noise – such as traffic, music, and our own voices.
The starting point for the energy-harvesting prototype was nanotechnology; working with materials that are thousands of times smaller than a strand of human hair.
At this minuscule size these materials behave very differently, for instance they can change colour, grow in strength or become much more chemically reactive. By breaking material down to a nano level it makes it easy to gather energy from movement and vibration – the key quality of sound that we wanted to utilise.
The crucial component of the device is Zinc Oxide, a piezoelectric material that can turn mechanical energy, or energy created by motion, into electrical energy. Piezoelectric materials have this capability due to their crystal structure that, when squashed or stretched, will generate a voltage.
For example, when you press the button on a lighter it puts pressure on a piezoelectric crystal, which creates a voltage spark to ignite the gas. In this instance we used this same principle, but instead the voltage was used to charge a phone.
Zinc Oxide can be made into nanorods or nanowires, which can be coated onto almost any surface. When this surface is squashed or bent, the nanorods then generate a high voltage. This means they respond to vibration and movement created by everyday sound e.g. our voices. If you then put electrical contacts on both sides of the rods you can use the voltage they generate to charge a phone.
In order to make it possible to produce these nanogenerators at scale, the team 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.
Additionally, whereas gold is traditionally used as an electrical contact, Dr Joe Briscoe, Dr Steve Dunn and the QMUL team worked out a method of using cheap and cheerful aluminium foil instead.
The final outcome: a device the same size as a Lumia 925. Incredibly, five volts can be generated; enough to charge a phone.
Starting with a simple hypothesis, we were able to imagine a future where we’d never have to look for a mains socket to charge our phones again.
What do you think about this experiment? Would you like to charge your phone with the use of sound? What other kind of mobile innovation would change your world today?