Scientists have designed a mobile phone that requires no batteries.

The device uses a fraction of the amount of power consumed by a regular handset.

Made from off-the-shelf components, it can power itself in two ways – either from a solar panel the size of a grain of rice, or from radio waves.

The new technology is detailed in a paper published in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies.

The device uses a fraction of the amount of power consumed by a regular handset

Professor Shyam Gollakota, of Washington University's computer science faculty, said: 'We've built what we believe is the first functioning cellphone that consumes almost zero power.

'To achieve the really, really low power consumption that you need to run a phone by harvesting energy from the environment, we had to fundamentally rethink the design.'

The team bypassed the most power-hungry element of a mobile phone – which is converting the 'analogue' sound of the human voice into digital data that can be transmitted.

Co-author Professor Joshua Smith said: 'The cellphone is the device we depend on most today. So if there were one device you'd want to be able to use without batteries, it is the cellphone.

'The proof of concept we've developed is exciting today, and we think it could impact everyday devices in the future.'

The team say that the technology was made to work with a custom-built base station.