Hawking has motor neurone disease - nerve decay that has left him almost completely paralysed. He currently communicates using a series of cheek twitches to select words from a screen. 'It is a very, very slow process,' says Philip Low at Stanford University in California, who is founder of healthcare company NeuroVigil.

As Hawking loses control of his cheek, Low hopes he might instead communicate using his company's portable device. The iBrain records brain activity from a single point on the scalp. An algorithm then extracts useful information from this activity.

In a preliminary trial, Low's team asked Hawking to imagine moving his hands and feet while wearing the device. They were able to identify what movement he was imagining through changes in his brain activity. They now hope to develop the technology to enable Hawking and others to use the imagined movements to instruct a computer to write or speak words.