After a hand has been amputated, the brain thinks it is still there and so sends signals to the nerves and severed muscles.

Intercepted by delicate sensors, the signals are used to move tiny motors hidden in the artificial fingers.

While traditional prostheses only have one motor, allowing limited movement, the i-Limb has five, with one concealed between the base and knuckle of each finger.

Covered in artificial skin, the one-size-fits-all hand has already won the approval of patients on both sizes of the Atlantic, including Iraq war veterans.

Father-of-two Juan Arrendondo (CORR), was a sergeant in the US army when he lost his hand to a roadside bomb in 2004. He tried several other artificial hands, before settling on the i-LIMB.

The 27-year-old from Texas said: 'Now I can pick up a Sytrofoam cup without crushing it.

'With my other hand, I would really have had to concentrate how much pressure I was putting on the cup. Every day I have this hand, it surprises me.'

Already available privately, the device could be available on the NHS as early as 2010.

Made of light-weight but strong plastic, of a sort more usually found in car engine components, the hand is attached to the arm via a laminated socket.

The socket, which slips over patient's arm, conceals a rechargeable battery and a pair of electrodes which sit on top of the skin, where they pick up signals destined for the person's real hand.

The signals are transmitted to a tiny computer which is housed in the back of the artificial hand and controls the motors hidden in the fingers.

The index finger can be pointed, allowing the wearer to type, punch their pin number into a cashline machine, or, simply point.

Small objects such as coins can be picked up between the index finger and thumb, while other grips allow turning a key in a lock, holding a plate and handing over a business card.

So flexible are the fingers that they can even open the ring-pull of a soft drink's can.

While a basic hand can be bought for around £8,500, the most life-like versions cost at least £5,000 more.

Although the artificial skin that covers the hand provides protection from dust and moisture, the device is not waterproof.

Nor can it perform all the functions of a living hand, with movements outside of its reach including the clicking of the fingers.

Phil Newman, of Livingstone-based Touch Bionics, which has developed the arm, said: 'We are a technology company but we are very aware we are making inroads into people's lives. The reaction we have had from patients so far has been phenomenal.

'For someone who was born without a hand to look at their hand and see their fingers moving, it is very emotional for them and very rewarding for us.'