Scientists have developed an ultra-light limb that they claim can mimic the movement in a real hand better than any currently available.

At present, prosthetic hands either do not move at all or have a simple single-motor grip.

But the University of Southampton team has designed a prototype that uses six sets of motors and gears so each of the five fingers can move independently.

Details of their design were presented at an Institute of Physics conference.

Every year 200 people in the UK lose their hands. Common causes include motorbike accidents and industrial incidents.

It is hard for scientists to replicate hand movement, as the real thing has 27 bones and can make a huge number of complex movements and actions.

The Southampton team believe their prototype is able to make movements and grip objects in the same way that a real hand does.

The new hand - called the Southampton Remedi-Hand - can be connected to muscles in the arm via a small processing unit and is controlled by small contractions of the muscles which move the wrist.

Clutching small objects

Researcher Dr Paul Chappell, a medical physicist who worked on the device, said: "With this hand you can clutch objects such as a ball, you can move the thumb out to one side and grip objects with the index finger in the way you do when opening a lock with a key, and you can wrap your fingers around an object in what we call the power grip - like the one you use when you hold a hammer or a microphone."

The latest design is also very light - at 400g it is lighter than the average human hand.

Heavy prosthetics can be extremely uncomfortable and cause injury to the area where it joins with the arm.

The hand was built in three parts - the three middle fingers are very similar in size and movement so those were made identical.

The little finger is a smaller version of the same.

Each of these four fingers are made up of a motor attached to a gearbox attached to a carbon fibre finger. All of this is fitted to a carbon fibre palm.

Thumb technology

But the thumb was much more complicated.

The human thumb can move in special ways the fingers cannot.

It can rotate as well as flex and also move in a variety of different directions. It can also oppose (touch) each of the fingers in the hand to form a 'pinch'.

To mimic this, the Remedi-Hand uses two motors - one to allow it to rotate and one to allow it to flex.

The researchers say it has the first artificially-made opposable thumb.

Dr Chappell said: "The real thumb can move in five types of way, we've managed to create a thumb that can mimic at least two of these which is a really exciting achievement.

"It's a thumb that has really good flexibility and functionality."

The next stage will be to integrate the latest sensor technology to create a 'clever' hand which can sense how strongly it is gripping an object, or whether an object is slipping.

Dr Chappell said: "The aim is to create a hand with the sort of functionality a human hand has but also a sense of touch."

Jared O'Mara, of the British Council of Disabled People, welcomed the Southampton work.

He said: "We are eager to see how such a device will work in practice and are hopeful that it will help many disabled people to lead easier lives, in particular during the course of day to day remedial tasks."

The worlds first fully articulating and commercially available bionic hand.

Touch Bionics is a leading developer of advanced upper-limb prosthetics (ULP). One of the two products now commercially available from the company, the i-LIMB Hand, is a first-to-market prosthetic device with five individually powered digits. This replacement hand looks and acts like a real human hand and represents a generational advance in bionics and patient care.

The Touch Bionics i-LIMB Hand was developed using leading-edge mechanical engineering techniques and is manufactured using high-strength plastics. The result is a next-generation prosthetic device that is lightweight, robust and highly appealing to both patients and healthcare professionals.

The i-LIMB Hand is controlled by a unique, highly intuitive control system that uses a traditional two-input myoelectric (muscle signal) to open and close the hand’s life-like fingers. Myoelectric controls utilize the electrical signal generated by the muscles in the remaining portion of the patient’s limb. This signal is picked up by electrodes that sit on the surface of the skin. Existing users of basic myoelectric prosthetic hands are able to quickly adapt to the system and can master the device’s new functionality within minutes. For new patients, the i-LIMB Hand offers a prosthetic solution that has never before been available.

Advanced Design

The modular construction of the i-LIMB Hand means that each individually powered finger can be quickly removed by simply removing one screw. This means that a prosthetist can easily swap out fingers that require servicing and patients can return to their everyday lives after a short clinic visit. Traditional devices would have to be returned to the manufacturer, often leaving the patient without a hand for many weeks.

In another industry first, the i-LIMB Hand’s finger technology has been adapted for patients who have a partial hand, due either to congenitally missing fingers or fingers lost through an accident. Partial hand is an area of prosthetics that has been without a satisfactory powered solution for patients until now.

ProDigits are another first from Touch Bionics. Not having fingers or a thumb to act in opposition to one another makes simple tasks such as holding a fork or a drink difficult and frustrating.

The modular nature of the ProDigit finger design and the individually-powered motor located within each digit means that a clinician can build replacement fingers to the correct anatomical length of the patient’s remaining undamaged fingers. This new solution can help the many individuals who so far have had no effective options available to them.