The Bionic Hand takes shape
December 4, 2005 The popular television series The Bionic Man was probably the first inkling most of us had that one day man would be enhanced by machinery to better-than-new condition. The promise has been a long time in coming, but medical scientists across the world are advancing towards the implementation of bionic limbs. In July we reported on the work of Brazilian doctor Miguel Nicolelis, and now the CYBERHAND Project, which involves collaboration between six tertiary institutions across four countries (Spain, Germany, Italy and Denmark) has finally produced a bionic hand. The project team led by Paolo Dario with Professor Maria Chiara Carrozza leading the development of the hand, has been working on re-creating the natural link which exists between the hand and the Central Nervous System (CNS) and if all goes according to plan, the first of these bionic hands will be implanted inside a real human arm within two years.
The hand will be suitable for amputees who have lost their arm below the elbow – following the transplant operation, the robotic prothesis will be covered with synthetic material but it will be fully integrated with the recipient’s nervous system, enabling sensory feedback from the hand to be sent to the brain, and instructions from the brain to at least partially control the hand.
So far, the project is racking up an impressive list of achievements. It has a complete, fully sensitised five-fingered hand. The CYBERHAND prototype has 16 Degrees of Freedom (DoFs) made possible by the work of six tiny motors.
Each of the five fingers is articulated and has one motor dedicated to its joint flexing for autonomous control. It features that miracle of evolution, the opposable thumb, so the device can perform different grasping actions.
Taking inspiration from the real hand, where a muscle pulls a tendon inside a synovial sheath, CYBERHAND's finger cables run through a Teflon sheath pulled by a DC motor. So the proximal, medial and distal phalanges, those bones between your finger knuckles, are all driven by the same tendon. This approach is called underactuation as there are more Degrees of Freedom than Degrees of Movement (motors); it means the prosthesis has a self-adaptive grasp.
"This is a fundamental feature of the CYBERHAND prosthesis because only a limited number of control signals are available for user’s voluntary control," says project manager, Dr Lucia Beccai. Importantly, it also means less user effort is required to control the hand during daylong use.
The CYBERHAND prototype integrates the two types of human senses. One senses where parts of the body are relative to other parts, whether our fingers are open or closed, for example. The other relates to taste, touch, sound, hearing and sight that tell us about the external world. CYBERHAND includes sensors for tension, force, joint angle, end stroke and contact in the final prototype.
This prototype uses Longitudinal IntraFascicular Electrodes (LIFEs) to connect the hand to the nervous system. Within the CYBERHAND project, in addition to traditional wire LIFEs, a new type of electrode has been developed to improve performance and make them less invasive in humans: the Thin Film LIFE (tfLIFE).
So far, the project has produced excellent science and engineering to create an impressive prototype. The next step is to test the device in humans.
Currently researchers are addressing all necessary medical and ethical issues for implantation in human volunteers. A clinical partner has been identified and the Local Ethical Committee has given the approval for the clinical validation of CYBERHAND system, which should begin in 2006.
The Universities involved in the project are:Scuola Superiore di Studi Universitari e di Perfezionamento Sant Anna