A new technology developed by Swedish researchers could help amputees to control an artificial limb in a very similar way as their own biological hand or arm. The robotic prosthesis mounted to the bone and controlled by thoughts is connected directly to the person’s own nerves and remaining muscles.Although it’s not the first time we hear about a prosthetics arm that ‘feels’ or a rewired nerve system that makes a brain-controlled bionic limb possible, however, today’s commonly used, standard socket prostheses are still very limited and difficult to control. They are attached to the body using a socket tightly fitted on the amputated stump, and are so uncomfortable and limiting that only half of the arm amputees are willing to use one at all.
Max Ortiz Catalan, an industrial doctoral student, claims that the world’s first truly advanced brain-controlled limb is being developed in his laboratory at Chalmers University of Technology. The brain signals are transferred via the nerves through the limb stump and captured by electrodes. These will then transmit the signals through a titanium implant (OPRA Implant System) to be decoded by the prosthetic limb. The prosthesis is anchored directly to the skeleton by a process known as osseointegration.
“We have developed a new bidirectional interface with the human body, together with a natural and intuitive control system.”, says Max Ortiz Catalan, who is planning to implant the prosthetic into a real patient this winter for the first time.
“Osseointegration is vital to our success. We are now using the technology to gain permanent access to the electrodes that we will attach directly to nerves and muscles”, says Max Ortiz Catalan.
Currently, in order to pick up the electrical signals to control the prosthesis, electrodes are placed over the skin. The problem is that the signals change when the skin moves, since the electrodes are moved to a different position. Additionally, the signals are also affected when we sweat, since the resistance on the interface changes.
In this project, the researchers are planning to implant the electrodes directly on the nerves and remaining muscles. Since the electrodes are closer to the source and the body acts as protection, the bio-electric signals become much more stable
With the new method, patients receive feedback as the electrodes stimulate the neural pathways to the patient’s brain, in the same way as the physiological system. This means that the patient can control his or her prosthesis in a more natural and intuitive way.