Thought-controlled robotic arm could change lives of amputees

"Every year, thousands of people across the world lose an arm or a leg," said Max Ortiz Catalan, an industrial doctoral student at Chalmers University of Technology. "Our technology helps amputees to control an artificial limb, in much the same way as their own biological hand or arm, via the person's own nerves and remaining muscles." Catalan and his team began by developing a bidirectional interface with the human body, together with a natural and intuitive control system called the Brånemark titanium implant instead (OPRA Implant System), which anchors the prosthesis directly to the skeleton. This is done by a process called osseointegration, which refers to the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant. "Osseointegration is vital to our success," Catalan noted. "We are now using the technology to gain permanent access to the electrodes that we will attach directly to nerves and muscles." 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. The signals are also affected by sweat, since the resistance on the interface changes. In this project, the researchers are planning to implant the electrodes directly to the nerves and remaining muscles instead. The idea is that because the electrodes are closer to the source and the body acts as protection, the bio-electric signals will become much more stable. "Osseointegration is used to enable the signals inside the body to reach the prosthesis," Catalan explained. "The electrical impulses from the nerves in the arm stump are captured by a neural interface, which sends them to the prostheses through the titanium implant. These are then decoded by sophisticated algorithms that allow the patient to control his or her prosthesis in a more natural and intuitive way." The first operations on patients are due to take place this winter. If successful, Catalan says the team will be the first in the world to make thought-controlled prostheses a reality.