Girl with prosthetic arm holding a mug

Mind-controlled bionic arm with sense of touch ‘could be available in two years’

Image credit: Albertshakirov | Dreamstime

Amputees across Europe could be able to control their bionic arms with their thoughts within the next two years, Swedish designers have said, as they add a feature to existing prototypes to give patients a touch sensation.

The system, which allows the use of a bionic arm without the need for any supporting equipment in the form of an implant, is already available in Sweden. Now, the system's designers at Chalmers University of Technology are working toward getting European certification (CE mark) for the product so it complies with the EU’s safety and health protection requirements.

This medical device, which can connect to any commercially available arm prosthesis, has been trialled for several years by three Swedish patients with an amputation above the elbow.

Dr Max Ortiz Catalan, an associate professor at Chalmers, said that their prosthesis could be a clinically viable replacement for a lost arm.

“People in Sweden can have this technology now,” he said, adding that the team were working to ramp up the production before the pandemic began. “We are aiming to have it CE marked soon, within two years, and once it is CE marked, it can be available in Europe as a product.”

Dr Max Ortiz Catalan (left), assisting a patient with their prosthetic arm.

Max Ortiz Catalan (left) in a follow up appointment with one of the patients, at the Chalmers Biomechatronics and Neurorehabilitation Laboratory.

Image credit: Chalmers University of Technology

Two of the three patients involved in the clinical trial have been using their bionic arms for around three years, while the third participant has been using his artificial limb for seven years. Furthermore, a new functionality – the sensation of touch – has recently been added to all three of the prosthetic arms.

Dr Ortiz Catalan said that the implant system is stable and can be used for long periods of time without any intervention from the scientists. He also said that the system can deliver sensations that feel like they are arising from the missing hand.

“The real breakthrough here is that this neuromusculoskeletal interface, as we call it, allows the artificial limb to be connected to the body,” he explained. “And when you have that intimate connection between the technology and biology, you can have better control and establish sensory feedback.”

Patients can feel when touching an object with their new neuromusculoskeletal prosthesis, which is essential for imitating a biological hand.

Patients can feel when touching an object with their new neuromusculoskeletal prosthesis, which is essential for imitating a biological hand.

Image credit: Johan Bodell/Chalmers University of Technology

In regard to how the system works, the implant system anchors the prosthesis to the skeleton in the stump of the amputated limb, through a process called osseointegration (from the Latin osseus, meaning 'bony', and integrare, meaning 'to make hole'). Electrodes are implanted in muscles and nerves inside the amputation stump, and the system sends signals in both directions between the prosthesis and the brain, similarly to a biological arm.

The prosthesis is mind controlled via the electrical muscle and nerve signals sent through the arm stump and captured by the electrodes. The signals are passed into the implant, which goes through the skin and connects to the prosthesis.

The signals are then interpreted by an embedded control system developed by the researchers. According to the team, this system is small enough to fit inside the prosthesis and processes the signals using artificial intelligence algorithms, resulting in control signals for the prosthetic hand’s movements.

The touch sensations arise from force sensors in the prosthetic thumb. The signals from the sensors are converted by the control system in the prosthesis into electrical signals, which are sent to stimulate a nerve in the arm stump. The nerve leads to the brain, which then perceives the pressure levels against the hand.

An X-ray Image and Illustration of the Mind-Controlled Prosthesis with Sensation

Image credit: Illustration: Sara Manca /Yen Strandqvist/Chalmers University of Technology

Patients are able to feel when they are touching an object, its characteristics, and how hard they are pressing it, the researchers added. However, Catalan noted: “We are not under the illusion that this technology is perfect – there is still a long way to go. In the meantime, we are looking to increase functionality by adding more sensations and more control.”

In March 2020, University of Michigan researchers developed ‘nerve interface’ technology that could allow amputees to move individual fingers at the end of prosthetic limbs using their mind.

Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.

Recent articles