European researchers have created a robotic hand that gave an amputee a sense of touch—something he had not felt in over a decade. In an experiment that lasted a week, a patient was able to feel differences in objects such as a bottle, a baseball, cotton, and a Mandarin orange, and distinguish whether they were soft, round, or slender, and adjust his grasp on the objects intuitively.
Amputee Dennis Aabo Sorensen lost his left hand in a firework accident. Doctors at Gemelli Hospital in Rome, Italy implanted tiny electrodes inside two nerves in the stump of Sorensen’s arm. When the nerves were stimulated with an electrical signal, Sorensen said it felt like his missing fingers were moving.
The team of doctors then put sensors on two fingers of a robotic hand in order to detect information about what the robotic fingers touched. This information created a loop that let the robotic hand rapidly communicate with Sorensen’s brain so that he could feel and react in real time.
This latest experiment is among the most advanced in the prosthetics field. Creating the sense of touch has been a difficult challenge, and is one of the reasons many patients don’t use their prosthetic hands as much as they would like to.
To make sure Sorensen used touch during the experiment, and didn’t cheat by looking or hearing, he wore headphones and a blindfold as the team handed him objects.
More research is needed on nerve implants, and whether or not they can last. For safety reasons, Sorensen’s were removed after the week of experimentation was complete.
Other approaches to prosthetics with a sense of touch have been made. A team in Ohio recently issued a video showing a blindfolded man pulling stems from cherries without crushing them. The man in the video also used implanted nerve stimulators and a sensor-equipped prosthetic hand. The difference between this experiment and the one conducted in Rome is that Sorensen’s nerve electrodes were implanted inside the nerve rather than around it in order to achieve better control. Researchers worry that this way could damage the nerve over time.
Another team in Pittsburgh is about to test another approach that would allow paralyzed individuals to ‘feel’ through electrodes implanted in the sensory cortex.
Touch is a complex sense, and although great strides are being made in the field of prosthetics, many aspects of touch have been largely ignored, such as texture and temperature. Though it will takes years of additional research before these sophisticated aspects of touch are implemented, these experiments are major milestones in the effort to create a more lifelike prosthetic.