Thanks to researchers from the University of Illinois (UI), losing a limb no longer means the attendant cessation of sensory feedback – coupled with a prosthetic arm, a new control algorithm delivers mild electrical stimulation to sensory nerves, thereby creating an actual sense of touch.
“We’re giving sensation back to someone who’s lost their hand. The idea is that we no longer want the prosthetic hand feel like a tool, we want it to feel like an extension of the body,” said lead author on the project Aadeel Akhtar, an M.D./Ph.D student at UI.
Prosthetic arms that offer nerve stimulation have sensors on the fingertips, so that when the user comes in contact with something, an electrical signal on the skin corresponds to the amount of pressure exerted.
However, up until now, delivering real-time feedback has been fraught with multiple problems, such as painful electrical shocks resulting from the electrodes peeling off and causing a build-up of current, and sweat impeding the connection and lessening felt sensations on the skin.
“A steady, reliable sensory experience could significantly improve a prosthetic user’s quality of life,” said Timothy Bretl, a professor of aerospace engineering, and principal investigator on the study.
The controller developed by the researchers monitors the feedback the patient is experiencing and automatically adjusts the current level to prevent uncomfortable over- and under-stimulation even when sweating or when the electrodes are 75 percent peeled off.
In order to make sure everything works as intended, the team conducted a series of tests on two volunteers who were asked to perform a physically strenuous task, designed to induce sweating, or had the electrodes in their prosthetics peeled off to varying degrees.
“What we found is that when we didn’t use our controller, the users couldn’t feel the sensation anymore by the end of the activity. However, when we had the control algorithm on, after the activity they said they could still feel the sensation,” Akhtar said.
According to the research team, their current goals are to miniaturise the controller, making it fit inside the prosthetic itself, and balance the costs so that the new system could be covered by regular health insurance.