The Artificial Hand that FeelsA new technology reconnects amputees to the world of sensation
Scientists have developed a system of electrodes and algorithms that has successfully enabled people to ‘feel’ through artificial hands. Read More
A team of scientists led by Dustin Tyler from Case Western Reserve University in Ohio is reporting a breakthrough that might soon enhance the lives of amputees around the world. They have developed a system of electrodes and algorithms that has successfully enabled people to ‘feel’ through artificial hands.
Igor Spetic and Keith Vonderhuevel both lost their right hands in accidents. Two and a half and two years ago respectively, electrodes were implanted around the major nerve bundles in their arms under the skin. The electrodes connect to a prosthetic system developed by Dustin and his team – with astonishing results. Not only are Spetic and Vonderhuevel able to control their artificial hands with more dexterity; they also report sensations they haven't felt since their accidents.
In the lab, a technician brushes a cotton ball over the back of the prosthetic hand of a blindfolded Spetic. This gentle touch is enough to trigger a pattern of electric signals sent by a computer to nerves in his arm and from there to his brain, and Spetic can identify the sensation. "I knew immediately it was cotton," he proclaims.
In similar experiments, Vonderhuevel felt water running across the back of his hand. He was also able to pick up grapes and cherries, and even remove the stems. "When the sensation’s on, it’s not too hard," he said after a session at the Case Western Reserve lab. "When it’s off, you make a lot of grape juice."
"The sense of touch is one of the ways we interact with objects around us"
The remarkable results are possible thanks to sensation algorithms that convert the input transmitted from sensors taped to the patient’s hand into electrical signals of varying intensity. "The sense of touch is one of the ways we interact with objects around us," says Dustin, associate professor of biomedical engineering. "Our goal is not just to restore function, but to build a reconnection to the world. This is long-lasting, chronic restoration of sensation over multiple points across the hand."
In addition to restoring sensations that were hitherto unthinkable for Vonderhuevel and Spetic, the treatment has caused another unexpected benefit: Both patients witnessed a remarkable decline in phantom limb pain as soon as the algorithm was up and running.
Ready for home use in five years
At the moment, the system itself is limited to the lab. A lot of the electrodes and technology developed at Case Western Reserve, however, are already on the market and used around the world. For example, the osseointegrated human-machine gateway biomedical engineer Max Ortiz-Catalan is currently working on at Chalmers University of Technology relies on electrodes from Ohio.
"The sense of touch is one of the ways we interact with objects around us."
Because of Vonderheuval’s and Spetic’s continuing progress, Dustin is hopeful the method will be suitable for lifelong use. He is optimistic his team can develop a system a patient could use at home within five years.
"The main challenges are the sensors themselves. They need to be incorporated into the prosthesis at the appropriate locations and be robust enough to sustain everyday usage. Next they need to be connected to the stimulation system and then to the electrode. All of this needs to be sufficiently tested to ensure the safety of our users. To be fully useful in more than a research setting, the whole system needs to be implanted. This is in our five year plan and will require significant effort and resources," explains Dustin, who emphasizes that he and his team are actively developing the technology and very optimistic about its realization.