New Prosthetic Hand Provides Wearer with a Sense of Touch

A newly developed artificial hand and its neural interface convey touch information to the wearer. The device, which includes 20 touch sensors, was recently demonstrated by a research team with members from Case Western Reserve University and the Cleveland Veterans Affairs Medical Center. A video (embedded below) shows a 48-year-old Ohio man using this prosthetic hand to pick up cherries and remove the stems without crushing the fruits.

Spearheaded by Dustin Tyler, PhD, of Case's Department of Biomedical Engineering, the team attached their prosthetic hand to a man who had lost his hand in an industrial accident three years earlier. In addition to the standard myoelectric interface that attaches to the subject's muscles to control movement of the hand, three pea-sized neural interfaces were surgically implanted on the radial, median, and ulnar nerve bundles in the subject's lower right arm to provide touch information from the sensors in the hand.

These neural interfaces, called cuff electrodes, directly stimulate nerve fibers, called axons. A novel design for the cuff electrodes slightly compresses the nerve from its normal round cross section into a more rectangular shape to maximize surface area. Also new is the technique of stimulating the axons from outside their protective sheath rather than penetrating it as had been previous practice. This approach may be the reason why the implanted interfaces have continued to work for 18 months, impressive when compared with useful lifespans usually measured in weeks for sheath-penetrating neural interfaces.

According to an article in the MIT Technology Review, the 20 sensors in the hand send signals to the cuff electrodes that in turn stimulate the axons to send signals to the brain, giving the sensation of touch to the wearer. The test subject, Igor Spetic of Cleveland OH, says he can perceive sensations that correspond to inputs from the device.

The prosthetic's output can be tuned to provide various sensations to the wearer. Spetic says that sometimes it feels like he's touching a ball bearing, while different adjustments cause the sensation of brushing against cotton balls, sandpaper, or hair. These observations would seem to open the door for a future generation of the device that can provide all these (and perhaps more) sensations as the situation may warrant. Though he hasn't been able to leave the lab wearing the device, Spetic says, "It's real exciting to see what they are doing, and I hope it can help people."

Such sensing technology could become even more sophisticated in the future.

University of Chicago researchers say that they were able to use electrodes attached to monkeys' brains to stimulate neurological patterns that normally arise from skin being touched.

Simulation of sensation of pressure on the fingers was also achieved -- as was the burst of brain activity that takes place when a hand first touches or releases an object.