Dennis Aabo Sorensen became the first amputee able to recognize different textures using a bionic finger that was surgically connected to nerves in his upper arm.

A machine controlled the movement of the fingertip over different pieces of plastic engraved with different patterns, smooth or rough. As the fingertip moved across the textured plastic, the sensors generated an electrical signal. This signal was translated into a series of electrical spikes, imitating the language of the nervous system, then delivered to the nerves. Sorensen could distinguish between rough and smooth textures 96 percent of the time.

“The stimulation felt almost like what I would feel with my hand,” said Sorensen. “I still feel my missing hand, it is always clenched in a fist. I felt the texture sensations at the tip of the index finger of my phantom hand.”

The technology to deliver this sophisticated tactile information was developed at Switzerland’s EPFL (Ecole polytechnique federale de Lausanne), NCCR Robotics and Italy’s SSSA (Scuola Superiore Sant’Anna) research institute. The researchers said this development could be used for other applications as well, including “artificial touch in robotics for surgery, rescue, and manufacturing.”

This same experiment was also tested on non-amputees. The tactile information was delivered through needles that were temporarily attached to the arm’s median nerve through the skin. The non-amputees were able to distinguish roughness in textures 77 percent of the time.

But does this information about touch from the bionic fingertip really resemble the feeling of touch from a real finger? The scientists tested this by comparing brain-wave activity of the non-amputees, once with the artificial fingertip and then with their own finger. The brain scans collected by an EEG cap on the subject’s head revealed that activated regions in the brain were analogous.

How the bionic fingertip works. Source: EPFL