Amputee Feels Textures in Real-Time with Bionic Fingertip

Amputee Dennis Aabo Sørensen was able to feel smoothness and roughness in real-time with an artificial fingertip that was surgically connected to nerves in his upper arm. The nerves of non-amputees can also be stimulated to feel roughness, without the need of surgery, meaning that prosthetic touch for amputees can now be developed and safely tested on intact individuals. The technology to deliver this sophisticated tactile information was developed by researchers at Switzerland's EPFL and Italy's SSSA. The results provide new and accelerated avenues for developing bionic prostheses, enhanced with sensory feedback. Sørensen is the first person in the world to recognize texture using a bionic fingertip connected to electrodes that were surgically implanted above his stump. Nerves in Sørensen's arm were wired to an artificial fingertip equipped with sensors. 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. Sørensen could distinguish between rough and smooth surfaces 96% of the time.

Transcript

00:00:00 I could tell the difference between where it was very rough and smooth, and yeah... that was amazing. When the scientists stimulated my nerves, I could feel the vibration and sense of touch in my phantom index finger. The touch sensation is quite close to when you feel it with your normal finger. You can feel the coarseness of the plates and the different gaps and ribs. We showed that it is possible to deliver to amputees a very sophisticated part of the sense of touch, which is texture discrimination. It is possible to achieve this thanks to electrodes surgically implanted into the peripheral nervous system of the subject.

00:00:48 So the fingertip, inside, has these miniaturized sensors that are MEMPS, so micro-electro-mechanical systems that are made in silicon, and they deform, and the output of those sensors is electrical signals and then is converted by means of an artificial neural model into the sequence of spikes. Spikes are like on/off the events that stimulate the nerves of the subjects by means of the neural interface. We also show that it is possible to deliver the same kind of sensation to intact subjects using electrodes temporarily implanted into the nerves. This is extremely important because now we know that many of the things we are testing in intact [subjects ] can be

00:01:38 used later, if successful, in amputees. This means that we can really accelerate the translation of different approaches.