A bionic fingertip lets amputees feel textures, marking a huge step forward in the progress of prostheses.
Through surgical installation, the device is connected to nerves, but even people who are not amputees will be able to test it via needles that penetrate the skin of the wearer's arm.
Neuroengineer Silvestro Micera worked on the technology with the help of his team at the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland and the Sant'Anna School of Advanced Studies (SSSA) in Italy.
The researchers carried out experiments with Dennis Aabo Sørensen from Denmark. About 11 years ago, he had an unfortunate firework accident that injured his left hand. After he was brought to the hospital, the doctors had to amputate it.
They started with a bionic hand that allowed Sørensen to determine whether an object in the prosthetic is either "soft or hard, round or square," as he put it, back in 2014. Because of that, little or no preparation was required to begin testing the artificial fingertip, as his ulnar and median nerves were already set with the interface.
The device sent out signals similar to what the nervous system delivers in the form of electric signals that are converted to electrical spikes, which were then transmitted to the nerves of Sørensen.
"The more we are able to reach the complexity of the natural sense of touch, the more usable the device will be," Micera tells Live Science.
With the fingertip in place, Sørensen was capable of telling the difference between smooth and rough surfaces with a 96 percent success rate. According to the researchers, he is the first person to be able to do so with a bionic prosthetic.
"The stimulation felt almost like what I would feel with my hand. 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," Sørensen says.
Non-amputees also tested the device, where the volunteers could only distinguish the two different surfaces 77 percent of the time. It's speculated that Sørensen had a better performance because the electrodes were surgically implanted.
The researchers also scanned the brains of Sørensen and the volunteers. They found out that they all exhibited similar activity, even with the non-amputees using their own fingers. This means that the fingertip is able to produce the same sensations as touching with natural fingers can.
The artificial fingertip has already been consolidated with a prosthetic hand. Micera says that the team intends to do more experiments using the whole device with patients before 2016 ends.
"This study merges fundamental sciences and applied engineering: it provides additional evidence that research in neuroprosthetics can contribute to the neuroscience debate, specifically about the neuronal mechanisms of the human sense of touch. It will also be translated to other applications such as artificial touch in robotics for surgery, rescue, and manufacturing," Calogero Oddo, a bioengineer at the BioRobotics Institute of SSSA, says.
The people behind the technology published their research in the journal eLife.
The video below shows how the tests were conducted and how the device works.