The bionic fingertip has enabled an amputee to distinguish between different textures in real-time with 96% accuracy.
Image credit: Hillary Sanctuary/EPFL
Dennis Aabo Sørensen, who lost his hand in a firework accident more than a decade ago, says the sensations he felt with the novel device were almost the same as those he felt with his real hand.
The creators of the artificial fingertip, including Silvestro Micera of the Ecole polytechnique fédérale de Lausanne (EPFL) in Switzerland, say the development brings us closer to "sensory restoration in the next generation of neuro-prosthetic hands."
In 2014, Medical News Today reported on another bionic creation from Micera and colleagues: a sensory-enhanced artificial hand.
Sørensen became the first amputee to feel objects in real-time with the artificial hand; he was able to detect the shape and consistency of objects with the device, as well as the strength of his grasps on them.
Now, Sørensen has taken the title of the world's first amputee to be able to distinguish between different textures - roughness and smoothness - using a novel bionic fingertip.
Bionic fingertip enabled accurate identification of rough, smooth textures
The artificial fingertip consists of an array of sensors, which were connected to electrodes implanted in the nerves of Sørensen's upper arm.
The movement of the bionic fingertip was controlled by a machine, which moved the device across a variety of textured plastics, some of which were smooth and some rough.
The sensors in the bionic fingertip generated an electrical signal as the device moved across the plastic. This signal was converted into a number of electrical spikes that mimicked nervous system signaling, simulating touch.
Using the bionic fingertip, Sørensen was able to distinguish between the rough and smooth plastics with 96% accuracy.
"The stimulation felt almost like what I would feel with my hand," says Sørensen. "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."
Findings show device can be safely tested in non-amputees
In a study published in the journal eLife, Micera and colleagues tested the efficacy of the bionic fingertip for identifying textures using four non-amputees.
The researchers used needle microstimulation, which involved using a fine needle to temporarily attach the bionic finger to the participants through an electrode implanted into the median nerve of the upper arm. The median nerve provides motor and sensory stimulation to parts of the forearm and hand.
Participants were then asked to distinguish between rough and smooth textures; they were able to do so with almost 77% accuracy.
To determine whether the touch sensations produced by the bionic finger were similar to those produced by a real finger, the researchers compared participants' brainwaves as they used the bionic finger and their own finger to touch different textured surfaces.
The researchers found that the brain regions the bionic finger and the real finger activated were comparable in each participant, suggesting the sensations felt using the bionic finger resembled those that were felt naturally.
The team says their findings are promising; they show that needle microstimulation delivers sensory information in a similar way to implanted electrodes, meaning the artificial fingertip can be developed and safely tested on non-amputees without the need for surgery.
Commenting on their overall results, the researchers say:
"The promising results obtained with microstimulation in four intact subjects, combined with robust translational indications from the hybrid model and an excellent outcome from one amputee, prompt the idea that neuromorphic stimulation could be a natural and effective tool for eliciting texture discrimination abilities via hand prostheses."
Last month, MNT reported on a study detailing the creation of a bionic brain implant that could help paralyzed people walk just by thinking about it.