[youtube]https://www.youtube.com/watch?v=zsuhazxu-HQ[/youtube]
A man who had his lower arm amputated has regained a realistic sense of texture using a bionic finger surgically connected to his nerves
鈥淚 could tell the difference between rough and smooth 鈥� it was amazing,鈥� says Dennis S酶rensen.
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People who have had their hand or arm amputated can use a prosthetic body part to help them lift or grip objects. A device that could also recreate their sense of touch would make it easier for them to identify and manipulate objects.
To replicate this sense, and his team at the 脡cole Polytechnique F茅d茅rale de Lausanne in Switzerland developed a bionic finger containing electromechanical sensors that deform when touched.
The sensors send an electrical signal to a computer. This converts the signal into a sequence of on-off commands, stimulating nerves via electrodes surgically inserted into the upper arm. The patterns of stimulation closely emulate those that naturally occur when you run your finger across different textures.
Realistic touch
To test the sensors, Micera鈥檚 team hooked the bionic finger up to a machine that moved it over different pieces of plastic engraved with smooth or rough textures. The finger was also connected to electrodes surgically implanted in S酶rensen鈥檚 upper arm.
When the finger moved, he experienced the sensation of texture where the index finger of his amputated arm had been. He could distinguish between surfaces 96 per cent of the time.
鈥淚t was very close to the feeling in my real arm 鈥� you can feel coarseness and the different gaps and ridges,鈥� says S酶rensen, who lost his lower arm in a firework accident in 2003 after a rocket blew up in his hand.
The idea is to eventually combine the fingertip sensors within a full prosthesis, allowing people to grip and feel objects.
No surgery required
Micera鈥檚 team also tested the bionic finger on four non-amputees using a single electrode inserted into the upper arm like an acupuncture needle. These volunteers were able to distinguish textures 77 per cent of the time.
The minimally invasive procedure should help accelerate the development of realistic-touch prostheses because it means they can be tested without the need for surgery.
By comparing the non-amputees鈥� brainwaves when they felt texture using their real finger and the bionic version, Micera鈥檚 team demonstrated that the sensations picked up by the bionic finger did indeed resemble those felt naturally.
鈥淭he brainwaves were similar in both experiments,鈥� says team member at the Biorobotics Institute in Pisa, Italy.
Rough and ready
A previous study by at the Louis Stokes Veterans Affairs Medical Center in Cleveland, Ohio, and his colleagues in 2014 gave amputees back a sense of touch and pressure, allowing them to without crushing the fruit.
Very important characteristics of sensations were shown in Tyler鈥檚 experiments, such as force and pressure, but not fine textures, says Oddo. 鈥淣ow we are working towards allowing amputees to experience more natural stimuli like the texture of jeans 鈥� the things you would touch in the real world.鈥�
Journal reference: eLife, DOI:
