Research on robotic prostheses is
coming along in leaps and bounds, but one hurdle is proving quite tricky to
overcome: a sense of touch. Among other things, this sense helps us control our
grip strength - which is vitally important when it comes to having fine motor
control for handling delicate objects. Thanks to biomedical engineers at the
University of Utah, for the participants of their experimental study, the arm
can now also produce an ability to feel. This spectacular advance allowed one
wearer to handle grapes, peel a banana, and even feel his wife's hand in his. The
arm has been in development for 15 years, and it taps into the way our brains
control our limbs by sending signals through the nervous system. This
technology is called peripheral nerve stimulation, and engineers have been
exploring its use in upper limb prostheses for years. Electrodes are attached
to the nerves in the arm above the amputation site, and to the prosthetic.
The user then thinks about moving
the hand and arm. It takes a bit of training but gradually the software that
runs the arm learns the user's neural signals for controlling the prosthesis,
and basic dexterity is restored. But sense of touch is relayed from the limb to
the brain, so to generate a robotic ability to feel, the research team needed
new tricks. The robotic hand has sensors that can mimic the feeling of touch. The
challenge to relay that information back to the brain in the correct way is the
next, more difficult step. A feeling prosthetic developed by DARPA and unveiled
in 2015 solved this with electrodes connected directly to the sensory cortex of
the brain, but the team wanted a less invasive solution. When you touch
something, a burst of signals is immediately sent up the nerves to the brain,
after which it tapers off. The team recorded this activity from the arm of a primate
and performed approximations to work out an approximation of how this happens
in humans.
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