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Dismemberment Plan: Lifehand 2 Develops Sensational Prosthetic

Christian Sager

Remember at the end of "The Empire Strikes Back" when Darth Vader lops off Luke Skywalker's hand? Just before the credits roll we see Luke in a medical bay with a droid testing the reflex sensitivity of an easily attached, new bionic hand. That science fiction always seemed awfully convenient. He could bounce back from dismemberment that easily? Well as of this week, reality is one step closer to that convenience.

In the February issue of "Science Translational Medicine," researchers reported that Denmark's Dennis Aabo Sørensen became the first amputee to experience feeling in real-time through a prosthetic hand. Obviously, losing a hand is both disabling and traumatic. Until now, Sørensen's worn a prosthetic that detects his muscle movements to open and close on objects. "Lifehand 2," a collaboration between several European universities and hospitals worked with Sørensen to develop sensation in his artificial limb. The team is led by Silvestro Micera at the Ecole Polytechnique Fédérale de Lausanne Center for Neuroprosthetics.

The problem Micera's team sought to address was a hand replacement that provided the same sensations we naturally perceive through contact, with the equivalent speed of our nervous system. By using a sensory-enhanced prosthetic that was surgically wired into the nerves of Sørensen's arm, they found their solution.

In January 2013, a group of surgeons and neurologists implanted transneural electrodes into the ulnar and median nerves on Sørensen's left arm. These electrodes are described as "ultra-thin" and "ultra-precise" so they can relay weak electrical signals directly into the human nervous system. Significant research was done beforehand to ensure these electrodes would work after Sørensen's arm formed post-surgery scar tissue over them.

The arm electrodes were just one part of this bionic hand's success. Micrea's team translated tension in the hand's artificial tendons into a coarse electrical current. Through computer programming, they transformed the signal into an impulse that Sørensen's nerves could interpret. This signal travelled through wires from the hand to the electrodes. For safety reasons, the electrodes were removed from Sørensen's arm after a month. But the "Lifehand 2" team thinks they could have been kept in there for several years. The arm however would require rigorous wound care to prevent infection.

Outside of this major breakthrough for amputees, consider the other applications of this science. Micera already studies other neural interfaces to:

  • rehabilitate stroke victims,
  • assess fall risks,
  • assist the disabled with lightweight exoskeletons
  • and to gauge our human response to the "uncanny valley" facial expressions of humanoid robots.

But there's transhuman value here as well, with possibilities for body modification replacements, or even extra limbs. Before we jump that far ahead though, Micera's group intends to miniaturize the sensory feedback electronics so this prosthetic is portable. It will also require some fine-tuning to improve its tactile resolution.

We're one step close to bionic hands and hopefully two steps back from maiming our children with laser swords.

Feature Photo Credit: © 2014 EPFL / Hillary Sanctuary

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