Michael De Gregorio, a doctoral candidate in mechanical engineering at Arizona State University, Tempe, is researching how to improve the sensitivity of prosthetic hands. He wants to uncover the mechanism that will make the artificial hand respond as if it were integrated with the human body’s signaling system, according to an online article published January 21 by De Gregorio’s undergraduate alma mater, Lafayette College, Easton, Pennsylvania.
“I’m trying to characterize human hand reflexive responses to put those reactionary forces into prosthetic or robotic hands so they behave more human-like and reduce the burden of having to connect directly to the nervous system,” De Gregorio was quoted as saying. “It’s like putting in pre-programmed reflexive responses so the hand knows how to react.”
This reflexive response, known as a spinal reflex, travels from an external stimulus to the spinal cord and back again without going all the way up to the brain. An example of a spinal reflex occurs when a hand is pulled away from a hot stove before feeling the sensation of heat. Harnessing this type of reflex is particularly challenging because, De Gregorio explains, no one has yet found an effective way to connect neurons to wires.
“There’s no real good interface for it,” he notes. “Researchers have done work with surface electromyography where the nerves from the…[residual limb] are redirected into the chest. The researchers were able to connect the electrodes so they read the signals to those nerves and the patient could control the hand using the chest muscles. But the real challenge is bridging the gap between human and machine, being able to place material inside the body that it won’t reject.”
Another main challenge, he says, is getting tactile feedback from a hand to a human so that the patient can actually feel what his or her artificial hand is grasping. The size and weight of any prospective device is also a concern because, De Gregorio points out, the device needs to be small and light enough so that people will actually use it.
