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Researchers at McCormick are exploring ways to build and control better prostheses for arm amputees. Todd Kuiken (PhD ’89, Feinberg ’90), associate professor of biomedical engineering and physical medicine and rehabilitation and director of the Neural Engineering Center for Artificial Limbs at RIC; Richard Weir (MS ’89, PhD ’95), clinical professor of biomedical engineering and research associate professor of physical medicine and rehabilitation; Michael Peshkin, professor of mechanical engineering; and Ed Colgate, Pentair–D. Eugene and Bonnie L. Nugent Teaching Professor and professor of mechanical engineering, are pursuing collaborative research that aims to allow arm amputees to control their prosthetic hands and arms just as you control yours — without even thinking about it.

Peshkin and Colgate are building on concepts developed in Kuiken’s work in nerve transfer. Kuiken takes the nerves that would have gone to a missing arm and transfers them into the pectoral muscle. The nerves grow into the new muscle, telling it to contract and relax based on the signals that would have controlled the arm. Using these signals, the patient is able to intuitively control a motorized prosthetic arm. Kuiken’s first patient, Jesse Sullivan, was dubbed the world’s first “bionic man” after his successful nerve transfer in 2003 and the fitting and implementation of new prosthetic arms.

Unexpected results

Kuiken discovered that the nerves transferred into Sullivan’s chest also grew into the skin on his chest, causing him to feel touch and temperature applied there as if it were in his hand. With this unexpected finding, Richard Weir and others worked to develop a proof of concept for a device that could communicate the sense of touch to a patient’s chest. The team then connected with Michael Peshkin and Ed Colgate, who have based a significant part of their research on the study of haptics, or the sense of touch, mostly in relation to robotics.

Colgate and Peshkin are now developing tactors — microrobots that can convey haptic sensations to a patient’s chest — for use in conjunction with prosthetic arms. While the research is still in its early phases, the results have been remarkable. The device can apply force in several directions and heat up and cool down based on temperature sensors. In testing, Sullivan and Claudia Mitchell, a single-arm amputee outfitted with the bionic arm, have been able to differentiate between satin ribbon and sandpaper and feel temperature changes. This advance has both practical and social importance.

“When I asked Jesse what he wanted to do with a sense of touch, he said he wanted to be able to hold his wife’s hand,” explains Colgate. “There’s a big social dimension to this work that is sometimes underappreciated.”

Humans and robots collaborate

Colgate and Peshkin are also focusing on developing an arm based on their work in cobotics, a class of robotic devices intended for direct physical collaboration with human operators. Their prosthetic hand runs off of a central motor in the forearm to control the hand through artificial tendons. This technology is inherently flexible, allowing the arm to have a similar amount of “give” as a human arm.

“I think this project may really advance the state of the art,” says Colgate. “Coupled with Todd Kuiken’s research, it has a shot at being really helpful.”

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