The art of prosthesis: Making fake hands real

By Heidi Li

Richard Weir, research assoiciate professor of bioengineering at the University of Colorado was showing the journalists artificial fingers at Health Journalism 2014. Photo by Heidi Li

Richard Weir, research associate professor of bioengineering at the University of Colorado showed the journalists artificial fingers at Health Journalism 2014. Photo by Heidi Li

DENVER — In The Empire Strikes Back, after Luke’s right hand was severed by his enemy Vader, he was fitted with a prosthetic hand. We are not far from the end of the movie, when Luke felt the pokes on his prosthetic fingers, as one might think, a bioengineering scientist said at Health Journalism 2014.

In the BioMechatronics Development Lab of the University of Colorado, the art of prosthesis is coming closer to make a fake hand real.

On March 27, Richard Weir, research associate professor of bioengineering at the University of Colorado, introduced the latest development in the BioMechatronics lab to a group of journalists attending the annual conference of the Association of Health Care Journalists.

As if he’d expected the curiosity of journalists about the 3D printers used to print prosthetic hands in the lab, Weir said, “The printers are just tools.” The real task for the lab is the mechanical design of prosthetic hands, including the electronic control of the hands, Weir said.

The toughest challenge is for the amputee to “talk to” the prosthetic hand, Weir said, which means, for instance, the finger doing what the brain wants it to.

Whenever a person want to move his or her fingers, the brain sends out a signal to the spinal cord. Nerves connected to the spinal cord transmit the signal to our fingers. Once the fingers get the signals from the brain, they can move as told.

The implantable myoelectric sensor (IMES) is used to sense the signals from the muscles.

The implantable myoelectric sensor (IMES) is used to sense the signals from the muscles. Photo courtesy of Alfred Mann Foundation.

However, as amputees don’t have a natural connection between their nerves and their prosthetic hands, bioengineers need to create an artificial one in order to allow the brain to control the hands freely.

That new connection is made possible by two main processes:

First, researchers have to sense the signals from the brain, which can be detected in the form of electric field on the surface of muscles. As the signals travel from the brain through nerves into the muscles, it also creates a byproduct: electric current. As a bioengineer, Weir finds the electric signal easier to work with than chemicals, since it can be put into computer and manipulated.

Second, as researchers sense the signal, they have to transmit this signal to the artificial hands, and even further to individual fingers. This process is achieved through sensors implanted in the prosthetic hands. And once those sensors are implanted and connected to the hands, the mission of mind-finger control is complete.

The metal printer in the BioMechatronics Lab. Photo by Heidi Li.

The metal 3D printer in the BioMechatronics Lab is used to print metal prosthetics. It spreads one layer of metal powder, and the laser welded the layer before it spreads another layer of powder. Photo by Heidi Li.

So far, Weir and his team have been working on the second part of the process. One of his group’s major projects is implantable myoelectric sensors (IMES). The project started in 2003, when they received their first grant from National Institutes of Health. The sensors, which are used to pick up the signals from muscles, are tiny cylinders made of ceramics. All the sensors used in this project are produced by their partners: Alfred Mann Foundation in Valencia, Calif. Weir and his team have worked with the foundation on this implantable system in an FDA approved clinical trial.

The first subject of this trial is James Sides, a Navy veteran at the Walter Reed National Military Medical Center, who lost his right forearm in Afghanistan in 2012. He has been wearing a prosthetic socket on his remaining forearm with a metal hand connected to it. There are eight sensors on the socket and they are put on different parts of muscles where signals related to finger control can be sensed.

The artificial finger was printed by the 3D metal printer in the lab. Photo by Heidi Li.

The artificial finger was printed by the 3D metal printer in the lab. Photo by Heidi Li.

Sides has been wearing this new limb since last June. He now can manage daily chores with his right hand fingers moving in different directions.

The metal hand on Sides’ artificial arm was printed by a metal printer in the BioMechatronics Lab, which is one of the few metal printers in the country. Steffen Huddle, the lab’s professional research assistant, said that the lab has had the printer for a year, and the team is now trying to print more prototype implants, as well as other mechanical parts.

Weir and his team are now working on the second generation of IMES, and their goal is to make the implants smaller and more efficient. The implants can last 70 years.

“The ultimate goal is to make them (implants) injectable.” Weir said.

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