University of Colorado Boulder (CU Boulder) biomedical engineer Jacob Segil is working to restore the sense of touch for amputees, including veterans of the wars in Iraq and Afghanistan.

An instructor in the Engineering Plus Program and program director for the Center for Translational Research at CU Boulder, Segil is designing artificial limbs that may one day allow amputees to feel the world around them through electronic sensors.

“In my field, we have a gold standard, which is the physiological hand,” Segil says. “We’re trying to recreate it, and we’re still so far off.”

Scientists may not be that far off, though. An effort led by Case Western Reserve University and the VA has allowed Segil and his colleagues to give a small number of amputees back the sense of touch in their missing fingers using a unique “neural interface.” The team demonstrated the effectiveness of this sensory restoration technology in a new study that was published in the May edition of the journal Scientific Reports. The team helped an amputee feel his hand adopt a series of postures, such as a gesture resembling the thumbs-up sign.

Segil, who is also a research healthcare scientist at the U.S. Department of Veterans Affairs, has received a $1 million Career Development Award from the VA to continue his work, which will allow him to help real people using his engineering skills. 

“A lot of us engineers would just be happy building stuff,” Segil says. “But as a VA researcher, your work can help the people who served our country. It’s a powerful motivator.”

Tricking the brain

Segil has long been fascinated by the idea of studying the human body as a machine. This interest led him to earning his PhD in mechanical engineering from CU Boulder. After receiving his PhD, Segil began a postdoctoral research position split between two VA centers: the Louis Stokes Cleveland VA Medical Center in Ohio and the Rocky Mountain Regional VA Medical Center in Aurora, Colorado.

During his time in Cleveland, Segil worked with Dustin Tyler, a biomedical engineer, and explored the benefit of prosthetic limbs that can feel. In the 2000s, Tyler invented a way to, essentially, hotwire the human nervous system. Known as a nerve cuff electrode, the interface surrounds the nerves and zaps them with electronic pulses. When those signals are adjusted just right, they will travel to the brain and trick it into thinking that it can feel fingers, even if there are no fingers to feel.

“We’re tapping into that wire before it gets to the brain, and then the brain can’t tell whether it’s coming from the finger or from our artificial system,” Tyler, a professor at Case Western and a VA researcher, explains.

Thus far, just four patients have undergone the surgery needed to receive that sensory feedback, but the project is a huge breakthrough in prosthetics, according to Segil, as he notes that while artificial hands have grown more high-tech in recent years, many amputees still choose not to use them in large part because they are numb.

“All prosthetic devices that have ever been used are ‘disembodied,’” Segil says. “They are tools, external to the body. They’re the equivalent of a tennis player and their racket.”

In the recently published case study, Segil and his colleagues began to examine whether sensing prosthetics could do more, and actually become a meaningful part of a person’s body.

The researchers worked with one volunteer, a man in his 40s who had lost his arm below his elbow six years before. They fed his neural interface varying patterns of sensory information, such as cues that he was picking up a penny. While his prosthetic was hidden from view, the man was asked to decide what position his hand was in from a menu of seven postures.

The interface worked. With enough practice, the man was able to identify the seven postures with up to 95 percent accuracy.

“When you have five points of information, the user is able to synthesize those to get a broader view of what the state of the hand is,” Tyler says.

Segil will use the funding he received to push his research forward. The research will be split between the VA centers in Ohio and Colorado. His current work will focus on the psychology of prosthetics as much as the engineering, i.e., what will it take for amputees to think of their artificial limbs as real body parts? Segil is hopeful that patients in Colorado will soon be able to receive their own neural interfaces.