Neuromorphs

If you really want to get an eyeful of what the future of technology holds in store- and we’re back at human scale now-check out one of the Web pages for the laboratory of electrical engineering Professor Ralph Etienne-Cummings. There’s a short video loop of a pair of metal robotic legs running-running! -on a treadmill. To achieve this, Etienne-Cummings and his colleagues built a computer chip that mimicked the “central pattern generator” signals that spinal neurons use to control walking in mammals. They even made it robust enough to adjust to obstacles and stumbles.

For the past few years, initially with help from a DARPA grant and now mainly with National Institutes of Health and Office of Naval Research funding, Etienne-Cummings has been trying to apply this technology not so much to make humanoid running bots but to make bots that help injured humans run again, or at least walk. In a way it’s the ultimate bio-inspired robotic design, for it is meant not just to mimic biology but to mesh with it.

“In a typical spinal cord injury, the link from the brain to the spinal cord is broken, but the link from the spinal cord to the muscles is still intact, even though the muscles may be somewhat atrophied,” Etienne-Cummings explains. “So our idea is to use electrical stimulation to activate the leg muscles via the spinal cord, as well as a light mechanical exoskeleton to provide extra support.”

He and his colleagues already have shown that they can stimulate a paraplegic cat’s hind-leg muscles, via spinal cord neurons, to enable the cat to run for hours without tiring. The next steps are to add the exoskeleton-the easy part-as well as sensory feedback, which is definitely the hard part. Natural motion, especially motion that involves contact with the ground and fine control of balance, requires a high degree of sensation, but reproducing the complex sensory feedback of touch and pain -something that even a big-brained human child takes years to learn-is really a fledgling area of robotics. Still, Etienne-Cummings is one of the pioneers in the field, and has long been working with Johns Hopkins neuroscientist Steven Hsiao on the problem. “Our idea initially is to use external sensors to stimulate the spinal cord or even the brain, to restore sensations of limbs and their positions and movements,” Etienne-Cummings says.

Could one use such technology to make 60 mph bionic humans?

Etienne-Cummings laughs. “You could make lots of bulky, power-hungry machines that carry a person along that fast, but our idea is to create something that’s as passive and integrated and efficient as possible at restoring natural function,” he says. “One thing you learn in this field is that biological systems are already very efficient; it can be hard to improve on their design.”