The SMU researchers are heading up the sensing effort, which will be based on an extremely sensitive "whispering gallery" micro-optical sensor technology that they have developed. The system uses micro-beads smaller than a thousandth of a millimeter in diameter that are attached to optical fibers in such a way that some of the light passing through the fiber is siphoned off into the bead where it travels around its circumference. The micro-beads are made of a material with optical properties that change when it is exposed to an electrical field. As a result, the intensity of the laser beam traveling through the optical fiber varies when the bead experiences an electrical field equivalent to that generated by a neuron when it fires.
Fortunately, the researchers do not have to work at the level of individual neurons to create a system to control prosthetic limbs. In the peripheral nervous system, nerves are organized into bundles called fascicles. Basic movements such as moving fingers and toes are controlled by different fascicles.
"So far, all the work we have done with stimulation involves exposing nerves and shining a laser on them at a right angle, Jansen said. "Obviously this won't work for a prosthetic limb application."
The researchers have developed a preliminary design for an implantable "cuff" that would wrap around a nerve. One part of the cuff would contain optical fibers that run parallel to the nerve that are capped with tiny, 45-degree mirrors that would aim laser beams at individual fascicles.
"We're certain we can stimulate the individual fascicles that lie just below the surface of a nerve. Reaching the internal fascicles will be more difficult, but we've got some ideas how to do this," said Jansen.
Another part of the cuff would contain the SMU nerve sensors. They would be used for controlling the prosthetic limb. Ideally, they would be implanted in the fascicles containing the mo
|Contact: David F. Salisbury|