Researchers are developing a laser-based system to connect the human nervous system to robotic prosthetic limbs. Brain-machine interfaces provide the output for controlling prosthetics but ideally the system would also provide feedback, for example the sensation of picking up an object. The challenge is that electrodes wired to a particular nerve can also zap surrounding nerves, triggering false sensations. Vanderbilt University researchers developed a method to precisely stimulate nerves with pulses of a laser. From IEEE Spectrum:
Using a similar laser aimed at the sciatic nerve of laboratory rats, they caused some part of the animal’s legs to involuntarily twitch with each laser pulse. A slight movement of the beam across the nerve bundle–which causes the narrow beam to shift its focus from one fiber within the nerve to another–can cause the rat to switch from, say, curling its toes to flexing its foot.
Stimulating nerves with lasers, says Anita Mahadevan-Jansen, a professor of biomedical engineering at Vanderbilt and the person who hit upon the idea of using light instead of current, may someday make artificial limbs as dexterous as human arms and might lead to such devices as patches that zap nerves to give relief to chronic pain sufferers..."Engineers Work on Laser-Based Brain-Machine Interface for Prosthetic Arm" (Thanks, Chris Arkenberg!)
To make the device as compact and inexpensive as possible, the researchers wanted to use a diode laser like the ones used in CD players and laser printers, says Jansen. For human trials, the Vanderbilt researchers are currently working with Aculight Corp., a Bothell, Wash.–based maker of laser systems for military applications, to ready a diode laser–based prototype that is roughly the size of a hardcover book.
The prototype laser has been used in the surgical suite at Vanderbilt’s children’s hospital during rhizotomy procedures in which a nerve identified as the cause of debilitating spastic jerking is removed from children with cerebral palsy. Before the nerve is cut, the laser is fired on it, and its response is recorded.