Stretching the boundaries of neural implants

    Rubbery, multifunctional fibers could be used to study spinal cord neurons and potentially restore function.

    Researchers have developed a rubber-like fiber, shown here, that can flex and stretch while simultaneously delivering both optical impulses, for optoelectronic stimulation, and electrical connections, for stimulation and monitoring. Video, Chi (Alice) Lu and Seongjun Park

    Implantable fibers have been an enormous boon to brain research, allowing scientists to stimulate specific targets in the brain and monitor electrical responses. But similar studies in the nerves of the spinal cord, which might ultimately lead to treatments to alleviate spinal cord injuries, have been more difficult to carry out. That’s because the spine flexes and stretches as the body moves, and the relatively stiff, brittle fibers used today could damage the delicate spinal cord tissue.

    Now, researchers have developed a rubber-like fiber that can flex and stretch while simultaneously delivering both optical impulses, for optoelectronic stimulation, and electrical connections, for stimulation and monitoring. The new fibers are described in a paper in the journal Science Advances, by MIT graduate students Chi (Alice) Lu and Seongjun Park, Professor Polina Anikeeva, and eight others at MIT, the University of Washington, and Oxford University.

    “I wanted to create a multimodal interface with mechanical properties compatible with tissues, for neural stimulation and recording,” as a tool for better understanding spinal cord functions, says Lu. But it was essential for the device to be stretchable, because “the spinal cord is not only bending but also stretching during movement.” The obvious choice would be some kind of elastomer, a rubber-like compound, but most of these materials are not adaptable to the process of fiber drawing, which turns a relatively large bundle of materials into a thread that can be narrower than a hair.

    The spinal cord “undergoes stretches of about 12 percent during normal movement,” says Anikeeva, who is the Class of 1942 Career Development Professor in the Department of Materials Science and Engineering.

    Read more at the MIT News Office.

    David L. Chandler | MIT News Office
    March 31, 2017