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. They 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. It was essential for the device to be stretchable, because the spinal cord is not only bending but also stretching during movement.

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. (Credit: Chi [Alice] Lu and Seongjun Park)

The team combined a newly developed transparent elastomer, which could act as a waveguide for optical signals, and a coating formed of a mesh of silver nanowires, producing a conductive layer for the electrical signals. The material was embedded in a polymer cladding that enabled it to be drawn into a fiber that proved to be highly stretchable as well as flexible. The cladding is dissolved away after the drawing process. After the entire fabrication process, what’s left is the transparent fiber with electrically conductive, stretchy nanowire coatings. The fiber can stretch by at least 20–30 percent without affecting its properties.

The team hopes the fibers can be used to combat spinal cord injury, but first they need to show that it is biocompatible and can withstand the stresses in the spinal cord without causing any damage.

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