Mechanical testing of metallic and polymeric intrafascicular electrodes

We are exploring alternatives to Pt/Ir wire for constructing ultra-flexible neural intrafascicular electrodes suitable for chronic implantation. In this study we measured the flexural properties of several kinds of fine metal wires and conducting polymer fibers. The fibers were made either of intrinsically conductive polymers (polyaniline, polythiophene) or good mechanical polymers (nylon, Kevlar). The latter were made conductive through sputter coating with a thin layer of platinum. While the fiber flexibility (moment required for a 7.5º deflection) of the nylon and Kevlar fibers ranged from 10-35 pg-cm, some 50 to 150 times less stiff than Pt/Ir wire, their tensile strengths were approximately equal to that of M r wire. Polymer fibers represent promising materials for ultra-flexible nerve electrodes.