A nerve interface electrode has a plurality of conductive fibers. The fibers have a nonconductive sheath (108) surrounding a conducting wire. A conducting region (105) of the wire is exposed to the interior of the nerve (200). The fibers are configured for insertion between fascicles (204) of the nerve. In other teachings, a layer of polymer material configured to switch from a high strength/tensile modulus state to a low strength/tensile modulus state upon introduction of the fibers into the nerve is disposed on the fibers.