Physiologically responsive mechanically adaptive optical fibers that are suitable for optical interfacing with living organisms. The optical fibers are particularly suited for applications in optogenetics. Dry, stiff fibers display a desirable tensile storage modulus and can be readily inserted into biological and in particular cortical tissue. Exposure to conditions encountered in vivo results in reduction, often a drastic reduction in modulus. When coupled with a suitable light source, the construction can be utilized to stimulate neurons in vivo. Methods for producing and utilizing the optical fibers and devices including the optical fibers are disclosed.
