a three - dimensional biological scaffold . the scaffold includes at least three sets of polymer waveguides extending along at least three respective directions . the at least three sets of polymer waveguides interpenetrate each other at a plurality of nodes to form a self - supporting structure . in some embodiments , the polymer waveguides may be bio - degradable . in still some embodiments , the three - dimensional biological scaffold may include one or more coating layers for covering surfaces of the polymer waveguides .