The past decade has seen an explosion of new capabilities in materials design. Production processes including bottoms-up chemistry and top-down micromachining have now been integrated, giving biomedical engineers a new level of control over the molecular and nanometer scale structure of polymers, ceramics, metals and semiconductors. Biomaterials are increasingly multi-functional offering delivery of drugs on command, electrical conductivity for nerve replacement, and optical activity designed for retinal and optogenetic applications.