Mechanisms for Imparting Conductivity to Nonconductive Polymeric Biomaterials

Traditionally, conductive materials for electrodes are based on high modulus metals or alloys. Development of bioelectrodes that mimic the mechanical properties of the soft, low modulus tissues in which they are implanted is a rapidly expanding field of research. Many polymers exist that more closely match tissue mechanics than metals; however, the majority do not conduct charge. Integrating conductive properties via incorporation of metals and other conductors into nonconductive polymers is a successful approach to producing polymers that can be used in electrical interfacing devices. When combining conductive materials with nonconductive polymer matrices, there is often a tradeoff between the electrical and mechanical properties. This review analyzes the advantages and disadvantages of approaches involving coating or layer formation, composite formation via dispersion of conductive inclusions through polymer matrices, and in situ growth of a conductive network within polymers. There is a need for soft, biocompatible materials to support regeneration, stimulation, and recording of excitable tissue activity. This review analyzes the key approaches used to fabricate soft, conductive polymers including: coating a bulk polymer with a conductive component, dispersion of conductive inclusions through a polymer, and in situ growth of a conductive network within a polymer matrix.