Advancements in Biological Neural Interfaces Using Conducting Polymers: A Review

Neural interfacing machines are interfacial devices that restores the purpose of the nervous system lost because of any disease or injury. In the current scenario, conventional metal-based electrodes are employed for neural interfacing; however, the challenge faced with these electrodes is signal degeneration, because of filling of the liquid gap (i.e., in extra systemic implants) between target tissue and electrode. Thus, this problem aroused a novel idea to use conducting polymers (CPs), because it provides excellent electrical conductivity for signal transduction, along with biocompatibility with human body. Implanted metal electrodes generate an immunological response in the human body and attempts to eradicate them by treating them as a foreign material. CPs are generally biocompatible with the bodies' immune system and does not induce any significant long-term negative effect in vivo and are much preferred and reliable over the conventional techniques, because of its high surface area, which promotes a good conductance with target tissues by reducing impedance and, hence, enhances the recording and simulation applications of various neural processes. Thus, this Review intends to study several neural interfacing applications by using polypyrrole and PEDOT as primary CPs, with brief explanation of their preparation and conductance mechanisms, and then focuses on neural implanting, interfacing behaviors, and superiority over other materials. Novel designing and applications of cochlear implants, bionic eyes, and brain-machine interfering are hereby reviewed.