Biological Considerations of Optical Interfaces for Neuromodulation

The success of devices such as cochlear implants and pacemakers has led to increasing interest in new applications of artificial neural interfaces, ranging from brain–computer interfaces to vagus nerve stimulators. Both the established and emerging applications of neural interfaces have highlighted the need for improvements in spatial selectivity and reduced invasiveness, which in turn has driven growing interest in optical interfaces. The delivery of light to—and collection of light from—neural tissue presents distinct challenges for optical devices. This review presents the status of optical interface technologies with a focus on biological considerations, such as biocompatibility, thermal loading, and tissue response. Attention is also paid to factors affecting the portability of optical interfaces, and issues around reliability and manufacturing that need to be considered for successful translation. Indeed, it is imperative that engineers work closely with physiologists, clinicians, and patients when developing devices for research and the clinic. Finally, emerging trends and the potential for new technologies to disrupt the field are discussed. While many engineering challenges remain to be overcome, the achievements to date suggest that optical neuromodulation techniques have significant potential to be deployed in future for a wide range of practical therapeutic applications.