Neuroflex: Intraneural and Extraneural Flexible Sensor Architectures for Neural Probing

The development of flexible, ultra-compliant neural interfaces has evolved to be a prerequisite to the realization of seamlessly integrable soft neural systems destined to be implanted within the neural milieu. The chapter provides a holistic view of Neuroflex, a class of flexible interface architectures employed to communicate with the neural tissues either by penetrating (intraneural mode of communication) or by being in contact with the target tissue surface (extraneural mode of communication). This flexible conformal class of neural interface designs is highly compatible for integration with the bendable electronic systems and has demonstrated tremendous potential as a starting point for the realization of soft flexible bioelectronics. We appreciate this motivation that led to the development of Neuroflex and further discuss the substrate materials and the electrode materials (for conductive traces and sensing sites) that have enabled such flexible designs. We provide brief descriptions of the design innovations in the intraneural and extraneural flexible electrode interfaces for the neural tissues such as the brain and the peripheral nerve. The chapter concludes with a road map of the flexible neural interface development and the application-specific material compatibility, the result of which identifies Neuroflex as a well-suited domain for future research toward preclinical studies and possibly clinical translation. The authors observe that Neuroflex has provided an invaluable opportunity to reimagine conventional biointegrated sensors and electronics.