Biofluid Barrier Materials and Encapsulation Strategies for Flexible, Chronically Stable Neural Interfaces

Abstract

Implantable bioelectronics that can serve as high-performance neural interfaces for electrophysiological sensing and stimulation are essential for fundamental biomedical research and clinical medicines. A critical challenge for developing advanced bioimplants as interfaces to the brain and other nervous system is the synthesis and deposition of interface materials that can enable long-term and intimate coupling to the biotissues within targeted operational timescales. This chapter summarizes recent progresses in this research field, with a focus on the science and engineering of thin-film materials which can serve as barrier materials against biofluids and sensing/stimulation interfaces for neural electrodes. This chapter begins with a brief overview of recent innovations in flexible bioimplants for neuroscience and neuroengineering, followed by a discussion on advantages and limitations of conventional thin-film materials as biofluid barriers. The next section focuses on a class of monocrystalline Si-based thin-film materials for the encapsulation of actively multiplexed transistor arrays in the context of electronic recordings with high spatiotemporal resolution across large areas in the nervous system, with an emphasis on the chemical and physical interactions between water/ions in biofluids and the thin-film materials. Finally, the conclusion section summarizes the remaining challenges in this field and provides perspectives on future directions in materials research for electronic platforms that support advanced diagnostics and therapeutics across a variety of applications for fundamental research and advanced healthcare.