Optoelectrical Devices for Neural Interfacing: Engineering Integration, Stability, and Multimodal Sensing.

In recent years, implantable optoelectrical devices have emerged as an effective resource for modulating and monitoring neural activity with high spatiotemporal resolution. By integrating optical stimulation, electrophysiological recording, and neurochemical sensing, these multifunctional interfaces offer novel ways to interrogate brain circuits in vivo. However, the greater the integration, the more sophisticated and consequently challenging the front-end of the implantable system becomes. The challenge revolves around three bottlenecks: (i) complexity of high-density optoelectrical integration, (ii) adverse long-term foreign body response (FBR), and (iii) limited incorporation of sensors for both cellular and biomolecular activity, including neurotransmitter activity and dynamics. Here we focus on the strategies to address these challenges in the context of device engineering at its interface with tissue. First, we present platforms developed by the scientific community for interacting with neural cells via electrical and optical means to achieve high resolution. Then we discuss soft, biocompatible materials and thermally-drawn polymer fibers to minimize mechanical mismatch and implementation of electrochemical, optical, and organic transistor-based sensors for multimodal neurochemical detection. Finally, we outline future perspectives for the development of next-generation neural interfaces capable of chronic, multisite, and multimodal interrogation of neural dynamics, with potential applications in both basic neuroscience and translational neurotechnologies.