Smart Dura: A Monolithic Optoelectrical Surface Array for Neural Interfacing with Primate Cortex.

Chronic interfacing with the brain to record and stimulate neural activity with high spatiotemporal resolution is highly desirable to advance the understanding of neural circuits and design of novel therapeutics. Traditional neural interfaces mainly rely on electrical recording and stimulation, which have inherent limitations such as lack of specificity and a large volume of tissue activation. With the advent of optogenetics, hybrid opto-electrical platforms have emerged as new bidirectional interfaces. In this paper, we introduce our groundwork towards the Smart Dura, a novel device that will ultimately integrate high density recording electrodes and light sources in the form of a chronic implant that can cover large cortical areas in the primate brain (300 mm ² ) for adaptive recording and stimulation of neural activity in a closed loop. Smart Dura has two main components, the electrical dura for recording and the optical dura for optogenetic stimulation. As the first step to implement this platform, we have implemented the electrical dura as a high density, transparent and flexible $\mu \text{ECoG}$ array, as well as the optical dura, which is a high-density LED array, independently. Both the electrical and optical dura are implemented in flexible polymer substrates that provide mechanical compliance with the brain tissue and can be integrated together in a vertical stack. Here we present the fabrication, bench top characterization and acute in vivo validation of both the electrical and optical dura. This work paves the way towards the ultimate Smart Dura, a functional device that can replace the native dura as a chronic, large-scale bidirectional interface to study cortical brain activity in non-human primates (NHPs), with the potential for translation to humans.