PROJECT SUMMARY Understanding the functional network in the brain is critical to the development of neural prostheses and effective treatment of neurological diseases. To that end, highly multiplexed and miniaturized probes have been developed to modulate and record neural activities in the brain. However, it remains a challenge to map the activities over a large area in the deep brain with minimal invasiveness. This proposal will leverage the advantages of two emerging technologies ? multimaterial fiber-based neural interfaces developed by the PI (Dr. Jia) and robotic origami developed by the PI (Dr. Cohen), with the goal of establishing a robotic fiber platform for minimally invasive, large area deep brain interfacing across mm length scales. Specifically, we propose to develop origami inspired mechanically actuating probes that can be interfaced with the inserted fiber electrodes, introduced into the brain in a compact form, and deployed to cover a footprint that is an order of magnitude larger than the fiber diameter. Once deployed, these probes will make neural recordings that are transmitted through the fiber. Two specific aims will be pursued in this work. In Aim 1, we will design and optimize robotic fibers as a deep brain interface. Specifically, we will develop an integrated fiber with mechanically actuating electrodes that inserts into elastic media in a compact form, deploys within the media to cover mm scale lateral areas, and makes recordings over mm scale lateral separations. In Aim 2, we will evaluate the performance of robotic fibers in deep brain large area recording and the biocompatibility of robotic fibers. We will deploy robotic fiber probes into the hippocampus region of a mouse brain to make in vivo recordings of endogenous neural activities across mm scale brain regions. We will also evaluate the tissue response of the robotic fiber probes using immunohistochemistry. These large area recordings at various depths will open the door to recording correlations in firing patterns of laterally organized neurons within a mammalian brain, and pave the way for new therapeutic strategies for treating neurological diseases.