The nervous system interprets a wide range of signals to help control how humans move. This process involves specialized circuits in both the brain and spinal cord. Although tools are available to measure circuits in the brain, it is still challenging to measure activity in the spinal cord. This project will develop new probes for studying the spinal cord that are small, flexible, and can study multiple regions of the spinal cord at the same time. Overall, the project will address how to engineer spinal cord probes that can be precisely positioned to target specific spinal neural circuits at different sites and depths. In addition to its scientific impact, this project will develop student talent in engineering. An “Adopt-a-Student” program will be established to introduce middle and high school students to STEM fields. This project will also enhance undergraduate education by implementing hands-on training and mentoring through new classroom laboratory modules and team projects. This project will accelerate the development of minimally invasive, multi-modal probe technologies for acute and chronic spinal interfacing. High-aspect ratio, dual-modality, mechanically flexible probes will be fabricated that deliver a small footprint of less than 10 μm, low electrical impedances, and sub 20 dB optical losses from source to tip that allow efficient activation of opsin-labeled neurons, and simultaneous high signal-to-noise ratio electrophysiological recordings with single-unit re