Wireless, Adaptable and Fully Implantable Battery-powered Devices for Optical Stimulation of the Spinal Cord in Small Rodents.

Existing technologies for optogenetic neuromodulation often rely on external power transmission or are only partially implantable, limiting their utility in mobile tissues such as the spinal cord. Here, we introduce a fully implantable, battery-powered system for light delivery to precise segments of the spinal cord in freely behaving small rodents, with operation and wireless recharging possible in any animal housing environments. Built from commercially available components with minimal in-house fabrication, the system integrates low-power electronic design, ultra-thin and flexible probes with multiple embedded microscale light-emitting diodes (µLEDs), coupled to a rechargeable battery in a modular configuration. The adaptable device can be used for optical stimulation with different wavelengths across various spinal levels with minimal system adjustments. Month-long stability as well as the device functionality were validated in small rodents. Furthermore, operator-free, targeted and transient paralysis of the hind limb was demonstrated through controlled optical stimulation of inhibitory interneurons.