Multisite microLED optrode array for neural interfacing

We present an electrically addressable optrode array capable of delivering light to 181 sites in the brain, each providing sufficient light to optogenetically excite thousands of neurons in vivo, developed with the aim to allow behavioral studies in large mammals. The device is a glass microneedle array directly integrated with a custom fabricated microLED device, which delivers light to 100 needle tips and 81 interstitial surface sites, giving two-level optogenetic excitation of neurons in vivo. Light delivery and thermal properties are evaluated, with the device capable of peak irradiances $>80\mathrm{mW}/{\mathrm{mm}}^2$ per needle site. The device consists of an array of 181 $80\mu m\times 80{\mu m}^2$ microLEDs, fabricated on a $150\text{-}\mu m$ -thick GaN-on-sapphire wafer, coupled to a glass needle array on a $150\text{-}\mu m$ thick backplane. A pinhole layer is patterned on the sapphire side of the microLED array to reduce stray light. Future designs are explored through optical and thermal modeling and benchmarked against the current device.