Implantable optical neuro stimulators with wireless power and data telemetry

Neural interfaces provide a direct communication pathway between nervous systems and the external environment. Clinical and therapeutic treatments for neurological diseases and events such as spinal cord injury, stroke, and traumatic major amputations have gained a promising pace through the introduction of these interfaces. Some Artificial neural interface relies on electrical signals to evoke sensation in the central- and peripheral- nervous systems (CNS and PNS respectively), and have most commonly been used in the scientific practice for decades. However, due to the limitations and difficulties of electrical stimulation, these neural interfaces require improved technology. Optogenetics, a recent and fascinating technique that combines optics and genetics, has established its ability by direct optical stimulation of genetically modified target neuron population and achieving sub-millisecond temporal precision. As neuron stimulation in optogenetics is achieved by light, efficient and validated engineered light delivery tools are of great importance towards an effective experiment or clinical trial. This dissertation provides a development process towards a wireless and fully implantable micro-LED based opto-neuro stimulator. GaN micro LED's were the source of the optical stimulation and a process was described for the fabrication, etching morphology and characterization of such LED's. In order to enhance the optical efficiency, a micro optic element (reflector) was coupled with the LED stimulator and the electrical, optical and thermal characteristics of the as-fabricated neuro stimulator were characterized. In order to realize a untethered optical neuromodulation and simultaneous neural data recording, a head mounted battery powered module has been developed, coupled with a 4 channel o-LED array stimulator and a 2 channel recording electrode. This module can wirelessly transmit and receive signals using Bluetooth low energy (BLE), store data in a PC and simultaneously show real time neural recordings on a GUI. Efficacy of the stimulation was validated by c-Fos biomarker detection and signal processing indicating phase lock synchrony. Finally, a demonstration of an intensity enhanced, miniaturized (millimeter scale), single channel optical stimulator has been developed, capable of being wirelessly powered through a transmitter (Tx) and millimeter scale receiver (Rx) coil link. The fabrication methods have been discussed with the electrical, optical, and thermal characteristics of the stimulator being quantified. The effect of two coil alignment were verified both from simulation and from experimental results. Sufficient power transfer (4mW) was achieved to drive the stimulator at a low frequency (96MHz), and an immunohistology analysis showing effective neuron activation with c-Fos biomarker expression establishes the efficacy of the stimulation.