Towards a Free-Floating Wireless Implantable Optogenetic Stimulating System

This paper presents a wirelessly-powered and free-floating implantable optogenetic stimulating (FF-WIOS) implant with negligible footprint and high power transfer efficiency (PTE). FF-WIOS ASIC with embedded mu LED and reflective lens is expected to stimulate the target cortical neuronal ensembles at high temporal and spatial resolution with minimal damage and no tethering effects. To improve the PTE, and stay below the SAR limit, a flexible planar transmitter (Tx) resonator, L-2, will be implanted under the scalp, but over the skull. The Tx coil, L-1, embedded in a headstage, L-2 resonator, and a wire-bond receiver (Rx) coil, L-3, wound around the FF-WIOS device, form a 3-coil inductive link operating at 135 MHz, which directly charges a surface-mount storage capacitor. At the onset of stimulation, the storage capacitor discharges into the mu LED, while the stimulation parameters are sent to FF-WIOS by amplitude modulating of the power carrier. Post-layout simulation results show functionality of the storage capacitor charging, forward data transmission, and optogenetic stimulation with adjustable parameters.