Wireless multichannel optogenetic stimulators enabled by narrow bandwidth resonant tank circuits

Optogenetic neuromodulation is a powerful technique used to study cells that form part of neuronal circuits. Light stimulation of neurons has led to a deeper understanding of autism, schizophrenia and depression. However, researchers are often limited to tethered systems involving percutaneous plugs, hence, wireless power transmission to an implantable device is desirable. This work details the design, fabrication and testing of multichannel wirelessly powered optogenetic devices. By employing several carefully tuned resonant tank circuits, this work demonstrates the ability to address a scalable number of light sources on a single device. Single channel, dual channel and 16 channel devices were fabricated, achieving light output readings of up to 15mW at 473nm, suitable for activating channelrhodopsin. Wireless power transmission was characterized in air and porcine tissue for implant depths up to 30mm, making device implantation feasible. The device was successful in activating endogenous (in retinal ganglion cells) and exogenously transfected channelrhodopsin in human embryonic kidney cells, providing biological validation. The significance of this approach is the removal of power-hungry and area-consuming electronics from the implant, while the ability to address and modulate individual light sources is maintained by shifting this complexity to the external wireless power transmitter.