Wireless Circuits and Systems: Energy-Neutral Links

Abstract

Neural interfacing devices enable new therapies based on neuromodulation for diseases and conditions, such as Parkinson’s disease and dystonia, which currently cannot be treated adequately with medication alone, thus potentially improving the quality of life for patients suffering from these diseases. It is well understood that like any other implantable medical device (IMD), neural interfacing devices need to be wireless and minimally invasive. This objective can be achieved by developing highly miniaturized implants with new distributed system architectures that in turn require novel circuit topologies. This chapter presents circuit design concepts, wireless operation strategies, and system-level integration of mm-sized wirelessly powered distributed neural interfacing IMDs for a particularly challenging subset of neuromodulation devices that can be used for untethered and battery-free optogenetic neuromodulation. Spanning from the integrated circuit (IC) design to the mm-sized implant microassembly and to the focused wireless power delivery and data communication, the development of each building block and how they come together to form the complete system are discussed. These details are further supported with IC level and in vitro experimental results followed by in vivo experiments to demonstrate the system performance and challenges that had to be overcome. Finally, this chapter will be concluded with a brief discussion of state-of-the-art miniaturized implants and future steps.