Hybrid neuroelectronics: towards a solution-centric way of thinking about complexproblems in neurostimulation tools

Responsive neuromodulation is increasingly being used to treat patients withneuropsychiatric diseases. Yet, inefficient bridges between traditional and newmaterials   and   technological   innovations   impede   advancements   inneurostimulation tools. Signaling in the brain is accomplished predominantlyby ionflux rather than the movement of electrons. However, thestatusquofor the acquisition of neural signals is using materials, such as noble metals, thatcan only interact with electrons. As a result, ions accumulate at the biotic/abioticinterface, creating a double-layer capacitance that increases impedance andnegatively impacts the efficiency of neural interrogation. Alternative materials,such as conducting polymers, allow ion penetration in the matrix, creating avolumetric capacitor (two orders of magnitude larger than an area-dependentcapacitor) that lowers the impedance and increases the spatiotemporal resolutionof the recording/stimulation. On the other hand, the increased development andintegration capabilities of CMOS-based back-end electronics have enabled thecreation of increasingly powerful and energy-efficient microchips. These includestimulation and recording systems-on-a-chip (SoCs) with up to tens of thousandsof  channels,  fully  integrated  circuitry  for  stimulation,  signal  conditioning,digitation, wireless power and data telemetry, and on-chip signal processing.Here, we aim to compile information on the best component for each buildingblock and try to strengthen the vision that bridges the gap among various materialsand technologies in an effort to advance neurostimulation tools and promote asolution-centric way of considering their complex problems