Microfabricated PZT‑on‑Silicon Ultrasonic Resonator for Implantable Neural Stimulation

Recent advances in miniaturized neural-interfacing probes have led to broadening of the knowledge on brain functions via recording of local field potentials and provide a great framework for interacting directly with neurons by different means of brain stimulation, typically by delivering electrical stimuli. Although fabrication of bidirectional implantable neural probes based on MEMS materials and methods is already a mature technology, the fact that electrical brain stimulation relies solely on a good electrical contact between the conductive electrode and the living tissue limits the lifespan of such implants, mainly due to foreign body inflammatory response and scar-tissue growth on the electrode-tissue interface. As a solution, we propose a neural probe for state-of-the-art biopotential recording, with a monolithic integrated miniaturized piezoelectric resonator for neural modulation which is fully encapsulated in biocompatible material.Theoretical analysis on piezoelectric resonating membranes is presented and its limitations are assessed and compared to finite element analysis (FEA), which is then used to tune the resonant frequency of the vibrating membrane to the desired value for neural stimulation. As well the acoustic output and penetration depth of the generated signal are analyzedFinally, the MEMS fabrication methodology for the proposed neural probe is presented.