PIEZOELECTRIC JANUS MICROPARTICLES ENABLE WIRELESS NEURAL STIMULATION VIA LOW-INTENSITY FOCUSED ULTRASOUND

Electrical stimulation underpins a wide range of neuroscientific and clinical technologies, yet existing approaches rely predominantly on implanted electrodes or genetically mediated actuators that limit spatial precision and scalability. Particle-based transducers have emerged as wireless alternatives, but their application to neural stimulation remains constrained by inefficient electric field confinement, high activation thresholds, and limited control over particle localization and orientation. Here, we present cell-sized piezoelectric magnetic Janus microparticles (PEMPs) designed to address these limitations by integrating electromechanical transduction, spatial confinement, and active control within a single microscale architecture. PEMPs consist of 20 μm porous silica spheres with an asymmetric surface composition, combining a barium titanate nanoparticle–conjugated piezoelectric hemisphere with a magnetically responsive hemisphere for controlled positioning and orientation under external magnetic fields. When activated by low-intensity focused ultrasound, PEMPs generate localized electrical stimulation of primary neurons at clinically relevant frequencies up to 200 Hz. Patch-clamp electrophysiology and calcium imaging experiments reveal robust, repeatable neuronal activation at ultrasound intensities below 100 mW.cm^-2, with no detectable stimulation in the absence of particles. The asymmetric design confines the electric field to the particle surface and enables directional, cell-scale modulation. Surface functionalization with targeting antibodies further allows selective binding and stimulation of dopaminergic neurons. Together, these results establish PEMPs as multifunctional, free-standing bioelectronic transducers for non-genetic, wireless neuromodulation with spatiotemporal and cellular specificity. Ongoing studies are extending this material platform toward in vivo validation and exploring its applicability across other excitable biological systems to assess generalizability beyond neuronal models.