A Millimeter-Scale Implantable Magneto-Mechano-Electric Transducer Based on BTO Piezoelectric Ceramics for Remote Wireless Electrical Stimulation of Injured Sciatic Nerves.

Electrical stimulation is widely recognized as an effective strategy for promoting functional recovery after peripheral nerve injury. However, conventional stimulators rely on wired connections or implanted batteries, severely limiting implantability, biosafety, and clinical translation. Recent wireless, battery-free piezoelectric systems, primarily based on ultrasound or pressure-driven transduction, remain constrained by auxiliary equipment, working distance, and external control. Here, we report a fully wireless, circuit-free neural stimulator built on a millimetric magneto-mechano-electric (MME) cantilever transducer (3 × 10 × 5 mm) with a barium titanate (BTO) piezoelectric ceramic core. Under low-frequency alternating magnetic fields, the MME cantilever mechanically oscillates, inducing stress on the BTO element and thereby converting magnetic energy into therapeutic electrical pulses. The use of BTO minimizes potential biosafety risks. Moreover, the device operates stably at 16 cm from the magnetic source, outperforming most existing wireless stimulators. In vitro, MME-mediated stimulation doubles PC12 neurite outgrowth and neuronal differentiation. In a rat sciatic nerve injury model, the implanted stimulator exhibits excellent biosafety and significantly enhances nerve regeneration and motor recovery, achieving a ∼1.5-fold improvement in the sciatic functional index.