Biocompatible PVDF Nanofibers with Embedded Magnetite Nanodiscs Enable Wireless Magnetoelectric Stimulation in Premotor Cortex.

Wireless neuromodulation technologies aim to eliminate the need for invasive hardware and enhance tissue compatibility. Magnetoelectric (ME) materials enable magnetic field-induced electrical stimulation, offering a minimally invasive neural activation. However, conventional ME systems use rigid ceramic components with limited biocompatibility. Here, a flexible, predominantly organic ME platform composed of polyvinylidene fluoride (PVDF) nanofibers embedded with anisotropic magnetite nanodiscs (MNDs) is reported. These MNDs are selected for their unique ability to exert magnetic torque due to vortex magnetization and their intrinsic magnetostrictive behaviour. The resulting ME fibers preserve the piezoelectric β-phase of PVDF and exhibit a magnetoelectric voltage coefficient of 1.26 VcmOe. Two magnetic activation strategies are compared, torque-based and high-frequency magnetostriction, finding that magnetostriction more effectively triggers neuronal responses. In vitro calcium imaging reveals robust activation in primary cortical neurons cultured on ME fibers. Biocompatibility post-stimulation is confirmed on ex vivo human brain tissue, with no increased cell death. Implanted into the premotor cortex of freely moving mice, the fibers enabled wireless modulation of motor behaviour under an alternating magnetic field. This work presents the first demonstration of wireless magnetoelectric neuromodulation using soft, biocompatible fiber composites, paving the way for future bioelectronic interfaces free from rigid components and tethered systems.