Novel Conformable Shielding Permalloy Composite for Controlling Field Profiles of Transcranial Magnetic Field Coils

Abstract

Permalloy nanoparticle-based composite films as a magnetic shield for transcranial magnetic stimulation (TMS) applications redirect magnetic field lines away from shielded regions to potentially protect implantable devices, mitigate overstimulation of cortical areas when targeting deep brain regions, and maintain patient comfort when compared to the non-conformable metallic shields that, due to Lorentz forces, cause noise issues when the magnetic field is applied to the metal. The shields are conformable and moldable to perfectly interface between the geometry of the TMS coil and that of the patient’s head. Our results show that a heavily loaded polydimethylsiloxane (PDMS) permalloy composite can effectively shield low strength magnetic fields from TMS coils. The composite saturates quickly with higher fields but with some modifications and further study, it shows promise as a conformable shielding material for TMS and other wearable shielding of low frequency and dc magnetic field applications. We also compared the experimental results to ANSYS Maxwell magnetostatic simulations and fully characterize the composite materials magnetic properties and microstructure.