Highly Efficient Transcranial Magnetic Stimulation Coil Based on Artificial Magnetic Conductor and Mu-Negative Metamaterial

Abstract

This letter demonstrates an innovative method to enhance the efficiency of conventional transcranial magnetic stimulation (TMS) coils. This method utilizes the in-phase reflection property of artificial magnetic conductor (AMC) and the evanescent wave amplification property of mu-negative (MNG) metamaterial to optimize the spatial magnetic field distribution surrounding the TMS coil, which leads to the improvement in coil efficiency. According to this method, the designed AMC and MNG are added to a conventional figure-8 coil, resulting in a nearly 5.9 times increase in stimulation intensity compared to the original coil. This significant increase in stimulation intensity, achieved without modifying the hardware driving circuit and coil structure, indicates a remarkable improvement in coil efficiency. In addition, compared to the original figure-8 coil, the addition of AMC and MNG demonstrates a 24.9% improvement in focality, with only a 11.9% reduction in penetration depth. These enhancements suggest that the method has the potential to promote the further development of TMS equipment and possesses the potential for widespread application. Lastly, simulation and experimental results are provided to validate the feasibility and advantages of this method.