FEA simulation of thin film coils to power wireless neural interfaces

To wirelessly transfer energy into active biomedical devices such as neural stimulators or bio-monitors implanted in the body, magnetic coupling of a pair of coils are often used. In order to design such power coils, an exact modeling and prediction of their electrical characteristics is essential prior to the fabrication when the coils should be fabricated through micromachining technologies to achieve small size and enough efficiency. This paper describes modeling and simulation methods to predict the electrical characteristics of thin film microcoils based on finite element analysis methods. Not only the inductance and quality factor of coils, but high-frequency effects such as skin and proximity effects as well as parasitic capacitances can be predicted. Based on the simulation results, strategies to design microcoils are suggested in the viewpoint of power transmission efficiency.