Design of differential electromagnetic transducer for implantable middle ear hearing device using finite element method

This paper describes the design and implementation of a differential electromagnetic transducer (DET), with similar frequency characteristics to those of a normal middle ear, for use in an implantable middle ear hearing device (IMEHD). To obtain the maximal electromagnetic force within the limited cavity dimensions of the middle ear, the length and thickness of the coil and magnet are, respectively, determined through an electromagnetic analysis using a finite element analysis (FEA) program. In addition, a dynamic analysis simulation is performed to examine the frequency vibration characteristics. The DETs designed according to the simulation results are implemented using micro-machining technology, then the frequency vibration displacements are measured in experiments and the results compared to those for a normal middle ear. Finally, the feasibility of the DET is investigated and verified through in vitro experiments using the ossicular chain from a human cadaver.