# Computationally Efficient Impact Estimation of Coil Misalignment for Magnet-Free Cochlear Implants

## TL;DR

This paper explores the feasibility of magnet-free cochlear implants by analyzing how coil misalignment affects power and data transfer efficiency.

## Contribution

A computationally efficient MATLAB model is introduced to estimate coil misalignment effects, validated against FEA with less than 8% error.

## Key findings

- MATLAB simulations using Neumann’s equation accurately predict coupling coefficient changes due to coil misalignment.
- The model achieves a median 8% relative error compared to FEA, making it suitable for studying magnet-free implants.
- Considering real-world constraints, the model shows magnet-free cochlear implants can be feasible with mean errors below 5%.

## Abstract

A cochlear implant (CI) system holds two spiral coils, one external and one implanted. These coils are used to transmit both data and power. A magnet at the center of the coils ensures proper alignment to assure the highest coupling. However, when the recipient needs a magnetic resonance imaging (MRI) scan, this magnet can cause problems due to the high magnetic field of such a scan. Therefore, a new type of implant without magnets would be beneficial and even supersede the current state of the art of hearing implants. To examine the feasibility of magnet-free cochlear implants, this research studies the impact of coil misalignment on the inductive coupling between the coils and thus the power and data transfer. Rather than using time-consuming finite element analysis (FEA), MATLAB is used to examine the impact of lateral, vertical and angular misalignment on the coupling coefficient using derivations of Neumann’s equation. The MATLAB model is verified with FEA software with a median 8% relative error on the coupling coefficient for various misalignments, ensuring that it can be used to study the feasibility of various magnet-free implants and wireless power and data transmission systems in general. In the case of cochlear implants, the results show that by taking patient and technology constraints like skinflap thickness and mechanical design dimensions into account, the mean error can even be reduced to below 5% and magnet-free cochlear implants can be feasible.