Development and Characterization of a Micromagnetic Alternative to Cochlear Implant Electrode Arrays

Area of Science:

• Biomedical Engineering
• Neuroscience
• Audiology

Background:

• Cochlear implants stimulate the auditory nerve using electrical current, but variability in speech perception exists.
• Electrical stimulation spreads through perilymph, negatively impacting cochlear function due to spatial dependence.
• Magnetic fields are unaffected by biological material properties, offering a potential alternative for stimulation.

Purpose of the Study:

• To develop and evaluate a microcoil array for electromagnetic stimulation of the auditory nerve.
• To assess the spatial selectivity and stimulation capabilities of the microcoil array.

Main Methods:

• A microcoil array was designed and fabricated (4-turn solenoids, 250 µm turn radius, 31.75 µm wire radius, Parylene-C coated).
• Frequency response analysis measured electromagnetic power radiation.
• Finite-element modeling and Rattay's activating function evaluated stimulation effects and predicted inflammation.

Main Results:

• Microcoils demonstrated efficient electromagnetic power radiation with 99.8% power loss over 100 µm separation.
• Predicted inflammation occurred after 10 minutes of continuous stimulation (60 mA, 5 kHz).
• Each microcoil requires a 400 µm-wide area, achieving 84% narrower channel width than commercial cochlear arrays.

Conclusions:

• The developed microcoil array offers superior spatial selectivity for auditory nerve stimulation.
• This technology has the potential to improve cochlear implant performance and reduce speech perception variability.