Medical-Grade Silicone Rubber-Hydrogel-Composites for Modiolar Hugging Cochlear Implants

Area of Science:

• Biomedical Engineering
• Materials Science
• Neuroscience

Background:

• Cochlear implant surgery is the standard for sensorineural hearing loss, primarily restoring speech comprehension.
• Limitations in music perception persist due to the electrode-to-auditory nerve gap in the modiolus.
• Reducing this gap is crucial for improving cochlear implant efficacy.

Purpose of the Study:

• To develop a mechanism for reducing the gap between cochlear implant electrodes and auditory nerve cells.
• To investigate a silicone rubber-hydrogel actuator for precise electrode array positioning.
• To create a hydrogel-actuated cochlear implant with modiolar hugging functionality.

Main Methods:

• Fabrication of a silicone rubber-hydrogel actuator within an electrode array.
• Material characterization of medical-grade PDMS and hydrogels.
• Parametrized bending curvature measurements and biocompatibility testing (ISO 10993-5).
• Development and validation of a mathematical model for actuator design.

Main Results:

• The hydrogel actuator demonstrated bending forces at low volume swelling ratios.
• Measured curvature radii align with anatomical requirements for close modiolus proximity.
• The actuator exhibited stage-one biocompatibility.
• A validated mathematical model for designing hydrogel-actuated cochlear implants was established.

Conclusions:

• The proposed hydrogel actuator effectively achieves electrode array bending for modiolar hugging.
• This technology has the potential to significantly improve cochlear implant performance, particularly in music perception.
• The developed mathematical model facilitates the design of next-generation cochlear implants.