Spiral-Shaped Piezoelectric MEMS Cantilever Array for Fully Implantable Hearing Systems

Area of Science:

• Biomedical Engineering
• Materials Science
• Acoustics

Background:

• Severe hearing loss significantly impacts quality of life.
• Current hearing aids often have external components, limiting convenience and aesthetics.
• Fully implantable, self-powered hearing aids are highly desirable but technologically challenging.

Purpose of the Study:

• To develop a miniaturized, piezoelectric micro-electromechanical system (MEMS) cantilever array for a fully implantable hearing aid.
• To achieve sensitivity in the lower voice frequency range (300-700 Hz).
• To demonstrate a self-powered device capable of direct signal conversion for cochlear implants.

Main Methods:

• Fabrication of a 16-cantilever array using bulk micromachining on a silicon-on-insulator wafer.
• Utilizing aluminum nitride (AlN) as a biocompatible piezoelectric material compatible with CMOS processes.
• Employing Archimedean spiral geometry and a silicon seismic mass for low-frequency sensitivity and compact footprint.

Main Results:

• Demonstrated a low-volume piezoelectric MEMS cantilever array sensitive to low voice frequencies (300-700 Hz).
• Experimentally validated resonance frequencies using an analytical model.
• Achieved an open-circuit voltage of 3-10 mV, sufficient for direct analog signal conversion.

Conclusions:

• The developed piezoelectric MEMS cantilever array is a promising component for fully implantable, self-powered hearing aids.
• The device's sensitivity and output voltage meet requirements for direct integration with cochlear multielectrode implants.
• This technology has the potential to significantly improve the quality of life for individuals with severe hearing loss.