| Hearing loss is one of the most prevalent chronic conditions in the U.S., affecting over 10% of the population, reaching 31.5 million. The focus of this dissertation is on two prosthetic technologies that were developed to help those with hearing loss.;The first auditory prosthesis technology is the direct hearing device, which combines conventional hearing aid and middle ear implant technologies into a single device. Both conventional hearing aids and middle ear implants have their shortcomings. For conventional hearing aids, these shortcomings include visibility, short battery life, and sound quality issues, such as feedback and the occlusion effect (echoing of sound, like talking in a barrel). Middle ear implants require invasive surgery, are typically irreversible, and the performance of the implant is not known until after implantation.;The direct hearing device solves these issues. It is not visible, does not require invasive surgery, has long battery life and does not suffer from feedback or the occlusion effect. The direct hearing device is located deep in the ear canal and touches the tympanic membrane. It detects sound that enters the ear, and recreates these sounds with mechanical movements.;The second auditory prosthesis technology is the hybrid microelectrode arrays (MEA), manufactured through specialized hybrid microfabrication methods. MEAs provide the ability to record and stimulate the nervous system and can enable those who are deaf to hear. A novel microfabrication methodology, hybrid microfabrication, was developed to fabricate MEAs for the auditory system. Hybrid microfabrication combines traditional lithographic techniques with precision micromachining and is capable of producing MEAs that cannot be made using other fabrication methods. For this work, a stimulating auditory nerve MEA and a recording inferior colliculus MEA were fabricated and tested.;The direct hearing device and hybrid MEA microfabrication both represent a major shift in traditional approaches and enable new types of auditory prostheses. |
