Background: Hearing loss is a common disability in aging seniors and people who work long hours in noisy environments. The majority of persons with hearing loss have sensorineural impairments, due to dysfunction or loss of cochlear hair cells. For mild to moderate hearing loss, conventional hearing aids amplify sounds delivered to the ear. For more severe hearing loss, cochlear implants can directly stimulate auditory neurons electrically via an electrode in the cochlea. Between these two extremes, there is a group of patients who have lost considerable high-frequency hearing but have some preserved low-frequency hearing. Many of these patients do poorly with hearing aids but are not candidates for cochlear implants. Recently, there is evidence that the most effective type of rehabilitation for this growing group of patients is to combine electrical and acoustic stimulation (CEAS) in the same ear. The CEAS strategy uses acoustic amplification (hearing aid) and electrical stimulation (cochlear implant) simultaneously. Results show that patients have better word recognition under noisy environments. To enable CEAS in a single device, stimulating electrodes and acoustic actuators could potentially be integrated and placed inside cochlea. While Intra-cochlear electrodes are well studied, intra-cochlear acoustic actuators are novel and have not been explored.
Objectives & Goals: The proposed research is to develop Lead-Zirconium-Titanium Oxide (PZT) thin-film acoustic micro-actuators for intra-cochlear use. There are two specific goals to achieve. The first goal is to design and fabricate a micro-actuator probe, whose tip has a PZT thin-film piezoelectric diaphragm serving as an acoustic actuator. The actuator aims to deliver 200-nm displacement for a bandwidth from 15 Hz to 3 kHz with a size less than 0.8 mm x 0.8 mm. The tip of the probe, sealed with a biocompatible material, is then implanted into the cochlea. The second goal is to conduct acute animal tests to demonstrate the feasibility of the proposed micro-actuator probe by measuring auditory brainstem responses in guinea pigs.
Intellectual Merits: The proposed research has ample intellectual merits. First, the proposed research is transformational. Results of this research will enable a new class of cochlear implants that integrate electric and acoustic stimulation in a single device. It will open a completely new direction for the current cochlear implant technologies. Second, the proposed research tremendously broadens the knowledge of the field. For example, the proposed research has a well-planned animal study to test our hypothesis and demonstrate the feasibility. This will be the first animal study on intra-cochlear acoustic actuators. Third, this research is translational. The PZT thin-film technology at the core of the proposed research forms a new research paradigm. It complements traditional technology of micro-electric-mechanical-systems (MEMS), which are not able to meet the challenges encountered in intra-cochlear applications. The PZT thin-film technologies can also enable a wide range of applications, such as scanning endoscopes, nano-positioners for DNA manipulation, and viscosimeters for biofluids.
Broader Impacts: Currently, it is estimated that 278 million people have hearing disability. A good population of these hearing-disabled patients can potentially benefit from the proposed intra-cochlear actuators. Hearing rehabilitation research will become progressively important, because US population is aging and life expectancy is increasing. The proposed research will also broaden its impact via development of new curriculum on PZT thin-film microdevices, recruitment of underrepresented and undergraduate students, technology transfer via patents and licensing, industrial and international collaboration, outreach, and continuing education.
