Direct Intracochlear Acoustic Stimulation Using a PZT Microactuator

Abstract

Combined electric and acoustic stimulation has proven to be an effective strategy to improve hearing in some cochlear implant users. We describe an acoustic microactuator to directly deliver stimuli to the perilymph in the scala tympani. The 800 µm by 800 µm actuator has a silicon diaphragm driven by a piezoelectric thin film (e.g., lead-zirconium-titanium oxide or PZT). This device could also be used as a component of a bimodal acoustic-electric electrode array. In the current study, we established a guinea pig model to test the actuator for its ability to deliver auditory signals to the cochlea in vivo. The actuator was placed through the round window of the cochlea. Auditory brainstem response (ABR) thresholds, peak latencies, and amplitude growth were calculated for an ear canal speaker versus the intracochlear actuator for tone burst stimuli at 4, 8, 16, and 24 kHz. An ABR was obtained after removal of the probe to assess loss of hearing related to the procedure. In some animals, the temporal bone was harvested for histologic analysis of cochlear damage. We show that the device is capable of stimulating ABRs in vivo with latencies and growth functions comparable to stimulation in the ear canal. Further experiments will be necessary to evaluate the efficiency and safety of this modality in long-term auditory stimulation and its ability to be integrated with conventional cochlear implant arrays.

Voltage readout from a piezoelectric intracochlear acoustic transducer implanted in a living guinea pig

“…Luo et al . 52,53 demonstrated an intracochlear PZT actuator that evoked an auditory brainstem response by generating acoustic signals inside a cochlea, an exciting proof-of-concept for this approach. Compared to Luo et al .’s design, the PIAT holds advantages because it is lead-free, smaller, and produces a larger displacement.…”

Improving disease prevention, diagnosis, and treatment using novel bionic technologies

“…For CI users with useful residual acoustic hearing, combining electrical CI stimulation with acoustic stimulation (electro‐acoustic or hybrid stimulation) has been shown to preserve residual hearing and improve performance. 109 , 110 , 111 Hybrid stimulation involves inserting a shortened, minimally traumatic, CI electrode array into the basal cochlea to stimulate the high‐frequency region, while a conventional acoustic hearing aid is used to deliver amplified acoustic and low frequencies. This combination augments the quality of sound and speech, performance in background noise and improved sound localization compared with hearing aids and CIs alone.…”

“…This combination augments the quality of sound and speech, performance in background noise and improved sound localization compared with hearing aids and CIs alone. 110 , 112 However, despite the relative high rates of success, postoperative acoustic hearing outcomes remain unpredictable and a subset of patients suffer from partial to total loss of acoustic hearing months to years following surgery. 105 Low frequencies contribute to speech perception and individuals with impaired low‐frequency hearing are usually only able to detect vowels, but few or no consonants; missing information such as pitch, temporal fine structure and dynamic changes in intensity.…”

Piezoelectric/Triboelectric Nanogenerators for Biomedical Applications

“…Biomedical applications PZT High piezoelectric coefficient, toxicity Energy harvesting from body motion, including the heart, lung, and diaphragm [4,28] Cochlear implant [29] Eye fatigue detection [30] PMN-PT High piezoelectric coefficient, toxicity Cardiac pacemaker [13,31] (Na, K)NbO A cardiac sensor, used for heart-rate monitoring, is a critical component in personal healthcare management. Self-powered nanogenerators have been employed in self-powered cardiac sensors, as shown in Figure 1 [5].…”