The mammalian cochlea has been the inspiration to develope contemporary cochlear implants and active dynamic sensors that operate in the sensor's resonance region and possess favorable nonlinear characteristics. In the present work, multi-channel and self-sensing active artificial hair cells (AHCs) made of piezoelectric cantilevers and controlled by a cubic damping feedback controller are developed numerically and experimentally. These novel AHCs function near a Hopf bifurcation and amplify or compress the output by a one-third power-law relationship with the input, analogous to the mammalian cochlear amplifier. The multi-channel AHCs have extended frequency bandwidth to sense over multiple resonant frequencies, unlike conventional single-channel AHCs. Therefore, the adoption of these AHCs reduces the number of required sensors to cover the desired bandwidth of interest in an array format. Furthermore, a novel self-sensing active AHC is created in this study using quadmorph beams for future cochlear implants or sensor design applications. The self-sensing scheme allows miniaturization of the system, embedding AHCs in a limited space, and fabrication of AHC arrays by omitting external sensors from the system for practical implementation. Preliminary research on the extension of this research to MEMS AHCs and arrays of AHCs is also presented. The active AHCs can lead to transformative improvements in the dynamic range, sharpness of the response, and threshold of sound detection in cochlear implants to aid individuals with sensorineural hearing loss. Additionally, they can enhance the dynamic properties of sensors such as fluid flow sensors, microphones, and vibration sensors for various applications. / Doctor of Philosophy / In the mammalian auditory system, the acoustic wave that enters the ear canal is transmitted to the cochlea of the inner ear where it is decomposed into its frequency components. The cochlea then amplifies faint sounds and compresses high-level signals and as these processes stop due to damage, severe hearing loss occurs. Therefore, the present work is focused on developing artificial hair cells (AHCs) that can accurately replicate cochlea's behavior and aid the creation of prostheses for hearing restoration. In this work, the AHC is a beam with piezoelectric layers that is integrated with a control system designed to apply the cochlea-like amplification/compression on the beam. Experimental and simulation results show that the AHC is able to amplify or compress the output based on its input level similar to the mammalian cochlea. In contrast to previous designs of AHCs where each AHC could sense a single frequency, the system developed in this work possesses multiple sensing channels to increase the frequency range of the AHC. Furthermore, the development of a novel self-sensing scheme allows the omission of the external sensor that was required for the AHC operation in previous devices. This advancement in the self-sensing AHC design paves the way for creating fully implantable AHCs to replace the damaged parts of the cochlea. These multi-channel self-sensing AHCs have the potential to be used in the creation of cochlear implants, or sensors such as accelerometers, microphones, and hydrophones with improved dynamic properties. AHCs with different lengths, i.e. different sensing frequencies, can be mounted in an array format to cover the speech frequency range for speech recognition in individuals with hearing loss.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/102098 |
| Date | 26 January 2021 |
| Creators | Davaria, Sheyda |
| Contributors | Mechanical Engineering, Tarazaga, Pablo Alberto, West, Robert L., Grant, John Wallace, Kurdila, Andrew J. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/x-zip-compressed |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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