Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | School of Fashion and Textiles | en_US |
| dc.contributor.advisor | Tao, Xiaoming (SFT) | en_US |
| dc.creator | Li, Wenbo | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/14625 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Design, fabrication, and characterization of fibrous acoustic sensors for bioacoustics applications | en_US |
| dcterms.abstract | Audible sound, spanning 20–20 kHz, is one of the most fundamental forms of human perception and communication, with applications extending from diagnostics and human-machine interaction to voice recognition. The rapid miniaturization and integration of microelectronics have fueled the growth of wearable electronics, enabling continuous physiological monitoring, personalized diagnostics, and seamless data acquisition. Within this context, acoustic sensing has become a key modality for health monitoring due to its ability to non-invasively capture subtle physiological vibrations. However, current wearable acoustic sensors face significant challenges, including limited sensitivity, mechanical mismatch between rigid electrodes and soft substrates, compromised comfort during prolonged wear, and instability or poor repeatability of physiological signal acquisition under dynamic conditions. | en_US |
| dcterms.abstract | This work addresses these limitations by developing a flexible, low-density, anisotropic electrospun piezoelectric nanofiber membrane integrated into a shape-adaptive wearable acoustic sensor with high sensitivity, broad frequency response, and mechanical robustness. Using PVDF-TER as the flexible polymer matrix and incorporating BTO nanoparticles, highly aligned nanofibers with strong dipole orientation were fabricated via controlled electrospinning. The synergistic effects of BTO-induced heterogeneous nucleation and interfacial polarization increased the all-trans (TTTT′) phase content to approximately 92%, yielding a piezoelectric constant d₃₃ of –30.9 pC·N⁻¹ and a transverse coefficient d₃₁ of 45.5 pC·N⁻¹. The porous microstructure reduced the apparent dielectric constant, enabling a high g₃₃ and efficient electromechanical coupling while maintaining mechanical compliance suitable for skin-conformal applications. | en_US |
| dcterms.abstract | To overcome the limitations of rigid electrodes, a conformal and durable silver nanowires (AgNWs) network was deposited via solution electrospraying. This flexible electrode maintained stable conductivity even after 10,000 bending cycles, demonstrating superior fatigue resistance compared to sputtered metallic electrodes. A multilayer diaphragm-cavity architecture was then designed to enhance acoustic impedance matching and amplify low-frequency response while preserving lightweight comfort. Initial prototypes achieved a flat frequency response across 20–600 Hz, with a sensitivity of approximately 47 mV·Pa⁻¹. | en_US |
| dcterms.abstract | To further broaden the bandwidth, a hybrid hard-soft clamping strategy was implemented to significantly increase the effective boundary stiffness of the diaphragm. This structure clarified boundary vibrations and extended the frequency response up to 1 kHz. Calibrated acoustic tests showed a low-frequency sensitivity of 76.6 mV·Pa⁻¹ at 150 Hz, and a relatively flat mid-to-high frequency response averaging 36 mV·Pa⁻¹, with stable dynamic performance across a 50–90 dB SPL range and high signal-to-noise ratio (SNR). | en_US |
| dcterms.abstract | In vivo evaluations demonstrated the sensor's capability for high-fidelity physiological signal acquisition. Pulse monitoring produced stable amplitudes with distinct pulse-wave features, while heart sound detection enabled clear identification of the first and second heart sounds (S1 and S2) and the observation of S2 splitting. Lung sound measurements captured broadband energy distributions with dominant frequencies between 100–800 Hz, consistent with clinical auscultation standards. | en_US |
| dcterms.abstract | This research establishes a scalable design and fabrication framework for high-performance, wearable piezoelectric acoustic sensors, integrating optimized electrospun membranes, flexible electrodes, and shape-adaptive device architectures. The acoustic system offers high sensitivity, broad frequency coverage, mechanical durability, and environmental stability, demonstrating strong potential for continuous, reliable bioacoustic monitoring in personalized healthcare and intelligent wearable systems. | en_US |
| dcterms.extent | xxiii, 183 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2026 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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