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UBC Theses and Dissertations

Design and performance of all-polymer acoustic sensors Sielmann, Christoph


All-polymer flexural plate wave (FPW) sensors based on piezoelectric polyvinylidene fluoride (PVDF) thin-film with interdigital transducer (IDT) electrodes composed of poly(3,4-ethylenedioxythiophene) poly-(styrenesulfonate) (PEDOT:PSS) are studied, optimized, and assessed for their potential in various sensing applications. PVDF offers unique opportunities as a substrate material due to its low stiffness, low cost, low density, and ease of preparation compared with many other piezoelectric materials commonly used in acoustic sensing applications. Substrates are prepared using a variety of material thicknesses of PVDF through a stretching and poling process, followed by conductive IDT patterning by inkjet printing using a PEDOT:PSS-based ink. Sensor behaviour is studied using electrical and optical measurement techniques. Material and gas loading tests are performed to demonstrate gas sensing and polymer characterization applications. The devices demonstrate good adherence to analytical and FEA models, and although the high attenuation and low coupling coefficients of the substrate material reduce signal to noise ratio and quality factor, vapour sensing and polymer/absorbent material characterization applications are realized experimentally. Other factors such as environmental influences are also considered, demonstrating a very high sensitivity to temperature and humidity changes. The sensors also demonstrate high sensitivity to variations in substrate and sensing layer stiffness, reducing their effective mass sensitivity, but also increasing their potential for simultaneous mass and stiffness measurements. Parameter sensitivity studies are generated to better optimize the design and improve performance of the sensor for specific applications, suggesting benefits from thinner substrates, lower in-plane stress, and more IDT fingers.

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