Flexible ultrasonic transducers incorporating piezoelectric fibres

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2009-09, Vol.56 (9), p.1999-2009
• Main Authors: Harvey, G., Gachagan, A., Mackersie, J.W., Mccunnie, T., Banks, R.
• Format: Article
• Language: English
• Subjects: Acoustics; Arrays; Ceramics; Channels; Devices; Exact sciences and technology; Fibers; Finite element methods; Frequency; Frequency ranges; Fundamental areas of phenomenology (including applications); General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Manufacturing; Mathematical models; Optical fiber devices; Physics; Piezoelectric ceramics; Piezoelectric materials; Polymers; Production; Surface impedance; Transducers; Transduction; acoustical devices for the generation and reproduction of sound; Ultrasonic transducers; Ultrasonics, quantum acoustics, and physical effects of sound
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2009.1276

It is possible to produce a high-performance, flexible 1-3 connectivity piezoelectric ceramic composite with conventional methods but the process is difficult and time-consuming. Extensive finite element modeling was used to design a piezocomposite structure which incorporated randomly positioned piezoceramic fibers in a polymer matrix. Simple manufacturing techniques were developed which resulted in the production of large numbers of fully populated fiber composites that offered performance comparable with a conventional 1-3 piezocomposite. A modified process facilitated the production of efficient fiber piezocomposite elements separated by polymer channels which conformed to a highly flexible (13 mm radius of curvature), 2-D matrix array configuration. This arrangement has been termed a Composite Element Composite Array Transducer, or CECAT. These devices were evaluated in terms of their impedance spectra, pulse-echo response, and surface displacement characteristics. The random piezoceramic fiber arrangements showed comparable sensitivity and bandwidth to periodic devices while minimizing the parasitic interpillar modes associated with periodic structures. Investigations have indicated that CECAT arrays constructed with 250 mum diameter fibers can be operated at frequencies of up to 3 MHz and transducers incorporating 10 mum diameter fibers can extend the frequency range above 6 MHz. Conversely, improved low-frequency devices can be produced with taller pillars than possible with conventional manufacturing techniques.