Search

A corrugated polyvinylidene fluoride (PVDF) bimorph power harvester with harvesting structure fixed at the two edges in the corrugation direction and free at the other edges is proposed. Results concluded that the adaptability of a harvester to operating environment can be improved greatly by designing the harvesting structure with adjustable resonant frequency.

An inexpensive acceleration measurement sensor that uses the piezoelectric polymer poly(vinylidene fluoride) (PVDF) has no moving parts. It achieves a sensitivity of 1.071 V sec sq per meter and a nonlinearity of less than 0.1%, with the limit of detection being 10 micrograms. The pyroelectric effects of the PVDF can be minimized with a symmetrical system. Various measurement ranges of acceleration can be achieved by utilizing the principle of this sensor.

A synthetic array experiment has been used to produce bowtie limited diffraction beams in water, which are in close conformity to those obtained from theory and computer simulations. A broad-band PZT ceramic/polymer composite transducer of one mm diameter is scanned in a raster format and placed at the center of elements of an equivalent two-dimensional array of 50 mm diameter aperture. A polyvinylidene fluoride needle hydrophone of 0.5 mm diameter receives the waves generated by the transducer. A depth of field of 216 mm is achieved for these bowtie beams, along with low sidelobes.

A study of the temperature-dependent dielectric and electromechanical properties of commercial polyvinylidene flouride (PVDF) films reveals their suitability for constructing inexpensive disposable transducers. The measured temperature dependence of the transducer's center frequencies and fractional bandwidths in the -40 to 80 degree celsius range matches very well with the predictions from computer simulations based on Mason's model. Various tests prove the usability of the same disposable transducers for ultrasonic and acoustic emission sensing nondestructive testing purposes.

A membrane hydrophone, capable of characterizing ultrasonic medical transducers, with a minus three dB bandwidth in excess of 150 MHz and spatial resolution of less than 100 micron has been developed. It has been fabricated on a superior coupling piezoelectric copolymer, polyvinylidene fluoride trifluoroethylene film. The frequency response can be evaluated by Bacon's shock wave method only. Absence of a proper technique makes open circuit sensitivity measurement difficult, leaving the only alternative of comparing the loaded end-of-cable sensitivity with a Marconi hydrophone.

The use of a polyvinylidene fluoride (PVDF) membrane hydrophone in calibrating air-coupled transducers was investigated. The potential and performance of PVDF as a hydrophone material with frequencies between 100 kHz and 5 MHz were examined using a one-dimensional theoretical analytical method. Experimental results showed that PVDF membrane hydrophones are highly suitable for calibration in air and that they offer certain advantages when used in air-coupled calibration. It was also found that the acoustic impedance of PVDF hydrophones is an order of magnitude lower than piezoceramic systems.