Application to Diagnostic Ultrasound

In other developments, voided PVDF film, that is film containing stretching-induced microvoids, has been used to constmct hydrophones that provided an almost exact acoustic impedance match to water, as opposed to the factor of 2.7 greater for nonvoided PVDF 

PVDF exhibits pyroelectric as well as piezoelectric properties [44], a feature that has made the material useful for infrared sensing in motion detectors and thermal cameras. This attribute has been used recently in a thermally based method to measure ultrasonic power [45]. A 52 pm thick film of PVDF 60 mm in diameter was used as the sensor, which was backed with a rubber based material that generated heat due to ultrasonic absorption. Powers up to 1 W over a frequency range of 1-3.5 MHz were measured in this preliminary study. 

PVDF also has been employed in the eonstraetion of broadband transmitters for the purpose of eaUbrating hydrophones [46,47]. In [46] the wide bandwidth of the 25 pm fihn allowed a single transdueer to be used for a rapid eaUbration in the 1—40 MHz range in [47] the teehnique was modified to extend the ealibration range to 100 MHz. 

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