Abstract

Pulse Ultrasonic Doppler Velocimetry (PUDV) transducers have been used in the study of fluid wall shear stress and intimal hyperplasia within vascular bypass grafts [1]. Although these devices have contributed significantly to the understanding between fluid mechanic and biological phenomena, errors as large as 20% have been reported [1] within theses devices. This level of error is unacceptable to many researchers, so methods must be developed to increase accuracy within PUDV devices. One technique commonly used in ultrasonic transducers is the application of acoustical lenses. Acoustical lenses have been found to focus the ultrasonic beam, increase the spatial resolution, and increase the signal-to-noise ratio (SNR) of acoustic sensors [2]. First attempts within our laboratory to develop these lenses consisted of placing PZT-5A piezoelectric crystals within micromachined polymethylmethacralate (PMMA) blanks milled with a 263 microns deep cavity. Subsequently, Eccosorb CR-112 epoxy was cast over the crystals and machined via diamond tuming/micro-lathe to form the lens. The crystal-lens systems were then released by placing the PMMA blanks in a solvent (Dichloromethane). This process was both time consuming and only produced a 5% yield. Therefore, the purpose of this study is to develop a new technique that reduces processing time and produces a higher yield.

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