60-MHz PMN-PT Single Crystal Transducers for Microfluidic Analysis Systems

This paper describes the design, fabrication and evaluation of high frequency ultrasonic needle transducers for microfluidic analysis system. The transducers with an aperture size of 0.4 mm have been fabricated using lead magnesium niobate-lead titanate (PMN-PT) single crystal as the active piezoelectric element. The PMN-PT has been bonded to a conductive epoxy backing and fixed within a stainless-steel needle housing. A parylene front-face matching layer has been formed by vapor deposition. The measured center frequency and -6 dB bandwidth of the PMN-PT transducer are 60 MHz and 36%, respectively. The two-way insertion loss is −15.8 dB. Such devices are successfully built into a microfluidic channel for measuring the acoustic velocity and attenuation of the medium flowing into the channel.