摘要
This paper presents novel self-focused ultrasonic transducers batch-produced by microfabrication. A PZT film, tens of microns thick, can be deposited on an engineered flexible substrate composed of an F-number controllable parylene shaped diaphragm and heat resistant RTV material, with no fractures after thermal annealing. The residual stress of the PZT film is released through the curvature change of the fabricated parylene/RTV, spherically shaped diaphragm. The experimental relationship between the designed and resultant F-number of the fabricated transducer is discussed. The shaped PZT electromechanical coupling coefficient k t is determined as 0.41. A pulse-echo experiment is performed directly using the parylene/RTV curved diaphragm as the backing of the device. The outcome displays a central frequency of 50 MHz and a -6 dB bandwidth of 30% as well as a lateral resolution of 40 νm. An experiment for measuring the averaged acoustic intensity generated by the transducer in air is designed and tested. The result shows a maximum value of 43 νW mm -2 at the focus when the transducer is driven by an 11 MHz continuous sinusoidal wave of 3 Vpp. © 2011 IOP Publishing Ltd.