Design of capacitive micromachined ultrasonic transducers (CMUTs) on a flexible substrate for intravascular ultrasonography (IVUS) applications

Effects of substrate bending to the characteristics of capacitive miniaturized ultrasonic transducers (CMUTs) on a flexible substrate are studied through finite element analysis (FEA) for the design purpose. The target application of the devices is intravascular ultrasonography (IVUS) where transducers are brought to the proximity of the imaging targets so that high resolution images can be obtained without much concern of signal attenuation. In order to eliminate mechanical rotation used in the conventional IVUS, the transducer array can be manufactured on a flexible substrate and to wrap it around a cylindrical frame. It can be anticipated that the characteristics of the transducers will be altered by such bending of the substrate through geometrical dimension changes and stress induced. Pullin voltages and resonant frequencies of CMUTs were studied via FEA for various bending radii and membrane thicknesses. It was found that both pull-in voltages and resonant frequencies become smaller for the transducers on a bent substrate compared to the ones on a flat substrate. It was also found that pull-in voltages decrease as the substrate bending radius is reduced.