Design of polymer-based PMUT array for multi-frequency ultrasound imaging

Multi-frequency piezoelectric micromachined transducer (PMUT) arrays have the potential to assist long-term monitoring with high resolution images at large penetration depth, paving the way for early diagnosis, follow-up and treatment. In this paper, we have demonstrated the design and characterization of multi-frequency polymer-based PMUT arrays intended for aforementioned applications. Starting from single PMUT devices, the resonance frequencies and mode shapes characterized in water agree well with the simulated counterparts. Based on these results, PMUT devices of 320 µm and 400 µm are selected to build up PMUT array. First, the maximum axial pressure of one 5×5 PMUT array has been measured in water at a frequency sweep of 1.7-20MHz. Moreover, the measured pressure map of a 16×32 PMUT array remains aligned with the acoustic simulation result. As an important step towards imaging applications, the pulse echo signal of the same PMUT array has been characterized by using a plate phantom in water.