Novel Phased Array Piezoelectric Micromachined Ultrasound Transducers (pMUTs) for Medical Imaging

Abstract

Two kinds of 128 channels pMUT-based phased array ultrasound transducers are described in this paper, one with a high frequency of around 6 MHz and another with a low frequency of around 1.5 MHz. The active area of the transducer is around 25 mm long and 10 mm wide. There are in total 6270 pMUT elements in the reported arrays. For the transducer with a center frequency of 6 MHz, each pMUT has a membrane diameter of 85 $\mu \text{m}$ and the pitch between every two channels is 200 $\mu \text{m}$ . The transducer benefits from a high transmission and receive sensitivity of 44 kPa/V/Channel @ 3 cm and 204 mV/MPa, respectively. For the transducer with a center frequency of 1.5 MHz, each pMUT has a membrane diameter of $160~\mu \text{m}$ and the pitch between every two elements is 214 $\mu \text{m}$ . The proposed transducer obtained a transmit and receive sensitivity of 430 Pa/V/Channel @ 3 cm and 190 mV/MPa, respectively. The transducer has a −3dB and −6dB bandwidth of 118% and 184%, respectively. The bandwidth is higher than any previously reported transducer in any technology, such as bulk-PZT, pMUT, or capacitive MUT (cMUT). The functionality of the transducer arrays is confirmed by obtaining B-mode images in water medium.