Imaging of simulated muscle based on single chip of AlN piezoelectric micromachined ultrasonic transducer

Abstract

Most of current portable B-mode medical imaging is based on traditional ultrasonic transducers (UTs) or capacitive micromachined UTs, both of them have defects that impede satisfying performance. Piezoelectric micromachined UTs (pMUTs) is a promising solution for portable/wearable B-mode imaging as alternative. This work demonstrates B-mode imaging of simulated muscle with an aluminum nitride (AlN) pMUT array for application of muscle disorder diagnosis. A 23 × 26 pMUT array with resonant frequency of 5 MHz (in oil) is fabricated based on cavity silicon-on-insulator process. It has transmitting sensitivity of 3.6 kPa V−1 at 10 mm, receiving sensitivity of 1.1 μV Pa−1 and −6 dB bandwidth of 40% (in oil). Feasibility of muscle imaging based on pMUT is demonstrated by using muscle-like phantoms. Imaging results shows clear interfaces among layers, the axial and lateral resolution is 0.20 mm and 1.23 mm respectively. Furthermore, ex-vivo B-mode scans towards porcine tissues based on pMUT are firstly demonstrated. Different tissues including muscle, subcutaneous fat, fascia and hematoma is distinguished. The maximum imaging depth inside the porcine tissue is above 40 mm. These results demonstrate great potential of the pMUT array in muscle imaging.