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A novel single-element dual-frequency ultrasound transducer for image-guided precision medicine

High-resolution ultrasound imaging of tissues provides a higher possibility for the early diagnosis of various diseases and plays an important role in high-precision targeted treatment. However, it unavoidably suffers from low penetration depth and short depth of field (DOF) due to its high operating frequency. A novel single-element dual-frequency ultrasound transducer (DFUT) has been designed and studied, which consists of three conductive metal layers, a large capacitive elastic layer used as the low-frequency capacitive micromachined ultrasonic transducer (CMUT), and a small piezoelectric layer used as the high-frequency piezoelectric micromachined ultrasonic transducer (PMUT). This capacitive-piezoelectric hybrid structure is able to operate at both CMUT and PMUT modes at two different frequencies. Both theoretical analysis and finite element method (FEM) simulations have been carried out towards the frequency performance and optimizing the dimensions of the DFUT. The results show that the novel structure could be in operation at both low frequency of 5.9MHz and high frequency of 26.6MHz, which can be adopted as imaging and/or therapy operations. With the combination of CMUT and PMUT modes, the single-element DFUT provides the advantages of high-resolution (<200μm for PMUT operation) and a wide detection distance (>3cm for CMUT operation), which may significantly inspire the imaging-guided precision medicine applications.