Development of 20 MHz linear array transducer for small animals imaging based on dual sub-element structure

This study focuses on overcoming the limitations of high-frequency array transducers, particularly their limited penetration depth resulting from weak transmitting energy. To address this issue, we propose a design strategy which can effectively suppress the sidelobe effects caused by the overwide aperture and ensure efficient acoustic energy transmission by increasing the element width based on dual sub-element structure. Finite element modeling (FEM) is conducted to analyze the influence of sub-element kerf on vibration modes, electrical impedance and acoustic field distribution, the radiating area, thereby optimizing the structure parameters. A 20 MHz linear array transducer with 128 elements was successfully fabricated based on the optimized parameters. Experimental results demonstrate that the transducer achieves a -6 dB bandwidth of 48%, lateral resolution better than 250 μm, axial resolution better than 100 μm, and imaging depth exceeding 5 cm. Vivo imaging experiments in small animals confirmed its practical applicability, which can capture the rapid beating of small animal heart in real time and perform high-sensitivity Doppler imaging of blood vessels. The obtained results suggest that the proposed sub-element based design strategy provides a feasible pathway for enhancing the performance of high-frequency linear arrays, offering promising potential for advanced small animal imaging applications.