In this work, a 3D-printed mesoscale acoustic generalized Luneburg lens based on cylindrical metamaterial is proposed. Compared to isotropic lenses, we numerically and experimentally demonstrate a series of advantages of lens including the super long work distance (over 17λ, 20 kHz in air), without obvious sidelobe, and better acoustic impedance matching. The ray tracing method is revealed to interpret the ultra-long acoustic jets mechanism. The adjustment of the lattice unit composition allows for the manipulation of air and underwater acoustic waves. The present work inspires a straightforward strategy for ultra-long acoustic jets, with promising applications in imaging and treatment in biological tissues.

An acoustic jet generated by a mesoscale particle has been proved to be able to achieve sub-wavelength focusing. In this work, we propose two kinds of mask structures to accurately modulate the characteristics of the acoustic jet, such as the focal distance, FWHM and decay length by adjusting the position of incident sound waves. Our simulations show that an ultra-narrow beam waist width (λ/3) in the near field and an ultra-long beam (7λ) in the far field can be achieved under plane wave illumination. This structure provides a simple method to precisely control the acoustic jet.

Owing to characteristics of single-step fabrication and rapid prototyping, 3D printing have potential applications in processing piezoelectric motors with complex structures. In this paper, a 3D printed resin-based bimodal piezoelectric motor is proposed. Four slots of the motor are designed to reduce the influence of large damping caused by polymer’s viscoelastic and enhance mechanical properties. Considering the viscoelasticity and internal structure of the stator, a dynamic model based on the proposed motor is developed. Furthermore, parameters of these slots are optimized using the Taguchi method. Prototypes are fabricated and experimentally investigated. The results demonstrate that the first longitudinal mode and the second bending mode are 17 765 Hz and 18 006 Hz respectively, which are consistent with the analytical model results. Under the voltage of 300 Vpp, the maximum no-load speed and maximum driving load of the slotted motor are 200 r min−1 and 20 g with a speed of 6 r min−1, respectively. Compared with the motor without slots, the speed and load capacity are increased by 25% and 33%. Therefore, the motor with slots exhibits better mechanical output performance.

Acoustic focusing has been widely applied in biological and industrial fields. In this work, a coding acoustic metasurface consisting of two kinds of hexagonal coding bits is designed. Using the metasurface, acoustic focusing can be implemented in three-dimensional space. Besides, by altering the coding sequence, the focal length can be manipulated flexibly to satisfy the practical demands. Furthermore, bifocal focusing, which has a great potential in multiplane imaging, can be realized by properly arranging the coding sequence. Our works broaden the prospects of the coding metasurfaces and have promising applications in the areas of biomedical therapy and imaging.

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