Circular orbital manipulation of positive-acoustic-contrast particles employing double-ring perfect acoustic-vortex beams.

Non-contact acoustic-vortex (AV) tweezers have gained prominence for high-precision manipulation. However, conventional AV beams are limited by their topological charge (TC)-dependent radii. While perfect AV beams address this radius issue, existing implementations struggle to achieve both flexible field control and stable trapping of particles with positive acoustic contrast. To overcome these limitations, this study introduces a robust method for constructing double-ring perfect acoustic vortex (DR-PAV) fields, enabling stable circular manipulation of positive-contrast particles along low-pressure trajectories. By integrating active phased-array techniques employing a sector transducer array with passive phase modulation via a composite saw-tooth structure, we establish a theoretical framework based on radial wavenumber multiplexing. Numerical simulations and experimental measurements demonstrate that the inter-ring spacing and peak-pressure ratio can be independently controlled by adjusting the base and central angles of the saw-tooth sectors, thereby facilitating stable particle trapping across different scales. Notably, while the pressure amplitude remains independent of TC, the azimuthal phase gradient increases with TC, enhancing the capability for orbital particle driving. Experimental validation using a 16-sector array confirms the underlying manipulation mechanism: radial gradient forces confine particles within the low-pressure ring, while azimuthal phase-gradient forces and acoustic streaming collectively drive orbital motion at speeds modulated by the TC. Building upon the specific implementation, the proposed framework establishes a versatile and scalable platform for programmable acoustic manipulation landscapes. Its applicability can be extended to multi‑ring vortex fields, real‑time trajectory reconfiguration, and multi‑particle manipulation, thereby opening new avenues for non‑contact control in biomedical engineering, microfluidics, and soft‑matter physics.