Generation of an enhanced acoustical quasi-Bessel beams with a grating Bessel interdigital transducer

The manipulation of micrometer-scale particles using surface acoustic waves has been demonstrated to have broad application potential across a range of disciplines, including materials science, precision engineering, the biomedical fields and chemical analysis. The device offers a number of advantages, including non-contact operation, good biocompatibility, the elimination of the need for chemical biomarkers, and straightforward integration. However, due to the structure of interdigital transducers, the performance in complex microfluidic environments remains constrained by limitations in energy efficiency and field uniformity. In this paper, a grating-Bessel interdigital transducer (GBIDT) is presented to produce modulating quasi-Bessel beam, which can enhance acoustic energy distribution in the manipulation region. Numerical simulations and experimental validation have been conducted to verify the preservation of the non-diffracting and self-healing properties of quasi-Bessel beams within the manipulation region by the proposed GBIDT. The results show that the integrated grating structure can enhance the main lobe intensity while suppressing side lobes (59.38% improvement in main-to-side lobe ratio), enabling a 29.41% acceleration in particle transport velocity under equivalent energy input. Then, the GBIDT is used in crystallization experiment and the results show that the device can produce pyramid-shaped NaCl crystals with controlled morphology, which distincts from naturally formed cubic crystals. This work demonstrates a practical approach to enhancing SAW-based manipulation systems, with potential applications in microfluidics, bioseparation, and programmable crystal engineering.