In-Petri-dish acoustic vortex tweezers†

Acoustic tweezers, with the capability to manipulate tiny objects without physical contact, hold substantial potential for biomedical and biological research. However, current acoustic tweezers platforms face challenges in precise, selective, and multi-degree-of-freedom (multi-DoF) manipulation of objects in Petri dishes, making it difficult to integrate them into typical laboratory workflows. This paper presents an acoustic vortex tweezers platform that enables contactless, precise, multi-DoF, and multifunctional manipulation of micro-to-millimeter-scale objects within a Petri dish. The platform features an acoustic holography-based module, which uses a holographic lens to transform acoustic waves and generate a focused acoustic vortex beam. This beam carries sufficient energy to propagate through a Petri dish's bottom wall, creating a ring-shape intensity field for trapping tiny objects. Using lenses encoded with different topological charge numbers, vortex beams with varying diameters can be generated, allowing for trapping various-sized objects. Additionally, in combination with a 3-DoF linear motion module, our integrated platform enables high-resolution translation of acoustically trapped objects along complex paths. We experimentally demonstrated our platform's diverse capabilities, including concentrating micro-objects, trapping flowing micro-objects to create an agglomerate, translating a microparticle and an agglomerate along complex paths, as well as trapping, rotating and translating a zebrafish larva in horizontal and vertical postures. With these capabilities, we expect our in-Petri-dish acoustic vortex tweezers to emerge as a valuable tool for the contactless, high-resolution, programmable handling of tiny biomaterials in biomedical and biological research.