Study on the migration and regional enrichment behavior of droplets and particles induced by surface acoustic wave

The oxidizability and fluidity of liquid metals challenge the stability and durability of wearable devices in extreme environments. Surface acoustic waves can achieve surface modification of liquid metal microdroplets by directing the trajectories of microdroplets and functional particles. In this paper, the force state of particles under acoustic induction is deeply analyzed, and the regulation mechanism of directional migration and regionalized enrichment behavior between droplets and particles is identified. The findings demonstrate that the wave source, which is generated by the diffraction of the acoustic surface wave at the two phases, interferes with itself and consequently produces curved acoustic-pressure interference patterns that are parallel to the droplet interface. The particles migrate toward the low-pressure region dominated by the acoustic radiation force, showing a directional migration behavior around the droplet. The acoustic pressure consists of the linear superposition of the diffraction patterns induced by each droplet. To achieve full particle-droplet contact and maximum enrichment in the unilateral region of the microchannel. The droplet spacing should be greater than the product of the microchannel width and the minimum angular tangent corresponding to the intersection of the peripheral orbits of the interference pattern. This paper elucidates the interaction mechanism of cross-scale object motion trajectories in the acoustic field, thereby providing a theoretical basis for the preparation of functional particle-liquid metal composite structure droplets under surface acoustic waves.