Intra-droplet particle enrichment in a focused acoustic field.

Particle enrichment is an important preparation or collection process in biomedical and biochemical experiments, but the enrichment process in droplets is harder to realize than in continuous fluid. Here we demonstrate an on-chip, label-free and controllable intra-droplet particle enrichment realized in a focused acoustic field. In this process, droplets containing microparticles are trapped, merged together and split off in the focused acoustic region, resulting in droplets with particles of high concentration. By changing the experimental conditions, the degree of enrichment of this method can be tuned up to 26 times, which enables it to meet requirements for sample preparation in various applications.