Acoustic tweezers use ultrasound for contact-free manipulation of particles from millimeter to sub-micrometer scale. Particle trapping is usually associated with either radiation forces or acoustic streaming fields. Acoustic tweezers based on single-beam focused acoustic vortices have attracted considerable attention due to their selective trapping capability, but have proven difficult to use for three-dimensional (3D) trapping without a complex transducer array and significant constraints on the trapped particle properties. Here we demonstrate a 3D acoustic tweezer in fluids that uses a single transducer and combines the radiation force for trapping in two dimensions with the streaming force to provide levitation in the third dimension. The idea is demonstrated in both simulation and experiments operating at 500 kHz, and the achieved levitation force reaches three orders of magnitude larger than for previous 3D trapping. This hybrid acoustic tweezer that integrates acoustic streaming adds an additional twist to the approach and expands the range of particles that can be manipulated.

声学镊子使用超声波对从毫米级到亚微米级的粒子进行非接触式操作。粒子捕获通常与辐射力或声流场有关。基于单束聚焦声涡流的声学镊子因其选择性捕获能力而引起了相当大的关注，但已证明难以在没有复杂换能器阵列的情况下用于三维 (3D) 捕获，并且对捕获的粒子特性有显着限制。在这里，我们展示了流体中的 3D 声学镊子，它使用单个换能器并将用于在二维中捕获的辐射力与流动力相结合，以提供三维中的悬浮。这个想法在以 500 kHz 运行的模拟和实验中得到了证明，并且获得的悬浮力比之前的 3D 捕获大三个数量级。这种集成声学流的混合声学镊子为该方法增加了额外的扭曲，并扩大了可以操纵的粒子范围。