On-chip generation of acoustical vortices with swirling surface acoustic waves for single particle manipulation and vorticity control

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Surface acoustic waves (SAWs) are versatile tools for the manipulation of fluids at small scales. These waves can be used to displace, divide, merge, and atomize sessile droplets, but also actuate fluids embedded in microchannels. In this presentation, we will show that IDTs array and inverse filter technique enable on-chip synthesis of a new type of SAWs, called swirling SAWs, which degenerate into bulk acoustical vortices when transmitted to a liquid. These acoustical vortices can be tailored to create a 3D particle trap and thus selective single particle acoustical tweezers, with digital control of the trap position. They can also induce controlled vortical flows, whose topology essentially relies on the topology of the underlying acoustical vortex.