Microparticle manipulation is of interest for applications such as colloidal self-assembly, selective clustering as sorting of particles and cells, and biological sample preparation. Particle manipulation is usually done in the bulk of a fluid in ultrasound applications. However, it can also be done on liquid surfaces. We show that deformations formed by focused ultrasound (either convex or concave) on a liquid surface allow contactless manipulation and trapping of microparticles on the surface. The particles are either attracted to or repulsed by the deformation depending on if the particles used were hydrophilic or hydrophobic due to the “Cheerios” effect. Hydrophobic particles gathered at the highest point of the deformation when the deformation pointed up and in a circular pattern around the deformation when it was pointed down. Hydrophilic particles behaved in the opposite way. Additionally, not trapped particles drifted away due to acoustic streaming. Trapped particles could potentially be collected by ejecting them from the surface using an acoustic fountain.
