Particles separation using the inverse Chladni pattern enhanced local Brazil nut effect

Particles separation and patterning in fluidic environment is fundamental for many mechanical, biomedical, and chemical applications. There still remain challenges for manipulation the external forces to separate different kinds of particles. Chladni patterns have raised great interest in the field of self-assembly for particles of different materials. The particles bounce randomly on the vibrating plate, and gradually accumulate to nodal lines or anti-node. However, existing utilization of the Chladni effect mainly focuses on patterns and trajectories manipulation. The mechanism for simultaneous manipulation of multiple kinds of particles is still unclear. In this work, the separation of multiple kinds of particles is investigated using the inverse Chladni pattern. The particles accumulate to different positions in the annulus or circular region, forming ordered pattern at the anti-node. Besides, the acoustic streaming vortex is achieved, which serves as the local virtual container for particles separation. Additionally, the local horizontal Brazil nut effect occurs due to the combined effects of acoustic streaming, collision with the vibrating plate, buoyancy, and gravity. Separation of particles with different sizes and densities can be realized horizontally by the acoustic streaming vortex. We realize the simultaneous separation of as many as four kinds of particles. This work investigates the manipulation mechanism for multiple kinds of particles by the inverse Chladni pattern, thereby potentially providing an effective platform for particles patterning and simultaneous separation of multiple kinds of particles.