Acoustic separation of materials has several features which make it ideal for biological separation, the main one being its ability to use the inherent contrast of the object to separate it from the surrounding fluids without the need for external particle tags, e.g., magnetic beads. The literature on acoustic techniques is vast, however there are generally two main flavors used to achieve separation, namely: 1) acoustic standing waves to organize particles into spatially periodic patterns, and 2) acoustic streaming to trap particles nearby sharp edges.
We have recently developed techniques based on acoustic traps to organize single cell arrays inside microfluidic channels. Our approach functions by first trapping single cells in hydrodynamic weirs, and next transferring those cells into adjacent apartments with an acoustic switch. The high density of these devices allows for thousands of single cells to be organized on chips that are the size of a typical 3” x 1” glass slide.
KA Ohiri, ST Kelly, JD Motschman, KH Lin, KC Wood, and BB Yellen. "An acoustofluidic trap and transfer approach for organizing a high density single cell array." Lab on a Chip 18, no. 14 (2018): 2124-2133.