Particle Patterning by Ultrasonic Standing Waves in a Rectangular Cavity

By means of the acoustic radiation force, standing waves of ultrasound can form a two-dimensional microarray to hold dispersed particles or cells in solution. This phenomenon can be used in lab-on-a-chip technology for single-cell analysis and analytical chemistry, though the physics behind ultrasound patterning is not fully understood. This study provides an analytical expression for the acoustic potential energy that traps cells, and reveals that the trapping points at pressure nodes, antinodes, and internode midpoints depend on a cell's size and mechanical properties. This theoretical approach should help to engineer acoustic-patterning devices, especially for ``one cell per well'' analysis.