Sequencing waves in single-transducer acoustophoretic patterning of microspheres

Acoustophoretic assembly uses acoustic waves to move dispersed particles into a geometric pattern. The pattern is typically created in a single step and often relies on wave-forming techniques to achieve the desired pattern geometries. We show that multiple acoustic waves can be applied sequentially in a multi-step process to create particle patterns not achievable by the individual waves alone. We demonstrate this approach in spherical particles using two planar pseudo-standing waves. Applied individually, each of the two waves would create linear particle bands with uniform spacing in between the bands. However, when applied sequentially, the banding pattern created in the first step is further manipulated by the second wave to create non-uniform spacing in between the bands. The experimentally achieved particle pattern geometry agrees well with the theoretical prediction.