Fig. 1.

(A) Schematic of the hybrid BAW/SAW acoustofluidic device from Cui et al. (5). A one-dimensional (1D) standing wave is generated by linearly coupled interdigitated transducers (IDTs) to develop a two-dimensional (2D) bulk acoustic field in a square glass microchamber oriented at 45° to the SAW propagation. In this way, the two overlapping orthogonal standing BAWs (in the X and Y directions) yield an array of trapping sites, similarly to the case of surface wrinkled topographies (21). Particles with a positive acoustic contrast factor, like Chlamydomonas reinhardtii cells, are pushed to these pressure nodes and become trapped. (B) The hybrid BAW/SAW device is capable of imaging and characterizing the swimming dynamics of microswimmers such as C. reinhardtii. Moreover, motility parameters such as ciliary beat frequency and synchrony can be investigated as a function of external factors like temperature and fluid viscosity. The image was created with https://www.biorender.com/.