Figure 2.

(a) At 217 kHz, 5 µm silica particles are trapped by acoustic bubbles, while 5 µm polystyrene particles follow with streamline due to the drag force. Reprinted with permission from reference [52]. (b) BAW-based separation of polystyrene and polydimethylsiloxane (PDMS) particles with different acoustic contrast factors. Reprinted with permission from reference [47]. (c) Size-sensitive sorting mixture of 5 µm and 2.5 µm particles by acoustic bubble. Reprinted with permission from reference [53]. (d) Angled lateral cavity acoustic transducers (LCATs) produce a directional flow from inlet to outlet, large-sized particles are selectively trapped and small-sized particles are transported to the outlet. Reprinted with permission from reference [20].