Figure 5.

A. Schematic of SSAW forces exerted on cells in the region between IDTs. All cells move toward the pressure nodes, but large cells experience a larger force and move with a faster velocity. B. Switchable TSAW system used as an actuator for cell sorting. The light blue stream, containing cells, flows into the left outlet channel unless the TSAW is turned on by applying an AC signal to the IDT electrodes. Reprinted with permission from (Franke, Braunmüller, Schmid, Wixforth, & Weitz, 2010) C. FIDT system for high-throughput cell sorting. The concentric design of the IDTs focuses the SSAW to a small region, allowing it to specifically actuate individual cells. This device sorted HeLa cells at ~7,000 Hz. Reprinted with permission from (Ren et al., 2015) D. Tunable SSAW device that employs chirped IDTs. Cells can be directed to one of five different outlets depending on the frequency of the signal applied to the IDTs. Adapted with permission from (Ding et al., 2012) E. The taSSAW device positions the fluidic channel at a small angle relative to the IDT fingers, thus positioning the pressure nodes at an angle relative to fluid flow. Whereas a traditional SSAW sorter can only achieve separation distances up to 1/4 of the acoustic wavelength, the taSSAW design can achieve greater separation and accordingly shows improved throughput and performance. The particle trajectories demonstrate that the 15μm beads were separated from the 4μm beads by >300μm (the acoustic wavelength was 300μm). Adapted with permission from (Ding et al., 2014)