Figure 4.

SAW-based particle or cell manipulation. a) Saw-based single particle/cell patterning. Particles are trapped at the node of the acoustic wave. (i) If the wavelength is much larger than the particle/cell diameter, multiple particles are driven to the force minima. (ii) By tuning the wavelength of the acoustic wave, single particle patterning can be achieved. Adapted with permission from Collins et al., Nat. Communications 6, 8686.¹⁵⁴ Copyright 2015. b) Acoustic-tweezer-based formation of spheroids. Suspended cells are aggregated at the trapping positions, defined by the acoustic force, the induced streaming force, gravity and the buoyant force. The photographs at the bottom show the formation of spheroids of different size, which were obtained by using cell suspensions of different cell densities. Adapted from Chen et al.¹⁵⁸ with permission from the Royal Society of Chemistry.