Fig. 4. Cell patterning via wave number–spiral acoustic tweezers.

The experimental results (optical microscopy images) show that U937 cells are successfully arranged in (A) a 1D parallel pattern at the frequency f₄, and (B) a 2D rectangular lattice with the frequency combination [f₁, f₄]. (C) For both U937 and HeLa cells, viabilities are nearly the same among three conditions: without any treatment (“Control”), flowing through the device (10 μl/min) without SAWs (“Flow”), and flowing through the device with SAWs with an excitation of 15 Vpp at 12 MHz (“Flow and SAW”). (D to F) Experimental results (optical microscopy images) after HeLa cells have been patterned and cultured for 1, 3, and 6 hours. These results show that cells patterned by SAWs can be cultured in the disposable microfluidic chamber. Meanwhile, the original pattern can be maintained with slight cell movements. Scale bars, 100 μm.