Fig. 3. Multiconfiguration 2D patterning of microparticles via wave number–spiral acoustic tweezers.

(A to C) Simulated Gor’kov potential fields for wave number–spiral acoustic tweezers, when excitation signals contain different frequency combinations [f₁, f₄], [f₁, f₅], and [f₃, f₄], respectively. (D to F) Experimental results (optical microscopy images) taken for the three frequency combinations [f₁, f₄], [f₁, f₅], and [f₃, f₄], respectively. The experimental results show that microparticles are patterned on 2D lattices with different spatial periods, edge lengths, and interior angles. The blue parallelograms are used for illustrating unit cells of 2D lattices. Scale bars, 100 μm.