Bioinspired Patterned Bubbles for Broad and Low-Frequency Acoustic Blocking.

Bubble crystals in water are expected to achieve the broad and low-frequency acoustic band gaps that are crucial for acoustic blocking. However, preparing patterned bubble crystals in water remains a challenge because of the instability of bubbly liquids. Here, inspired by biological superhydrophobic systems, we report a simple and rapid approach to prepare patterned bubble arrays in water and their applications in low-frequency acoustic blocking. Patterned bubbles with the desired size, shape, and position can be prepared. Single-layer bubble arrays can block the sounds at low frequencies because of local resonance. By varying the size and distance of the bubbles without changing the thickness, the operating frequency can change from 9 to 1756 kHz. Besides, by preparing multilayer bubbles, broad and low-frequency acoustic band gaps can be achieved, with the generalized width of γ (ratio of the bandgap width to its start frequency) reaching 1.26. This method provides a feasible strategy to control acoustic waves at low frequencies for applications such as acoustic blocking, focusing, imaging, and detecting.