Dexterous formation of unconventional Chladni patterns using standing bulk acoustic waves
Junjun Lei, Feng Cheng, Guotian Liu, Kemin Li, Zhongning Guo
Abstract
Classical Chladni patterns formed by vibrations of flat plates have been studied for centuries and are well understood. In this Letter, we show dexterous formation of unconventional Chladni patterns in a fluid using standing bulk acoustic waves. A neat acoustofluidic resonator enabling visualization of microparticles in the fluid channel both on its cross section and in its flow direction was designed. In contrast to classical Chladni patterns, which depend on resonant modes of flat plates, the Chladni patterns herein are generated by vibrations of cylindrical walls and are related to resonant modes of fluid channels. The behavior of the acoustofluidic resonator is numerically predicted by applying an acoustic-structure interaction model to calculate the acoustic pressure distribution at different modes of resonances and the Gorkov theory to obtain the potential of the acoustic radiation forces that act on suspended particles. We also demonstrate numerically and experimentally that further focusing of microparticles can be achieved if the actuation of ultrasound continues after Chladni patterns are formed on the cross section of the fluid channel.