Sound waves can be powerful - powerful enough to move large groups of particles. Recently, scientists at the Chinese Academy of Sciences announced an acoustic sieve that can sift, move, trap, or align large groups of particles by size and density under water. They began by focusing an ultrasound beam on a flat plate. The brass plate has a grating on top made of materials (phononic crystals) specifically for manipulating acoustic waves. Below the plate is a container of glass spheres of various sizes and densities. When the ultrasound beam turns on, it creates a localized field underneath the plate that can trap the particles. The experimental setup used, where an ultrasound beam is focused on a plate to trap particles. Image Credit: Phononic-Crystal-Based Acoustic Sieve for Tunable Manipulations of Particles by a Highly Localized Radiation Force . The plate moves closer to the particles, and scientists can manipulate the particles as they wish.
