Acoustic tweezer for capturing and moving microparticles based on a focused ultrasonic transducer

The problem of trapping and moving microparticles with a single focused transducer at a frequency of 2 MHz is considered. The spatial distribution of the radiation force acting on solid silica particles in the field of a focusing transducer with a focal length of 70 mm and an aperture of 64 mm is calculated. It was shown that there are regions at a distance of 64 mm from the surface of the transducer, where particles with a diameter of 150 μm can be trapped and retained at amplitudes of the vibrational velocity on the transducer surface, exceeding 6 cm/s. Measurements of the displacement of the microparticles in horizontal planes, located at distances of 60-70 mm from the transducer, were carried out. It was shown that the microparticles are moved by the action of radiation force and regions of a clean surface are formed, which sizes and position depend on the distance from the transducer and the ultrasound intensity. The experimental results are corresponded well to the theoretical calculations. The proposed scheme of simple acoustic tweezers can be used in bioengineering for trapping and transport of cells and cellular structures.