Measurement and calculation of lateral trapping strength of focused beams generated by a two-dimensional ultrasound array

This study is aimed at developing a method to controllably manipulate kidney stones in the human body using a single ultrasound source. Calculation and measurement of the lateral force on a sphere using various acoustic beams (vortex and radially-varying phased beams) were compared. A 256-element, 1.5-MHz array was used to synthesize the beams. Spheres of 1–6 mm (6 < ka < 20) diameter made of glass, ceramic, or brass were positioned on an acoustically matched platform at the focus rigidly attached to the transducer by a frame. The transducer and platform were rotated to the angle at which the trapped sphere fell. The acoustic power was