  The concept of a single-beam acoustical tweezer device which can
simultaneously trap microparticles at different points is proposed and
demonstrated through computational simulations. The device employs an
ultrasound beam produced by a circular focused transducer operating at 1 MHz in
water medium. The ultrasound beam exerts a radiation force that may tweeze
suspended microparticles in the medium. Simulations show that the acoustical
tweezer can simultaneously trap microparticles in the pre-focal zone along the
beam axis, i.e. between the transducer surface and its geometric focus. As
acoustical tweezers are fast becoming a key instrument in microparticle
handling, the development of acoustic multitrapping concept may turn into a
useful tool in engineering these devices.
