Theoretical Aspects of Single-beam Multitrapping Acoustical Tweezers

1 Abstract The concept of a multitrapping acoustical tweezer based on a focused ultrasound beam is presented and theoretically investigated. The beam is described in the paraxial approximation and it is generated by a concave transducer. The resulting focused beam exerts a radiation force on a small particle that is much smaller than the incident wavelength (i.e. the so-called Rayleigh scattering regime). It is shown that several trapping points are developed in the pre-focal zone (i.e. the region between the transducer and its geometric focus point) along the beam axial direction. Additionally, the possibility of using a zeroth-order Bessel and a Gaussian focused beam as a multitrapping acoustical tweezer is analysed.