Single Bessel tractor-beam tweezers

TL;DR

This paper demonstrates the theoretical behavior of a finite circular aperture zero-order Bessel acoustic beam acting as a tractor beam on a fluid sphere, providing conditions for attractive forces and numerical analysis for device design.

Contribution

It introduces a theoretical analysis of finite-aperture Bessel beams as acoustic tractor beams, including conditions for attraction and numerical predictions for design applications.

Findings

Conditions for attractive forces depend on beam parameters.

Numerical predictions support practical device design.

Finite aperture effects are significant in beam behavior.

Abstract

The tractor behavior of a zero-order Bessel acoustic beam acting on a fluid sphere, and emanating from a finite circular aperture (as opposed to waves of infinite extent) is demonstrated theoretically. Conditions for an attractive force acting in opposite direction of the radiating waves, determined by the choice of the beam's half-cone angle, the size of the radiator, and its distance from a fluid sphere, are established and discussed. Numerical predictions for the radiation force function, which is the radiation force per unit energy density and cross-sectional surface, are provided using a partial-wave expansion method stemming from the acoustic scattering. The results suggest a simple and reliable analysis for the design of Bessel beam acoustical tweezers and tractor beam devices.