Application of Acoustic Bessel Beams for Handling of Hollow Porous Spheres

Abstract

ABSTRACT-Acoustic manipulation of porous spherical shells, widely used as drug delivery carriers and magnetic resonance imaging contrast agents, is investigated analytically. The technique used for this purpose is based on the application of high-order Bessel beams for as a single-beam acoustic manipulation device, using which particles lying on the axis of the beam can be pulled toward the beam source. The exerted acoustic radiation force is calculated using the standard partial-wave series method and the wave propagation within the porous media is modeled using Biot's theory of poroelasticity. Numerical simulations are performed for porous aluminum and silica shells of different thicknesses and porosities.Results have shown that manipulation of low-porosity shells is possible using Bessel beams with large conical angles, over a number of broadband frequency ranges; while that for highly porous shells generally occurs over some narrowband frequency domains at much smaller conical angles.

Prediction of negative radiation forces due to a Bessel beam

“…In the case of a zero-order Bessel beam (ZOBB), for instance, numerical studies have shown that the radiation force on rigid/soft particles is always repulsive, whereas that for acoustically penetrable objects may become negative under specific conditions. [1][2][3][4][5][6][7][8][9][10][11][12] In the absence of gradient and absorption forces, this can only be interpreted to be due to the scattering forces and the structural properties of the object itself. Despite the recent works on the emergence of NRFs due to Bessel beams, [3][4][5][6][7] to the best knowledge of the author, the relation between the structural properties of the particles, e.g., mechanical properties and eigenfrequencies, and the emergence of NRFs on spheres due to an acoustic ZOBB has not been studied before.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Studies have shown that spherical particles placed on the axis of a Bessel beam may be attracted toward the source of the beam for appropriately selected beam parameters (shape and frequency) and particle properties (optical or mechanical). [1][2][3][4][5][6][7][8][9][10][11][12][13] Several theoretical studies have been carried out over the past few years to explore the feasibility of using ordinary (zeroth-order) and high-order Bessel beams for handling of on-axis objects with different mechanical properties. [3][4][5][6][7][8][9][10][11][12] The scattering of Bessel beams by liquid, solid elastics, and porous spheres have also been investigated in some recent papers.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Several theoretical studies have been carried out over the past few years to explore the feasibility of using ordinary (zeroth-order) and high-order Bessel beams for handling of on-axis objects with different mechanical properties. [3][4][5][6][7][8][9][10][11][12] The scattering of Bessel beams by liquid, solid elastics, and porous spheres have also been investigated in some recent papers. 10,11,[14][15][16] Unlike high-order Bessel beams, an ordinary Bessel beam does not carry an orbital momentum and has no on-axis phase singularity, and therefore the emergence of NRFs using an ordinary Bessel beam, in a way, is even more intriguing.…”

“…[3][4][5][6][7][8][9][10][11][12] The scattering of Bessel beams by liquid, solid elastics, and porous spheres have also been investigated in some recent papers. 10,11,[14][15][16] Unlike high-order Bessel beams, an ordinary Bessel beam does not carry an orbital momentum and has no on-axis phase singularity, and therefore the emergence of NRFs using an ordinary Bessel beam, in a way, is even more intriguing.…”

“…[3][4][5][6][7][8][9][10][11][12] It has been tried before to relate the emergence of such negative axial forces to the far-field characteristics of the object. For instance, for an optical Bessel beam, Chen et al have shown that only if the radiation is emitted predominantly in the forward direction may a large backward recoil force then occur and give rise to NRFs on the object.…”