Zhao D, Thomas J-L, Marchiano R
Sorbonne Université, CNRS, Institut des Nanosciences de Paris, INSP, F-75005 Paris, France; Sorbonne Université, CNRS, Institut Jean le Rond d'Alembert, d'Alembert, F-75005 Paris, France.
Sorbonne Université, CNRS, Institut des Nanosciences de Paris, INSP, F-75005 Paris, France.
Ultrasonics. 2021 Mar;111:106296. doi: 10.1016/j.ultras.2020.106296. Epub 2020 Nov 18.
Recent studies have shown the possibility to manipulate small elastic spheres in 3D with a single-sided beam. Acoustical tweezers are very appealing because they provide a fine spatial control of the motion of a single particle in space. Their main limitations are due to the weak restoring axial force and improving this force is still a challenge. We show theoretically that the spherical vortex beams can trap large particles and enhance the axial force. Indeed, the special features of these unusual beams look like the bottle beams in optics. Nevertheless, their spatial complexity presupposes that they can be produced with sufficient precision. Therefore, attention is paid to the synthesis of the spherical vortices. A method based on the inverse filter method is proposed. It allows to synthesize them with a very good precision since the theoretical force is recovered experimentally with an error smaller than 10%. Then, the spherical vortices are used to trap polyethylene beads with radii between 500 and 590µm. Experiments show that the radial trap is working while no beads have been trapped in the axial direction. This failure is analyzed in detail and is shown to be mainly due to sensitivity to the properties of the materials which influences the resonance modes of the elastic sphere. This study paves the way to the optimization of acoustical tweezers for the manipulation of large objects.
最近的研究表明，利用单侧光束在三维空间中操纵小弹性球体是可能的。声镊非常有吸引力，因为它们能对单个粒子在空间中的运动提供精细的空间控制。其主要局限性在于轴向恢复力较弱，而提高这种力仍然是一个挑战。我们从理论上表明，球形涡旋光束可以捕获大粒子并增强轴向力。实际上，这些特殊光束的特性类似于光学中的瓶形光束。然而，它们的空间复杂性意味着需要以足够的精度来产生它们。因此，人们关注球形涡旋的合成。提出了一种基于逆滤波方法的方法。由于理论力通过实验恢复时误差小于10%，所以它能够以非常高的精度合成球形涡旋。然后，利用球形涡旋捕获半径在500至590微米之间的聚乙烯珠。实验表明径向捕获有效，但轴向没有捕获到珠子。对这种失败进行了详细分析，结果表明这主要是由于对影响弹性球体共振模式的材料特性敏感所致。这项研究为优化用于操纵大物体的声镊铺平了道路。
