Technology for generating acoustic vortices and capturing, rotating and moving material objects using an acoustic grating with line bifurcation

Purpose. Creation of a method for capturing, rotating and moving millimeter-sized objects using acoustic vortices to make it possible to increase the size of objects exposed to acoustic fields compared to optical fields.

Specifications. Acoustic wave frequency – 10 MHz–1 GHz. The polarization of the acoustic wave is longitudinal. For different environments in which the acoustic wave propagates and for different frequencies, the technical characteristics will differ. For an acoustic wave frequency of 10 MHz and its propagation, for example in water, the acoustic wave length is Λ = 148 μm, the speed of propagation of the acoustic wave is 1500 m/s. Diffraction angle of an acoustic wave on an acoustic grating for ±1 maximum θ1 = ±10.4 degrees. Diffraction angle for ±2 maximum θ2 = 19.9 degrees. The period of the diffraction grating is d=0.8523 mm. The mass of the object that can be manipulated depends on the power of the acoustic wave in the diffracted order. For example, to manipulate an object with mass m = 2.5×10–3 g, it is sufficient to provide a power of the excited acoustic wave of ~1 W. The rotation frequency of an object with such a mass under the influence of ±1 diffraction maximum is ±6.28 rps. Under the influence of ±2 diffraction maximum, the rotation frequency doubles.

Application area. Manufacturers of consumer electronics, military equipment, acoustoelectronic medical devices

Advantages. The closest technology currently used to manipulate microparticles is optical vortex technology. Optical vortices can manipulate microparticles weighing ~10–11 g with a continuous laser radiation power of ~1 W. The power of laser radiation, and accordingly the mass of the object that can be manipulated, is limited by the technical characteristics of the laser. While the power of an acoustic wave generated in different ways has no such restrictions.

Technical and economic effect. The main technical effect of using the technology is remote, non-contact manipulation of material objects. The economic effect of introducing technology will depend on the sector of the economy in which this technology will be introduced. Possible economic sectors include consumer electronics, military equipment, acoustoelectronic medical devices, etc.

Description. The technology for generating acoustic vortex beams that transfer orbital angular momentum is based on the diffraction of acoustic waves on a grating with fork-shaped splitting of lines, as a result of which the phase front of diffracted waves takes a helical shape with a topological defect in the wave phase on the beam axis. Since the intensity of the beam on its axis is zero and the phase is uncertain, such an acoustic beam carries an acoustic vortex with an orbital angular momentum, which allows it to capture objects, rotate them and move them in space. The developed solution for the first time uses acoustic vortex beams generated by the method of diffraction of acoustic waves on a grating with line splitting.

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