Department of Nanoscience and Nanotechnology, Faculty of Arts and Science, Mehmet Akif Ersoy University, 15030 Burdur/Turkey.
Department of Computer Education and Educational Technology, Faculty of Education, Inonu University, 44280 Malatya/Turkey.
Sci Rep. 2017 Mar 2;7:43374. doi: 10.1038/srep43374.
We numerically demonstrate acoustophoretic separation of spherical solid particles in air by means of an acoustic Fresnel lens. Beside gravitational and drag forces, freely-falling millimeter-size particles experience large acoustic radiation forces around the focus of the lens, where interplay of forces lead to differentiation of particle trajectories with respect to either size or material properties. Due to the strong acoustic field at the focus, radiation force can divert particles with source intensities significantly smaller than those required for acoustic levitation in a standing field. When the lens is designed to have a focal length of 100 mm at 25 kHz, finite-element method simulations reveal a sharp focus with a full-width at half-maximum of 0.5 wavelenghts and a field enhancement of 18 dB. Through numerical calculation of forces and simulation of particle trajectories, we demonstrate size-based separation of acrylic particles at a source sound pressure level of 153 dB such that particles with diameters larger than 0.5 mm are admitted into the central hole, whereas smaller particles are rejected. Besides, efficient separation of particles with similar acoustic properties such as polyethylene, polystyrene and acrylic particles of the same size is also demonstrated.
我们通过声学菲涅耳透镜数值证明了在空气中通过声悬浮对球形固体颗粒的分离。除了重力和阻力之外，自由下落的毫米级大小的颗粒在透镜的焦点周围会受到大的声辐射力，在那里，力的相互作用导致颗粒轨迹根据尺寸或材料特性而发生差异。由于在焦点处存在强声场，辐射力可以使具有比在驻波场中悬浮所需的源强度小得多的源强度的颗粒发生偏移。当透镜被设计为在 25kHz 时具有 100mm 的焦距时，有限元方法模拟显示出具有半最大值全宽度为 0.5 波长的尖锐焦点和 18dB 的场增强。通过力的数值计算和颗粒轨迹的模拟，我们在源声压级为 153dB 的情况下证明了基于尺寸的丙烯酸颗粒分离，使得直径大于 0.5mm 的颗粒进入中心孔，而较小的颗粒则被拒绝。此外，还证明了具有相似声学特性的颗粒（例如聚乙烯、聚苯乙烯和相同尺寸的丙烯酸颗粒）的有效分离。
