Acoustic sorting of airborne particles by a phononic crystal waveguide

• Published in: Ultrasonics 2022-08, Vol.124, p.106777-106777, Article 106777
• Main Authors: Korozlu, Nurettin, Biçer, Ahmet, Sayarcan, Döne, Adem Kaya, Olgun, Cicek, Ahmet
• Format: Article
• Language: English
• Subjects: Acoustic radiation force; Acoustics; Computer Simulation; Linear defect waveguide; Phononic crystal; Size-based sorting; Transducers; Ultrasonic Waves; Ultrasonics
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/j.ultras.2022.106777

[Display omitted] •A phononic crystal linear waveguide is employed for size-based particle sorting.•Millimeter-sized particles in air are sorted according to either radius or density.•Contact-free fractionation is achieved in a compact manner.•Separation of glass beads with 0.5 mm and 1.0 mm radii is experimentally shown. A two-dimensional phononic crystal linear defect waveguide is utilized for size-based sorting of millimeter-sized solid particles in the air through acoustic radiation force. The waveguide channels ultrasonic waves at 20 kHz, as calculated through Finite-Element Method simulations. Spherical solid particles released from rest at the top of the vertically aligned waveguide experience the combined effect of the acoustic radiation, gravity, and drag forces. When the particles are released from the symmetry plane of the waveguide, they follow straight paths where the ones with radii smaller than a threshold value are trapped at the waveguide nodal planes, whereas larger particles are let pass through. This requires input sound pressure levels between 173 dB and 177 dB. Moreover, such particles can also be differentiated with respect to density. Alternatively, the release of particles with a slight offset from the symmetry center induces unbalanced acoustic radiation potential, and thus uneven radiation force, resulting in the initiation of horizontal displacement whose extent depends on particle radius. Thus, both simulation results and experimental findings suggest that this scheme can be employed in size-based particle separation. Sorting of spherical glass particles with 0.5 mm and 1.0 mm radii are experimentally demonstrated for low ultrasonic transducer acoustic power output up to 90 W. The proposed approach can be utilized in applications where contact-free separation of airborne particles is required.