Particle deflection in a macroscale ultrasonic angled wave device

Macroscale bulk ultrasonic standing waves oriented at an angle relative to a fluid velocity field offer a novel method for sensitive particle separation. We have previously reported on the theoretical development of such a system [Proceedings of Meetings on Acoustics Vol. 30, 045004 (2017), https://doi.org/10.1121/2.0000652]. Particle deflection is uniquely defined by two parameters, i.e., the non-dimensional ratio of the acoustic radiation force to the fluid drag force exerted on the particle and the angle of the standing wave with respect to the fluid velocity. Here, we highlight the development and testing of a novel30 deg acoustofluidic angled wave device with a 0.5″ × 0.5″ main fluid flow channel. A 0.5″ × 0.5″ PZT-8 3 MHz air-backed transducer was fabricated. Acoustic resonance quality factors of 3000 were measured using electrical impedance measurements. The particle suspension enters the fluid channel through a 4 × 0.4 mm2 inlet centrally located in the square channel. The particle inlet is surrounded by a buffer flow. Testing was performed with 3, 6, and 10 μm polystyrene particles at a total flow rate of 31 ml/min, corresponding to a peak velocity of 5 mm/s. Successful deflection of all particles were achieved at electrical powers in the range of 1–5 W.