Axial acoustic field barrier for fluidic microparticle separation at high-throughput

Abstract

An acoustic field barrier integrated within a flow tubing system to achieve high-throughput separation of particles in fluid will be reported. We investigate the axial acoustic field of a piezo-tube with an inside diameter of 34 mm, a length of 25 mm, and an operating frequency of 1.15 MHz. Energy concentrates within the tube, and leakage at the ends provides a sharp monotonic acoustic pressure field within a fluidic circuit. This process is not the conventional standing wave mechanism; instead, the geometry produces a spatially stable filtering action without fouling. This powerful filtering action is confirmed theoretically via a COMSOL simulation and demonstrated experimentally by concentrating suspensions of 5 μm proteoglycan tracer particles at a flow rate of 20 ml/min: The corresponding acoustic contrast factor is 0.243, and the trapping force is 11 pN. This tube geometry tackles the limitations of microfluidic standing wave based acoustic concentrators, namely, complex extraction, low-throughput, and distributed focus, by harnessing a stable monotonic field profile.