Axial acoustic field barrier for fluidic particle manipulation

An acoustic field barrier integrated within a flow tubing system to achieve high-throughput separation of particles in fluid is reported in this work. 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 11pN. 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.