Multi-level separation of particles using acoustic radiation force and hydraulic force in a microfluidic chip

Combined with acoustic separation and hydraulic separation technology, a microfluidic chip, which can achieve multi-level particle separation, is proposed in this work. The chip uses the sheath flow on both sides to align the mixed particles in the set area (near the side of the channel) of the separation channel. And then, the mixed particles successively pass through the acoustic surface wave and hydraulic action area, which are generated by modulating interdigital transducers and adjusting the flow ratio, respectively, and finally realize multiple particle separation under the acoustic radiation and hydraulic force. The corresponding separation experiments were carried out using polystyrene (PS) microparticles with diameters of 1 mu m, 5 mu m, and 10 mu m, respectively. Moreover, we explored the influence of the peak-to-peak voltage (Vpp) and flow ratio on the PS microparticles separation effect, and the separation effect is optimal at the flowrate in the main channel is 4mm/s, Vpp=25V, A(1)=0.2, A(2)=0.5. Under these conditions, the separation purity of 1 mu m, 5 mu m, and 10 mu m PS microparticles are 95.60%, 91.67%, 93.75%, respectively, and their separation rates are 96.67%, 89.19%, and 96.77%, respectively. The combined multi-level separation chip has the advantages of simple structure, high separation accuracy, high separation efficiency, and the ability to sort multiple particles, which can be applied to chemical analysis, cell sorting, biomedicine.