2D acoustic focusing in a rectangular micro-channel of commercial flow cytometers

Flow cytometer plays an important role in cell sorting and analysis. Traditional flow cytometers adopt hydrodynamic focusing method which works well when the low flow velocity is relatively low. However, in order to have a higher analysis efficiency for clinical laboratories, a higher flow velocity is preferred, which sometimes will lead to cells siltation when using sheath flow. In this paper, an acoustic focusing method is proposed to help the cell flowing travel faster and smoother in a rectangular micro-channel in a commercializing flow cytometer. Two transducers are adopted to generate a stable standing wave to capture the cells in two different dimensions respectively. By simulating and comparing the transient and frequency-domain sound field in the micro-channel generated by the couple transducers, a series of parameters are optimized, related experimental devices are designed and fabricated. Particles whose diameter is 3μm made of polystyrene are adopted to test the focusing effect. The experiment results verify the two-dimension focused is realized. At a flow velocity of 100μl/min, focusing still functions well. All these results suggest The 2D acoustic focusing method can be modified in a commercial flow cytometers to improve its performance.