三维液力聚焦的计算设计及其在血细胞分析仪中的应用

Computational design and application of three-dimensional hydrodynamic focusing in hematology analyzers

目的研究三维液力聚焦的分析和计算设计方法,并应用该方法设计实现血细胞分析仪的液力聚焦流动室。方法利用势流理论和层流模型对液力聚焦进行理论分析,推导共轴圆柱环式三维液力聚焦直径的预测公式,再结合数值仿真探讨加速段收缩角、进样管出口与加速段相对位置等流动室结构参数和鞘液/样本液速率比对聚焦效果的影响,并以此为基础构建血细胞分析仪的液力聚焦流动室系统。结果由仿真结果可知,在保证层流的前提下,鞘液/样本液平均速率比越大,聚焦的过渡越短,稳定聚焦液流的直径也越小;加速段收缩角、进样管出口与加速段相对位置的变化通常不会改变最终的聚焦液流直径,但增大加速段收缩角、令进样管出口与加速段较大直径端平齐均有助于聚焦尽快完成过渡而达到稳定状态。基于仿真结果和工程实际设计构建的血细胞分析仪液力聚焦流动室系统在模拟运行中获得了与理论预测相一致的结果。结论三维液力聚焦的计算设计方法可为血细胞分析仪的流动室设计提供指导,但在实际应用时必须考虑工程的可实现性,根据需求综合确定三维液力聚焦的各项参数。

Objective To develop a method of analysis and computational design for three-dimensional hydrodynamic focusing and apply it to realize flow cells in a hematology analyzer.Methods The potential flow theory and the laminar flow model were employed in theoretical analysis of the three-dimensional hydrodynamic focusing,and the prediction equation of the focused diameter in co-axial cylindrical flow cells was proposed.The flow field inside the flow cell was numerically simulated.The effect of the relative sheath and sample flow rate,and such device geometry as the convergence angle of the accelerated interval and the location of the inner nozzle on the focusing of the center flow were explored systematically.Finally,a micro-machine based flow cell for the hematology analyzer was designed and fabricated.Results Given laminar flow,the focusing transition was shortened and the fully-developed focused diameter scaled down as the relative sheath and sample flow rate increased.The convergence angle of accelerated interval and the location of the inner nozzle would not change the fully-developed focused diameter.However,the focusing transition would be shortened faster while the convergence angle of the accelerated interval increased and the inner nozzle aligned with the beginning of the accelerated interval.The three-dimensional hydrodynamic focusing was verified using of microscopic visualization of water sheath flow and dye-containing sample flow in the flow cell of a hematology analyzer.The measurement result of focused diameter was consistent with theoretical prediction.Conclusion The computational design method of three-dimensional hydrodynamic focusing can be used to guide the construction of the flow cell system for a hematology analyzer.The optimal parameters of three-dimensional hydrodynamic focusing have to be determined in terms of the engineering realizability.