Analyte mixing and delivery to a functionalized sensor surface are important to realize several advantages associated with biosensors integrated with microfluidic channels. Here, we present a comparison between a herringbone structure (HBS) and a curved passive mixing structure of their efficiency at facilitating mixing and surface saturation using fluorescein included in one of the inlets of a Y-channel microfluidic device. We performed a large parametric study to assess the effects of varying the height of the microfluidic channel as well as the height, width, and spacing of the passive mixing structures. Scanning confocal microscopy combined with a custom-designed image-analysis procedure were utilized to visualize and quantify the observed changes in efficiency in inducing solute mixing by the different designs. The flow patterns within the channels were found to vary significantly with changes in the geometry of the passive mixing structures, which in turn affected the efficiency of the channel at mixing the fluid and saturating the surface opposite the mixing structures. The solute mixing as a function of the channel length was also determined; an initial slow mixing rate does not always coincide with a low mixing index (MI). We found that the range of MIs for the curved mixing structure 1 cm downstream from the inlet was 0.85–0.99 whilst for our HBS it was 0.74–0.98, depending on the design parameters of the passive mixing structures. Overall, this study shows that the curved passive mixing structure family is more robust in inducing efficient mixing than the HBSs.

分析物的混合和向功能化传感器表面的输送对于实现与集成有微流通道的生物传感器相关的多项优势非常重要。在这里，我们介绍了人字形结构（HBS）和弯曲被动混合结构之间的比较，这些结构在使用Y通道微流装置入口之一中的荧光素促进混合和表面饱和的效率上。我们进行了一项大型参数研究，以评估改变微流体通道的高度以及被动混合结构的高度，宽度和间距的影响。扫描共聚焦显微镜结合定制设计的图像分析程序被用来可视化和量化观察到的不同设计诱导溶质混合的效率变化。发现通道内的流动模式随着被动混合结构的几何形状的变化而显着变化，这继而影响了通道在混合流体并使与混合结构相对的表面饱和时的效率。还确定了溶质混合随通道长度的变化。最初的缓慢混合速率并不总是与低混合指数（MI）一致。我们发现，在进气口下游1 cm处的弯曲混合结构的MI范围为0.85–0.99，而对于我们的HBS，MI的范围为0.74–0.98，具体取决于被动混合结构的设计参数。总体而言，这项研究表明，与HBS相比，弯曲的被动混合结构家族在诱导有效混合方面更坚固。