Customised bifurcating networks for mapping polymer dynamics in shear flows
Customised bifurcating networks for mapping polymer dynamics in shear flows
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DOI：
10.1063/1.4989978
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发表时间：
2017-11-01
期刊：
影响因子：
3.2
通讯作者：
Oliveira, Monica S. N.
中科院分区：
文献类型：
--
作者：
Fidalgo, Joana;Zografos, Konstantinos;Oliveira, Monica S. N.
了解不同剪切力对单个聚合物动力学的影响对于聚合物驱油、聚合物诱导减阻或DNA分离设备的设计等应用非常重要。在所有情况下，都需要了解单个聚合物对不同剪切流的响应。最近提出了一种用于等深矩形槽道分叉网络的仿生设计准则。这些定制的微流体几何形状代表了在单个设备中研究多个良好控制的剪切应力的优雅选择。在这里，我们展示了这种定制的微流体网络的首次实验实现，该网络由一系列具有不同横截面的矩形微通道组成，并展示了它们在测试聚合物动力学方面的潜力。我们使用的微流控几何形状针对牛顿流体和幂定律流体进行了优化，这些流体的平均壁面剪应力恒定或增加。用粒子跟踪测速仪对实验模型系统进行了测试，以验证剪切变稀黄原胶溶液和牛顿流体的理论预测的流场。然后，以k-DNA分子作为剪切敏感聚合物的例子，测试不同的剪应力分布对其拉伸的影响。通过观察单个分子在连续通道中的构象，我们演示了不同外加应力的影响。所得结果与前人关于剪切流作用下k-DNA延展的研究结果吻合较好，验证了分叉网络的设计。因此，定制的微流体网络可以用作研究单个聚合物动力学的平台，只需一次实验，就可以在很大范围内很好地控制局部和累积剪切应力。由AIP出版公司出版。
Understanding the effect of varying shear stresses on individual polymer dynamics is important for applications such as polymer flooding, polymer induced drag reduction, or the design of DNA separation devices. In all cases, the individual polymer response to varying shear flows needs to be understood. A biomimetic design rule was recently proposed for bifurcating networks of rectangular channels of constant depth. These customised microfluidic geometries represent an elegant option to investigate, in a single device, multiple well-controlled shear stresses. Here, we present the first experimental realisation of such customised microfluidic networks, consisting of a series of rectangular microchannels with varying cross-sections, and we demonstrate their potential for testing polymer dynamics. We used microfluidic geometries optimised for both Newtonian and power-law fluids of constant or increasing average wall shear stress. The experimental model systems were tested using particle tracking velocimetry to confirm the theoretically predicted flow fields for shear-thinning xanthan gum solutions and a Newtonian fluid. Then, k-DNA molecules were used as an example of shear sensitive polymers to test the effect of distinct shear stress distributions on their extension. By observing the conformation of individual molecules in consecutive channels, we demonstrate the effect of the varying imposed stresses. The results obtained are in good agreement with previous studies of k-DNA extension under shear flow, validating the bifurcating network design. The customised microfluidic networks can thus be used as platforms for the investigation of individual polymer dynamics, in a large range of well-controlled local and cumulative shear stresses, using a single experiment. Published by AIP Publishing.