Biological Physics, School of Physics and Astronomy, University of Manchester, Oxford Rd., Manchester, M13 9PL, UK.
Photon Science Institute, University of Manchester, Oxford Rd., Manchester, M13 9PL, UK.
Sci Rep. 2017 Apr 26;7(1):1186. doi: 10.1038/s41598-017-01303-4.
The flow instabilities of solutions of high molecular weight DNA in the entangled semi-dilute concentration regime were investigated using optical coherence tomography velocimetry, a technique that provides high spatial (probe volumes of 3.4 pL) and temporal resolution (sub μs) information on the flow behaviour of complex fluids in a rheometer. The velocity profiles of the opaque DNA solutions (high and low salt) were measured as a function of the distance across the gap of a parallel plate rheometer, and their evolution over time was measured. At lower DNA concentrations and low shear rates, the velocity fluctuations were well described by Gaussian functions and the velocity gradient was uniform across the rheometer gap, which is expected for Newtonian flows. As the DNA concentration and shear rate were increased there was a stable wall slip regime followed by an evolving wall slip regime, which is finally followed by the onset of elastic turbulence. Strain localization (shear banding) is observed on the boundaries of the flows at intermediate shear rates, but decreases in the high shear elastic turbulence regime, where bulk strain localization occurs. A dynamic phase diagram for non-linear flow was created to describe the different behaviours.
使用光学相干断层扫描速度仪研究了高分子量 DNA 溶液在缠结半稀浓度范围内的流动不稳定性，该技术可在流变仪中提供有关复杂流体流动行为的高空间（探针体积为 3.4 pL）和高时间分辨率（亚微秒）信息。作为平行板流变仪间隙距离的函数测量不透明 DNA 溶液（高盐和低盐）的速度分布，并测量其随时间的演化。在较低的 DNA 浓度和低剪切速率下，速度波动很好地用高斯函数描述，并且速度梯度在流变仪间隙中是均匀的，这是牛顿流动所预期的。随着 DNA 浓度和剪切速率的增加，首先是稳定的壁滑区，然后是不断发展的壁滑区，最后是弹性湍流的开始。在中间剪切速率下，在流的边界观察到应变局部化（剪切带），但在高剪切弹性湍流区减少，在该区域发生整体应变局部化。创建了一个用于非线性流动的动态相图来描述不同的行为。
