Shear-induced instabilities leading to various kinds of inhomogeneous flow profiles play an important role in the processing of complex fluids, ranging from polymeric materials to various types of biological systems. In previously studied systems, either Taylor banding, or gradient banding, or fracture is observed. In the present work we study a system for which all instabilities occur in orientation textures (OTs), and where Taylor banding occurs simultaneously with gradient banding. The system here consists of crowded suspensions of long and thin DNA-based rods (at a low ionic strength of 0.16 mM salt), where the applied shear rate is systematically varied, for concentrations well below and above the glass-transition concentration (12.4 mg ml⁻¹). To simultaneously measure the velocity profile along the gradient direction, in fracture and gradient banding, the optical cell is placed in a specially designed heterodyne light scattering set up, where the scattering volume can be scanned across the cell gap. The results confirm that Taylor bands and gradient banding occur in the concentration of DNA rods and applied shear-rates (35–80 s⁻¹). Taylor bands clearly show the flow access in vorticity-direction, while the gradient banding is rearranged as thick rolling flows of OTs, at the middle shear-rate (50 s⁻¹). The observations can be then useful to facilitate other biological complex fluids and the glass-forming liquids.

导致各种不均匀流动剖面的剪切引起的不稳定性在复杂流体的处理中起着重要作用，从聚合物材料到各种类型的生物系统。在先前研究的系统中，观察到泰勒带、梯度带或断裂。在目前的工作中，我们研究了一个系统，该系统的所有不稳定性都发生在取向纹理 (OT) 中，并且泰勒带与梯度带同时发生。这里的系统由长而细的基于 DNA 的棒（在 0.16 mM 盐的低离子强度下）的拥挤悬浮液组成，其中应用的剪切速率系统地变化，浓度远低于和高于玻璃化转变浓度（12.4 mg毫升^-1）。为了同时测量沿梯度方向的速度分布，在断裂和梯度带中，光学单元被放置在一个专门设计的外差光散射装置中，在那里可以跨单元间隙扫描散射体积。结果证实，泰勒带和梯度带出现在 DNA 棒的浓度和应用的剪切速率 (35–80 s ^-1 ) 中。泰勒带清楚地显示了涡度方向的流动通路，而梯度带重新排列为 OT 的厚滚动流，在中等剪切速率 (50 s ^-1 ) 下。这些观察结果可用于促进其他生物复杂流体和玻璃形成液体。