从宏观到纳米尺度粘度的再认识
Revisiting viscosity from the macroscopic to nanoscale regimes
摘要：
流体对剪切应力引起的变形的响应称为剪切粘度。这个概念来自宏观的观点，最早由艾萨克·牛顿爵士提出。尽管如此，流体是一系列受容器形状约束的运动分子。这种观点要求从微观或分子的角度来处理粘性，这是爱因斯坦和Smoluchowski独立承担的任务。在这里，我们重新审视粘度的概念，并通过实验验证，在分子水平上的粘度，它描述的阻力，是相同的宏观剪切粘度，因此，桥接不同的长度和时间尺度。为了捕获流体的剪切应力响应，我们使用经典的流变学;在分子水平上，我们使用探针扩散来确定平移和旋转运动的局部粘度。在这些情况下，我们分别使用荧光相关光谱和时间分辨荧光。通过增加渗压剂（葡萄糖-D）的浓度，我们改变了粘度，并发现这些方法提供了一个统一的观点，粘度弥合宏观和纳米级制度之间的差距。此外，葡萄糖的粘度遵循更通常与支化聚合物溶液相关的比例因子，因为探针尺寸与施加阻力的渗透剂的尺寸相当。
英文摘要：
The response of a fluid to deformation by shear stress is known as shear viscosity. This concept arises from a macroscopic view and was first introduced by Sir Isaac Newton. Nonetheless, a fluid is a series of moving molecules that are constrained by the shape of the container. Such a view begs the treatment of viscosity from a microscopic or molecular view, a task undertaken by both Einstein and Smoluchowski independently. Here we revisit the concept of viscosity and experimentally verify that the viscosity at a molecular level, which describes the drag force, is the same as the macroscopic shear viscosity; hence, bridging different length- and time-scales. For capturing the shear stress response of a fluid, we use classical rheometry; at a molecular level we use probe diffusion to determine the local viscosity from the translational and rotational motions. In these cases, we use Fluorescence Correlation Spectroscopy and Time Resolved Fluorescence, respectively. By increasing the osmolyte (Glucose-D) concentration, we change the viscosity and find that these methods provide a unified view of viscosity bridging the gap between the macroscopic and nanoscale regimes. Moreover, Glucose's viscosity follows a scaling factor more commonly associated to solutions of branched polymer because the probe dimensions are comparable to the dimensions of the osmolyte that exerts the drag.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
