Drying path dependence in microrheological characteristics of cellulose nanofiber dispersion revealed by single particle tracking
Drying path dependence in microrheological characteristics of cellulose nanofiber dispersion revealed by single particle tracking
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DOI：
10.1088/1361-6463/abf70a
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发表时间：
2021-07-22
影响因子：
3.4
通讯作者：
Hanasaki, Itsuo
中科院分区：
文献类型：
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作者：
Koitabashi, Takuma;Hanasaki, Itsuo
纤维素纳米纤维(CNF)分散体的流变性表征对纳米纸制备工艺设计具有重要意义。然而，现有的宏观方法很难揭示干燥的微观信号或非平衡性质，不同于平衡时的浓度依赖关系。报道了基于探针粒子单粒子跟踪(SPT)的显微胶片分析对CNF分散体干燥过程的微观表征。由于SPT不需要对感兴趣的系统进行侵入式剪切流动，因此可以实现干燥过程中的流变性表征。我们重点考察了初始CNF浓度的作用，以考察干燥的非平衡效应。对于较高初始CNF浓度的干燥路径不是简单的对较低初始浓度路径的时间压缩。由探测粒子的广义扩散系数和标度指数随时间的演化曲线揭示了这一现象。这种对初始CNF浓度的路径依赖的来源之一是干燥过程的宏观空间不均匀。因此，宏观条件的影响是在微观上确定的。
Rheological characterization of cellulose nanofiber (CNF) dispersion is important for the process design of nanopaper fabrication. However, the existing macroscopic approach is difficult to reveal microscopic signal, or nonequilibrium nature of drying, distinct from the concentration dependence in equilibrium. We report the microscopic characterization in the drying process of CNF dispersion by the microscopy movie analysis, based on the single particle tracking (SPT) of probe particles. Since SPT does not require invasive shear flow to the system of interest, the rheological characterization in the drying process can be realised. We focused on the role of initial CNF concentration to examine the nonequilibrium effect of drying. The path of drying for a higher initial CNF concentration is not simply a time compression of the path of the lower initial concentration. It is revealed by the time-evolution curves of the generalised diffusion coefficient and the scaling exponent for probe particles. One of the origins of this path-wise dependence on the initial CNF concentration is the macroscopic spatial nonuniformity of the drying process. Thus, the effect of macroscopic condition is microscopically determined.