The relaxation time of a viscoelastic fluid is an essential parameter for characterizing the degree of elasticity. However, measuring the relaxation time of dilute polymer solutions with low viscosity using conventional rotational rheometers remains challenging because of the low instrument sensitivity. In this study, we demonstrate an efficient microfluidic method for measuring the relaxation time of a dilute polymer solution by utilizing elasticity-driven lateral particle migration in a microchannel. First, the previous theoretical model was refined, based on the Oldroyd-B constitutive equation, in order to predict lateral particle migration in a viscoelastic fluid with constant shear viscosity, considering the inlet and finite particle size effects. This model was utilized to determine the relaxation times of dilute poly(ethylene oxide) (PEO) aqueous solutions. Direct comparison of the measured relaxation times with those obtained from Zimm theory verified the reliability of the proposed method. The current approach is expected to be useful in characterizing the relaxation times of a wide range of polymer solutions.

粘弹性流体的弛豫时间是表征弹性程度的重要参数。然而，由于仪器灵敏度低，使用传统的旋转流变仪测量具有低粘度的稀聚合物溶液的弛豫时间仍然具有挑战性。在这项研究中，我们展示了一种有效的微流体方法，通过利用微通道中弹性驱动的横向粒子迁移来测量稀聚合物溶液的弛豫时间。首先，基于Oldroyd-B本构方程对先前的理论模型进行了改进，以预测具有恒定剪切粘度的粘弹性流体中的横向粒子迁移，同时考虑入口和有限粒径效应。该模型用于确定稀聚 (环氧乙烷) (PEO) 水溶液的弛豫时间。测量的弛豫时间与从 Zimm 理论获得的弛豫时间的直接比较验证了所提出方法的可靠性。目前的方法有望用于表征各种聚合物溶液的弛豫时间。