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UBC Theses and Dissertations

Mechanics of hydrogels in flow fields Xu, Zelai

Abstract

This thesis investigates the mechanical behavior of hydrogels in flow fields, with a focus on developing and applying a poroelastic model to understand their complex interactions with surrounding fluids. The research is grounded in the Biot poroelastic theory, which treats the hydrogel as a porous and elastic medium, with the surrounding fluid undergoing Stokes flow. The study begins by formulating the governing equations and boundary conditions at the fluid-hydrogel interface, which are essential for modeling the coupled fluid-hydrogel system. It introduces the arbitrary Lagrangian-Eulerian method to solve these equations. Due to the fact that the second law of thermodynamics provides a sufficient but not necessary condition, three possible sets of boundary conditions are explored. These, along with previously proposed conditions, are applied to various flow scenarios to analyze how hydrogels deform and interact with the fluid in different flow fields. Additionally, a pore-scale model is used to investigate the permeability condition at the interface, leading to theoretical predictions of the interfacial permeability as a function of the local porosity. In addition to the theoretical developments, the thesis presents a detailed analysis of hydrogel behavior under normal flow-induced compression, highlighting the occurrence of hysteresis in the deformation response. Applied to the kidney disease of albuminuria, our model offers a mechanistic explanation for how proteins may leak because of flow-induced deformation of the glomerular basement membrane. Finally, the thesis proposes a new model that integrates two aspects of hydrogel mechanics: chemically driven swelling and deswelling in a static bath, and external flow around and through the hydrogel. Previous models have primarily considered swelling in a quiescent fluid. In contrast, our study models the interaction between swelling dynamics and external flow, validating our theory with previous experiments and revealing several novel phenomena. The findings of this thesis have significant implications for the design and optimization of biomedical devices, drug delivery systems, and the study of biological tissues, where the mechanical behavior of hydrogels plays a critical role. The models and insights developed in this research provide a foundation for future studies aimed at improving the performance and application of hydrogels in various fields.

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Attribution-NonCommercial-NoDerivatives 4.0 International