Multiphysics Simulations of Colloidal Phase Separation

了解胶体相变的动力学是一个至今仍在研究的百年问题。胶体体系为利用光学显微镜研究物质在相变过程中的分子或原子相互作用提供了一个很好的微观模型系统。近半个世纪以来，人们利用胶体-聚合物(CP)体系对相变动力学进行了广泛的研究。然而，限制几何形状和附加外场中的重要问题仍然悬而未决。已经开发了各种模拟技术和方法来深入了解胶体体系的相分离。虽然这些模拟方法有助于我们理解胶体相分离现象，但由于对系统动力学的描述过于简单化，忽略了流体动力相互作用、重力沉积、热波动、复杂的几何形状、不同的颗粒性质以及加入外力场方面的挑战等因素，导致了局限性。为了解决这些局限性，我们提出了一种基于有限元方法的数值模型，将多个物理模型结合在一个模型中，以全面研究胶体相变。我们提出的数值模型将胶体颗粒的流体动力相互作用与影响颗粒运动的多种力结合在一起。通过实验验证，该数值模型将提供对胶体聚合物混合物中复杂凝胶化过程的全面理解。

Understanding the kinetics of colloidal phase transitions is a century old problem still investigated to date. Colloidal systems provide a great model system at a microscale level for studying the molecular or atomic interactions of matter during the phase transitions by using light microscopy. Phase transition kinetics have been extensively studied using a colloid-polymer (CP) system for almost half a century. However, important question in confining geometries and additional external fields are still open. Various simulation techniques and approaches have been developed to gain insights into phase separation of colloidal systems. While these simulation methods have contributed to our understanding of the colloidal phase separation phenomenon, limitations arise due to an oversimplified representation of system dynamics, overlooking factors like hydrodynamic interactions, gravitational sedimentation, thermal fluctuation, complex geometries, diverse particle properties, and challenges in incorporating external force fields. To address these limitations, we propose a numerical model based on the finite element method by combining multiple physics in a single model to comprehensively study colloidal phase transitions. Our proposed numerical model combines the hydrodynamic interactions of colloidal particles with multiple forces effecting the particle motion. The numerical model, validated by the experimental demonstrations, will provide a comprehensive understanding of the complex gelation process in a colloid polymer mixture.