Multi-scale modelling of particles and interfaces in complex fluids

我的研究重点是模拟粒子和复杂流体中的界面现象，特别是液晶中的胶体和微米和纳米尺度的界面驱动流体动力学。目标有三个方面：（1）提供用于研究各向异性流体环境的体内微观流变学的工具，例如在生物系统中自然发生的那些。(2)为了提高我们对胶体悬浮液的理解，以便自组装结构，如那些建议作为3D光子带隙材料的基础，可以以可控的方式操纵和构建。 (3)为了实现这些目标，我将使用连续介质模型，其函数形式和本构系数将基于分子动力学（MD）模拟的结果。 具体而言，MD模拟将被用来表征浸没在液晶中的物体之间的相互作用，如纳米线，所产生的大量取向有序的液晶和胶体夹杂物的表面处的优选排序之间的竞争。 将探索固体和液体包裹体表面弹性和取向有序的分子起源。分子动力学模拟的结果将指导格子玻尔兹曼模型的设计。 这些模型将用于研究（1）纳米线浸入各向异性流体中的粘弹性响应和（2）形成自组织晶格结构的液晶中的球体的胶体悬浮液。 目标（3）将涉及类似的分子动力学映射到极性流体的连续模型。 有必要超越流体的标准连续描述，并包括与表面电荷密度有关的静电效应。 由此产生的模型将被用来探索微流体装置中的液滴运动的问题，在固体-流体壁的电润湿和其他表面应力梯度驱动。

My research focus is on modelling particles and interface phenomena in complex fluids, particularly colloids in liquid crystals and interface-driven fluid dynamics at the micro- and nano-scale. The objectives are three-fold: (1) To provide a tool for studying in-vivo microrheology of anisotropic fluid environments, such as those naturally occurring in biological systems. (2) To improve our understanding of colloidal nematic suspensions so that self-assembled structures, such as those suggested as the basis of 3D photonic band-gap materials, can be manipulated and constructed in a controlled fashion.  (3) To construct models for surface-dominated flow regimes relevant for micro- and nano-fluidic devices.To achieve these goals I will use continuum models whose functional form and constitutive coefficients will be based on the results of molecular dynamics (MD) simulations.  Specifically, MD simulations will be used to characterize the interactions between objects immersed in a liquid crystal, such as nanowires, that arise from a competition between the bulk orientational order of the liquid crystal and the preferred ordering at the surface of the colloidal inclusion.  The molecular origin of the surface elasticity and orientational ordering for both solid and liquid inclusions will be explored. The results of the MD simulations will guide the design of lattice Boltzmann models.  These models will be employed to study  (1) the viscoelastic response of nanowires immersed in an anisotropic fluid and (2) colloidal suspensions of spheres in liquid crystals that form self-organized lattice structures.  Goal (3) will involve a similar mapping of molecular dynamics to continuum models for polar fluids.  It will be necessary to go beyond a standard continuum description of the fluid and to include electrostatic effects related to surface charge densities.   The resulting model will be used to explore the problem of droplet motion in microfluidic devices driven by electrowetting and other surface stress gradients at the solid-fluid wall.