Multi-scale modelling of particles and interfaces in complex fluids

我的研究重点是模拟复杂流体中的颗粒和界面现象，特别是液晶中的胶体和微观和纳米尺度上的界面驱动流体动力学。目的有三个方面：(1)为研究各向异性流体环境（如生物系统中自然发生的流体环境）的体内微流变学提供工具。(2)提高我们对胶体向列悬浮的理解，使自组装结构，如那些被认为是三维光子带隙材料基础的结构，能够以可控的方式被操纵和构建。(3)建立与微、纳米流体装置相关的表面主导流态模型。为了实现这些目标，我将使用连续体模型，其功能形式和本构系数将基于分子动力学（MD）模拟的结果。具体来说，MD模拟将用于表征浸入液晶中的物体（如纳米线）之间的相互作用，这种相互作用是由于液晶的体取向顺序和胶体包裹体表面的首选顺序之间的竞争而产生的。将探讨固体和液体包裹体的表面弹性和取向有序的分子起源。MD模拟的结果将指导晶格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球体的胶体悬浮液。目标(3)将涉及将分子动力学映射到极性流体的连续介质模型。有必要超越流体的标准连续体描述，并包括与表面电荷密度有关的静电效应。所得模型将用于探讨电润湿和固液壁面其他表面应力梯度驱动的微流控装置中液滴运动问题。

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.