(7m) Hydrodynamic Model of Complex Liquids with Microstructure

Complex liquids, such as liquid crystals (LCs) and colloidal suspensions, have unique properties that find wide applications in mechanical, chemical and material engineering areas. How the underlying microstructure of such material determines its mechanical, optical and electromagnetic characteristics is not fully elucidated. The inverse problem, that what specific microstructure is needed to satisfy certain material properties, is however fundamentally important for the design of next-generation functional, active and smart materials. The goal of my proposed research is to develop and generalize continuum and molecular models to understand the physics of known experiments on structured liquids and propose the recipe of materials that can be useful for the future energy and bio-inspired material applications.

Specifically, I plan to model and simulate the following systems:

1) LC smectic phase. Highly periodic self-assembling materials are important for optoelectronics and nanotechnology applications. Focal conic domains (FCD), a typical periodic structure formed from smectic A phase when strongly confined, is the candidate for such materials. I plan to use a Q-tensor model of Landau-de Gennes free energy funtional to simulate the 3D structure of FCD. We can control the spatial configurations of FCD by introducing patterned surface. As a template, FCDs may selectively trap nanoparticles, which then show highly ordered self-assembling structure. My work should help design new periodic patterns for the future 3D electronic devices.

2) Biopolymer networks. Active nematic liquids, e. g. microtubule-kinesin-ATP film exhibits many peculiar non-equilibrium behaviors, such as active turbulence at very low Reynolds number, oscillating defect structure when confined within a shell, and long-range orientational order among +1/2 and -1/2 defects. The underlying physics is poorly understood. I plan to develop both continuum and molecular models to explain the above phenomena at different length scales. Validated by reproducing known phenomena, my model can help understand such active materials and may guide the design of new bio-inspired materials.

3) Dense suspensions. They are important for petroleum industry, food manufacture and functional material design. Current research is focused on steady state rheology, spherical particle shape and single length scale. I plan to generalize the current simulation method, Stokesian dynamics, to account for the transient dynamics as well as multi length scale particles. My model should help understand the underlying physics of dynamic jamming, and enable the simulation of impact mitigation applications.

During my Ph. D study, I worked with Prof. Joel Koplik at Levich Institute in CCNY, on multi scale simulations of microfluidic phenomena. During my postdoc experience with Prof. Juan de Pablo at the University of Chicago, I developed the hybrid lattice Boltzmann method to simulate flowing LC system in the continuum level, and applied to the microtubules system to understand the active nematics phenomena.

Research Interests:

Theory and modelling of soft matter physics:

- Liquid crystals and its hydrodynamics

- Active nematics

- Colloidal self-assembly

- Dense suspensions

Simulation expertise:

- Molecular Dynamics

- Lattice Boltzmann method

- Stokesian dynamics

Teaching Interests:

- (Computational) Fluid Mechanics

- Statistical physics

- Molecular modelling

- Transport phenomena

- General physics