Spherically symmetric colloidal particles and suspensions have been extensively studied, both theoretically and experimentally. While spherical colloids have many potential uses, particles with anisotropic interactions have a much higher potential as the synthetic building blocks for self-assembled materials with desirable properties, such as a photonic band-gap, at the nano- or micro-scale. The anisotropic nature of liquid crystals (LCs) makes them an ideal candidate to generate non-spherically symmetric interactions between colloidal particles. We demonstrated that a spherical particle in a cholesteric LC can generate a tetravalent bonding structure and showed how the particles could self-assemble into double-bonded chains.
Square gradient models for fluids are extensively used because they are believed to provide a good qualitative understanding of the essential physics. However, unlike elasticity theory for solids, there are essential no quantitative results for specific (as opposed to generic) fluids. Indeed the only numerical value of the square gradient coefficients for specific fluids have been inferred from attempts to match macroscopic properties such as surface tensions rather than from direct measurement. We employed all-atom molecular dynamics, using the TIP3P and OPLS force fields, to directly measure the coefficients of the density gradient expansion for several real fluids. For all liquids measured, including water, we found that the square gradient coefficient is negative suggesting the need for some regularization of a model including only the square gradient, but only at wavelengths comparable to the molecular separation of molecules. The implications for liquid-gas interfaces was also examined.
Our research focuses on modelling particles and dynamic processes in complex fluids. We study systems involving micro- and nano-scale objects, soft colloids or polymers for instance, in a complex fluid such as a liquid crystal. An important aspect of our work is the development of models and multi-scale computer simulation techniques to investigate these systems.
If you are interested in joining our group, please send me an email. We accept applications any time of the year. For more information about applying to the graduate program in Applied Math at Western, see our web page.