Research

Liquid crystals are most famous for the display industry, but they are also found throughout nature - from nanoscopic DNA to macroscopic organs. Liquid crystals are composed of rods that have a preference to order with one another. There are energetic costs to distorting the liquid crystal away from this preferred ordering. When they are greatly distorted, instead of having smooth deformations throughout the entire system, liquid crystals can often lower their energy by creating local disorder in regions called defects. Defects can be used to arrange inclusions, such as particles, and have interesting optical properties.

The confinement of liquid crystals affects the defects formed. The minimum number of required defects depends on the local and global geometry of the system. This can be intuitively understood by examining a globe --- ordering lines of longitude and latitude necessarily creates the North and South poles, points where the lines are ill-defined. Just as the North and South poles are required by the spherical topology of the globe, ordering a liquid crystal on a sphere likewise requires the presence of defects.

We apply interfacial phenomena and lithographic techniques to control the confinement of liquid crystals in order to investigate the influence of geometry on liquid crystal patterns and defects.

The organization of particles is important for tuning material characteristics, impacting electronic and optical properties. Systems in nanotechnology are reliant upon self-assembly. Recently, liquid crystals have been employed to self-assemble particles, due to the system's ability to form complex patterns. However, the exact interactions between solids and liquid crystals at the submicron scale remain ambiguous and is fundamentally important for designing liquid-crystal-based technologies. We seek to elucidate these submicron interactions through examining the effects of system geometry and chemistry on liquid-crystal-mediated, particle assembly.

We are also broadly interested in out-of-equilibrium particle assembly, specifically in how dynamic assembly processes can be coordinated to achieve complex particle organization.

Producing long-lasting, environmentally-sustainable coatings is a modern industrial problem. Most inks are composed of chemical pigments that absorb light and degrade with sun exposure. Materials researchers begin to address this problem by turning instead to colors that arise from non-absorbing light interactions with submicron features – structural color.

The most complex, structurally-colored materials are found in nature. Over time, evolution designed organisms with iridescence and reflectance, desirable for industrially-produced coatings. One notable specimen is the jeweled beetle, Chrysina gloriosa. Its exoskeleton is composed of a chiral liquid crystal that twists in space with submicron periodicities. Its patterns are shaped into spiralled domains that serve as micromirrors, creating a reflective exterior. However, mimicking these domains in the laboratory is challenging. We aim to apply our liquid crystal and particle assembly expertise to generate reflective structural color.