Magnetic Probes of Elastic Energy, Dynamics, Interactions, and Shape Transitions of Anisotropic Colloids in Liquid Crystals

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This proposal aims to advance substantially the field of colloids in liquid crystals through the study of magnetic inclusions in nematic liquid crystals. While most previous research on colloids in nematics has focused on spheres, the proposed experiments will elucidate the behavior of aspherical particles. The additional degrees of freedom associated with the orientation of an aspherical particle can lead to new forms of nematic-mediated interactions with interesting and potentially useful consequences. Through precision measurements employing high-speed video microscopy and time-resolved external magnetic fields, the static and dynamic properties of such suspended particles and the surrounding liquid crystal matrix will be elucidated. The proposed experiments will address five specific areas: (1) the orientation-dependent energy of isolated cylinders with homeotropic anchoring; (2) pair interactions between such cylinders; (3) the dynamics of suspended cylinders and spheres; (4) the behavior of disk-shaped inclusions; and (5) the deformations of soft colloids. This project, which combines themes in liquid crystal physics, magnetism, and nanofabrication, will be a joint effort between two investigators with the complementary expertise needed to address these problems and with a strong track record of collaboration.%%%Broader Impacts: By investigating in detail the mechanical coupling of magnetic particles tonematic order and by exploring new particle geometries, this work will have potentially significant impact on both the research on and the technology based on liquid crystalnanocomposite materials. The broader impacts of the project will also include research training and education for graduate and undergraduate students in physics. To help promote the participation of women in science, female high school students will be recruited through theWomen in Science and Engineering (WISE) Program, a Johns Hopkins University outreach initiative, to participate in the research.