Juan de Pablo (University of Chicago)
Thu. April 20th, 2017, 4:00 pm-5:00 pm
Nanoparticles in liquid crystals, and liquid crystals in nanoparticles.
Liquid crystals are remarkably sensitive to interfacial interactions. Small perturbations at a liquid crystal interface can in fact be amplified over relative long distances, thereby providing the basis for a wide range of applications. Our recent research efforts have focused on the reverse phenomenon; that is, we have sought to manipulate the interfacial assembly of nanoparticles or the organization of surface active molecules by controlling the structure of a liquid crystal. This presentation will consist of a review of the basic principles that are responsible for liquid crystal-mediated interactions, followed by demonstrations of those principles in the context of two types of systems. In the first, a liquid crystal is used to direct the assembly of nanoparticles. Through a combination of molecular and continuum models, we explain how minute changes in interfacial energy and particle size can lead to liquid-crystal induced interactions that can span multiple orders of magnitude. In the second application, the structure of a liquid crystal is controlled by confinement. We explain how confinement in micro-droplets causes the morphology of liquid crystals to depend on a delicate balance between bulk and interfacial contributions to the free energy; that balance can be easily perturbed by adsorption of analytes at the interface, thereby providing the basis for development of inexpensive, ultrasensitive devices for chemical or biological sensing.