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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, it is found that minute changes in interfacial energy and particle size lead to liquid-crystal induced attractions that can span multiple orders of magnitude. Theoretical predictions are confirmed by experimental observations, which also suggest that LC-mediated assembly provides an effective means for fabrication of plasmonic devices. In the second application, the structure of a liquid crystal is controlled by confinement. It is shown that when confined to submicron droplets, the morphology of the liquid crystal depends 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 chemical or biological sensors. Theoretical predictions also indicate that the three-dimensional order of a liquid crystal can be projected onto a two-dimensional interface, and give rise to novel nanostructures that are not found in simple isotropic fluids.
Juan de Pablo Biography
Much of Juan de Pablo’s work entails conducting supercomputer simulations to understand and design new materials from scratch and to find applications for them.
de Pablo is a leader of simulations of polymeric materials, including DNA dynamics — how DNA molecules arrange and organize themselves and interact with other DNA molecules. He also studies protein aggregation and its poorly understood relationship to various diseases, including type II diabetes and neurodegenerative disorders.
In 2011, de Pablo joined The Institute for Molecular Engineering at the University of Chicago as a Liew Family Professor. Prior to that time, he was part of the University of Wisconsin faculty and served as the Howard Curler Distinguished Professor and Hilldale Professor of Chemical Engineering. He holds over 20 patents on multiple technologies and is the author or co-author of more than 400 publications. He currently serves as Co-Director of the Center for Hierarchical Materials Design.
The International Technology Roadmap for Semiconductors has identified one of de Pablo ‘s collaborative inventions for directed self-assembly as a technology critical to the semiconductor industry’s miniaturization goals. Directed self-assembly provides engineers a means of coaxing organic materials to form patterns that direct the deposition of metals on integrated circuits.
A food manufacturer has licensed another of de Pablo’s patents for stabilizing proteins in bacteria or cells for long periods of time without refrigeration, but the patent also has potential pharmaceutical and medical applications. He is a fellow of the American Academy of Arts and Sciences, the American Physical Society, the Mexican Academy of Sciences and the European Academy of Sciences.
de Pablo earned a bachelor’s degree in chemical engineering from Universidad Nacional Autónoma de México in 1985. After completing his doctorate in chemical engineering from the University of California, Berkeley, in 1990, he conducted postdoctoral research at the Swiss Federal Institute of Technology in Zurich, Switzerland.