Coherent Anti-Stokes Raman Scattering and Fluorescence Confocal Polarizing Microscopy of Three-Dimensional Structures in Liquid crystals

Kent State University, Kent OH

Investigators

Abstract

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)." TECHNICAL SUMMARY: Liquid crystals are the key material in many modern technologies. As stated by the Nobel Prize winner P.G. de Gennes, ''...the study of liquid crystals is complicated because it involves...a certain sense of vision in three-dimensional space in order to visualize complex molecular arrangements''. Until recently, to substantiate this sense of vision..., researchers and educators relied on indirect information, such as integrated 2D images. This project will expand the recently developed techniques of 3D visualization of the molecular orientation in liquid crystals, the so-called Fluorescence Confocal Polarizing Microscopy (FCPM) and Coherent Anti-Stokes Raman Scattering (CARS) microscopy, to the studies of complex three-dimensional structures in liquid crystals, both static and dynamic. A unique feature of CARS, namely, label-free chemical sensitivity, will be used to establish orientation of chemical bonds in compounds with potentially biaxial orientational order. FCPM will be used to explore the dynamics of colloidal particles in the liquid crystal medium. Director distortions, introduced in the system by finite surface anchoring at the particle surface, strongly affect the dynamics of particle, making it radically different from the dynamics in regular fluids. The problem is very complex and can be accessed only with a 3D visualization tool that this project will provide. This research will be conducted at the Liquid Crystal Institute at Kent State University which offers well established mechanisms for graduate and undergraduate training (supported by NSF Research Experience for Undergraduates grant), and a fertile ground for industrial partnership (Industrial Partnership Program with about 30 companies membership). The acquired knowledge would help in other projects with the potential practical benefits to society, namely, in the development of fast switching displays and liquid crystal-based optical and microfluidic devices. NON-TECHNICAL SUMMARY: Liquid crystals combine properties of both crystals and liquids. They show optical properties similar to that of regular solid crystals but at the very same time they are very sensitive to even the weakest external factors, such as a small voltage pulse. It explains why the liquid crystals are a key material in what is universally known as "LCDs", liquid crystal displays. As stated by the Nobel Prize winner in the field, P.G. de Gennes, ''...the study of liquid crystals is complicated because it involves...a certain sense of vision in three-dimensional space in order to visualize complex molecular arrangements''. Recently, researchers at the Liquid Crystal Institute, Kent State University, Ohio, have developed special microscopy techniques to obtain truly three-dimensional images of the complex molecular arrangements in liquid crystals. The researchers will employ these instruments to look into the new promising phenomena in liquid crystals that simply could not be studied before. One theme is a search for the so-called biaxial nematic that promises to dramatically improve the switching speed of LCDs. The second theme is to explore principles that control a motion of a small particle in a liquid crystal environment. The goal here is to learn whether the unique properties of the liquid crystal can be used to propel the particles and thus create a colloidal micromotor. This research will be conducted at the Liquid Crystal Institute at Kent State University that combines graduate and undergraduate training with industrial partnership program. The acquired knowledge would help in the development of fast switching LCDs, microfluidic and optical devices. Three-dimensional visualization of liquid crystals would help both graduate and undergraduate students to grasp the essence of modern science of advanced materials.