LAB’RINTH: Liquid crystal-bead reflectors illuminating the needle in the haystack

Just as the full title of the project hints, LAB’RINTH aims to explore the use of liquid crystals (LCs) to enhance the detectability and locatability of objects or people of interest in complex environments. We focus on chiral LC mixtures which spontaneously develop a helix structure with a pitch that can be tuned via the mixture composition. When manifested in spherical shape, these peculiar liquids, called cholesteric LCs (ChLCs), generate attractive and unique optical phenomena such as omnidirectional selective reflection with specific polarization and wavelength.
As the mode of information transfer envisaged in LAB’RINTH is based on the particular optical properties of CLCs in spherical shape, a complete understanding of the optics of these materials is key. Under the restriction of the most basic illumination and observation conditions, illumination and observation along exactly the same direction with the CLC sphere sample residing in the plane perpendicular to this direction, the optical behavior has been quite well elucidated. Therefore, a step out of the lab and into realistic scenarios will be the main objective of this project. If a range of illumination directions is used and if, in addition, the observation direction is left arbitrary with respect to the illumination direction the optical behavior becomes significantly more complex. No systematic or quantitative in-depth investigation has been carried out for these conditions. Since a realistic field application entails these types of uncontrolled illumination and observation at arbitrary angles, the development of a more complete understanding of the optical behavior is a vital fundamental challenge in order to, later on, reach the applied goals. Equally important is the choice of chemical components that will be used in the production of ChLC spheres that will allow us to retain their optical behavior in extreme conditions. A high and uniform optical quality throughout the reflectors is a vital criterion, and can greatly diversify the application range.
While LAB’RINTH is primarily a materials science and physics project, aiming for a deeper understanding of the optical behavior of ChLC shells; we work conjointly on carrier substrates design, and image analysis techniques that will allow us to study the performance of these shells in realistic conditions. In the context of assessing the application potential, Prof. Mathew Schwartz, an architect working since many years with robotics and motion capture, today at the New Jersey Institute of Technology, will give guidance in terms of designing the macroscopic materials to be incorporated in the objects to be locatable, and help in developing prototypes and demonstrators.

Members
This project was carried out at the University of Luxembourg, with Dr. Hakam Agha and Prof. Jan Lagerwall as the main personnel involved in this project.

Funding and duration
LAB’RINTH was funded by the Office of Naval Research Global (ONRG) from 1 July 2019 through 30 June 2022.