Liquid Crystal-Plasmonic System Generates Actively Tunable Structural Color

Abstract

Researchers at the University of Central Florida have developed a liquid crystal (LC)-plasmonic system capable of continuous color tuning over the entire visible color spectrum. Structural color produced from nanostructured plasmonic materials offers many benefits over conventional pigmentation-based color filtering for display technologies, such as increased resolution, efficiency, and scalability of the optical response with structure dimensions. However, once the structures are fabricated, their optical characteristics typically remain static. Though dynamic plasmonic structures exist, most deal with infrared or terahertz frequencies. Those that support the visible colors remain limited to a small range of color tunability due to modest shifts (approximately 10-40 nanometers) in plasmon resonance.

As a solution, the UCF invention combines the advantages of color derived from metallic nanostructures with the millisecond reconfigurability of liquid crystals. The invention offers the ability to support large area, thin-film display elements on rigid and flexible substrates. It can also improve the active tunability of general plasmonic and metamaterial systems.

Technical Details

The UCF invention comprises a liquid crystal (LC)-plasmonic display device with a voltage source coupled to a top electrode and bottom electrode. The top electrode and a homogeneous LC-alignment layer are transparent over the visible spectrum, while the bottom electrode comprises a voltage-tunable-color surface that is optically reflective over the visible spectrum. The innovation enables continuous tuning of plasmonic resonance over 95 nm or more, for liquid crystal birefringence differences equal to or greater than 0.45. In combination with underlying nanostructures of varying periodicity, a full range of visible colors is achievable.

Using a continuous plasmonic surface and high birefringent liquid crystal materials, UCF researchers demonstrated an LC-tunable reflective surface where the color of a nanostructured surface changes as a function of applied voltage. The physical phenomenon occurs at an LC-metal nanostructure interface. To facilitate the interface, the researchers made a cell to contain and align (so as not to scatter light) an LC with the ability to realign the LC with an electric field.

In one example, an LC-plasmonic cell included a visibly transparent substrate with a rubbed polyimide layer for LC alignment on an indium tin oxide (ITO) coated glass, forming a top electrode and a vertically aligned bottom electrode. This included a substrate and a metallic nanostructure for color generation, with the LC in between.

Partnering Opportunity

The research team is seeking partners for licensing and/or research collaboration.

Stage of Development

Prototype available.

Benefit

Market Application

Publications

Polarization-independent actively tunable colour generation on imprinted plasmonic surfaces. Nature Communications 6, Article number 7337 (2015). https://doi.org/10.1038/ncomms8337