Korean POSTECH develops stretchable color adjustable photonic devices

Liquid crystal elastomers are expected to be applied in displays, sensors, smart devices, and wearable devices.
A team from POSTECH University in South Korea, led by Professor Su Seok Choi and Professor Seungmin Nam, has developed a new type of stretchable photonic device that can control the wavelength of light in various directions.

This work was carried out by the Department of Electrical Engineering at the university and described in the journal Nature, Light: Science and Applications.

Structural colors are generated through the interaction between light and microscopic nanostructures, and do not rely on traditional color mixing methods to produce bright hues. Traditional displays and image sensors combine three primary colors (red, green, and blue), while structured color technology utilizes the inherent wavelength of light to produce more vivid and diverse color displays.

POSTECH's announcement states that this innovative method is being recognized as a promising technology in the nanooptics and photonics industries.

"Free adjustment of solid colors"
Traditional color mixing techniques using dyes or luminescent materials are limited to passive and fixed color representations. In contrast, adjustable color technology dynamically controls the nanostructure corresponding to a specific wavelength of light, allowing for free adjustment of pure colors.

Previous research was mainly limited to unidirectional color adjustment, typically converting colors from red to blue. Reversing this transition from blue to longer wavelength red has always been a major challenge.

The current technology only allows for adjustments to shorter wavelengths, making it difficult to achieve diverse color representations in the ideal free wavelength direction. Therefore, a new type of optical device capable of bidirectional and omnidirectional wavelength adjustment is needed to maximize the utilization of wavelength control technology.

Professor Cui's team solved these challenges by combining chiral * 1 liquid crystal * 2 elastomers (CLCE) with dielectric elastomer actuators (DEA). CLCE is a flexible material that can change the color of the structure, while DEAs cause flexible deformation of the dielectric in response to electrical stimulation.

The team optimized the actuator structure to combine with CLCE, enabling it to expand and contract, and developed a stretchable device with strong adaptability. The device can freely adjust the wavelength position in the visible spectrum, from shorter to longer wavelengths, and vice versa.

In their experiment, researchers demonstrated that their CLCE based photonic devices can use electrical stimulation to control the structural colors over a wide range of visible light wavelengths (from blue at 450nm to red at 650nm). Compared to previous technologies, this represents significant progress, which were limited to unidirectional wavelength tuning.

This study not only lays the foundation for advanced photonic devices, but also highlights their potential in various industrial applications.
Professor Cui commented, "This technology can be applied to displays, optical sensors, optical camouflage, direct optical simulation encryption, biomimetic sensors and smart wearable devices, as well as many other applications involving broadband electromagnetic waves beyond the light, color, and visible light bands. Our goal is to expand its application scope through continuous research.".

This study was supported by the Samsung Research and Incubation Center of Samsung Electronics and the Technology Innovation Program (Flexible Intelligent Variable Information Display) of the Korea Industrial Technology Planning and Evaluation Institute.

Source: Laser Net