Technology

The new gel proves to be a highly adjustable color filter

SeedGel can act as a temperature-sensitive gate for light of a particular wavelength. Here you can see the representation of the light passing through the gel. When heated in a certain temperature range, the gel will initially become opaque to all but individual colors. Then, as the heat rises, it first passes the short blue wavelengths and then the gradually longer red wavelengths. Eventually, beyond the temperature range, the gel will once again become opaque to all visible light.

credit:

N. Hanasek / NIST

Let’s make these scientists happy. The exotic gels they studied at the National Institute of Standards and Technology (NIST) have unexpected properties. The temperature of the material determines the color of light that can pass through.

The material, which the research team calls “Seed Gel,” has already shown to be a promising versatile tool for applications ranging from batteries to water purifiers to tissue engineering. The team’s new dissertation Nature Communications, It emphasizes the new ability of the gel as a temperature sensitive optical filter. When a gel is exposed to white light, only certain wavelengths or colors pass through the gel, depending on the temperature of the gel. Temperature changes of less than 1/10 Celsius may be sufficient to change the permissible wavelength. Allowable wavelengths can be any color in the visible range, and part of UV and infrared light.

“our Previous work We have shown that SeedGel can go from transparent to opaque and back again, but we didn’t investigate what color could do, “said a scientist at the NIST Neutron Research Center (NCNR). , University of Delaware. “The ability to precisely control color was a new discovery.”

Creating a team is different from other teams that may be familiar to you in the market. Not to be confused with the mood ring where the thermochromic liquid crystal changes color with temperature. Nor is it a variation of photochromic sunglasses lenses that darken when exposed to UV light. Instead, the gel acts as a temperature-sensitive gate for light of a particular wavelength.

Their gel begins as a clear fluid made of water and a liquid solvent with silica nanoparticles added. When this mixture is heated to a specific temperature, the liquid and nanoparticles form a physical gel. This gel initially remains transparent, but now has a different internal structure.A liquid is formed instead of a shapeless fluid Microscopic channel interlockingNanoparticles are trapped in one of them.

Heating at a certain range of high temperatures reveals newly discovered effects. The gel becomes opaque to all colors except individual colors, first passing short blue wavelengths and then gradually increasing red wavelengths. Ultimately, beyond this temperature range, the gel becomes opaque to all visible light.

“Our previous work has shown that SeedGel can go from transparent to opaque and back again, but … its ability to precisely control color was a new discovery.” — Yun. Liu, NCNR Scientist, Professor, University of Delaware

Neutron scattering experiments conducted at NCNR explain this anomalous behavior. Changing the temperature exchanges liquid molecules between the fine channels, changing the overall index of refraction of these channels. Light of one wavelength passes through, but the other colors scatter.

This behavior is an example of the Christiansen effect identified in 1884. There are filters that rely on the Christiansen effect, but researchers have shown that the new gel offers a clear advantage to the industry. Gels are not only more sensitive to temperature changes. However, it can be customized anywhere between 15 and 100 degrees Celsius, giving you a wider temperature range of possible operation. It can be adjusted to cover a wide range of wavelengths, from ultraviolet light (less than 400 nanometers) to near infrared light (up to 2500 nanometers). It also allows more light to pass through than a normal Christian Sen filter.

According to Yuyin Xi, a team member at the University of Delaware, gels benefit the industry because they are made of inexpensive, readily available materials, regardless of customization.

“This approach is versatile, easy to adjust, and easy to scale up the manufacturing process,” he said. “This is a promising candidate for use in a variety of smart optics and new classes of materials with color applications.”


Paper: Y. Xi, F. Zhang, Y. Ma, VM Prabhu, Y. Fine-tunable dynamic coloring using the Liu bi-continuous micrometer domain. Nature Communications. Published online on June 24, 2022. DOI: 10.1038 / s41467-022-31020-0

https://www.nist.gov/news-events/news/2022/06/novel-gel-proves-itself-be-highly-tunable-color-filter The new gel proves to be a highly adjustable color filter

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