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Algae-Inspired Polymers May Reduce Night-Vision Cost

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TSUKUBA, Japan, Oct. 29, 2020 — An infrared-transmitting polymer based on common low-cost materials may lead to low-cost night-vision lenses that retain focus while imaging at variable distances. The polymer, developed by researchers from the University of Tsukuba, keeps its shape after stretching.

Designing conventional infrared night-vision lenses capable of easily changing focus from one position to another is typically difficult and costly. Without fabricating lenses to feature variable-focus capability, details that are important to capturing and understanding an image can be lost. Using a flexible polymer made from common materials is desirable for creating lower-cost, more readily available lenses.
The infrared lens is made from an elastic polymer derived from algae and plant compounds, and is capable of variable focus. Courtesy of University of Tsukuba.
The infrared lens in the researchers' system is made from an elastic polymer derived from algae and plant compounds. It is capable of variable focus. Courtesy of University of Tsukuba.

The polymer is based on sulfur and compounds derived from algae and plants. The researchers prepared it using a chemical process called inverse vulcanization, in which the constituent compounds are mixed and stirred together as they are heated. They then poured the material into a silicon mold and heated it further.


In tests to determine transparency to infrared light, the researchers determined that even a 3.3-mm-thick lens was able to transmit 10% of incoming infrared light.

“The lenses have two wavelength ranges that are infrared-transparent,” said senior author Takaki Kanbara. “No lens is completely transparent; 10% transmission is an excellent value for these materials.”

To test the lens for variable-focusing, the researchers projected an image through the lens and monitored the image that came through as the lens was elongated. Squalene and other long unsaturated hydrocarbons, which help optimize the cross-linking structure, gave the polymers the necessary elasticity.

The lens is able to return to its original shape after being stretched repeatedly by 20%. 

“The lens retained 54% of the focus variation, which is sufficient for practical uses,” said Takashi Fukuda, senior researcher at the National Institute of Advanced Industrial Science and Technology. “The lens also retained its full initial focus after contracting back to its original shape.”

The research was published in ACS Applied Polymer Materials (www.doi.org/10.1021/acsapm.0c00924).

Published: October 2020
Glossary
polymer
A material whose molecular structure consists of long chains made up by the repetition of many (usually thousands) of similar groups of atoms.
lens
A transparent optical component consisting of one or more pieces of optical glass with surfaces so curved (usually spherical) that they serve to converge or diverge the transmitted rays from an object, thus forming a real or virtual image of that object.
infrared
Infrared (IR) refers to the region of the electromagnetic spectrum with wavelengths longer than those of visible light, but shorter than those of microwaves. The infrared spectrum spans wavelengths roughly between 700 nanometers (nm) and 1 millimeter (mm). It is divided into three main subcategories: Near-infrared (NIR): Wavelengths from approximately 700 nm to 1.4 micrometers (µm). Near-infrared light is often used in telecommunications, as well as in various imaging and sensing...
Research & TechnologyMaterialsOpticspolymerpolymersTsukuba UniversityUniversity of TsukubalenslensesAsia-Pacificalgaeinfrarednight visionnight-visionvariable focusvariable focus lenses

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