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Friedrich Schiller University Jena develops optical lens that senses gas

03 Jul 2024

Light refraction behavior of “hybrid” glass changes when gas is present.

Researchers from the University of Jena, Germany, have developed an optical lens just a few millimeters in size whose light refraction behavior changes when gas is present.

As the researchers report in Nature Communications, this intelligent behavior of the micro-lens is made possible by the hybrid glass material it is made of. The molecular structure of the lens consists of a three-dimensional lattice, the cavities of which can absorb gas molecules; this process affects the optical properties of the material.

“We are developing so-called multi-responsive materials, with the support of the Carl Zeiss Foundation,” commented Lothar Wondraczek, Professor of Glass Chemistry at Jena. “Using the example of the hybrid glass lens, this means that it refracts light more or less strongly, depending on whether gas is absorbed in the lens material or not.”

“The metal-organic frameworks we used here,” said Wondraczek, “are being developed as materials for storing or separating gases.” Oksana Smirvona, doctoral student and first author of the publication, added, “However, most of these substances decompose when heated and are therefore very difficult to shape.”

Together with Dr. Alexander Knebel, junior research group leader at the Chair of Glass Chemistry, the Jena researchers first had to develop a suitable synthesis process for high-purity materials. Then they had to identify the optimal conditions under which the material can be brought into the desired shape.

“We melt the material and then transfer it into a 3D-printed negative mold in which it is pressed. Within this process, the desired shape can be chosen almost arbitrarily,” said Smirvona. “We deliberately chose the lens as the shape because even the smallest impurities are noticeable because they directly influence the optical properties.”

Variety of geometries

A variety of shapes and geometries are now possible, beyond the specific application as micro lenses, said Wondraczek. “Because these multi-responsive materials react to several influences simultaneously, they can be used for logic circuits, for example,” he said.

“This means that two conditions are linked together for the observable reaction. If, for example, a beam of light falls on the lens and a gas is absorbed in the lens material at the same time, the light is refracted in a certain way and can thus provide combined feedback,” he said.

Membranes for gas separation would therefore also be possible, the optical properties of which change when gas molecules are present in them. Such optical components could be used in sensor technology, for example, and could make measurement processes more efficient.

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