Researchers develop foldable ice microfibers

By producing “microfibers” of water ice of almost perfect purity, the researchers have demonstrated the astonishing properties of ice: under optimal conditions, it is flexible and behaves a bit like a fiber. optical.

Researchers from the universities of Hangzou (China), Taiyuan (China) and Berkeley (United States) have developed what they called water ice “microfibers”, which have amazing properties. They conduct light so well that they are able to behave like optical fibers. But above all, unlike the ice cream in our freezer, it is flexible and elastic! An astonishing and counter-intuitive peculiarity; in everyday life, if you try to bend a lambda ice cream, it will obviously break quickly.

A structural problem

However, from a purely theoretical point of view, ice should not be so fragile: it is a material capable of undergoing what is called elastic deformation. This term designates a reversible deformation; when you stop applying the constraint, the object returns to its original shape. In the case of ice, the maximum elastic deformation is about 15%. So why is it impossible to fold ice in winter? The answer lies in the structure of the ice crystals. Theoretically, once the water has frozen, the molecules are organized in a very organized crystal lattice.

But in reality, this network is not perfect: it has many imperfections, which appeared during the crystallization process. As soon as a force is applied, these imperfections become so many potential breaking points. It is also because of these imperfections that the ice is rarely perfectly transparent. To achieve their result, the researchers therefore had to hunt down impurities.

Close to theoretical limits

To create ice fibers free of any impurities, the researchers cooled a tungsten spindle to -50 ° C. They then applied an electric field of 2000 volts to it, allowing it to “capture” the water molecules suspended around it. These are placed wisely on the spit, in a much more orderly fashion than with any other freezing method, resulting in an extremely pure and fine thread of ice, which the researchers succeeded in bending and then unfolding. without residual deformation.

Scientists calculated that this elastic deformation was about 10.9%. This is much higher than the 0.1% of a “standard” ice cream. But above all, it is relatively close to the theoretical maximum of 15%. This is a small feat in materials science. “Rarely have mechanical properties so close to the theoretical limit been achieved in any material”Says Erland Schulson, a materials engineer unrelated to the study.

These ice “fibers” are excellent optical conductors. © Xu and. al.

A concept that is difficult to use as it is

Beyond the proof of concept, it is still difficult to imagine concrete applications for this technology. There are many logistical constraints; the fibers obtained are tiny, remain very fragile, and must be maintained at very low temperature. But some leads do exist. The most interesting has to do with pollution; we know that certain harmful particles have the annoying habit of clinging to the ice particles. These fibers could therefore be used to analyze air quality.

More importantly, other researchers could draw inspiration from their method to remove imperfections in other crystalline materials. If this concept turns out to be transposable to materials such as those that make up our optical fibers, this could be a way to improve the performance of our communication networks.

The text of the study is available here.

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