09-22 bendable ice

[Image above] Researchers in China succeeded in bending ice microfibers near the theoretical elastic limit. Credit: Science News, YouTube

If you read the October/November Bulletin that came out last week, then you know how excited we all are for the International Year of Glass (IYOG) taking place in 2022.

IYOG is a United Nations International Year that will celebrate the heritage and importance of glass in our lives. We have a new webpage where you can learn the history of the initiative and explore the planned events.

For readers who are just starting their materials science journey, they may wonder why we are dedicating a whole year to celebrate glass. But look through our CTT archives and you will quickly see how glass has shaped not only our built environment but electronics, medicine, and energy as well.

Perhaps surprisingly, some of these applications rely on flexible glass. In general, glass is a brittle material that cannot bend very much before it fractures. However, when glass is produced very thin—on the scale of micrometers—it can bend quite a bit while retaining its other characteristics, due to lower defect density and more uniform stress distribution.

Optical fiber is an established technology that uses flexible glass. Among emerging devices, Schott and Corning are locked in intense competition to develop flexible glass displays.

In a recent paper, researchers at Zhejiang University in China took this idea of reducing thickness to increase the flexibility of another traditionally brittle material—ice.

Previous studies on low-dimensional ice structures such as whiskers and needles have focused on the ice’s growth and morphology rather than investigating the mechanical properties. But because of the known effect that low dimensions can have on a material’s flexibility, the researchers wanted to see if the same phenomenon applied to ice as well.

To create ice microfibers, they applied an electric voltage to a needle within a chilled chamber. The electrified needle attracted water vapor, which transformed into very thin ice whiskers less than a few micrometers in diameter.

The researchers conducted bending tests at –70°C (–94°F) and –150°C (–238°F), and they recorded maximum elastic strains of about 4.6% (in a 4.6-μm-diameter ice microfiber) and about 10.9% (in a 4.4-μm-diameter ice microfiber), respectively.

“These values are much higher than those reported in other forms of ice (e.g., <0.3%), and the strain maxima measured at −150°C (>10%) are approaching the theoretical elastic limit,” they write.

In addition, all the bent ice microfibers returned to their original shape, “indicating the absence of the type of creep that ice in other forms generally suffers from under high strain,” they add.

Credit: Science News, YouTube

The researchers also optically characterized the ice microfibers and showed they can serve as optical waveguides with very low loss and can support whispering gallery wave modes in the visible spectrum.

Thus, “We could imagine the use of [ice microfibers] as low-temperature sensors to study, for example, molecular adsorption on ice, environmental changes, structural variation, and surface deformation of ice,” they conclude.

The paper, published in Science, is “Elastic ice microfibers” (DOI: 10.1126/science.abh3754)