Water ice is not exactly known for its flexibility. In fact, it is the opposite: stiff and crisp, easy to crack and snap. This is the reason for avalanches and fragmentation of sea ice.
That is also why new research is so fascinating. Researchers have just grown microfibers of water ice that can bend in a loop – breaking the previous maximum load by a significant percentage and opening up new possibilities for exploring ice physics.
Ice cream does not always behave as we expect, and its elasticity – or rather lack thereof – is a perfect example. Theoretically, it should have a maximum elastic load of about 15 percent. In the real world, the maximum elastic load ever measured was less than 0.3 percent. The reason for this discrepancy is that ice crystals have structural imperfections that drive up their brittleness.
So a team of scientists led by nanoscientist Peizhen Xu from Zhejiang University in China tried to create ice cream with as few structural imperfections as possible.
The experiment consisted of a tungsten needle in an ultra-cold chamber that sat around minus 50 degrees Celsius, much colder than previously attempted. Water vapor was released into the chamber and an electric field was applied. This attracted water molecules to the tip of the needle, where they crystallized and formed a microfiber with a maximum width of about 1
The next step was to lower the temperature to between minus 70 and minus 150 degrees Celsius. Under these low temperatures, the researchers tried to bend the ice fibers.
At minus 150 degrees Celsius, they found that a microfiber of 4.4 micrometers across was able to bend in an almost circular shape with a radius of 20 micrometers. This suggests a maximum elastic load of 10.9 percent – much closer to the theoretical limit than previous experiments.
Even better, when scientists released the ice, it jumped back into its former form.
Although ice cream may look the same to us, its crystalline structure can vary quite a bit. Each configuration of molecules in an ice crystal is known as a phase, and there are a large number of these phases. Transitions between phases can occur under a number of conditions that have to do with pressure and temperature.
With their bent ice, the team noticed such a phase transition from a form of ice known as ice Ih, the hexagonal crystal form of ordinary ice as it is found in nature, to the rhombohedral form ice II, which is formed by compression of ice Ih. This transition occurred during sharp bends of the ice microfiber at temperatures below minus 70 degrees Celsius and was also reversible.
This, the researchers noted, could offer a new way to study phase transitions on ice.
Finally, the team tried to use their almost perfect ice as a waveguide for light by attaching an optical light to one end of the microfiber. Multiple wavelengths were transmitted as efficiently as advanced on-chip waveguides, such as silicon nitride and silica, suggesting that ice microfibers could be used as flexible wavelengths for optical wavelengths at low temperatures.
“We could imagine the use of IMFs as low-temperature sensors to study, for example, molecular adsorption on ice, environmental changes, structural variation and surface formation of ice,” the researchers wrote in their paper.
“In short, the elastic microfibers shown here can offer an alternative platform for exploring ice physics and opening up previously unexplored possibilities for ice-related technology in various disciplines.”
Very freaking cool.
The research is published in Science.