"Ice cold" just got even colder, thanks to researchers who created ice from tiny droplets only a few hundred molecules in size, pushing water's freezing point lower than ever before.
Understanding how water transforms into ice is important for understanding a wide range of natural processes. Climate fluctuations, cloud dynamics and the water cycle are all influenced by water-ice transformations.
Wood frog's bodies freeze in the winter on land. This allows them to come out of hibernation quicker than other species. Animals that use this technique need to find a way to prevent ice from forming in their cells and tissues. Understanding how water freezes could lead to better understanding of these extreme species.
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Under certain conditions, water can stay liquid over a range of chilly temperatures. It was thought that the range stopped at minus 36 F and that the water must freeze. The researchers were able to keep the droplets of water in a liquid state at temperatures as low as minus 44 C.
There were two keys to their breakthrough. They began with droplets ranging from 150 nanometers to 2 nanometers, a cluster of only 275 water molecule. The researchers discovered the role of size in the transformation from water to ice.
The study co-author, a mechanical engineering professor at the University of Houston, told Live Science that they covered all of the ranges so that they could understand which ice condition was going to form. The water droplets can be covered with soft materials, which will help to suppress the freezing temperature.
The soft material they used was octane, an oil that surrounded each droplet in the anodized aluminum oxide membrane. The researchers say that preventing ice formation at these low temperatures is dependent on the shape of the droplets.
The researchers used measures of electrical conductance and light from the spectrum of theIR to get the exact temperature and moment at which the droplets transformed from water to ice.
The rate of ice formation dropped dramatically for droplets that were 10 nanometers and smaller, because they found that the smaller the droplet, the colder it had to be for ice to form. The water had reached a bone-chilling minus 44 C when they measured the smallest droplets.
Does this mean that the droplets in the clouds can get even colder than we thought? "As a scientist, I would say we don't know yet," he said.
The discovery could mean big things for ice prevention in aviation and energy systems. Engineers could use a mix of soft and hard materials to keep ice out of designs if water on soft surfaces takes longer to freeze.
There are many ways to design the surfaces to avoid ice formation. The next step is the engineering of these surfaces based on soft materials once we have a fundamental understanding.
Live Science published the original article.
