Researchers from the Massachusetts General Hospital Center for Engineering in Medicine (MGH-CEM) have found a new approach to keep water from freezing at temperatures below the usual freezing point.
The freezing point of water is zero degrees Celsius (0°C) or 32 degrees Fahrenheit (32°F), which means water and other water-based solutions, in most real-world environments, start to freeze at 0°C temperature. Freezing starts with random formation of ice crystals where liquids contact air or impurities in the solution.
In liquid state, molecules in water are in constant motion, and continue to move from one place to another. When the freezing starts, the movement of molecules slows down, and they start settling into places, and eventually line up in regular formations as in crystal. If any other substance (such as salt or sugar) is added to liquid water, the freezing point of water drops below 32°F with new freezing point depending on the type and amount of the substance added.
While, water normally freezes at 32°F, it is not always the case. Researchers have also found liquid water as cold as -40°F in clouds. In some experiments, researchers have also got success in cooling water down to -42°F in the lab.
Now, MGH-CEM team claims to have developed a novel approach that can be used to maintain water and water-based solutions in a liquid state for extended periods of time and at temperatures far below the usual “freezing point”. Researchers have named their new technique as ‘deep supercooling’.
O. Berk Usta, PhD, of the MGH-CEM, and co-corresponding author of the report, explained that in this new technique, the surface of liquid is covered with a solution that does not have a tendency to mix with water (for example, mineral oil, olive oil or paraffin oil). Use of such solutions allows blocking the interface between air and water—the main site of crystallization. So far, researchers have got success in demonstrating the new technique for volumes of only a few ounces.
Researchers hope this new approach, after further advancement, might allow preserving blood cells and even organs for extended periods of time in future. It could also help in improving food preservation.
In their initial experiments, the team used a small amount of water sample (1 ml) and sealed its surface with hydrocarbon-based oil. This method was found to suppress ice formation at temperatures as low as -13°C (around 9°F) for up to a week. in other experiments, researchers used more complex oils as well as pure simple hydrocarbons, such as alcohols and alkanes, and were able to keep 1 ml samples of water and cell suspensions supercooled at -20°C (-4°F) for 100 days.
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The technique was also used to supercool and preserve red blood cells (RBCs) for extended periods of time. The initial results suggested that the technique could allow preserving RBC suspensions of up to 100 ml at -13° C for as long as 100 days.
“We currently are conducting experiments to increase the volume of red blood cell storage samples up to the more clinically relevant 300 to 500 ml range,” says Usta, who is an assistant professor of Surgery at Harvard Medical School.
Usta also revealed that they are now working to apply this technique o some other cells and on translating it to large tissues and whole organs like the liver.
The detailed findings of the study titled “Long-term deep-supercooling of large-volume water and red cell suspensions via surface sealing with immiscible liquids” are published in the journal Nature Communications.