We are all very familiar with ice – from scraping our windscreens and tackling slippery roads, to putting frozen peas on an injury and ice cubes in our drinks. But, even though ice is present in our everyday experiences, it turns out we don’t fully understand it. Scientists at Warwick are researching the properties of ice with a view to harnessing its power. No – not to build a magical crystal castle and set off an eternal winter - but to unlock the many real life applications with an icy key.
18 types of ice
Dr Gabriele Sosso, assistant professor in computational physical chemistry, is working to understand the structure and behaviour of ice using computer simulations.
He explains: “As ice is such a familiar thing to us, you’d think that in 2019 we must know everything we need to know about it – but we don’t! Ice, like many other things that involves water, is a very complex system. There are actually about 18 different types of ice. It is a crystal - a periodic arrangement of water molecules, neatly ordered in a particular way. It turns out, you can orderly arrange water molecules in many different ways.
“However, most of these ices can only be found at crazy pressures and temperatures. Some of them exists only on paper, and we think they might be found within the innards of rather chilly planets such as Pluto.
“Back on earth the overwhelming majority of ice we deal with what is called hexagonal ice. Just an apparently minimal structural change gives us cubic ice (looks almost identical, but it’s not!) and to make things more interesting in some rare cases we might find stacking disordered ice - a mixture of the hexagonal and cubic variants.”
Know the freezing facts
So, ice has many different structures. But there is one fact we definitely know about ice - water freezes at 0 Co.
Dr Sosso continues: “There is one big myth to get rid of when we talk about ice formation. We generally learn that water freezes into ice at exactly 0 Co . But in order to freeze pure water into ice you need to go down to -40 Co. Our freezers (unless you happen to own a seriously expensive one) won’t cool water to that sort of temperature, and yet we are perfectly able to make ice cubes. We worry about glaciers melting now, but ice in our polar regions would not exist at all if sea water had to cool down to -40 Co before it froze. I’d say even Elsa will struggle to craft an ice castle if this is really the temperature we are talking about.
“So how come ice exists at much lower temperatures? The trick is that virtually all the ice found on Earth forms thanks to the presence of some sort of impurities: almost everything contributes to this, like the salts you have in your tap water and even the plastic walls of your ice tray. But some things work really, really well: mineral dust, bacterial fragments, volcanic ash and birch pollen are just some examples.
“Some of my research seeks to understand why some of these impurities are so very effective in helping water to freeze; this is a long-standing challenge for physical chemistry, as it’s very difficult to study ice formation by means of either experiments or simulations. The process still holds many secrets, but understanding it is vital to unlock huge areas of translational and regenerative medicine which are relying on our capacity to store biological material via freezing it.”
Cryopreservation - The next frozen frontier
Cryopreservation came to prominence in the 1950s when Lovelock and Polge managed to freeze sperm by adding organic solvents, which prevent ice crystals from forming. Today cryopreservation is widely used to preserve samples, but there is still a real need to improve it so unlock its potential for use in preserving blood and organs for transplant. Professor Matthew Gibson works jointly between chemistry and Warwick Medical School and aims to understand and improve the methods of cryopreservation already in use, to make them more efficient, enabling improvements in modern medicine.
He explains: “Lowering the temperature is a great method for preservation – but the standard process is destructive to most living tissues, hence cryoprotectants are needed. Some animals have natural antifreeze proteins - like fish which can survive in arctic waters. Our research aims to understand how we can mimic the function of these specialised proteins with aim of enabling cells and tissues to survive the freezing process.
“We use large synthetic molecules, or polymers, which are cheaper to make, and also highly tunable. We have shown that several synthetic polymers can behave like antifreeze proteins and stop ice crystals from growing. We have now shown that some of our polymers dramatically improve the number of cells which survive being frozen. This is crucial as without freezing donor cells like blood can only be stored for around 35 days before it expires, and similar problems exist with other donor cells and tissues. We hope that by improving this process, we can increase the availability of these cells for medical procedures, and support the advances being made in regenerative medicine.
“The goal of my lab is to remove, or significantly reduce, the amount of organic solvent required for traditional freezing, and increase the cells recover by adding our unique polymers.
“This area of research has the potential to improve the availability and volume of cells and tissue available for transplantation. It could also provide new tools to improve fundamental bioscience research.”
Unlocking the mysteries of sea ice
Climate change is the major environmental challenge of the present and future. Temperatures in the Arctic are rising twice as fast as the global average. The higher temperatures are bad news for sea ice, with the record lowest ice coverage recorded in the Arctic Ocean in recent years. Some modelling studies suggest that the Arctic Ocean may even be ice free during parts of the year by the middle of this century - a situation which is unprecedented in human memory.
Dr Hendrik Schaefer, an environmental microbiologist in the School of Life Sciences, explains: “Ice in the Arctic is an important part of the climate system. It is highly reflective compared to the dark ocean water, so, when the Arctic is covered in ice, sunlight is reflected and less heat is absorbed. Loss of sea ice through melting could therefore have even more negative consequences for climate change, by allowing more heat to be absorbed in an ice-free Arctic Ocean.
“It’s not just polar bears which depend on the sea ice. It is also a habitat for lots of species including microscopic life like algae and bacteria. Some of these microscopic organisms are driving the production of large amounts of atmospheric trace gases that can affect cloud formation and regional climate. When sea ice melts in spring and summer, large blooms of phytoplankton can occur which produce the organic sulfur compound dimethylsulfoniopropionate (DMSP). When DMSP is degraded by bacteria in seawater, dimethyl sulfide is formed, which, when it is emitted into the atmosphere, contributes to formation of atmospheric particles involved in cloud formation.”
A team led by Dr Schaefer is contributing to an international research programme called MOSAiC, which sees an ice breaker being kept frozen in the Arctic for an entire year. The project is live now and will run until September 2020. During this time scientists are studying a wide array of chemical, physical and biological properties of the sea ice and Arctic ocean water.
Dr Schaefer continues: “Our team will help determine the concentrations of relevant atmospheric trace gases and the organisms producing and degrading them. This work will help to better understand the environmental controls on the production of these climate affecting compounds and help to better predict what may happen in an ice-free Arctic Ocean in the future.”
Preserving the green credentials of electric vehicles
As the world embraces electric vehicles, scientists working in battery technology are continuing to make advances in terms of storage and power. But they are also working to address emergent issues associated with these new technologies.
Currently damaged and waste automotive Li-ion battery packs must be transported in explosion-proof steel containers to be disposed of at official sites to meet stringent international regulations. It makes disposal expensive, resource-heavy and wasteful – opposite to the goals of the industry and those who purchase an electric vehicles.
Researchers at WMG, University of Warwick, funded by the WMG Centre High Value Manufacturing Catapult (Innovate UK) and working in collaboration with Jaguar Land Rover, have identified freezing as a potential means to avoid the significant costs and resources involved in battery disposal. Cryogenically frozen cells are safe and therefore need less stringent transportation legislation.
Dr Thomas Grandjean from the battery research team explains: “Once frozen, Li-ion batteries are so unreactive you can drive a nail through them and they do not release any current, let alone explode – making them safe for transportation in larger numbers without the need for metal casing. We have also shown that freezing has little effect on the electrical performance of the cells – so in the case of a damaged battery pack, if frozen properly, there is the potential preserve and reuse undamaged cells.
“Our research is looking at the optimal rate and temperature to freeze a Li-ion battery with a view to prolonging its useful life, which means we reduce raw material consumption and improve the environmental sustainability of electric vehicles.”
20 November 2019
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