Cryogenics describes the science that deals with the production, effects, and uses of a wide variety of materials at very low temperatures1. To put this into perspective, water undergoes a phase transition from liquid state to solid state at 32° F (0° C), whereas cryogenic temperatures range from -150° C to -273° C. At -273° C or 0 Kelvin (K), which is also known as absolute zero, the movement of molecules ceases, thereby resulting in these molecules to be at their lowest energy state1, 2.
At such low temperatures, gases undergo a phase transition from its gaseous state to a liquid state. For example, when present at a temperature of -183° C, oxygen transitions to a liquid state. These extreme temperatures alter the physicochemical properties of materials, which can be a useful tool for researchers interested in taking advantage of these extraordinary properties at different states.
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Applications of Cryogenics
When at cryogenic temperatures, certain properties of materials, such as their mechanical strength, ductility, thermal conductivity, and electrical resistance, will be significantly altered. Some of the applications where cryogenics are utilized include:
Storage and Transportation of Gases
As a result of the inter-atomic or inter-molecular distances present in gases, the transportation or storage of gases can present several challenges. However, through the use of cryogenic technology, gases can be converted into liquids, which, as a result, saves a significant amount of space while also reducing the associated cost of transportation and potential hazards that can arise when these chemicals are resent in their gaseous state. The most widely known example of this is liquified natural gas (LNG), which is a mixture of methane, ethane and other flammable gases. These gases are liquefied at 110 K, which results in a significant reduction of occupied space by as much as 600 times as compared to when stored as a gas2,3. As a result, transportation-related expenses, particularly those that are associated with the transportation of these chemicals in insulated tankers, are significantly reduced.
Food Preservation
It is well known that chemical reactions proceed more rapidly in the presence of heat. To preserve packaged produce, food products can be sprayed with liquid nitrogen, which results in rapid absorption of the heat present within the produce2,3. The sprayed nitrogen contents will also eventually evaporate, thereby eliminating any potential threat of this chemical treatment to human health upon consumption.
Electronics
Cryogenic temperatures allow the electrons present within the materials to move freely with little to no resistance, thereby facilitating them to behave like superconductors2. As a result, these materials could be used in the manufacturing of superconducting electromagnets for particle accelerators.
Aerospace Industry
Oxygen and hydrogen, when stored as cryogenic fuels, are useful fuel sources that can be used to power rockets for space flight3.
Surgery
Certain types of biological tissues that have been damaged, as well as some tumors, can be removed from the body through the use of cryosurgery. During cryosurgery, a probe or scalpel that has been cooled by a cryogenic liquid, such as liquid nitrogen, is used to freeze unhealthy cells to allow them to die2,3. These dead cells can then be naturally eliminated from the body through normal physiological processes.
Cryopreservation
Cells or biological tissues obtained from animals, such as those acquired following animal experiments or experiment-related surgical procedures, are often preserved in liquid nitrogen in laboratories for a prolonged period. This is a particularly useful tool when researchers are interested in studying the macromolecules present within the cells or tissues. Furthermore, researchers are also able even to utilize cryopreserved specimens for various downstream research applications.
Cryonics
It is common practice for human embryos to be frozen in procedures involving in vitro fertilization. Furthermore, nematodes have been revived to life after being frozen at -196 °C4. In fact, there have been several cases where dead bodies of human patients were cryogenically preserved in the hope that the bodies can be brought back to life following the development of future scientific advancements. This process involves a gradual reduction of body temperature soon after the patient’s death, the complete replacement of the patient’s blood with anti-freeze liquid and cryopreservation in liquid nitrogen over the next few weeks4. The Cryonics Institute of Michigan, Alcor in Arizona and KrioRus in Russia are three well-known organizations that offer cryogenic freezing.
References:
- “Cryogenics” – Chemistry Explained
- “Cryogenics” – Britannica
- “Cryogenics” – New World Encyclopedia
- “What is cryogenics and how do freezing bodies work?” – Express
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