Cryogenics (not to be confused with cryonics or human cryopreservation) is the branch of physics that studies the production and behavior of material at temperatures between −150 °C and −273 °C. You might think that these temperatures are way too low to have any practical applications. Yet, the uses of cryogenics in our society are varied!
At hundreds of degrees below zero, individual molecules come as close to complete standstill as theoretically possible. The result is that the properties of the material subjected to these temperatures, such as strength, thermal conductivity, ductility, and electrical resistance, are altered.
Where Do We Already Use Cryogenics?
As cryogenic temperatures don't exist in nature, they are mainly used for scientific research. The results of these studies have led to the discovery of various applications in everyday life. Some of these enable us to discover the unknown, others make it possible to cure and save lives, and others are for simple entertainment. Let us look at them together.
Rocket Fuel
Have you ever seen huge white clouds billowing a rocket launch and wonder what they’re made of? There are three main liquid propellants for rocket and spacecraft:
- The first one is hydrazine, a compound of liquid nitrogen and hydrogen. Hydrogen has the lowest molecular weight of any known substance, making it ideal for keeping the weight of a rocket relatively small. Unfortunately, it’s rather toxic.
- The second option is RP1/LOX, which is a mixture of kerosene and liquid oxygen. It’s the most popular and cheapest fuel, as well as being relatively environmentally friendly.
- The last option is LH2/LOX, a mix of hydrogen and oxygen, both of which are in liquid form. When combined with liquid oxygen, hydrogen creates the most efficient thrust of any rocket propellant. Liquid hydrogen is in fact highly environmentally friendly and gives a specific impulse of about 30-40% higher than most other rocket fuels.
Most of these elements (nitrogen, hydrogen, oxygen) are found in a gaseous state in nature. Only when brought to cryogenic temperatures do their molecules bond to form a liquid.
The tank of the space shuttle is loaded with over 500,000 gallons of super-cold propellant. When the liquids are mixed and burned together in the combustion chambers, they produce a high-pressure gas. This, expelled in one direction (the ground), causes the rocket to fly at a certain acceleration in the opposite direction (the sky).
Liquified Natural Gasses
Transportation and supply is an important aspect of the gas business - with the EU being the biggest importer of natural gas (predominantly methane) in the world.
However, moving gasses from one country to another can be expensive and, in some cases, risky. Transporting a gas requires pressurized storage equipment that could, if damaged, explode or disperse its contents into the atmosphere.
This is why natural gasses are usually cooled down with the use of cryogenic temperatures, until they reach the form of liquified natural gasses (LNG). This guarantees safety for storage and transportation.
Food Industry
Besides transporting gas in liquid form, the use of cryogenic temperatures is an economical way to transport and store food for long periods of time. But why use such low temperatures when you could simply freeze food by bringing it below zero?
If you are familiar with cryonics, you should be well aware of the damage that freezing causes to tissues. Ice crystals formed at sub-zero temperatures affect adjacent molecules. In the food industry, they degrade the quality of the products, changing their textures, which often causes them to lose important nutrients.
To reduce this problem, liquid nitrogen is used. The food is sprayed or immersed in this liquified gas, which reacts with the food it comes into contact with. This results in the formation of small crystals that solidifies it without affecting the taste.
Special Effects
One of the little known uses of cryogenic gasses is for special effects like smoke, fog and mist. Cryo fog machines are very popular when it comes to ghostly Halloween effects, nightclubs and music venues. They are usually preferred because of their compact size, low weight, powerful output, low noise and ease of use.
Liquified gas at cryogenic temperatures (mostly carbon dioxide) is only used with a specific type of fog machine that can withstand extremely low temperatures and high pressures. As liquified natural gasses go beyond refrigeration temperatures, using a standard fog machine will end up freezing it instantly.
Medicine
To conclude, cryogenics have several uses in the medical field.
- In cryosurgery, the medical practitioner freezes cancer cells with liquid nitrogen to destroy the abnormal tissue. Below a certain temperature, ice crystals start forming, which decreases cell density and breaks the tumor down. This technique can help treat skin, prostate, cervix, and liver tumors, to name a few.
- Liquid helium is often used as a cryogenic coolant of the magnets used in MRI scanning. The liquid is at just the right temperature to provide the correct level of superconductivity required. Cooling down the magnets allows the machine to generate images of the patient to a temperature below -269°C.
- Additionally, cryogenic temperatures are used to achieve cryopreservation. This is the process of preserving cells, tissues, and other biological materials by lowering core temperatures to sub-freezing levels (usually at -196°C) without ice formation. This technology is used to preserve tissues, sperm, eggs, organs, and human beings. The purpose of cryopreservation is future warming and revival.
Cryonics aka Human Cryopreservation
In cryonics, a whole human body (or just the head) is preserved at cryogenic temperatures. After a patient has legally been declared dead, the cooling process should start immediately, so that oxygen deprivation doesn’t damage the cells (especially the ones in the brain). Once the procedure has been performed to allow the body to enter a state of vitrification (at around -120°C) all biological processes are paused, and the body can be preserved for an indefinite amount of time. We don’t know in fact how long it will take for medical technology to develop sufficiently to cure the causes of death and revive cryopreserved patients.
The use of containers filled with liquid nitrogen, called cryogenic storage dewars, allow for an easy and economical storage. The patient, brought to -196°C and placed in the cryogenic tank, can be kept waiting for as long as necessary. The dewar is periodically refilled with liquid nitrogen. With this method, no electricity is needed to keep patients cryopreserved. This secures the patients against power outages and makes long-term maintenance financially feasible.
Conclusion
Cryogenics has a broad application in our daily lives. Its extremely low temperatures allow different processes to happen, such as enabling food supply worldwide or safely cryopreserving a patient for an indefinite amount of time - possibly saving their lives.
You had never heard of cryonics and this article left you stunned? You can do three things: check out our website Tomorrow Bio, read some interesting articles in our Tomorrow Insight editorial or download the ebook below, which will give you an introduction to the subject.
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