How Does Cryosleep Work? The Science of Cryonics Explained

by toddy

The concept of reanimating a body has slowly moved from being a novelty of science fiction to our current reality. The ability to preserve the human body in a state of suspended animation under frozen conditions may eventually lead to a future of immortality! But unfortunately, nothing is ever so straightforward.

Cryonics is the preservation of the human body in a suspended, animation state, under freezing temperatures of -196 0C or -320.8 0F, by replacing blood and tissue fluids with cryoprotectants and storing the body in a cryo-chamber for future reanimation.

Cryonics involves a precise step-by-step procedure that ranges from selecting cryoprotectant materials to the maintenance of all conditions necessary to keep the body in a state of suspension until it can be reanimated (or for a lack of better terms – revived) (1).

In this article, we will dig to the roots, based on scientific and technological finds, the mechanisms of Cryosleep, its social and economic impacts on society, and, above all, its achievability.

How Cryosleep and Cryonics Work

Before diving into the intricacies of cryosleep and cryonics, we must emphasize one essential aspect of human life — our lifespan. Disregarding all the sicknesses, wars, and natural disasters globally, most would wish they could have a little more time for unfulfilled wishes, die without regret, or hug and speak to deceased loved ones again. Well, fortunately, cryonics opens up a whole realm of possibilities.

Cryosleep or Cryonics is a state of being where the human body is preserved in a suspended state under extremely frigid conditions. The methods involved in carrying out this process are intricate, but because of their practicality and versatility, space agencies and scientific organizations are beefing up their courage to invest in its success. Nevertheless, there’s no scientific evidence as of now to suggest the possibility of reanimating cryogenically frozen bodies.

However, if it can be done, then it can be undone.

As the human body is made up of approximately 80% of water, it suggests every cell, tissue, and organ comprise this ingredient of life. And this is where it gets dangerous. From our definition of Cryonics, the basis of its functionality depends on extreme freezing conditions, in which case, water will lose its density, increase its volume and solidify under such frigid conditions. (2)

Without protection, the increase in volume as water freezes will cause human cells to break when it exceeds their elastic limit. The formation of ice crystals will also cause irreversible damages to the cells, tissues, and organs.

To counteract the many side effects of freezing temperatures, the introduction of an anticoagulant, Heparin, is administered to prevent blood from clotting, during which a constant and abundant supply of oxygen is sent to the brain. Although declared legally dead (when the heart stops and the status a patient must be in to undergo cryonics), the administration of Heparin and Oxygen will help stabilize the body’s metabolic rate as the brain, and certain cellular functions remain.

A glycerol-based chemical mixture known as a Cryoprotectant is then administered to replace the water in the cells and tissues to serve as a human anti-freeze. This liquid helps to maintain cellular integrity in the state of suspended animation under extremely low temperatures. (3)

Once vitrified (deep cooling without ice crystallization due to cryoprotectants), the body is laid on a bed of dry ice until it reaches -130°C or 202°F. The body is then inserted in an individual container immersed upside down in a large metal tank filled with liquid Nitrogen, at -196°C or -320.8°F.

Bodies under such conditions are considered cryopreserved or cryo-conserved, and there is still no guarantee for their reanimation in the near future. With that said, the success of the current cryonics industry is solely dependent on the possibility of future technology to cure any existing ailments once a patient has been reanimated/thawed. And just maybe, the answer lies in nanorobotics.

The Basis of Cryopreservation

Interestingly, cryopreservation began with the need for the cryogenetical conservation of animal genetic resources for the breeds commonly used by humans for food (Food and Agriculture Organization of the United Nations). The success of such preservations has paved the way for the cryonics industry.

Lately, scientists have embarked on research to replace blood and body fluids with a new type of antifreeze, proving to be far less toxic than the traditional cryoprotectant. Instead of forming ice crystals, the water in cells and tissues will cluster up as a single, glass-like mass through the vitrification process. However, there are doubts regarding preserving organs such as the brain, heart, and liver within the scientific community.

Regardless, to ensure the success of cryopreservation, cells, tissues, organs, extracellular matrix, or any physiological component prone to damage caused by unfettered chemical kinetics must undergo vitrification.

As such, is there any hope for life after death (legal death that is) as we know it?

Well, I can only say the evidence looks promising.

What Are the Materials Used For Cryogenics? 

The term cryogenics suggests the usage of cryogenic fluids to produce a cooling effect. As such, cryonics is the use of cryogenic fluids to cool the human body.

Their application covers a wide variety of areas, such as:

  • Metallurgy
  • Medicine
  • Chemistry
  • Food processing by refrigeration
  • Power Industry
  • Rocket Population
  • Space Simulation

Nowadays, a skillset in cryogenics is in high demand for a variety of technical fields, but it can most commonly be seen in industries such as advanced energy production, storage technology, space programs, and transportation.

The cryogenic fluids include liquified permanent gases such as N2 and O2. The following is a table of cryogenic gases and their liquefaction temperature points.

Cryogenic GasHeCO2H2N2NeCH4ArO2
Liquefaction Point/oC-268.95-192.05-252.75-195.85-245.85-161.45-185.75-183.05

Generally speaking, cryogenics is a multidisciplinary science that involves branches of chemistry and physics. This implies that the selection of materials used in cryogenic equipment must withstand the drastic property changes when exposed to extremely low temperatures.

For example, materials with ductile or flexible properties under ambient temperatures might become brittle due to increased stiffness and reduced size when stressed under cryogenic conditions. At the same time, another material may actually improve its ductility under such harsh conditions.

Ensuring that the materials selected produce the desired performance is the key to success. But that’s not to say proper welding, brazing, or soldering in the joining of materials is not also an absolute requisite for preparing any cryogenic procedures.

In theory, the ratio of a material’s change in energy to its change in temperature is known as its Specific Temperature. The ratio of a change in volume of a material to its change in temperature is known as Thermal Expansion.

A special relationship correlates specific Temperature and Thermal Expansion – all materials experience a change in physical dimensions when cooled to low temperatures – which is significant as the thermal and differential contraction of any materials is “especially important to the design of vacuum seals, structural supports, and electrical and thermal insulation” for cryogenic devices (4).

Has Anyone Undergone Cryonics?

Aside from the sci-fi films that inspired the many possibilities in making cryosleep a reality, there have been several occasions where bodies were found immersed in frozen lakes and snow. In 1999, Dr. Anna Bagenholm (29 years old) was revived after her heart was stopped for 3 hours after being submerged under ice while skiing and her body temperature dropped to 14°C.

Such films and occurrences have made cryosleep seem an achievable feat. Nevertheless, this does not stop the scientific community from relenting to make this dream come true. Soon, space agencies like Blue Origin and SpaceX would likely consider investing in the cryonics sector, as they have the most to gain from its success with plans to commercialize spaceflight and send humans to Mars, then further into the cosmos.

Dr. James Bedford, 1967, was the first person to be cryopreserved in a cryo-chamber after he passed from kidney cancer.

A fiction writer and “the father of cryonics,” Robert Ettinger, also lay in metal flasks (-196°C) with his mother and two wives at the Cryonics Institute in Michigan.

Cryonics and Ethics

JS, a 14-year-old dying girl, spent months researching the science of Cryonics and proposed that her body be cryopreserved after her immediate death. She hoped that she could be reanimated sometime in the future when the cure for her illness has been found.

Before her death, she won the court case to be legally cryopreserved, which had set the precedence for the Judge to claim the legitimacy of cryonics under the UK’s Human Tissue Act. Despite having no prior regulations, the Judge acknowledged the need for new legislation linked to Cryonics. (5)

Which leaves us with the question: Is Cryonics the door to post-humanism?

The science of cryonics gives hope for immortality; if it ever succeeds in crossing the limit of our science and technological struggle, the world as we know it might become one cosmic laboratory.

For the sake of further evidence on the subject, a few multicellular organisms can replace their internal water content with trehalose (a sugar-based antifreeze) that prevents their cell membrane from crystallizing and breaking open during freezing conditions. We can observe such tendencies in the water bear and wood frogs.

However, we should note that the above method occurs naturally without artificial influencers, such as cryoprotectants. So… might this mean that Cryosleep can also be achieved if these conditions are followed?

Is Reanimation Possible?

Reanimating a human being from their “frozen” state seems far from possible for the time being, as the only success we’ve had is with the cryogenic reanimation of the embryo. Cryogenics specialists care for their patients with the singular hope that Molecular Nanotechnology will one day actualize new methods for reversing the damages caused by cryogenics.

Given our current state of technology, it would be fair to assume that Cryosleep will require further research before being implemented in our societies.

Science aside, the sole intention of Cryogenics is the preservation of human life, which would also make one curious regarding the effects of ageing during such a procedure.

So… what really happens?

Well, even at death, certain processes, such as hair and nail growth, still take place for a given period. But, in cryonics, all such processes are isolated, and the body is kept in a state of suspension.

This implies that cryonics puts a temporary stop to all processes that coordinate the functioning of the human body. This, however, doesn’t leave us with the assurance that cryonics is a safe procedure for preserving life if the said life can’t be reanimated.

It sounds a little more like some snake oil pitch by the science community to make money off people’s backs.

Nonetheless, a step towards immortality is worth celebrating. If reanimation from Cryosleep is made possible, sensations like pain, agony and many other emotional dilemmas will no longer be a part of humanity’s inherent faculties.

Is Cryonics Illegal?

In our society today, it is illegal to carry out Cryonics on individuals who are still alive. But that doesn’t stop one from paying $400 to be cryopreserved after his/her death.

Although, this ‘death’ isn’t one where we would commonly think of.

Patients are only allowed to undergo cryonics after being declared legally dead. This recognition (legal death) occurs when a medical professional officially declares that your heart had stopped beating.

During Cryosleep, every form of metabolism and coordination is halted, with the brain only functioning for some time before reaching point zero in its functionality. This implies that when a man has been pronounced legally dead, it is actually the perfect time for the cryonic procedure to begin as their heart has officially stopped beating with all body functions shutting down. The cryonics team, at this point, only has a few minutes to stabilize the body and transport it to their facility.

Although, this brings another concern into the fold. As Cryonics preserves the body in a state of suspended animation in an unconscious state, there’s no guarantee that the patient will exhibit the same mental faculties, such as recognizing friends and family or even themselves before the procedure.

Several recorded cases of patients put under general anesthesia have woken up and couldn’t remember their own names or experiences for hours. Since cryonics doesn’t handle human faculties such as thought and memory, emotions, and desire, but exhibits similar effects to anesthesia, a person under cryonics may end up never knowing who he was before he died.

Objectively, the possibility of reanimating bodies from Cryosleep may lead to an odd species of humans depending on our success in preserving the body’s organs.

But, why do we say odd, you might ask?

Well. Our current methods of carrying out a successful cryogenic procedure do not preserve organs such as the brain and the heart.

Dr. Amour made an interesting discovery in 1991 that the heart actually has its own “brain,” or otherwise referred to as the “intrinsic cardiac nervous system.” This “heart” contains about 40,000 neurons that exist in clusters. It forms the basis of the Intrinsic Cardiac Nervous System (ICNS) that aligns with the Autonomic Nervous System (ANS) for transmitting impulses to our actual brain.

Further findings reveal that besides pumping blood, the heart exhibits certain brain-like tendencies, such as pain, relay feedbacks and emotional cycles.

With that said, for cryonic specialists and researchers to reanimate human beings and NOT turn them into the walking dead, special considerations HAVE to be made on issues concerning cryopreservation of the heart and brain.

Is Cryosleep Different from Death?

To understand the difference, it’s important to understand what occurs in the body when it whittles away to point zero to compare it with the processes involving cryonics.

Without digging into the fundamental intricacies of both concepts, it is quite easy to say they manifest the same state of being.

At both death and the state of Cryosleep, there is a definite loss of consciousness and a loss of heart functions (heart stops beating). However, death in its truest sense isn’t when the heart stops beating as the brain continues to function (for a short little while). Death is complete when all processes in the body stop.

At this stage, there’s no hope of reviving the body and any efforts for cryopreservation will be in vain.

Frequently Asked Questions on Cryonics and Cryosleep

Is Cryonics Like Mummification?

As Cryogenics aims at preserving life and keeping the body in a suspended state of animation, one may think that it draws inspiration from an ancient Egyptian or Chinese ritual that involved the preservation of royal corpses with the hope that they’ll live in the afterlife.

Cryonics is similar to mummification on the level of preserving the human body, but their differences will require an in-depth study of mummification. Nevertheless, Cryonics inspires the world to believe in the theory of life after death in a more technological manner while embalming a body after death would require the body to be kept without hopes of a revival.

Is Cryonics A Form Of Prolonged Anesthesia?

No. During anesthesia, the body is maintained under ambient conditions and doesn’t require extreme temperatures to function. Cryonics largely relies on freezing temperatures and it cannot be exercised on someone who’s still alive.


  1. Cryonics:
  3. What Is Cryonics? – How Cryonics Works | HowStuffWorks


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