Respirocytes are hypothetical, microscopic, artificial red blood cells that can emulate the function of its organic counterpart, only with 200 times the efficiency, so as to supplement or replace the function of much of the human body's normal respiratory system. Still entirely theoretical, respirocytes would measure 1 micrometer in diameter[1]. In the original paper by Robert Freitas[2], titled, "A Mechanical Artificial Red Blood Cell: Exploratory Design in Medical Nanotechnology"[2], it was proposed that respirocytes would mimic the action of the natural hemoglobin-filled red blood cells[3]. The proposed design of the spherical nanorobot is made up of 18 billion atoms arranged as a tiny pressure tank, which would be filled up with oxygen and carbon dioxide[1], making one complete transfer point at the lungs, and the reverse transfer at the body's tissues.
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Respirocytes are spherical micron-scale robotic red blood cells. They contain nano-meter-scale components, which have an internal pressure of 1000 atmospheres of compressed oxygen and carbon dioxide. Two separate high pressure vessels, likely to be made up of the strongest materials such as pure diamond[3][2] or sapphire[3], would be able to safely contain this intense pressure. The intense pressure allows the respirocyte to hold 236 times more oxygen and carbon dioxide than our natural red blood cells[2].
Respirocytes are powered by glucose in the blood. They also contain an on board internal nano-computer, as well as a range of chemical/pressure sensors, which provide the respirocyte the ability to manage carbonic activity[2].
The key to the successful operation of respirocyte lies in providing an active means of conveying gas molecules in and out of pressurized micro vessels. A respirocyte exchanges gases via molecular sorting rotors, which have specially shaped tips to catch particular types of molecules. Each rotor has binding site "pockets" along the rim. These are exposed alternatively to the blood plasma and interior chamber by the rotation of the binding site. When exposed to the plasma, each pocket binds a specific molecule selectively. Further, as the binding site continues to rotate, it is exposed to the interior chamber. Here, the bound molecules are forcibly ejected by rods thrust outwards by the calm surface[3].
Molecular sorting rotors, measuring roughly 7nm Χ 14nm Χ 14nm in size and with a mass of 2 Χ 10-21 kg, can be designed from 105 atoms (including the housing). These devices could be capable of sorting 20 or fewer atoms at the rate of 106 molecules/second. For this, they would only require a laminar flow for energy cost upto 10-6 joule/molecule. Being fully reversible, rotors can be used to load or unload gas storage tanks, depending on the direction of their rotation[3].
Each respirocyte consists of three types of rotors:
The diameter of a respirocyte is only 1µm, which is much smaller as compared to the 8µm diameter of a natural red blood cell. This small size makes respirocytes potentially suitable for unique medical applications. For instance, respirocytes may be used for the treatment or prevention of ischemia (inadequate oxygen delivery to the tissues). Thier small size can enable them to squeeze into much thinner blood vessels, for delivering vital oxygen to the cells[2].
Per proposals, each respirocyte could store and transport 236 times more oxygen than a natural red blood cell[2], and could release it in a more controlled manner. If an adult human's red blood cells were entirely replaced with these devices, that person could hold his/her breath underwater for hours, making such devices extremely suitable for divers, who would then be able to dive for hours in a single breath, while avoiding both blends or narcosis (Afflictions caused by breathing compressed air under water, thus allowing more nitrogen, than at one atmosphere of pressure, to be dissolved into the bloodstream)[2].
Respirocytes also have the potential to allow an adult human to sprint at top speed for at least 15 minutes without taking a breath.[4][2].
Muscle fatigue results from inadequate supply of oxygen to the muscles during intense exercise, leading to inefficient anaerobic respiration. If respirocytes could increase the supply of oxygen despite exercise, it should be possible to reduce muscle fatigue, increasing a person's endurance.
Theorist Robert Freitas has proposed respirocytes as a superior alternative to naturally occurring red blood cells, and has similarly proposed "microbivore" robots that would attack pathogens in the manner of white blood cells.[5]
By definition, respirocytes qualify as molecular nanotechnology, a field of technology still in the very earliest, purely theoretical phases of development. Current technology could, therefore, not be sufficient to build a respirocyte due to considerations of power, immune reaction or toxicity, computation and communication. The dramatic enhancement of human performance, caused by respirocytes, may have desirable or undesirable consequences. The enhancement can cause the body to overheat. It also possible that the enhancement caused by such devices to one part of the body may produce unforeseen consequences on the other bodily systems[2].
As a result, to determine how nano technological respirocytes will eventually behave in the real world, actual testing of these devices in the living body will be required[2].
Because respirocytes and related technologies would, if successful, improve the user's abilities beyond normal human limits, their design is associated with the Transhumanism movement which seeks such advances.