Medical centrifuges come in various sizes and apply to many different applications, making them an extremely useful device whether in a doctor's office, hospital environment, or laboratory.
Modern centrifuges are basically compact, made either of plastic or metal, and are visually appealing; they usually sit on a counter top on rubber feet so so they do not move while in operation. The bottom may be weighed to make it stable while in use. Size will determine how many glass test tubes or vials it may hold at one time. They are controlled by a timer and have at least two speeds, low and high. Many also have the capability to keep the interior cool so when the appliance is working, particularly on high speed, the contents will remain cool instead of heating up as would normally happen when the centrifugal force is applied.
There are many medical applications for a medical centrifuge including studies of viruses, proteins, polymers, nuclearic acids, and blood. They can separate serum as well as plasma from blood, and solids from liquids. The uses are many and not restricted to the medical field alone.
Having a timer is convenient when uses include extended periods of time required for separation of ingredients. The high speed spin creates an artificial gravity that, depending on the substance, will separate the ingredients quickly or slowly.
Medical centrifuges can spin at amazing speeds, especially the variable speed models. They can produce from eight hundred revolutions per minute (RPM) up to a blazing two and a half million RPM. Average use and application for most centrifuges with a minimum of two speeds (low and high) are from two thousand RPM up to sixty thousand RPM. Most uses require the higher speeds but for shorter periods of time.
It is a difference in density that causes most substances to separate when run through a cycle in a medical centrifuge. The high speed units are called ultracentrifuges and these are generally bench top units which require some means of fastening them down on the counter or bench top so they stay in place while in use. Uses for ultracentrifuges include the separation of gases to determine the molecular weight of certain liquids. They are put to use as a means of separating uranium 235 for nuclear reactors. The temperature requires strict control in many of these applications due to sensitivity of the ingredients. They will become extremely hot at high revolutions which are actually a form of friction.
While an average medical centrifuge may cost anywhere from a few hundred to several hundred thousand dollars, there is one instance of an efficient device being created by chemists at a university which cost a mere two dollars to make. The device is basically an old fashioned egg beater to which was added plastic tubing held on by tape. It is capable of creating a low speed centrifugal force that actually will separate blood cells from plasma and has proved useful for simple laboratory tests in situations where no lab or equipment is available. It proves that human ingenuity can work many wonders.
