subject: Understanding The Evolution Of Ferrofluid [print this page] Understanding The Evolution Of Ferrofluid
Ferrofluid is a slippery oil that sticks to magnets. Although it takes a strong physics and chemistry background to understand it completely, the basic concept is that very small magnetic pieces of ferro, or iron, are suspended in a fluid, usually oil, with a surfactant (a compound that lowers the surface tension). Without a magnet nearby, the ferrofluid is not magnetized, but once aligned with a magnet, it aligns almost immediately. That is what ferrofluid is. To understand how it is used, one must to look at its history.
It was first developed in the 1960's through NASA in response to the need for moving liquid fuel in a gravity-free outer space setting. It was then developed further in the 1970's and used as a magnetic liquid leak-free sealing system for rotary applications like computer disk drives, which prevented contamination and increased memory capacity. Later it was used in the manufacturing process of semiconductor wafers and other vacuum processed high tech products, and now most computer drives have a ferrofluidic seal.
Ferrofluid is also used in medicine, particularly in molecular diagnostics and genetics.A ferrofluid seal formed with a magnetic circuit makes a hermetic seal against vapor and contaminants. This seal technology is used in gas systems such as sterilization equipment, radiology, X-ray and other imaging systems. It is also used where rotation is required in the vacuum process. With no friction between the rotating and the stationary components, it creates a liquid o-ring around a rotating shaft. This becomes a seal for rotating mechanisms, locking out atmosphere and contaminants.
Over the years, additional uses have been discovered for including everything from power transformers to bearings to improved loudspeaker performance. It has also been used in motors and sensors, where it cools down the wires, and as a sealant in engine pistons, bearings, and dampers. Sometimes it is used for testing other components, too, such as magnetic tapes, stainless steel and turbine blades. It can also improve performance in flow meters, tilt, vibration, pressure, and level sensors, and in some kinds of switches.
It is important to make sure the material that is exposed to ferrofluid is chemically compatible. There can be exposure to gases, as in the semiconductor and laser industries, or liquid sprays such as in the tool and aircraft industries. There might also be exposure to lubricant vapors in the computer industry, adhesives in the speaker industry, or plastics and plating materials. Temperature ranges also enter the picture. The ferrofluid may be expected to perform in winter conditions (-20C) and space environments (-55C), and might need to hold up to nuclear radiation. Therefore, it is extremely important to analyze the exposure carefully to determine which particular ferrofluid is appropriate.
