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A magnetic fluid contains particles of magnetic materials mixed with a liquid that acts as a carrier. Under normal conditions, the material behaves like a viscous fluid. When it is exposed to a magnetic field, the particles inside align and it responds to the field, exhibiting magnetized behavior. There are a number of uses for magnetic fluids, ranging from medicine to industrial manufacturing, and they are produced by a variety of companies.
This is an example of a colloidal solution, where particles of one substance are suspended inside another in an even mix. Nanoparticles of magnetic elements are utilized in the production of magnetic fluid to create a smooth, consistent fluid that will perform well in a variety of settings. The mixture typically includes a surfactant that acts to prevent clumping in the presence of a magnetic field. Magnetic fluid needs to perform well in a variety of conditions and must be produced with care to avoid impurities that might impede performance.
One use for magnetic fluid is in medical imaging studies. The fluid can be injected as a contrast agent for patients receiving magnetic resonance imaging (MRI) studies. As the fluid moves through the body, it will respond to the magnetic field, highlighting structures of interest and concern for care providers. The patient's body naturally eliminates it over the course of several days or weeks, depending on which contrast agent is used, and it does not pose undue risk to the patient's welfare.
It is also possible to use magnetic fluids in dampers, friction control devices, seals, and a variety of other applications. The ability to precisely engineer a fluid can allow for the control of a number of characteristics. Companies can determine the necessary temperature and pressure range for the fluid to develop a product that will withstand potentially harsh environments. It can also hold up to strong chemicals and other environmental contaminants while remaining functional.
Magnetic colloidal fluid, as it is also known, has some less serious applications as well. Some artists work with it to create interactive pieces that may be displayed in settings like galleries and science museums. Members of the public can play with the magnetic fluid, using magnets to change the polarization of the field around it. The fluid can also be left to its own devices in a contained environment that the artist programs to exhibit shifting magnetic properties so the fluid moves, and it can be colored or stained to create vivid visual images and a dynamic, changing scene.