Suspensions and Colloids
Ishan Wathuthanthri
iwathuth@stevens.edu
Department of Mechanical Engineering
Stevens Institute of Technology
New Jersey, USA
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Suspensions
• Particles larger than ~1000nm.
• Separated by gravity.
• Examples (sand/water, dust/air)
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Making An Interesting Suspension
Mix two parts cornstarch to one part water.
• 100ml cornstarch (large beaker)
• 50ml water (small beaker)
• Place cornstarch into a ziploc bag and add
water.
• Close bag and mix.
Write down some characteristics of this
suspension.
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Colloids
• Particles upto ~100nm.
• Cannot be separated by gravity
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Example of a Colloid- Ferrofluids
• Ferrofluids- “ferro” iron.
• Polarized in a magnetic field.
• Colloidal mixture of iron particles
suspended in a carrier fluid.
• Generally particles ~10nm.
Reference- L.Mao and H. Koser.
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History
• Developed by NASA in the 1960’s.
• Method of controlling fluids in space.
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Review of Magnetism
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Electromagnet
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Applications of Ferrofluids
• Liquid seals in bearings. Used in hard
drives/ o-rings.
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Speakers
• Used for and cooling around coils.
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Dampening
• Internal dampers in shock absorbers
and stepper motors etc.
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Biomedical Application
• Magnetic cell separation chambers
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• Target delivery agents.
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Telescopes for Astronomy
• Research conducted in using
ferrofluids for liquid mirrors.
http://www.newscientist.com/article/dn15154-morphingmirror-could-clear-the-skies-forastronomers.html?feedId=online-news_rss20
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Thank you.
Questions?
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