Ferrofluids SRJC, ENGR45, Fall 2013

Eric Hagstrom and Jeremy Ho

What is ferrofluid?

• Ferrofluid is a liquid that becomes strongly magnetized when in the presence of a magnetic field.

• Homemade ferrofluids are typically made of particles suspended in a carrier fluid.

• Iron, magnetite and cobalt are examples of particles that would work.

History of ferrofluids

• Ferrofluids were discovered in the 1960s at the NASA Research Centre while exploring various techniques of controlling liquids in space.

• Ultimately, this application failed. However, there are many modern applications today for ferrofluids.

Chemistry of ferrofluids • In a true ferrofluid, the magnetic attraction of

the nanoparticles are weak enough that the Van der Waal forces of the carrier fluid prevents agglomeration (the clumping of particles). This leads to the fluid appearance of the ferrofluid.

• The particles are held stably in the carrier fluid due to Brownian forces. Brownian force is the random movement of particles suspended in a fluid.

Properties unique to ferrofluids • Without the presence of a ferrofluid, the

particles have no magnetization and flow randomly.

• Ferrofluid will assume the shape of the magnetic field passing through it.

• The retention force and apparent density of the fluid gets stronger proportional to the magnetic field passing through it.

Applications of ferrofluids

• Biomedical • Mechanical

Medical applications • Magnetic Drug Targeting - Drug surrounded by ferrofluid is kept inplace by a magnetic field, thus only affecting the designated area • Magnetic Field Hyperthermia - An isolated part of the body is filled with magnetic nanoparticles. When subject to an alternating magnetic field of specific frequency, only this localized area heats up.

Mechanical Applications • Loudspeakers - Ferrofluids passively remove heat from the voice coil as well as dampen the movement of the cone. • Seals and Bearings - Act as highly effective liquid bearings for applications such as hard drives and rotating shafts. - Can function as a liquid o-ring seal when paired with permanent magnets. - Used as a heat transfer agent via thermomagnetic convection. Ferrofluid becomes less magnetic the hotter is gets, therefore when paired with a magnet, colder ferrofluid is attracted to the magnet which absorbs the heat.

Our Ferrofluid • Our first batch of ferrofluid was created using iron oxide

shavings grinded to a fine particulate and then emulsified with motor oil. This was not a colloidal mixture.

• This mixture was not a true ferrofluid because the magnetic particles were not small enough to create the viscosity needed. Therefore, it’s appearance was granulated and did not have the telltale spikes of true ferrofluid.

Younes’s Ferrofluid

• Younes’s ferrofluid was colloidal and was an actual fluid rather than the paste that we made.

• A colloidal fluid is a substance microscopically dispersed throughout another substance. In this case, it was ferrite particles in a carrier fluid.

Informational references

• http://www.innovateus.net/science/what-ferrofluid

• http://dspace.mit.edu/bitstream/handle/1721.1/16937/53225503.pdf

• http://www.sbfisica.org.br/bjp/files/v35_718.pdf

Picture references • http://vector-magz.com/logo/nasa-logo-vector-item-4/ • http://www.mpipks-dresden.mpg.de/~adlange/research.html • http://www.instructables.com/id/New-way-of-making-a-ferrofluid.-Cost-

only-1.00$!/ • http://davidmark.us/archives/439 • http://trialx.com/curetalk/2012/11/cancer-treatment-multifunctional-

magnetic-nanoparticles-for-molecular-imaging-and-hyperthermia/ • http://www.liquidsresearch.com/en-GB/for_sealing_applications-52.aspx • http://www.intechopen.com/books/smart-actuation-and-sensing-

systems-recent-advances-and-future-challenges/new-perspectives-for-magnetic-fluid-based-devices-using-novel-ionic-liquids-as-carriers

• http://www.instructables.com/id/Make-your-own-ferrofluid-in-5-minutes/