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Ferrofluids

Composed of magnetic nanoparticles
Shape is determined by the interaction between magnetization, surface tension, and gravity
Invetned by Steve Papell at NASA in 1963

Originally intended to move fuel in zero gravity
Used for seals in hard drives, semi-active magnetic dampers, and in loudspeakers for cooling to name a few examples

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Nanoparticle synthesis

Metal solution

Add reducing agent

Particle growth

Terminate growth by coating particles with a charged shell