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liquid-state-machine
magnetite ferrofluid
“Ferrofluids can be suspended in water or in an organic fluid. A typical ferrofluid is about 5% magnetic solids, 10% surfactant, and 85% carrier, by volume. One type of ferrofluid you can make uses magnetite for the magnetic particles, oleic acid as the surfactant, and kerosene as the carrier fluid to suspend the particles.” http://chemistry.about.com/od/demonstrationsexperiments/ss/liquidmagnet.htm
eg. citric acid and light silicone oil/biodiesil
use to 'measure' oscillations from Berlin Tempelhof wheel (eg. seal 10% in tube and fill rest with ethanol/isopropanol and attach to wheel)