Editing Ferrofluid (section)

====Electronic devices====
{{main|Ferrofluidic seal}}
Ferrofluids are used to form liquid [[Seal (mechanical)|seals]] around the spinning drive shafts in [[hard disk]]s.  The rotating shaft is surrounded by magnets. A small amount of ferrofluid, placed in the gap between the magnet and the shaft, will be held in place by its attraction
to the magnet. The fluid of magnetic particles forms a barrier which prevents debris from entering the interior of the hard drive. According to engineers at Ferrotec, ferrofluid seals on rotating shafts typically withstand 3 to 4 psi;<ref>{{cite patent|country=US|number=4478424A|gdate=1984-01-27}}</ref> additional seals can be stacked to form assemblies capable of withstanding higher pressures.