Ferrofluidic seal

Ferrofluidic seals, or magnetic liquid rotary seals, are used in rotating equipment to enable rotary motion while maintaining a hermetic seal by means of a physical barrier in the form of a ferrofluid. The ferrofluid is suspended in place by use of a permanent magnet. Since their development in the 1970s, the seals have seen use in specialized applications such as computer disc drives, vacuum, and nuclear systems.