Ferrofluidic Seal Technology
A Ferrofluidic® seal takes advantage of the response of a magnetic fluid to an applied magnetic field. The basic seal components include ferrofluid, a permanent magnet, two pole pieces and a magnetically permeable shaft.The magnetic circuit, completed by the stationary pole pieces and the rotating shaft, concentrates magnetic flux in the radial gap under each pole piece. When fluid is applied to this gap it assumes the shape of a liquid O-ring and produces a hermetic seal.
Ferrofluidic vacuum rotary feedthroughs utilize multiple rings of ferrofluid contained in stages formed by grooves machined into either the shaft or pole pieces. Typically a single stage can sustain a pressure differential of 0.2 atmospheres (200 mbar). The pressure capacity of the entire feedthrough is approximately equal to the sum of the pressure capacities of the individual stages.