A magnetic fluid sealing device includes a housing, a shaft, a magnetic fluid sealing assembly, a thermal conductive gasket and a resistance wire. The housing has a cavity. The shaft is pivotally arranged in the cavity, and at least one end of the shaft extends out of the cavity. The magnetic fluid sealing assembly is arranged in the cavity and fitted over the shaft. The thermal conductive gasket is arranged in the cavity and fitted over the shaft, an inner peripheral surface of the thermal conductive gasket is spaced apart from the shaft along a radial direction of the shaft, and the magnetic fluid sealing assembly is spaced apart from the thermal conductive gasket along an axial direction of the shaft. The resistance wire is arranged in the thermal conductive gasket and configured to vaporize a sealed fluid medium between the thermal conductive gasket and the shaft.

A hydraulic shock absorber having an inner housing portion slidably coupled to an outer housing portion to define a variable size chamber for containing shock absorber fluid. The region where the inner and outer housing portions overlap defines an annulus between adjacent surfaces of the inner and outer housing portions which varies in size in accordance with the extension state of the shock absorber. A dynamic seal is coupled to a surface of the shock absorber within the annulus for confining shock absorber fluid to the chamber. The shock absorber fluid is an electro-rheological or magneto-rheological fluid and the shock absorber includes a device for generating a magnetic or electric control field within the chamber at a region adjacent dynamic seal in order to increase the viscosity of the shock absorber fluid adjacent to the dynamic seal to inhibit passage of the shock absorber fluid beyond the dynamic seal.