Electrorheological Fluids

Stiffening of an ERF in the electric field (left) and after switching off the field (right).
© Fraunhofer ISC
Stiffening of an ERF in the electric field (left) and after switching off the field (right).

Electrorheological fluids (ERF) are suspensions of electrically polarizable particles in a carrier liquid. When an electric field is applied, the fluid reversibly stiffens within a few milliseconds as a result of electrical interactions between the particles. The shear stress which is characteristic of the stiffening increases with the electric field strength by a factor of up to about 100. This strong stiffening effect of the ERF can be used for numerous technologies such as adaptive dampers, controllable clutches and brakes as well as haptic actuators.

The particles in the ERF consist, for example, of polyurethane doped with a soluble salt for polarization. Silicone oils are usually used as carrier liquids, but other carrier liquids are also possible.

Numerous ERF formulations have already been developed at the Center Smart Materials and Adaptive Systems and can be adapted for special applications if required. For the determination of the rheological properties of the ERF at different temperatures and shear rates, outside as well as in the electric field, appropriate measuring methods are available.


  • Controlling the composition-property relationships of ERF
  • Electrically polarizable particle materials for ERF
  • Sedimentation stabilization of ERF with additives
  • Process for producing electrorheological fluids


  • Development of electrorheological fluids
  • Adaptation of manufacturing processes for electrorheological fluids
  • Characterization and testing of electrorheological fluids