Elastomers can be turned into actuators

August 05, 2015 // By Christoph Hammerschmidt
Wherever mechanical movements need to be damped, elastomers are an ideal material. But this group of synthetic material has more to offer: Under certain circumstances it can be made to actively deform. Thus, it can be used as actuator, researchers from Fraunhofer institute have found. Its properties can even exceed piezo electric actuators.

Dielectric (DE) elastomers deform when high voltages are applied, a property these elastomers share with piezo actuators. However, dielectric elastomers can reach much higher strain than the latter ones at comparably low forces. Researchers at Fraunhofer LBF, a research institute that focuses on materials and reliability research, developed a concept for DE elastomers that works with perforated metallic electrodes. Thanks to this structure the material can leak locally through the holes if a voltage is applied. The concept is suited for designing dynamic, load bearing actuators. Based on this principle the researchers have developed a functional demonstrator for active bearings.

In contrast to passive bearings, the active DE elastomer-based bearing does not exhibit any increase in the amplitude of vibrations as the resonance frequency is applied. Quite the contrary, the active bearing can reduce oscillations across the entire relevant frequency spectrum. The detrimental characteristic non-linearity – a deflection disproportional to the voltage applied – could have been supressed through the use of electronic control techniques.

This design from Fraunhofer LBF is suited for bearing of devices susceptible to oscillations such as sensitive microscopes or extremely precise manufacturing processes. Likewise it is possible to uncouple machines, pumps or motors from their environment and thus minimise the vibrations transmitted. Case the control electronics fail, the positive passive properties of the elastomer remain, a clear advantage over conventional actuator technologies.

In addition it is possible to integrate sensor functions, enabling designers to implement closed-loop control circuits.

Practical applications are possible in automotive as well as in machine-building industries, the Fraunhofer researchers said.