A lot of devices, such as shock absorbers, currently use elastomers to help minimize vibrations. While the malleable, yielding qualities of these materials do indeed allow them to absorb energy that would otherwise take the form of rattles and jolts, they are nonetheless passive – basically, they just sit there. Researchers from Germany’s Fraunhofer Institute for Structural Durability and System Reliability, however, are developing a new system in which elastomers actually “fight back” against vibrations.
These “electroactive elastomers” work by changing their form when exposed to an electrical field. If that field should be an alternating current, the material changes rapidly back and forth between two forms – it vibrates. Using smart electronics that monitor the frequency of vibrations in the environment, these elastomers can be made to vibrate at a complimentary frequency, resulting in the two frequencies essentially canceling each other out.
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The Fraunhofer team demonstrated the technology in a setup known as a “stack actuator,” a cigarette pack-sized model in which 40 thin elastomers and activating electrodes were layered together. Although the electrodes were made from metal, which isn’t generally known for its flexibility, they were punched full of microscopic holes that the elastomer sheets were able to deform through – sort of like what your skin does when you press your palm up against a screen window. When an alternating current was applied via the electrodes, this design was sufficient to allow the stack to rise and fall by a few tenths of a centimeter, at a rate of several times a second.
An oscillator was attached to the stack and at first vibrated wildly, as the actuator matched and amplified its vibrations. Those vibrations ceased, however, as the frequency of the stack actuator was adjusted to counteract them.
Interestingly enough, the stacks are also capable of producing energy from external vibrations in their environment. The researchers believe that this quality could make them useful for powering devices in places where electricity isn’t available, such as the sensors used to monitor the condition of bridges and other structures.
According to Fraunhofer, the technology has been mostly perfected, and lends itself well to automated production. Its long-term endurance still needs to be tested, however. Ultimately, one of the places that the stack actuators could end up is in cars, to eliminate vibrations caused by the engine.