It is a polymer having elasticity properties -low young's modulus, high yield strain. The elasticity is due to the long polymer chains that redistribute themselves on application of stress . There is covalent cross-linkage formed during vulcanization that ensures the elastomer to return to its original position when stress is removed. The flexibility is 5-700% depending on its specific material composition .
Elastomer that deform upon applying electric field are known as Dielectric Elastomer. These are characterized by a low elastic stiffness and high dielectric constant so that they may be used to induce a large actuation strain under the influence of an electrostatic field . Dielectric elastomers are smart materials as they change their shape under the application of electric field .
The usage of DE as actuator is still under research state as few actuators made of DE material can be readily used in a system. Presently there are 3 types of actuators which are widely used they are as follows.
1. Pneumatic actuators
2. Hydraulic actuators
3. Electro-mechanical actuators
These actuators have their own shortcomings. Pneumatic actuators require a compressed air generator which is very large. A pneumatic system generally uses long tubes and must have a control system that can deal with the delay between control signal and the effective actuation . Hydraulic actuators have heavy components like reservoirs, filters and hydraulic pumps. These operate at high pressures and there is a chance of leakage, to prevent we need additional overhead which increases system complexity . Electro-mechanical actuators are compact, cheap and easily controllable. But the main drawbacks of electro-mechanical actuators are they are prone to wear and actuation delay.
From the above discussion we can say that the traditional actuators are not suitable for micro-scale environment or for large actuation. Therefore there is need for development of DE actuator as it can produce large strain and is compact in size.
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 G. Kofod, "Dielectric elastomer actuator", PhD thesis, Technical University of Denmark, 2001.
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