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  • Dielectric Elastomer

    VHB film

    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 [1]. 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 [2].

    Advantages

    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 [1]. Dielectric elastomers are smart materials as they change their shape under the application of electric field [3].

    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 [4]. 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 [5]. 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[2].
    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.

    Reference:

    [1] Raj Kumar Sahu, Munshi Imran Hossain, Karali Patra and Shovan Bhaumik, "Dielectric elastomers: materials for future actuators", 10th National Conference on Industrial Problems on Machines and Mechanisms (IPRoMM 2010), MNIT, Jaipur (Rajsthan) December 17-18, 2010.
    [2] G. Kofod, "Dielectric elastomer actuator", PhD thesis, Technical University of Denmark, 2001.
    [3] Alexander Barnes, Qiang Liu, George Young, Tien Fu Lu, "Evaluation of selected dielectric elastomer for use in an Artificial Muscle Actuator", Proceedings of the Australasian Conference on Robotics and Automation, pp. 1-9, 2007.
    [4] Hazem I. Ali, Samsul Bahari B Mohd Noor, S. M. Bashi and M. H. Marhaban, "A Review of Pneumatic Actuators (Modeling and Control)", Australian Journal of Basic and Applied Sciences, vol 3 no 2, pp 440-454, 2009.
    [5] R. L. Hecker, G. M. Flores, Q. Xie and R. Haran, "Servocontrol of Machine-tools: A Review", Latin American Applied Research, Vol 38, pp 85-94, 2008.

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