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  • Dielectric Elastomer: Electrode-coating

    VHB film

    As mentioned previously, DE actuators consists of a DE film between two electrodes i.e. electrodes are coated on both sides of the DE film. Compliant electrodes should conform to the shape of the DE film to which these are attached to [2]. The different kinds of electrodes that can be used for DE actuators are listed below [1]:
    1. Carbon-grease electrode
    2. Graphite electrode
    3. Ultra-thin metal electrode
    4. Ion-implanted electrode
    5. Single-walled nano tube electrode coated with dielectric oil
    6. Polypyrrole electrodes
    7. Rubber electrodes

    The criteria required for selection of electrode is its conductivity under strain as the electrodes are conducting only up to certain percentage of actuation strain, after which due to cracking they become obsolete. Among the electrodes carbon grease electrode have conductivity up to 215% of strain which is highest among the previously mentioned electrodes [3].

    The criteria required for selection of electrode is its conductivity under strain as the electrodes are conducting only up to certain percentage of actuation strain, after which due to cracking they become obsolete. Among the electrodes carbon grease electrode have conductivity up to 215% of strain which is highest among the previously mentioned electrodes [3].

    Carbon grease electrodes are most commonly used electrodes for DE actuators [4]. In our work, we also used carbon grease electrodes. Electrode material is prepared as a homogeneous distribution of graphite particles in grease and are applied using a brush onto the DE film. It is however suitable only for devices with area greater than 1 sqcm [1].

    Electrode plays an important role depending on the actuation strain. It is very important to evaluate the electrodes for their electrical conductivity and actuation strain properties before we select it for a specific application. Electrodes cannot be selected based solely on conductivity, because at high strain values these electrodes may become non-conductive due to cracking. So we must consider conductivity under strain.

    Reference:

    [1] R Pelrine, R Kornbluh, Q Pei and J Joseph, "Highspeed Electrically Actuated Elastomers with strain greater than 100%", Science, vol 287, pp 836-839, 2000.
    [2] Ravi Shankar, Tushar K. Ghosh, Richard J. Spontak, "Dielectric elastomers as next generation polymeric actuators", The Royal Society of Chemistry, pp.1116- 1129, 6th June, 2007.
    [3]Akbay Mehmet Cuneyt, "Performance of Compliant Electrodes in Electro Active Polymers(EAP) Actuators", North Carolina University, Ph. D. thesis, 2004.
    [4] Guggi Kofod, Peter Sommer-Larsen, "Dielectric Elastomers as electromechanical transducers", Chapter 7, Elsevier. January 2008.

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