Dielectric Elastomer: Electrode-coating
Conductivity under Strain
Electrode materials remain conducting only up to a certain amount of strain, after which they become non-compliance due to cracking. The strain values up to which various electrodes remain conductive is listed in table below.
Table: Actuation strains up to which the electrodes remain conducting [1, 2]
|Metal electrode (Ag)
|Thickened electrode solution
From the above table it is evident that carbon-grease electrode has highest conductivity under strain value. The carbon-grease electrode has been selected for coating on DE film. The coating is done on the film by first drawing a circle at centre of desired diameter. On both sides of the film electrode coating inside the circle is done. This acts as a capacitor there by providing the electric field on the DE film. Then for conduction on either side electrolyte is coated in rectangular shape as shown in figure 3.6. With this the preparation of sample is almost finished. For connecting the DC voltage source to the carbon-grease electrode copper tape is used. Two small strips of copper tape are attached to either side of carbon-grease electrode from which we can connect DC voltage source. With this the preparation of sample is done.
DE sample after electrode coating
Actuation of DE film
The actuation of the electrode-coated DE film when voltage is applied is discussed in most of the papers mentioned in the reference. The actuation is due to the electrostatic pressure applied on the DE film which is called Maxwell stress. The actuation of DE film is different for different pre-stretch values. For the actuation to take place the voltage applied is in terms of Kilo Volts.
 Akbay Mehmet Cuneyt, "Performance of Compliant Electrodes in Electro Active Polymers(EAP) Actuators", North Carolina University, Ph. D. thesis, 2004.
 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.