Dielectric elastomer actuators actuation principle

Fig. 6.1 Operational principle of the dielectric elastomer actuator, from [Chuc et al. (2011)] with permission from IEEE, Copyright 2011.

Figure 20.1 Principle of operation ofdieiectric eiastomer actuators, (a) Functionai element of dielectric elastomer actuators. Polymer film compresses in thickness and expands in area when a voltage is applied across the film, (b) Typical thickness or planar strain in response to applied...

Figure 23.1 Actuation principle of a dielectric elastomer actuator (a) voltage OFF (b) voltage ON.

Actuators based on dielectric elastomer technology operate on a simple principle as shown in Figure 10.4. When an electric field is apphed to the electrodes, positive charges appear on one... 

The multi-stacked actuator is designed to be directly driven by the Maxwell stress without any strain as mentioned above. Its fundamental principle of operation is shown in Fig. 7.1. When a voltage is applied between the two electrode layers, Maxwell stress is produced and thus, the dielectric elastomer is compressed along the axial direction. The compression of each layer results in the lateral expansion of the actuator because of the incompressibility of the polymer. Consequently, the deformation of the multi-stacked actuator is the summation of the deformations of individual layers and, thus, the total deformation is expressed as follows. 

Fig. 6.107. Working principle of a dielectric elastomer planar actuator...

Actuators based on dielectric elastomer technology operate on the simple principle shown in Figure 20.1. When a voltage is applied across the compliant electrodes, the polymer shrinks in thickness and expands in area. 

In any case, polyurethane dielectric elastomers have continued to be studied in the last decade, particularly with regard to the possibility of increasing their actuation performance. It is well known that both dielectric and mechanical properties are key parameters governing the electromechanical response of any dielectric elastomer, which can be in principle improved by an increase of the dielectric constant and by a decrease of the elastic modulus. In order to increase the dielectric permittivity of a polymer elastomeric matrix, various methods are available (Carpi et al. 2008), such as making composites or blends with highly polarizable phases. Table 1 constitutes a non-exhaustive list of works fi-om the literature, mostly relying on such methods for improving the performance of polyurethane dielectric elastomers. The studies are classified in terms of system complexity and component materials. 

Non-ionic polymer gel, swollen with dielectric solvent, can be extremely deformed as is the case for non-ionic polymer plasticised with non-ionic plasticiser. Instead of the charge-injected solvent drag as a mechanism of the gel actuation, the principle is based on local asymmetrical charge distribution at the surface of the gel18. The mechanism can also be applied to non-ionic elastomers in which the motion of the polymer chain is relatively free. In spite of their many difficulties for practical actuators, polyelectrolyte gels and related materials are the most interesting electroactive polymer materials. 

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