Dielectric elastomer actuators configurations

Figure 20.3 Representative dielectric elastomer actuator configurations.

Several configurations for dielectric elastomer actuators have been proposed and demonstrated so far planar, tube, roll, extender, diaphragm, bi-morph and unimorph bender represent the most significant. 

Fig. 6.108. Linear elongating dielectric elastomer actuators a tube and b roll configuration...

Fig. 6.109. Linear contractile dielectric elastomer actuators a helical and b folded configuration...

Another type of linear configuration known as bow-tie is shown in Figure 10.10. The actuator is constmcted using dielectric elastomer film having the shape of a bow-tie with two compliant electrodes configured on its two surfaces. Application of the electric field results in planar actuation which because of the bow-tie shape is translated into linear motion. Typical applications of these types of actuators comprise a hexapod robot, to mimic the motion of insects like walking, to manufacture various animated devices like face, eyes, skin, etc., or the design of micro-air vehicle/omithopter. 

Yet another interesting DE actuator configuration, dubbed DEMES, which stands for Dielectric Elastomer Minimum Energy Structure, has been introduced by Kofod et al. [244, 245] and further developed by O Brien et al. [246]. This type of actuator relies on a thin bendable frame. The frames are designed such that, when a prestrained DE layer is fixed to the frame, the forces exerted by the prestrained DE layer will cause the frame to curl until the forces balance the result is that the device is curved in the equilibrium rest state. Upon actuation the DE layer will relax causing the actuator to uncurl until it reaches the equilibrium actuated state, which will vary with the applied field. 

In order to easily assemble a linear contractile DE actuator, a recently described simple structural configuration, known as a folded actuator [14], can be advantageously adopted. Such a device consists of a monoUthic strip of dielectric elastomer, which is first coated with compliant electrodes and then folded several times in order to obtain a compact structure (Figure 24.5). 

Different dielectric elastomers used in DBAs have been described in a previous chapter of this book. By far, the most widespread dielectric material for simple experimentation is the acrylic elastomer VHB made by 3M, which is sold as industrial adhesive (it was not designed for DBAs but rather for fixing objects on walls). VHB allows for large actuation strain in DBA configuration and can be easily obtained. VHB tapes type 4905 and 4910 are 500 pm and 1 mm thick and can be ordered in many different widths (Fig. 1). 

The dielectric synthetic elastomers were studied in multi-stacked configuration. In addition to relative simplicity, it produces notably high strain. In order to control it, a PWM-PID controller was designed. The designed actuator has very high force-to-weight ratio, is cost effective and easy to fabricate. Furthermore, it serves as a biomimetic actuator due to soft musclelike characteristics. 

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