Dielectric elastomer transducers

Kornbluh R, Pelrine R, Pei Q, Heydt R, Stanford S, Oh S, Eckerle J (2002) Electroelastomers applications of dielectric elastomer transducers for actuation, generation, and smart structures. Proc SPIE EAP AD 4698 254... 

In this analysis, the dielectric elastomer transducer and energy harvesting circuits were modeled with highly simplified, experimentally validated lumped parameter models that did not include the interactions resulting from Eq. 3.1. Such models also did not include aU of the nonlinear effects detailed in Sect. 3.2 above. The circuits were also modeled separately using more specialized circuit modeling... 

Fig. 3.10 Highly modular distributed ocean wave energy harvesting system based on dielectric elastomer transducers...

Fig. 3.11 Water mill generator using a dielectric elastomer transducer upper left of photo) [Source HYPER DRIVE Corp.]...

There have been few studies on the lifetime of dielectric elastomer transducers and fewer still that consider lifetime of dielectric elastomer generators. Plante and Dubowsky [32] smdied failures in acrylic materials and identified factors to predict performance limitations. Kornbluh et al. [33] did report some generator lifetime results, which will be highlighted here. The requirement for long lifetime can have... 

Fig. 3.13 Effect of electrode type, humidity, maximum operating field and strain on the lifetime of dielectric elastomer transducers a Electrodes distribution of circular high strain actuators operated with different electrodes formulations (3M VHB 4910 film, 50% RH, 300% X 300% prestrain, actuation real strain 30-40% at 5 Hz, Max field 140 MV/min). b Humidity difference in high-fleld lifetimes for six circular actuators, three in open air and three in a dry environment (VHB 4910, 300% x 300% prestrain, IHz, Max field 140 MV/ min), c Electric field average life time versus electric field of high-humidity actuators (VHB 4910, 100% RH, 300% x 300% prestrain, 5% uniaxial strain at 5 Hz), d Strain lifetime of ten actuators with differing strain operated at high humidity (VB 4910, 100% RH, 300% X 300% prestrain, uniaxial strain at 5 Hz)...

Dielectric elastomer transducers are based on the electromechanical response of an elastomeric dielectric film with comphant electrodes on each surface. These transducers may be actuators, generators, or sensors. In aU cases, the basic stmcture is the same. 

Since the electric impedance and the output of a dielectric elastomer transducer are related to the deformation of the polymer film, it follows that these transducers could also be used to detect strain. For example, a linear actuator could be designed such that film capacitance is directly related to the amount of actuator linear motion. Rosenthal [10] discusses the use of dielectric elastomers as a sensor. 

While the performance of a dielectric elastomer transducer depends upon the dielectric and elastomeric properties of the polymer material, a great many polymer materials can be used. Because of this flexibility, unlike most other electroactive polymers (EAPs), different polymer materials can be selected for different applications, depending on the desired performance and physical properties. The best performing materials (those with greatest strains) are based on commercially available formulations of silicone rubber (polydimethyl siloxane) and acrylic elastomers such as the VHB series from 3M Corp. (Minnesota, USA) [11]. 

In this context, the possibility to tune tire piezo- and pyroelectricity of specific composites (Floss et al. 2000) by means of separate poling of the inorganic particles and of the polymer crystallites should also be mentioned. In addition, piezo-, pyro-, and ferroelectric polymers such as PVDF and its relevant copolymers may be optimized by controlling fire poling of the amorphous and of the crystalline phase, as well as of the interface between fiiem (Maxwell-Wagner interface polarization) separately (Rollik et al. 1999). Furthermore, it is possible to follow the examples of the classical electret transducers (witti polymeric space-charge electrets) or of the dielectric-elastomer transducers (sometimes also called electro-electrets) and to... 

As with other eleetromeehanieal teehnologies, the behavior of dielectrie elastomer transducers depends both mechanically and electrically on the boundary conditions. To illustrate. Fig. 3 shows a dielectric elastomer transducer with a constant charge Q in strain State A and the same charge Q in strain State B. 

General Considerations for Dielectric Elastomer Transducers and Common Failure Modes... 

Humidity. The electric breakdown strength (and leakage) of dielectric elastomer transducers is often affected by humidity. Lower humidity can dramatically raise the breakdown strength of many dielectric elastomer materials. Humidity can be artificially lowered by using, for example, desiccants. Packaging is an issue for low-humidity operation however, most designs operate at atmospheric conditions. 

In some cases, the configurations for dielectric elastomer transducers are similar to those used for piezoelectric (or other field effects) ceramics and polymers. In other cases, owing to the large strain capabilities of elastomers, the configurations are more novel. 

Chen B, Lu J, Yang C et al (2014) Highly shetchable and transparent ionogels as nonvolatile conductors for dielectric elastomer transducers. ACS Appl Mater Interfaces 6(10) 7840-7845... 

Son S, Goulboume N (2010) Dynamic response of tubular dielectric elastomer transducers. Int J... 

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