A dielectric elastomer is capable of giant electromechanical actuation but fails at breakdown due to instability under certain conditions with a small deformation. By applying a mechanical pre-stretch, one obtains a stabilized large actuation.

In this paper, we measured the dielectric constant and critical voltage of a polyacrylic dielectric elastomer subject to both equal and unequal biaxial stretch, and modelled its actuation by employing the Gent strain energy function with a microscopic view to characterize the nonlinear stiffening behaviour and the electrostrictive effect in the deformation.

A dielectric elastomer is capable of largevoltage-induced deformation, particularly when the voltage is applied on theverge of snap-through instability.  Thispaper describes a model to show that the snap-through instability is markedlyaffected by both the extension limit of polymer chains and the polarizationsaturation of dipoles.  The model mayguide the search for high-performance dielectric elastomer transducers.

International Journal of Smart and Nano Materials 2011 2 (2), 59-67

Article citation: Miguel Piñeirua, Soft Matter, 2010, DOI: 10.1039/c0sm00004c

Capillary origami controlled by an electric field

Miguel Piñeirua, José Bico and Benoît Roman

From: Bar-Cohen, Yoseph (355N) <yoseph.bar-cohen@jpl.nasa.gov>

Dear Colleague,

I am very pleased to inform you that the 23rd issue of the WW-EAP Newsletter is now available at: 

According to the Japan Science and 

 Dielectric elastomer can undergo giant deformation, but are susceptive to various failure modes. i.e electrical breakdown.

Some experimental papers (Kofod, Plante, Chen, see the attachment) reported the dielectric strength of VHB material (a kind of dielectric elastomer) under difference pre-stretch, equal bi-axially or unequal bi-axially. And the strength (maximum voltage can be applied before breakdown) has be greatly improved by these mechanical stretches.

 So here comes the question: is the dielectric strength dependent or independent of stretch？

 For ideal rubbery material, the dielectric strength is a material constant, and should not be affected by the change in thickness.

In the study of thermoelastic actuation of dielectric elastomer, we can write the Helmholtz free-energy as a function of stretch ratio, nominal electric displacement and temperature (T).

The entropy (S) is the negative partial differential coefficient of W with respect of temperature (T). And we can see the change of S is due to three components: deformation, heat conduction and polarization. In an isothermal state, the deformation part has been fully investigated by Arruda and Boyce in 1993, but the polarization-induced entropy (Sp) has not been clearly stated.