Enhancing the electro-mechanical response of Maxwell stress actuators

The need for high electric fields to drive dielectric elastomers is still retaining their diffusion as actuators in some areas of potential application, as in the case of biomedical disciplines. The development of new materials offering superior electromechanical properties is thus an essential requirement in order to effectively reduce the driving fields. In this light, the present work is aimed to enhance the electromechanical properties of two silicone and polyurethane based dielectric elastomers, both by making particulate composites with high-permittivity ceramic fillers, and by blending with a highly polarisable polymeric phase. Due to a consequent worsening of the mechanical properties, pure composite architectures yielded only limited results on the overall electromechanical response. With the blend approach, instead, both an increase of the dielectric permittivity and an unexpected reduction of the tensile elastic modulus were observed, leading to an overall increase of the electromechanical response. In any case, a key role appears to be played by the nature and intensity of polarisation phenomena arising at interfaces between different phases. Partial financial support for this work has been provided by the EU Commission under the IP project FLEXIFUNBAR (contract number: NMP2-CT-2004-505864).