Soft elastic modulus and high dielectric constant: a synergistic matching for elastomeric actuators

Dielectric elastomer actuators represent an emerging technology for polymer based electro-mechanical transduction. Owing to its good mechanical and electrical properties, in fact, that assure large strains and relatively high breakdown strengths, this kind of material is particularly suitable for actuation. Different configurations for expanding and contractile devices have been already developed but many are the unexplored potentialities of the field. In order to further develop the dielectric elastomer technology, a step forward in the direction of reducing the driving voltages should be done. With a reference to the current state of the art on the topic, the present paper describes the dielectric, mechanical and electromechanical performance of different elastomeric actuators prepared by adding inorganic and organic fillers (such as ceramic ferroelectric and carbon black powders, carbon nanotubes, conjugated polymers) to a commercial soft silicone rubber, easy to manufacture and extremely cheap. The possibility to enhance the real dielectric permittivity of the silicone matrix (up to 18 times), contemporarily maintaining a low elastic modulus (maximum 150 kPa), is investigated. The different compositions reported are compared in order to highlight which one gives the most interesting performance with a minimum content of filler (maximum tested content of filler was 15 vol%) in a way that the good characteristics of the silicone matrix are preserved, and costs limited. Practical considerations and comments about breakdown strengths and elastic energy densities of the obtained materials are reported.