Nano-scale materials science for soft dielectrics: Composites for dielectric elastomer actuators

Electro-mechanical transducers based on soft elastomers can be improved by suitable manipulation of dielectric properties, mechanical stiffness and electric breakdown strength. The dielectric constant of an elastomer can be improved by mixing with other components with a higher dielectric constant, and both insulating or conducting filler materials may be employed. We present our results on insulating nanoparticulate TiO₂ with various chemical modifications, which may lead to devices with improved properties. Conducting nanoparticles such as carbon black may lead to percolation-related enhancement, though with strongly detrimental side effects. On the other hand, a “molecular composite” approach, in which the conducting nanoparticles are grafted chemically to the backbone, appears valuable.