Enhanced actuated strain of titanium dioxide/nitrile-butadiene rubber composite by the biomimetic method

Abstract

In order to improve compatibility between the dielectric filler and polymeric matrix, we used bio-inspired polydopamine (PDA) to modify titanium dioxide (TiO₂) nano-particles. The PDA coated TiO₂ (TiO₂-PDA) nano-particles were incorporated into nitrile-butadiene rubber (NBR) which contains a large amount polar groups to obtain a dielectric elastomer composite with a large actuated strain under a low electric field. The relatively soft insulating PDA layer on the TiO₂ nano-particles led to the composites filled with TiO₂-PDA nano-particles displaying better filler dispersion, much lower elastic modulus, lower dielectric loss, and higher electric breakdown field compared with the composites filled with pristine TiO₂ nano-particles, resulting in a high electromechanical sensitivity (β). At last, an actuated strain of 5.2% at a relatively safe electric field of 12.5 kV mm⁻¹ without any pre-strains was obtained by the 10 phr TiO₂-PDA/NBR composite, a 140% increase in actuated strain compared with the actuated strain (0.69%) of pure NBR at 20 kV mm⁻¹ without any pre-strains. This biomimetic method is simple, efficient, nontoxic, and easy to control, which can be used in other dielectric fillers to improve electromechanical properties of dielectric elastomers.