Improving actuation strain and breakdown strength of dielectric elastomers using core-shell structured CNT-Al₂O₃

Reducing the operating voltage of dielectric elastomer actuator (DEA) without compromising breakdown strength (E_b) and elasticity has been one of the grand challenges to its practical application in various fields, such as the wearable devices. In this study, novel dielectric elastomers offering intrinsically good integrated performances are achieved by introducing CNT-Al₂O₃ core-shell nanostructures to form various nanocomposites. Dielectric constants (ε_r) of these nanocomposites show a rapidly increasing with the increase of loading amount of CNT-Al₂O₃ fillers, while the elastic modulus (Y) and the breakdown strength (E_b) vary slightly. By incorporating 0.9 wt% CNT-Al₂O₃ fillers, the dielectric constant and actuation coefficient of the nanocomposite increase more than by 200% compared with the pristine DEA, and the breakdown strength remains above 65 V/μm. Correspondingly, the actuation strain of the 0.9 wt% composite is 200% higher than that of pristine DEA under the same driving voltage. For the same actuation strain or deflection, the required driving voltage of the actuator made of CNT-Al₂O₃ nanostructure-based composite is only 50% of that of pristine DEA. Consequently, the achieved balance among a high ε_r, high E_b, and stable Y in our system can assure a high actuation strain under a low driving field, stable stiffness, and improved safety for DEA. In addition, since the tunable electromechanical sensitivity encompasses a wide range, the as-prepared nanocomposites offer an alternative candidate to fabricate the smart devices integrated with various strain components by modulating the composition of the materials.