Tailoring conductive nanofiller alignment for high actuation strain and output force in electroactive polymers

Abstract

An intrinsic conflict between high deformability and rigidity hinders the development of electroactive polymer (EAP)-based soft robots. Here, we employ an external electric field to align Al2O3-coated carbon nanotubes (Al2O3@CNTs) in a poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) matrix. Compared with pure P(VDF-TrFE-CTFE), the thickness strain of nanocomposites with horizontally and vertically aligned Al2O3@CNTs increases by 473% and 814%, respectively. It results in a high bending angle up to 215° for their actuator beams. Importantly, the horizontally aligned Al2O3@CNTs enhance the local stiffness via ‘face-enhanced effect’, yielding a high output force per unit volume (1.25 mN/mm3 at 30 V/μm). It is not only ~346% higher than pure P(VDF-TrFE-CTFE) but also higher than the reported ceramic actuators. Accordingly, the soft robots made by the designed nanocomposite actuators could climb slopes up to 52° and carry loads equivalent to eight times their body mass. Consequently, this modulating strategy develops a high-performance actuation for soft robots. Electroactive polymers can be used for soft robotics, though it is challenging to balance rigidity and deformability. Here the authors designed a polymer composite using an electric-field assisted tape-casting method to orient the Al2O3-coated carbon nanotubes to tailor the dielectric and mechanical properties.