Breaking the Trade‐Off in Dielectric Elastomers: A Synergistic Microencapsulation and Layered‐Structure Strategy

ABSTRACT

Simultaneously achieving a high dielectric constant, low elastic modulus, and high breakdown strength in elastomer composites constitutes a critical challenge for high‐performance dielectric elastomer actuators (DEAs). In this work, a synergistic strategy integrating microencapsulated multi‐walled carbon nanotubes (MWCNTs) and a sandwich structure is proposed to address this dilemma. Core‐shell structured melamine‐formaldehyde‐coated MWCNTs (MF@MWCNTs) fillers were synthesized via in situ grafting, where the insulating melamine‐formaldehyde shell not only enhances the dispersion of MWCNTs but also improves interfacial compatibility within the polydimethylsiloxane (PDMS) matrix. At an ultralow filler loading of 0.5 wt.%, the MF@MWCNTs/PDMS composite exhibits a significantly enhanced dielectric constant of 9.2 at 10 kHz while retaining a low elastic modulus. Furthermore, by constructing a sandwich‐structured composite with the configuration of MF@MWCNTs/PDMS‐PDMS‐MF@MWCNTs/PDMS, a remarkable synergistic improvement in breakdown strength is achieved, reaching 103.4 V/μm—an 85% enhancement compared to the single‐layer composite filled with pristine MWCNTs. This performance enhancement is attributed to the combined effects of the melamine‐formaldehyde shell's scattering on electrical tree channels and the barrier function of the middle PDMS layer. Consequently, the sandwich‐structured actuator demonstrates a bending deformation that is 200% higher than that of unfilled PDMS elastomer under the same driving field. This work provides a novel and effective design paradigm for the development of advanced dielectric elastomers with integrated high electromechanical performance, holding great potential for applications in soft robotics and flexible electronics.