Enhanced Dielectric Properties of P(VDF-TrFE-CTFE)/PMMA Composites with MWCNTs@SiO₂ Core–Shell Fillers

Dielectric materials with superior dielectric properties are pivotal for enhancing the performance of electrowetting-on-dielectric (EWOD) devices. In this work, MWCNTs@SiO2 core–shell-structured fillers were fabricated by coating multiwalled carbon nanotubes (MWCNTs) with a uniform SiO2 outer layer. This innovative core–shell structure was incorporated into a poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) and poly(methyl methacrylate) (PMMA) organic matrix to fabricate composite films with enhanced dielectric properties. The incorporation of core–shell fillers significantly enhanced the microcapacitor effect and Maxwell–Wagner–Sillars interface polarization. At a low filler loading of 4 wt %, the composite achieved a high dielectric constant of 25.4 (at 100 Hz), representing a 108.2% enhancement compared to the pristine polymer matrix, while maintaining a low dielectric loss as low as 0.05. Furthermore, the SiO2 shell effectively mitigated inhomogeneous electric field distribution induced by dielectric constant mismatch, reducing field distortion and consequently enhancing the breakdown strength. Notably, under a DC voltage below 50 V, a high contact angle modulation range of 38.3° was achieved, representing a 151.97% enhancement compared to the pristine polymer matrix. These findings provide a new strategy for developing high-performance dielectric materials for EWOD applications.