Field-assisted alignment of lanthanum-based nanofillers in elastomeric composites for dielectric elastomer actuators

• Lanthanum-based nanofillers enhance the dielectric properties of Polydimethylsiloxane composites. • Dielectrophoresis aligns fillers into an anisotropic chain, increasing permittivity 4-fold compared to randomly distributed fillers. • Alignment yields a 3-fold increase in the electromechanical figure of merit (e’/Y) for dielectric elastomer actuators. • Charge tunneling in aligned chains increases leakage current. This study explores a pathway for enhancing the electromechanical performance of Polydimethylsiloxane (PDMS)-based dielectric elastomer actuators (DEAs) by combining a high-permittivity lanthanum-based filler with a specialized dielectrophoretic (DEP) assembly process. The elastomeric composite was fabricated by incorporating a commercially sourced lanthanum nanoparticle precursor into the PDMS matrix. Using a custom DEP setup with an ITO-coated glass substrate and metal plate electrodes, an alternating high voltage was applied during curing to organize the fillers into anisotropic chain structures. This alignment achieved a three-fold increase in the electromechanical figure of merit, the ratio of dielectric permittivity to elastic modulus, compared to randomly dispersed fillers. However, this structural modification introduces a critical trade-off: the aligned chains create conductive pathways that facilitate charge tunneling, thereby reducing breakdown strength and increasing leakage current at high electric fields. Electromechanical testing revealed an optimal performance using a 0.5 vol% filler loading, where the DEP alignment yielded a 15% improvement in actuation strain compared to pure PDMS. These findings validate the proposed DEP-driven fabrication route as a promising approach to maximize filler efficiency, provided that high-field leakage currents can be further mitigated.