Soft gel microparticles for enhanced softening and high dielectric constant in elastomeric composites

Dielectric elastomers (DEs) can deform under electric fields, forming the cornerstone of soft actuators. For optimal performance at low operating voltages, a high dielectric constant (ε r ) and a low Young's modulus (Y) are essential. While embedding particles in elastomers is a well-established strategy to increase ε r , conventional rigid particles inevitably raise Y, creating a fundamental conflict in DE performance. Here, we present an approach that incorporates soft gel microparticles to simultaneously enhance ε r and resolve this contradiction. The stretchable gels conform to the elastomer during deformation, exhibiting a softening effect. As the concentration of gel microparticles increases, Y progressively declines, avoiding the stiffness issue. At the same time, the gradual enhancement in ε r significantly amplifies the actuation sensitivity of gel-infused polydimethylsiloxane (PDMS), increasing it from 2.6 MPa −1 in the pristine elastomer to 49.1 MPa −1 at 60% gel content. Furthermore, the tunability of the gel filler composition allows for customization to accommodate various DE systems. A soft micropump fabricated from these composites demonstrated a remarkable reduction in operating voltage. This work highlights the transformative potential of soft gel fillers in DE composites, addressing the limitations of rigid fillers and paving the way for further advancements in soft actuator technologies.