Influence of rod-like TiO 2 fillers orientation on stretch-dependent permittivity and power generation of silicone rubber-based dielectric elastomer

Abstract Permittivity is a key parameter for dielectric elastomer (DE) and incorporating high-permittivity particles into the DE matrix is a promising approach to enhance the power generation output of DE generators (DEGs). However, permittivity in DEs often decreases under mechanical stretch, and the impact of this stretch-dependent behavior on DEG output remains unclear. To investigate this, we fabricate silicone rubber composite sheets filled with rod-like TiO₂ particles and evaluate their stretch-dependent permittivity and power generation output performance through experimental and theoretical analysis. Incorporating 2.5 vol% of rod-like TiO₂ particles increases the DE permittivity from 3.6 to 5.1 (a 42% increase at 1 Hz), but also enhances its stretch-dependent behavior. Finite element analysis indicates that the reorientation of rod-like particles toward the stretching direction (away from the electric field direction) reduces the contribution of particle shape anisotropy to the effective permittivity, thereby accelerating the decrease in permittivity. As a result, the composite sheet generates 2.54 mW―only a 6% increase compared to the 2.39 mW of the pure silicone rubber―substantially lower than the expected value based on permittivity gains alone. This discrepancy is attributed to the enhanced decrease in permittivity and increased charge leakage, which reduce both input and output charge. These findings indicate that, in designing DEG materials for high power output, it is important to consider not only enhancing permittivity but also suppressing its decrease during stretching. Based on this insight, we propose an approach that introduces a low-permittivity gap to improve the power generation performance of DEG.