DLC: Flexible bridge across heterogeneous interface between alumina filler and epoxy resin matrix

•DLC films form exponential modulus transition zones, bridging filler and matrix with disparate elastic properties.•DLC increase adhesion of heterogeneous interface regions.•Heterogeneous interfaces created by DLC demonstrate enhanced dielectric sensitivity. The heterogeneous interface between filler and matrix within composites often acts as a bottleneck for material performance. Carbon materials, particularly Diamond-Like Carbon (DLC), are representing a novel trend in interface design. This study investigates the nanoscale mechanical and electrical properties of the heterogeneous interface between DLC-coated alumina fillers and an epoxy resin matrix. The results demonstrate that the DLC layer is instrumental in creating a harmonious modulus transition between materials that exhibit significant variance in their elastic moduli, characterized by an exponential relationship, and approximately 50% enhancement in interfacial adhesion. Additionally, the DLC layer exhibits elevated sensitivity in dielectric response, attributed to a small RC time constant. This interface transition technology offers new tools for composite material design.