3D Non-destructive imaging via in situ autofluorescence unravels field-driven electric tree dynamics and microfiller synergy in polymers

Precise, dynamic, and in situ characterization of material microstructures is essential for understanding failure mechanisms and tailoring material properties. In polymer insulating materials, prolonged electrical stress induces the formation of microscale dendritic defects, known as electrical trees. However, existing characterization techniques such as scanning electron microscopy (SEM) cannot capture the dynamic three-dimensional (3D) evolution of these trees under strong electric fields, thereby limiting mechanistic understanding and materials design. Here, we report that electric field excitation induces stimulated autofluorescence within polymer microstructures, enabling an in situ, non-destructive, and dynamic characterization approach. This technique achieves submicron spatial resolution, allowing for the first real-time visualization of electrical tree growth and morphological evolution under high electric fields. It demonstrates broad applicability across various polymer types and aggregation states. Using this method, we reveal the suppression effect and spatial action mechanism of SiO2 microfillers on electrical tree propagation. The observed fluorescence mechanism arises from electric field-induced molecular rearrangement in defect regions, leading to autofluorescence upon laser excitation. As the first method capable of dynamically characterizing microstructures under strong electric fields, it complements conventional tools such as SEM and optical microscopy, offering a new pathway for addressing key challenges in dynamic microstructural analysis.