Combined effect of bio-inspired surface patterning and plasma treatment on the bonding performance of 3D-printed polycarbonate

Additive manufacturing, especially Fused Deposition Modelling (FDM), is increasingly adopted for producing functional end-use products. However, a key limitation of FDM is the build chamber size, which restricts the maximum dimensions of 3D-printed parts. This constraint impacts the stability, deformation and cost of the final product. To overcome this, larger components are often assembled from smaller parts, with adhesive bonding presenting a viable solution for joining these subassemblies. This study investigates how combining atmospheric-pressure plasma (APP) treatment with various surface patterns affects the surface properties and shear strength of 3D-printed polycarbonate joints. Four types of surfaces were examined: as-printed, polished (P1000), FS (fish scales), and TF (tree frog) textures. The findings reveal that APP treatment improve shear strength for P1000 and as-printed surfaces by 37% and 22%, respectively, due to the formation of polar functional groups that enhance surface wettability and adhesive bonding. However, FS and TF bio-textures show no additional strength improvement after APP treatment, likely due to their already strong mechanical interlocking. Additionally, the non-treated TF joint, which had the highest shear strength among all tested joints, has demonstrated a shear resistance of 21% lower than that of the fully 3D-printed specimen. This indicates that incorporating an appropriate surface pattern, such as TF, directly into the 3D printing process of the parts to be assembled can achieve joint strength comparable to that of a fully 3D-printed component without additional treatments.