Photopolymer resin formulation and surface modification for enhanced coating applications in SLA-Printed devices

Stereolithography (SLA) has emerged as a superior additive manufacturing technique compared to Fused Deposition Modeling (FDM), offering smoother surface finishes and higher dimensional accuracy. However, conventional SLA resins remain limited by brittleness, poor thermal stability, and weak coating adhesion. In this study, a hybrid photopolymer resin incorporating nano-silica fillers (0.5–2.0 wt%) and functional oligomers was formulated, alongside plasma–silanization surface treatments, to enhance coating performance of SLA-printed parts. Mechanical testing showed a peak improvement at 1.0 wt% nano-silica, where tensile strength increased by 35.9% (from 32.5 MPa to 44.2 MPa), Young’s modulus by 36.2% (870 MPa to 1185 MPa), and flexural strength by 29.9% (58.9 MPa to 76.5 MPa). Shore D hardness rose from 78 to 84, while thermal analysis revealed an upward shift in glass transition temperature from 64.2 °C to 70.5 °C and degradation onset temperature from 281 °C to 301 °C. Surface wettability improved significantly, with water contact angle reduced from 89.3° to 54.7°, raising surface energy from 32.4 to 51.1 mN/m. Coating adhesion (ASTM D3359) improved from grade 3B to 5B, and wear resistance increased by 40% (wear index reduced from 0.125 to 0.075 mg/cycle). These results validate the dual-pathway approach of resin reinforcement and post-print surface modification, enabling SLA-printed parts to overcome typical FDM limitations of poor surface fidelity and weak interfacial bonding. The developed system demonstrates strong potential for high-performance coatings in biomedical, optical, and microfluidic device applications.