Bio-based photosensitive resin with dynamic covalent networks: High-strength-toughness, biocompatible, and biodegradable elastomers for DLP 3D printing

Dual-matrix bio-based resin with HUB dynamic networks solves drawbacks of traditional biophotoresins: high viscosity, poor printability, weak mechanics and non-degradability. • IPDI-PUA treated at 100 °C achieves superior mechanics: 21.4 MPa tensile strength, 811% elongation at break and 96.6 MJ/m 3 toughness. • Materials pass ISO 10993-5 cytotoxicity test; fully degrade in alkaline solution in 24 days and keep stable under oral physiological pH environment. • This resin is suitable for DLP fabrication of transparent orthodontic aligners, offering a sustainable route to biodegradable personalized medical devices. To meet the demand for sustainable additive manufacturing, this study addresses the bottlenecks of conventional bio-based photosensitive resins, including high viscosity, poor printability, weak mechanical properties, and non-degradability. Using bio-based castor oil (CO) and degradable polycaprolactone (PCL) as dual matrices, we synthesized a polyurethane acrylate (PUA) photosensitive resin containing hindered urea bonds (HUBs) dynamic covalent networks. High-strength-toughness, biocompatible, and biodegradable elastomers were fabricated via digital light processing (DLP) 3D printing and photo-thermal dual curing. A systematic comparison of three diisocyanates (HMDI, HDI, IPDI) revealed that IPDI-PUA exhibited the optimal comprehensive performance after heat treatment at 100 °C: tensile strength of 21.47 ± 0.85 MPa, elongation at break of 811.35 ± 0.21%, toughness of 96.60 ± 1.27 MJ/m 3 , and excellent thermal stability. The materials were non-cytotoxic, complying with ISO 10993-5; they degraded completely in alkaline conditions within 24 days and gradually disintegrated in soil after 150 days, while remaining structurally stable in the oral physiological environment. This system was successfully applied to DLP 3D printing of transparent orthodontic aligners, providing a new strategy for green degradable bio-based 3D printing materials in personalized medical devices. Download: Download high-res image (293KB) Download: Download full-size image