Translating Plasticization-Responsive Shape Memory Polymers from Conventional Casting to High-Resolution Stereolithography for Custom Biomedical Devices

Shape memory polymers (SMPs) capable of plasticization-induced shape recovery offer unique opportunities for implantable biomedical devices, but translating these materials from conventional casting to high-resolution stereolithography (SLA) remains a critical challenge. This study develops and evaluates thiol–ene SMP formulations for SLA printing and compares their performance with conventionally cast counterparts to enable rapid fabrication of customizable implantable devices. Resin formulations based on TATATO and TMTMP were optimized using the photoinitiator TPO and printing additives (Pyrogallol and Sudan I) for SLA fabrication, while cast formulations were prepared without additives. Comprehensive characterization included FTIR to quantify thiol conversion, rheological analysis to assess printability, and dynamic mechanical analysis (DMA) under dry and physiological (PBS) conditions to monitor thermomechanical properties. The printed networks exhibited water-induced plasticization, as evidenced by a reduction in glass transition temperature (Tg) following PBS immersion. Specifically, the Tg of the cast networks decreased from 31 to 35 °C in the dry state to 21–26 °C following hydration, whereas the SLA-printed networks exhibited lower initial Tg values of 17–23 °C, which further decreased to 10–15 °C upon hydration. These results demonstrate that water-responsive thermomechanical behavior was retained following translation to SLA printing, although the reduced dry-state Tg of the printed formulations indicates a need for further optimization for applications requiring temporary shape stability at room temperature. Mechanical testing demonstrated that while cast networks exhibited a dry modulus of approximately 1.2 GPa, the SLA-printed formulations displayed a dry modulus of 80–125 MPa. Following physiological hydration, all formulations underwent significant plasticization, with the modulus uniformly decreasing to 5–15 MPa while maintaining excellent dimensional stability and minimal swelling (<1.9%). Both cast and printed materials exhibited excellent shape memory performance, achieving recovery ratios of approximately 98–100%, while SLA-printed devices demonstrated rapid water-triggered actuation within 1.29–1.75 s. Furthermore, the SLA-printed thiol-ene polymers were non-cytotoxic and biocompatible, combining high-resolution manufacturability with robust shape memory performance and rapid plasticization-induced shape recovery. These findings demonstrate the feasibility of translating thiol-ene SMPs from conventional fabrication to SLA-based additive manufacturing, establishing a foundation for further material optimization toward customizable, patient-specific biomedical devices.