Computational modeling-enhanced photo-DSC for rapidly developing 4D printable body temperature-responsive self-healing and shape-memory photopolymers

Abstract Four-dimensional (4D) printing is a cutting-edge technology with vast potential in the fourth industrial revolution, enabling digitally designed structures that respond dynamically to external stimuli. However, optimizing printing parameters, such as exposure time in vat photopolymerization (VP), while preserving dynamic material responsiveness, poses a significant challenge. This study integrates photo-differential scanning calorimetry (Photo-DSC) and computational modeling (CM) to optimize the printing parameters of a stearyl methacrylate (SMA)-based resin containing 2-hydroxyethyl methacrylate (HEMA) or 2-hydroxyethyl acrylate. Photo-DSC was utilized to investigate the effect of diverse parameters on photopolymerization speed, while the CM built using response surface methodology predicted curing speed based on resin composition. The model demonstrated a level of confidence exceeding 95%, and it provided a regression equation for estimating photo-curing speed. This information is then used to ascertain the requisite normal and bottom exposure times for VP. A case study was conducted using a 70/30 SMA/HEMA resin, which exhibited optimal printability with a normal exposure time of 21 s. The printed material demonstrated excellent healing efficiency with maximum tensile strength and tensile strain recovery of 94% and 97%, respectively. Additionally, it shows exceptional shape-memory behavior, with shape fixity and recovery ratios surpassing 95%, as well as rapid actuation at body temperature within 45 s. To further illustrate the application of this photopolymer in biomedical and personalized therapeutic devices, a wearable wrist brace was printed and activated successfully above 37 °C. Overall, this study underscores the efficacy of integrating CM with photo-DSC in reducing the development time and resources required for creating advanced 4D printing photopolymer resins.