Shape memory polymers (SMPs) represent an innovative class of materials that possess programmed, reversible shape-changing capabilities in response to external stimuli. The recent emergence of SMPs’ advanced manufacturing, specifically 4D printing, has created exceptional opportunities for use in biomedical engineering. This review presents a critical synthesis of the latest advances in the chemistry, biomedical applications, manufacturing strategies, and clinical translation of SMPs, highlighting vat photopolymerization techniques, such as stereolithography (SLA) and digital light processing (DLP). Notably, 4D-printed SMPs can promote spatiotemporally controlled architectures, and applications include minimally invasive implants, dynamic tissue scaffolds, and multifunctional drug delivery. This paper focuses on recent advances in resin design, multi-responsive and nanocomposite resins, AI-guided material discovery, and emerging biocompatible and biodegradable formulations, while outlining current roadblocks to clinical implementation, including cytotoxicity, sterilization, regulatory compliance, and device shelf-life. Our goal is to elucidate the relationship between material design, processing, and biomedical performance to inform researchers of potential future directions for 4D-printed SMPs and next-generation, patient-centered medical devices.

The push for sustainability in all facets of manufacturing has led to an increased interest in biomass as an alternative to non-renewable materials. Hemp bast fiber mats were produced from a bacterial retting process, named BFM, as the fiber reinforcement. The objective of this study was to evaluate the feasibility of laminating BFM with polylactic acid (PLA) for a composite panel product. Since both BFM and PLA are biodegradable, the resulting BFM-PLA composites will be 100% biodegradable. PLA pallets were processed into thin polymer sheets which served as the matrix. The BFM and PLA plates were laminated in five layers and compression-molded into composite panels. Experiments were conducted on the three BFM-to-PLA ratios (35/65, 45/55, and 50/50). Mechanical properties (tensile and bending properties) and physical properties (thickness swell and water absorption) were tested and compared to the currently commercial sheet molding compound (SMC) from fiber glass. The thermal behavior of the BFM/PLA composites was characterized using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The developed BFM/PLA composite product is a sustainable alternative to existing synthetical fiber-reinforced polymer (FRP) that is biodegradable in landfill at the end of life.

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 (T_g) following PBS immersion. Specifically, the T_g 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 T_g 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 T_g 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.