4D printing of bio-composite tailored for NIR-light responsivity using liquid crystal display technique and its recovery modeling using central composite design

• Bio-photopolymer resin (BPR) has been tailored to print 4D light-responsive material • 5% blend of bio-benzoxazine (BBZ) in BPR gives LCD 3D prints without thermal cracks • 1% polypyrrole (PPy) powder in BPR gives homogenous LCD 3D prints • 95%BPR, 5%BBZ, and 1%PPy of 3D printer resin used formed homogenous formulation • Robust and 4D NIR-light responsive bio-composite achieved without additional diluents This study demonstrated the development of a cleaner, renewable, and sustainable 4D bio-composite that is robust and near-infrared (NIR)-light responsive with bio-photopolymer resin (BPR), bio-based benzoxazine (BBZ) monomer, and polypyrrole (PPy) powder blends used in the liquid crystal display (LCD) technique of 3D printing. BBZ monomer was synthesized from the abundant cardanol and blended with a poly lactic acid (PLA) based BPR to improve flexibility, and the PPy was added to impact photothermal capacity in the resulting composite. Smoothed surfaced and well-cured composite samples were obtained, and the effects of NIR-light intensity, PPy amount, and thickness of the composite against the shape recovery time of the composite was optimized and defined by a model obtained using a central composite design (CCD). Interestingly, the optimized composite sample has exhibited excellent shape fixity and recovery ratios, and recovery time of 98±2%, 94±3%, and 90±2 seconds, respectively at a very low NIR-light intensity of 40 mW/cm 2 , and PPy amount of 0.3 wt.% of the total resin used in the 3D printer. Additionally, good mechanical properties were also achieved, for instance, flexural stress, modulus, and strain of: 47.4±1.7 MPa, 1.37±0.1 GPa, and 5.08±0.2% were recorded. While tensile stress, modulus, and strain of: 43.5±0.5 MPa, 1.16±0.1GPa, and 4.1±0.3% were also recorded. Thus, a robust and NIR-light responsive 4D bio-composite has been achieved without using additional diluents and photoiniators, suggesting that this study has provided solution to the challenge of low biomass content and mechanical strength peculiar to bio-based photosensitive resins.