Photo-thermal staged-responsive shape memory polymers prepared by fused granular fabrication 4D printing

4D printing technology is advantageous for developing new shape memory effects and new functionalities. Herein, a new kind of photo-thermal staged-responsive shape memory polymers (SMP) were prepared by fused granular fabrication (FGF) 4D printing technology. The integration of azobenzene-containing oligomer with the commercialized thermal-responsive SMP pellets resulted in PEC-Bisdi with good compatibility and higher thermal stability, suitable for FGF 4D printing. The pellets made from the composite can also be used directly in the FGF printing technology. The resulting FGF-printed SME specimens illustrated excellent photo-thermal staged responses with UV-responsive bending, thermal-responsive shape recovery, and good fixation at room temperature. The FGF-printed specimens also displayed good mechanical properties with up to 380% elongation at break and 1.5GPa glassy storage modulus. The influences of material factors and printing parameters were systematically investigated and the results showed an increase in the curvature of the spline as a function of Bisdi content and elongation, while a decrease was recorded as a function of the spline thickness. The optimal printing parameters for the highest curvature were determined as 140 extrusion rate, 230℃ extrusion temperature, 80 routing rate, and parallel infill pattern. Overall, the proposed PEC-Bisdi composites showing programmable and remotely controllable shape memory capabilities have the potential for use in advanced engineering and soft robotics.