4D printing of PLA/PCL shape memory composites with controllable sequential deformation

Shape memory polymers (SMPs) are a promising class of materials for biomedical applications due to their favorable mechanical properties, fast response, and good biocompatibility. However, it is difficult to achieve controllable sequential shape change for most SMPs due to their high deformation temperature and the simplex deformation process. Herein, shape memory composites based on polylactic acid (PLA) matrix and semi-crystalline linear polymer polycaprolactone (PCL) are fabricated using 4D printing technology. Compared with pure PLA, with the rise of PCL content, the 4D-printed PLA/PCL composites show decreased glass transition temperature (T-g) from 67.2 to 55.2 degrees C. Through the precise control of the deformation condition, controllable sequential deformation with an outstanding shape memory effect can be achieved for the PLA/PCL shape memory composites. The response time of shape recovery is less than 1.2 s, and the shape fixation/recovery rates are above 92%. In order to simulate sequential petal opening and sequential drug releasing effects, a double-layer bionic flower and a drug release device, respectively, are presented by assembling PLA/PCL samples with different PLA/PCL ratios. The results indicate the potential applications of 4D-printed PLA/PCL composites in the field of bio-inspired robotics and biomedical devices.