Fig. 4: The effects of distribution of bi-material on the out-of-plane deformation of 4D printed disks.

The peripheral edge of the PLA disks was printed from a softer material (i.e., TPU) and its size was varied. Such designs resulted in diverse types of shape transformations depending on the size of the region printed from the soft phase (a–left). This multi-material design approach also altered the local mean and Gaussian curvatures of the shape-transformed specimens (a–right). Swapping the printing order of the soft and hard polymers such that the soft TPU was printed at the center of the disk completely changed the overall shape transformation of the disks (b–left) as well as the local curvature values (b–right) as compared to the case where the core of the disk was printed from the hard material. The first and last deposited layers are denoted as F.D.L and L.D.L, respectively.