4D printing of ceramic structures

Four-dimensional (4D) printing allows a controllable shape-morphing of 3D printing and enables numerous possibilities of complex shapes design. However, 4D printings are generally studied with soft materials which are easy to deform. Ceramics are intrinsically hard and brittle which hinders their development in 4D printing. In this study, through utilizing stress mismatch of printed ceramic in sintering, 4D printing of ceramic structures is realized. Generally, shrinkage of a 3D printed ceramic body after sintering is in inverse proportion to the solid content of ceramic ink used. By printing bilayer zirconia (ZrO2) ceramic with high solid content in the bottom layer and low solid content in the top layer, the shrinkage mismatch after sintering results in shape-changing from a flat plane to a curved structure. We also find that we can tailor the shape-morphing behaviors of ceramic structures by routing the printing process. Finally, through programming the solid content of ceramic inks and printing paths, 4D-printed ceramic flowers with various characteristics are achieved.