Dehydration-triggered shape transformation of 4D printed edible gel structure affected by material property and heating mechanism

3D printed structures illustrating a post-printing programmed shape change could be defined as 4D printing. Currently, the dehydration-induced shape-change of 3D printed edible structures has never been reported. Herein, in this study, spontaneous dehydration-triggered shape-change of starch-based edible 3D printed structure was firstly introduced. The relationship between material's properties, heating mechanism and shape-change behavior were investigated. Results indicated that a certain degree of adhesion of printing materials was required to realize the programmed shape-change of printed samples. The bending degree is proportional to the water evaporation amount and shrinkage ratio, but inversely proportional to the dielectric constant loss factor (epsilon ''). The rapid dehydration rate and internal heating model of dielectric microwave dehydration (MD) were not conducive to bend the samples. While, during air dehydration (AD), the greater shrinkage ratio and the "bending accumulation effect" caused by from surface to inward dehydration mechanism were beneficial to improve the bending degree of samples. Next, effects of infill structures on shape-change were then investigated to create complex structures (like butterfly). The knowledge obtained may provide a universal applicable information on the production of dehydration-triggered shape transformable 3D printed foods.