Investigation on simultaneous change of deformation, color and aroma of 4D printed starch-based pastes from fruit and vegetable as induced by microwave.

Conventional 3D printing exhibits serious limitation for it requires a support layer upon which more layers can be formed. A designed structure that lacks such a layer is therefore very difficult, if not impossible, to be printed. A novel means to allow 4D deformation of simple 3D-printed object into complex suspended structure is therefore proposed; microwave irradiation was used to induce the desired directed deformation. In this study, yellow flesh peach-buckwheat paste was used to study the effects of model structure and microwave power on directed 4D deformation behavior. Then, finite-element based simulation was conducted to investigate interactions between the printed object and microwave irradiation. Experiments and simulations showed that local high temperature generated by microwave (200 W) caused directional micro puffing at resulting hot spots, forming a driving force to allow 3D-printed objects to rapidly undergo 4D deformation (within 90 s). The verification test also proved that puffing was the main factor driving 4D deformation. This strategy could combine with color and flavor changing microcapsules to realize the synchronous 4D printing process of deformation, color changing, and aroma changing within 15 s, induced by a household microwave oven (700 W). The purpose of this study is to provide a new 4D printing method interacting with consumers in a short time, which could be applied to children's food.