3D printing with stimuli-responsive materials is called 4D printing. 4D printing enables 3D printed structures to change its configurations over time and is used in a wide variety of fields such as soft robotics, flexible electronics, and medical devices. The development of a water-responsive cholesteric liquid crystal ink and the accompanying direct ink writing (DIW) procedure is extending 4D printing to structurally colored inks. This is the first demonstration of a humidity-responsive ...