New technique turns 2D patterns into 3D objects using only light

The novel process involves taking a pre-stressed plastic sheet and running it through a conventional inkjet printer to print bold black lines on it. The material is then cut into a desired pattern and placed under an infrared light, such as a heat lamp. Because the bold black lines absorb more energy than the rest of the material, the plastic contracts – creating a hinge that folds the sheets into 3D shapes. "This is a novel application of existing materials, and has potential for rapid, high volume manufacturing processes or packaging applications," said Dr Michael Dickey, an assistant professor of chemical and biomolecular engineering at NC State. Dr Dickey and his team have used the method to create a variety of objects, such as cubes and pyramids, without ever having to physically touch the material they are dealing with. More complex structures have also been created by varying the width of the black lines and patterning them on either side of the material, which causes the hinges to fold in different directions. The researchers found that in order for the materials to fold, the surface temperature of the hinge had to exceed that of the glass transition of the material. They also found that the heat had to be localised to the hinge in order to have fast and effective folding. "This finding stems from work we were doing on shape memory polymers, in part to satisfy our own curiosity. As it turns out, it works incredibly well," Dickey concluded.