Science Advances | Magic ink transforms 2D printing into 3D and 4D printing

UNIST Jiyun Kim of South Korea and Sunghoon Kwon of Seoul University published an article entitled “Direct 2D-to-3D transformation of pen drawings” on Science Advances.

Abstract: 2D drawing is a method that allows simple, inexpensive and intuitive two-dimensional (2D) manufacturing. In order to integrate these advantages of pen drawing into the manufacture of 3D objects, researchers have developed a technology that can directly convert the 2D precursors drawn by pens into 3D geometric shapes. When the pen is immersed in the monomer aqueous solution, the capillary peeling driven by the surface tension and the dried ink film floating can promote the 2D to 3D conversion of the pen image. The selective control of the floating and anchoring parts of the 2D precursor allows the 2D engineering drawing to be converted into the designed 3D structure. The surface-induced polymerization can then be used to fix the transformed 3D geometry through structural reinforcement. By converting simple strokes 2D structure into complex 3D structure.

Printing principle: This method is based on a shape deformation mechanism that relies on surface tension-driven selective ink peeling and dry ink film floating, which is called surface tension assisted conversion (STAT) (Figure 1C). The dry erase marker ink containing PVB resin forms a hydrophobic film after drying. When immersed in an aqueous solution, the PVB film will fall off the substrate as the solution penetrates into the interface between the film and the substrate driven by capillary force. Then, due to surface tension, the separated PVB film floats on the surface of the solution (Figure 1C). In order to extend its application to 2D to 3D conversion technology, the researchers first introduced selective peeling and floating of the film to convert the 2D drawing into a 3D structure. Since the occurrence of peeling depends on the adhesion between the film and the substrate, we developed two inks with different adhesion by controlling the ink composition. In this way, the programmable design of 2D to 3D conversion can be performed by selectively determining the floating part and the anchoring part of the figure. After the pen drawing was converted from 2D to 3D based on the water level, the 3D structure of the PVB film was fixed and further enhanced by surface catalyzed radical polymerization (SCIRP) (a polymer coating process). Even after being removed from the solution, it allows the transformed 3D object to retain its structure. As a result, the initial precursor will deform according to the water level and can be further fixed by SCIRP by using a monomer solution containing potassium persulfate (KPS) (Figure 1D).