Direct 2D-to-3D transformation of pen drawings

Abstract

Pen drawing is a method that allows simple, inexpensive, and intuitive two-dimensional (2D) fabrication. To integrate such advantages of pen drawing in fabricating 3D objects, we developed a 3D fabrication technology that can directly transform pen-drawn 2D precursors into 3D geometries. 2D-to-3D transformation of pen drawings is facilitated by surface tension-driven capillary peeling and floating of dried ink film when the drawing is dipped into an aqueous monomer solution. Selective control of the floating and anchoring parts of a 2D precursor allowed the 2D drawing to transform into the designed 3D structure. The transformed 3D geometry can then be fixed by structural reinforcement using surface-initiated polymerization. By transforming simple pen-drawn 2D structures into complex 3D structures, our approach enables freestyle rapid prototyping via pen drawing, as well as mass production of 3D objects via roll-to-roll processing.

Fig. 1. Pen-based 4D printing enables simple transformation of 2D pen drawings into 3D structures.

(A) Conceptual illustration of pen-based 4D printing. Pen-based 4D printing enables simple and intuitive 3D fabrication via 2D-to-3D transformation of 2D pen drawings. (B) Pen-based 4D printing process. A pen is used to generate a hydrophobic thin film after the ink dries. This 2D pen drawing transforms into a 3D structure via STAT when immersed in a monomer solution. The transformed 3D shape is fixed via SCIRP during a 3-min incubation period in the monomer solution. (C) STAT and SCIRP mechanisms. The type of ink applied determines whether a specific part of the structure floats or is anchored. A polymer coating layer is generated around the 3D structure of the dried ink film to strengthen its architecture. (D) Sequential view of the 2D-to-3D transformation depending on water level. The 3D structure can be further fixed by SCIRP using a monomer solution including KPS ions (right). Scale bars: 5 mm. Photo credit: Seo Woo Song, Sumin Lee, and Junwon Kang; Seoul National University.

Fig. 2. 2D pen drawings can be transformed into complex 3D structures depending on water level height.

(A) Compositions of the floating and anchoring inks. The presence or absence of surfactant determines the floating properties of the PVB film. (B) Fracture strain of the PVB film depending on the proportions of PVB and plasticizer in the ink (see also figs. S4 and S5). Error bars represent SD. (C) Pen drawing combined with an automatic printing system for precise drawing and mass production. (D) Sequential transformations at different water level heights as compared with simulated transformation results. (E and F) Scalability of pen-based 4D printing. (E) Millimeter scale (see also fig. S13). (F) Meter scale (see also fig. S14). Scale bars: 5 cm (C) and 2 cm (D). Photo credit: Seo Woo Song and Sumin Lee, Seoul National University; Jun Kyu Choe, Ulsan National Institute of Science and Technology.

Fig. 3. Structural strengthening of transformed 3D shapes via SCIRP.

(A) Schematic of the SCIRP mechanism. A pen-drawn precursor transforms into a 3D structure after submersion in a monomer solution. Subsequently, iron microparticles embedded in the PVB film induce local polymerization surrounding the PVB film. (B) Stiffness enhancement via polymer coating. Forty weight % of iron microparticles and 3-min incubation time were used. Stiffness of the structure increases 1000-fold after polymer coating as compared with the uncoated PVB film. (C) Dependence of the coating thickness on the iron microparticle concentration in the ink as well as on incubation time. Error bars represent SD. (D) Distinct 3D structures formed from the same precursor design using different solution depths. (E) Various 3D structures fabricated via pen-based 4D printing. Inset images show the initial precursor designs. Red and black areas were drawn by floating ink and anchoring ink, respectively. Shaded area represents sacrificial layer. Scale bars: 0.5 cm [(A), (D), and large images of (E)], 300 μm (B), and 1 cm [small images of (E)]. Photo credit: Seo Woo Song and Sumin Lee, Seoul National University.

Fig. 4. Pen-based 4D printing enables “3D printing anywhere” and R2R 3D fabrication.

(A) Pen-based 4D printing on various substrates. A pen-based approach allows the fabrication of 3D structures even on curved surfaces. (B) Demonstration of an “impossible bottle” construction. Drawing on the flexible PDMS film enables on-site reconfiguration of a 3D architecture inside a narrow space that would be inaccessible to conventional 3D printers. (C) R2R pen-based 4D printing for rapid prototyping and mass production. Quantitative analysis of the products made by R2R fabrication is presented in fig. S24. Scale bars: 2 cm. Photo credit: Seo Woo Song and Sumin Lee, Seoul National University.