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. 2016 Apr 13:6:24224.
doi: 10.1038/srep24224.

Multi-shape active composites by 3D printing of digital shape memory polymers

Jiangtao Wu  1 , Chao Yuan  2 , Zhen Ding  3 , Michael Isakov  1 , Yiqi Mao  1 , Tiejun Wang  2 , Martin L Dunn  3 , H Jerry Qi  1
Affiliations

Multi-shape active composites by 3D printing of digital shape memory polymers

Jiangtao Wu et al. Sci Rep. .

Abstract

Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers - digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications.

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Figures

Figure 1
Figure 1. Schematics of the printed SMP composite design.
(a) The design of the two layer SMP composite strips and (b) the characterization of the design. The purple color represents the fiber with higher Tg and the green color represents the fiber with lower Tg. (c) The typical programming steps for SMPs and desired response.
Figure 2
Figure 2. Multi-shape memory effects of a printed active composite strip.
(a) The design and dimensions of the sample. The enlarged drawing is the cross section of the structure. (b) The original printed sample. The length scale in the bottom is in mm. (c–f) Shape change of the sample at different temperature.
Figure 3
Figure 3. Bending actuation of the printed active composite strip during the recovery process.
(a–f) Snapshots of the sample bending at different times. All six images are the side view of the sample. (g) Variation of the bending curvature during the recovery process.
Figure 4
Figure 4. Comparison of the curvatures between experiments and theoretical model.
(a) Bending curvature of the SMP composite vs heating time. (b) Effects of the programming strain and (c) the volume fraction of fibers on the initial and maximum curvature.
Figure 5
Figure 5. Self-assembling and disassembling trestle.
(a) The design of the trestle. (b) The cross section of the composites strip. (c) The shape of the structure after programming. (d–g) The deformation behavior of the structure in the recovery process.
Figure 6
Figure 6. Active helix shape.
(a) The details of the design. (b–e) The deformation behavior of the active helix in the recovery process.
Figure 7
Figure 7. Active “wave” shape.
(a) The design of the structure. The positions of fibers are exchanged in two segments. The figure is used for describing the design method, not to scale. (b–e) The deformation behavior of the active “wave” shape when heated to a temperature of 70 °C.
Figure 8
Figure 8. Mimicking an insect.
(a) The design of the structure. The figure is used for describing the design method. Not to scale. (b,c) The deformation behavior of the active insect when put in the hot water with temperature of 30 °C. (d) Rotated view of the structure in hot water. (e) Recovered shape in 60 °C water.
Figure 9
Figure 9. Smart hook.
(a)The programmed hook. (b,c)The bending deformation of the structure under hot water with temperature of 30 °C. (d,e) A small box is lifted up from water. (f-h)Releasing the small box into another container. The water in the container is in 70 °C.
Figure 10
Figure 10. Dynamic mechanical analysis (DMA) test results of the SMP materials.
(a) Tan δ and (b) storage modulus for three printed materials.
See this image and copyright information in PMC

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