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

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.

Graphene‐Based Polymer Bilayers with Superior Light‐Driven Properties for Remote Construction of 3D Structures

“…Folding is actually localized bending, so these terms are sometimes used interchangeably 8. So far, many stimuli‐responsive polymers have been investigated and employed to fabricate 3D structures including hydrogels,9 shape memory polymers,10 thermoresponsive polymers,11 and gradient polymeric composites 12. Moreover, the frequently used external stimuli to trigger a shape change in stimuli‐responsive polymers include solvents,13 electricity,14 pneumatic stimulus,15 mechanical stimulus,16 heat,17 and light 18.…”

Technological considerations for 4D printing: an overview

“…Other novel work includes parts that are capable of self-assembly and disassembly. For example, Wu [12] proposed a multipolymer 3D printed trestle design with four equal active composite strips connected to the center (Fig. 21).…”

“…Reversibility of the transformation has been relatively unexplored, especially for applications that require cycles of folding and unfolding, or wetting and drying. Comprehensive tests are required to 21 Design of the trestle, cross section of the composites strips, and the 3D printed part [12] fully understand the complete lifespan and the degradation of the materials. Future research will need to investigate how we can generate, store, and use passive and abundant energy sources to activate those shape memory or stimuliresponsive materials.…”

4D printing of polymeric materials for tissue and organ regeneration

“…The inks are commercially available from the 3D printing company Stratasys (Edina, MN, USA) [53–55]. By combining two model materials VeroWhite® and Tangoblack®, the so-called digital materials were created.…”

“…When the structure is subjected to a uniform temperature, temporal sequencing of activation was achieved by the time-dependent behavior of each polymer, which was illustrated via a series of 3D printed structures that respond rapidly to a thermal stimulus and self-fold to specified shapes in a controlled shape-changing sequence (Figure 5B) [53]. By integrating both material design and the shape memory digital materials, active structures were further developed [55]. Glassy shape memory polymer fibers were directly printed in an elastomeric matrix; after a programmed lamina and laminate architecture and a subsequent thermomechanical training process, the shape memory effect transformed a thin plate into complex three-dimensional configurations including bent, coiled, and twisted strips, folded shapes, and complex contoured shapes with non-uniform, spatially varying curvature [55].…”