4D Printed Multifunctional Composites with Cooling‐Rate Mediated Tunable Shape Morphing

Abstract

Multifunctional composites can accomplish multiple tasks such as shape morphing, sensing, and load bearing using a single structure. Smart materials including liquid crystal elastomers (LCE) and shape memory polymers (SMP) have long been used as the primary components of multifunctional composites because of their shape and property changes in response to external stimuli. However, LCEs can generate rapid and reversible shape changes but are soft and require a constant temperature to retain their deformed shape; SMPs have favorable mechanical properties but few can achieve reversible actuations. Moreover, both LCEs and SMPs have limited capability for tunable shape morphing. Multi‐material 3D printing of smart materials, also known as 4D printing, has seen significant advances enabling the fabrication of composites with novel functionality. In this work, 4D printing is leveraged to create an LCE‐SMP composite that can achieve not only rapid and reversible shape changes, but also cooling‐rate regulated tunable shape morphing. The latter is achieved by harnessing the distinct time‐dependent thermomechanical properties of LCEs and SMPs. Furthermore, the composite has a high stiffness at low temperature to support heavy loads. The LCE‐SMP composite hence offers a novel approach to achieve tunable shape morphing for future engineering applications.

Recent Advances in 4D Printing of Liquid Crystal Elastomers

“…Typically, chain‐extension reactions include aza‐Michael addition of diacrylate RMs with primary amines and thiol‐Michael addition of stoichiometrically excess diacrylate RMs with thiols. [ 52,67,71–73,92 ]…”

“…[ 141 ] c) SMP–LCE metamaterial with a tunable final shape and mechanical properties depending on the unique cooling profiles. [ 73 ] d) Mechanical properties of monodomain LCEs: (i) quasi‐static compression test, (ii) drop test, (iii) impact‐rate compression test, and (iv) anisotropy‐controlled buckling. [ 160 ] a,d) Reproduced with permission.…”

Computational design for 4D printing of topology optimized multi-material active composites

“…The emergence of increasingly ground-breaking scientific advancement of the additive manufacturing sector over the past decades as well as cutting-edge discoveries in the domain of active materials have birthed a novel class of (meta)material(s): active composites. As its name suggests, active composites consist of at least two different materials, one, if not both 1 , comprising of a smart material and another passive or inert material. Smart materials are an umbrella term that englobes a variety of materials that can be subjected to transformations in shape as well as other properties such as stiffness, state (of matter), color, etc., with a specific actuation.…”

Sustainable Approach for the Synthesis of a Semicrystalline Polymer with a Reversible Shape-Memory Effect

“…Additionally, there may be challenges arising due to the uneven light penetration depending on the light source and material thickness. This process can also be difficult to apply on bulky complex origami. , We further noted that 3D printing techniques could provide a complicated permanent shape for SMP. − However, the printing precursors must fulfill specific requirements such as viscosity, higher curing rates, and the need to cure under a safe light radiation zone, which can limit the selection of sustainable materials …”