Light‐Coded Digital Crystallinity Patterns Toward Bioinspired 4D Transformation of Shape‐Memory Polymers

Abstract

Spatially heterogeneous distribution of active components is key to the diverse shape-morphing behaviors of biological species and their associated functions. Artificial morphing materials employing similar strategies have widened the design space for advanced functional devices. Typically, the spatial heterogeneity is introduced during the material synthesis/fabrication step and cannot be altered afterward. An approach that allows spatio-selective programming of crystallinity in a shape-memory polymer (SMP) by a digital photothermal effect is reported. The light-patternable crystallinity affects greatly the shape morphing behavior. Consequently, a pre-stretched 2D film with spatial heterogeneity in crystallinity can morph with time into designable 3D permanent shapes, achieving the 4D transformation. This approach utilizes a reprocessible thermoplastic SMP (polylactide) and the programming relies on a physical phase transformation (crystallization) instead of chemical heterogeneity. This allows repeated erasing and reprogramming using the same material, suggesting a versatile and sustainable means for manufacturing advanced morphing devices.

Development of Thermoinks for 4D Direct Printing of Temperature‐Induced Self‐Rolling Hydrogel Actuators

“…[ 4 ] 4D printing, on the other hand, is a term that refers to the combination of 3D printing with new classes of shape memory materials (SMMs) to fabricate time‐dependent objects that can be switched between various configurations under external stimuli, e.g., temperature, electric field, moisture, or light. [ 5–8 ] Natural phenomena and biological systems with shape transformation behavior inspire scientists and engineers all over the world to create artificial patterns and designs for 4D printing from various SMMs. [ 9–11 ] Among SMMs, stimuli‐responsive hydrogels capable of shape‐changing have gained particular attention because of their biocompatibility and ability to mimic functions of extracellular matrices.…”

Future of additive manufacturing: Overview of 4D and 3D printed smart and advanced materials and their applications

“…SMPs can be easily tuned to their environments/applications by controlling the crystalline content of the polymer, which can be used to programme transition temperatures such as the Tg and Tm. [57] [58]…”

Shape Memory Polyurethane as a Drilling Fluid Lost Circulation Material

“…These polymers are set in temporary shape, and when triggered by an external stimulus such as heat, pH, light, electric field, water and magnetic field recovered their original shape. [24][25][26][27][28] For example, thermo-responsive SMP effectively plugged fractures once triggered by formation temperature (≈70 °C). [29][30][31][32] In another study, a thermoset SMP mixed with fibers having wide size distribution increased the fracture plugging efficiency significantly.…”