Pattern Transformation of Heat-Shrinkable Polymer by Three-Dimensional (3D) Printing Technique

Abstract

A significant challenge in conventional heat-shrinkable polymers is to produce controllable microstructures. Here we report that the polymer material fabricated by three-dimensional (3D) printing technique has a heat-shrinkable property, whose initial microstructure can undergo a spontaneous pattern transformation under heating. The underlying mechanism is revealed by evaluating internal strain of the printed polymer from its fabricating process. It is shown that a uniform internal strain is stored in the polymer during the printing process and can be released when heated above its glass transition temperature. Furthermore, the internal strain can be used to trigger the pattern transformation of the heat-shrinkable polymer in a controllable way. Our work provides insightful ideas to understand a novel mechanism on the heat-shrinkable effect of printed material, but also to present a simple approach to fabricate heat-shrinkable polymer with a controllable thermo-structural response.

4D printing of polymeric materials for tissue and organ regeneration

“…The internal strain/stress during FDM 3D printing has been used to induce patterned transformation(s) [80]. During FDM printing, PLA filaments were maintained in a high temperature furnace and then extruded through a nozzle.…”

“…Release of the internal stress/strain is achieved by heating the printed architecture above the T g which triggers shrinkage, or pattern transformation. Figure 6A illustrates the transforming process from a ring structure into quadrangles [80]. The shrinkage of printed structures at high temperature is an unwanted effect of FDM, but predesigned structures can be achieved by applying this internal stress/strain to drive a controlled dynamic process.…”

“…(C) Schematic image of the cell origami: the cells are cultured on micro-fabricated parylene microplates which are self-folded by CTF. Adapted with permission from [24, 80, 95]. …”

Multistable Thermal Actuators Via Multimaterial 4D Printing

“…[10][11][12][13][14][15][16] An SMP can have arbitrary temporary shapes and return to a memorized, permanent shape again upon a proper external stimulus (usually heat or light). In 4D printing, components created by 3D printing can be transformed in shape to realize active structures in reaction to environmental stimuli such as heat, moisture, light, or pH value.…”

Phase-transforming and switchable metamaterials

“…Examples of phase transitions at the meso-and macroscale include colloidal suspensions [13,14] , 2D arrays of polymeric spheres [15] , heat-shrinkable polymer patterns [16] , meso-scale silicon rods embedded in a hydrogel [17][18][19] , and slabs of elastomer with an array of holes [20][21][22][23] . In broad terms, an emerging opportunity in materials science and engineering is to create phase-transforming materials by integrating materials-elastomers, liquids, metals, and even open spaces and voids filled with gas or liquids-through geometry and mechanics, at meso-or macro-scale.…”