Direct Ink Writing Based 4D Printing of Materials and Their Applications

Abstract

4D printing has attracted academic interest in the recent years because it endows static printed structures with dynamic properties with the change of time. The shapes, functionalities, or properties of the 4D printed objects could alter under various stimuli such as heat, light, electric, and magnetic field. Briefly, 4D printing is the development of 3D printing with the fourth dimension of time. Among the fabrication techniques that have been employed for 4D printing, the direct ink writing technique shows superiority due to its open source for various types of materials. Herein, the state‐of‐the‐art achievements about the topic of 4D printing through direct ink writing are summarized. The types of materials, printing strategies, actuated methods, and their potential applications are discussed in detail. To date, most efforts have been devoted to shape‐shifting materials, including shape memory polymers, hydrogels, and liquid crystal elastomers, showing great prospects in areas ranging from the biomedical field to robotics. Finally, the current challenges and outlook toward 4D printing based on direct ink writing are also pointed out to leave open a significant space for future innovation.

4D Printing: A Review on Recent Progresses

“…In this way, the ink experiences a quick transition from liquid to solid state, and the desired filament structure is obtained. Zolfagharian et al 4D printed photoresponsive structures consisted of shape memory polystyrene, chitosan, and carbon black [ 53 ]. Polystyrene was firstly printed above Tg and cooled into the shape below Tg ( Tg ≈ 102 °C).…”

Four-Dimensional (Bio-)printing: A Review on Stimuli-Responsive Mechanisms and Their Biomedical Suitability

“…The concept of 4D printing is relatively young, becoming very fashionable for numerous engineering applications, including structural, aerospace, and biomedical, namely, in those applications where the microenvironment changes play a fundamental role in the material function [181][182][183][184][185][186]. 4D (bio-)printing, despite a full consensus on the exact definition, has the potential to physically replicate the path of developmental biology and bring organ printing a step closer to reality, thus combining life sciences with engineering in a dynamic fashion.…”

Fused Filament Fabrication-4D-Printed Shape Memory Polymers: A Review

“…[ 20 , 21 , 22 , 23 , 24 ]. However, in addition to the high temperature required to melt the raw filaments that can have a detrimental effect on the mechanical properties of the parent material [ 25 ], its intrinsic accuracy and surface finish limit its applications in many respects [ 26 ]. In response to these drawbacks, the DIW technique has advantages due to the free choice of materials, small amount of raw material, open code, low cost, viability for multi-material printing, and construction of complex shape/structures without additional masks or dies [ 25 , 26 ].…”

“…In this context, while the shear-thinning performance facilitates the extrusion of the ink, when under pressure in the nozzle, it should have a high shear elastic modulus and shear yield strength outside the nozzle due to the abrupt decrease in shear force [ 26 , 27 ]. Photopolymerization is another group in which the stereolithography (SLA) and digital light processing (DLP) are the most important techniques [ 21 , 25 , 28 , 29 ]. The main advantages are associated with a fast printing speed and excellent print resolution, although they are limited only to photocurable resins and confined essentially to heat stimulus [ 25 , 29 , 30 ].…”

“…Photopolymerization is another group in which the stereolithography (SLA) and digital light processing (DLP) are the most important techniques [ 21 , 25 , 28 , 29 ]. The main advantages are associated with a fast printing speed and excellent print resolution, although they are limited only to photocurable resins and confined essentially to heat stimulus [ 25 , 29 , 30 ]. Finally, the material jetting, also known as photopolymer inkjet printing or multi-jet modelling, is a liquid-based printing method that uses multiple materials to produce a component [ 31 ].…”