4D Printing: A Review on Recent Progresses

Abstract

Since the late 1980s, additive manufacturing (AM), commonly known as three-dimensional (3D) printing, has been gradually popularized. However, the microstructures fabricated using 3D printing is static. To overcome this challenge, four-dimensional (4D) printing which defined as fabricating a complex spontaneous structure that changes with time respond in an intended manner to external stimuli. 4D printing originates in 3D printing, but beyond 3D printing. Although 4D printing is mainly based on 3D printing and become an branch of additive manufacturing, the fabricated objects are no longer static and can be transformed into complex structures by changing the size, shape, property and functionality under external stimuli, which makes 3D printing alive. Herein, recent major progresses in 4D printing are reviewed, including AM technologies for 4D printing, stimulation method, materials and applications. In addition, the current challenges and future prospects of 4D printing were highlighted.

Polylactic Acid (PLA) Biocomposite: Processing, Additive Manufacturing and Advanced Applications

“…The self-transformation of the structure is also called self-assembly as the structure can be designed to assemble itself. The concept of 4D printing is a smart structure that consists of rigid materials connected with expandable elements, or it can also be a whole structure made from expandable materials depending on what materials properties are needed and what are the applications [170,171]. The expandable elements can change their shape when exposed to certain stimuli, and this causes the hard parts to move or rotate, resulting in the whole structure transformation.…”

Recent Advances in bis-Chalcone-Based Photoinitiators of Polymerization: From Mechanistic Investigations to Applications

“…Indeed, hydration and dehydration of the hydrophilic PEG polymer can be advantageously used for shape modification. More precisely, 4D printing consists of elaborating an object of precise thickness and shape that can be modified subsequent to the polymerization process by means of an external stimulus such as heat [225][226][227][228], light [229], water [230][231][232], or other stimuli. Thus, after printing a cross with a high spatial resolution via 3D printing using the three-component chalcone/Iod/EDB (1.5%/1.5%/1.5%, w/w/w) photoinitiating systems based on chalcones C60 and C64, swelling and thermally induced dehydration resulted in significant modification of the shapes of the crosses.…”

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.…”