4D printing of polymeric materials for tissue and organ regeneration

Abstract

Four dimensional (4D) printing is an emerging technology with great capacity for fabricating complex, stimuli-responsive 3D structures, providing great potential for tissue and organ engineering applications. Although the 4D concept was first highlighted in 2013, extensive research has rapidly developed, along with more-in-depth understanding and assertions regarding the definition of 4D. In this review, we begin by establishing the criteria of 4D printing, followed by an extensive summary of state-of-the-art technological advances in the field. Both transformation-preprogrammed 4D printing and 4D printing of shape memory polymers are intensively surveyed. Afterwards we will explore and discuss the applications of 4D printing in tissue and organ regeneration, such as developing synthetic tissues and implantable scaffolds, as well as future perspectives and conclusions.

4D Self‐Morphing Culture Substrate for Modulating Cell Differentiation

“…The shape memory effect provides a programmed control over both dynamic topography and dynamic internal stress, which is released automatically from the polymer as the object is transformed between different geometrical structures. [ 22 ] The incorporation of topographical features and mechanical force to form a dynamic microenvironment may be the most effective approach to precisely guide stem cell differentiation toward the desired cell lineage. Figure a shows a typical shape change process of thermoset SMPs.…”

“…4D fabrication is a highly innovative, next generational additive manufacturing process which can be used to fabricate predesigned self‐assembly structures with a time‐dependent dynamic shape change. [ 22,23 ] Within the diverse 4D mechanisms, shape memory polymers (SMPs) have attracted particular attention owing to their reversible “temporary‐permanent” thermomechanical reprogramming characteristics. [ 24,25 ] Based on our previous experience in 4D fabrication, [ 24,26,27 ] it was expected that the addition of the 4th dimension (time) would benefit the field of neural tissue engineering.…”

Advances in 4D Printing: Materials and Applications

“…Using the microplates without the flexible joint, hollow microstructures such as a cube can be self‐folded (Figure c). 3D printing of porous bioscaffolds shows tremendous potentials for soft tissue reconstruction . Kang et al reported an integrated tissue–organ printer (ITOP) that can fabricate stable, human‐scale tissue constructs of any shape.…”

“…In addition, novel molecular designs, such as double network, can be adopted to achieve robust mechanical properties . Specific to tissue and organ regeneration applications, biocompatible, biodegradable, and physiological environment adaptive hydrogels or other soft materials could be the focus for 4D bioprinting processes . LCE is also a promising material due to its reversible shape‐changing capability.…”

“…In this sense, 4D printing has greatly accelerated the smart material and structure research. There are various review papers of 4D printing with different focuses . In this paper, we review the major advances in 4D printing of polymeric materials from the materials standpoint and their potential applications.…”