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Since the advent of 3D printing technology, a significant effort has been made to develop new 3D printable materials. Despite the recent progress in the field of 3D printing, the limited availability of photoactive resins has motivated continuous research endeavors to develop novel photoresins with multifunctional capabilities. Herein a biobased photoresin derived is reported from modified olive oil, designed for high‐resolution solvent‐free 4D printing with multifunctional capabilities. The physicochemical properties of the printed polymers are fine‐tuned using acrylic acid as a diluent cum comonomer. The mechanical properties of the printed polymers are similar to various soft tissues, such as ligaments, articular cartilage, and soft collagenous bone, showcasing its potential for soft tissue engineering applications. While the excellent temperature‐responsive shape memory 4D attributes coupled with exceptional antimicrobial properties toward gram‐negative and gram‐positive bacteria highlight the multifunctional nature of the printed polymers. Moreover, the printed polymers exhibited outstanding hemocompatibility and good cytocompatibility toward mouse fibroblast cells, suggesting their potential soft tissue engineering applications. In sum, the newly developed biobased resin can be employed to minimize the environmental impact of additive manufacturing while being competitive with existing fossil‐based photoresins, thereby meeting the growing demand for advanced photoresins with superior high‐resolution printing and smart properties for biomedical applications. [ABSTRACT FROM AUTHOR]

Fibre‐based wearables for embroidery, chemosensing, and biofluid's unidirectional draining with good flexibility, tunability, and designability drive technological advance. However, synthetic polymer fibres are non‐degradable, threatening the environment and human health. Herein, we have developed versatile microfibre‐based wearables by combining many advantages in one platform of biodegradable polylactic acid (PLA) and melt electrowriting strategy. Diverse potential applications of PLA wearables are achieved by flexibly designing their printing files, components and structures. Three‐dimensional printing files are generated from two‐dimensional images to fabricate 'embroidery‐like' patterns. PLA/aggregation‐induced emission fluorogens (AIE) chemosensors exhibit colorimetric and fluorescent colour changes upon exposure to amine vapours. Janus PLA‐cotton textiles with a hydrophobic/hydrophilic structure could facilitate unidirectional draining of sweats which is favourable for the management of temperature and humidity on the surface of skin. The proposed platform can not only broaden the design possibilities in 3D/4D printing but also offer wide potential applications for functional wearables. [ABSTRACT FROM AUTHOR]

Stimuli‐responsive polymers (SRPs) are special types of soft materials, which have been extensively used for developing flexible actuators, soft robots, wearable devices, sensors, self‐expanding structures, and biomedical devices, thanks to their ability to change their shapes and functional properties in response to external stimuli including light, humidity, heat, pH, electric field, solvent, and magnetic field or combinations of two or more of these stimuli. In recent years, additive manufacturing (AM) aka 3D printing technology of these SRPs, also known as 4D printing, has gained phenomenal attention in different engineering fields, thanks to its unique ability to develop complex, personalized, and innovative structures, which undergo twisting, elongating, swelling, rolling, shrinking, bending, spiraling, and other complex morphological transformations. Herein, an effort has been made to provide insightful information about the AM techniques, type of SRPs, and their applications including, but not limited to tissue engineering, soft robots, bionics, actuators, sensors, construction, and smart textiles. This article also incorporates the current challenges and prospects, hoping to provide an insightful basis for the utilization of this technology in different engineering fields. It is expected that the amalgamation of 3D printing with SRPs would provide unparalleled advantages in different engineering arenas. [ABSTRACT FROM AUTHOR]

In this article, a first of its kind blend of polyvinyl chloride (PVC) and biocompatible polycaprolactone (PCL) is introduced by melt mixing and then 3D printed successfully via Fused Filament Fabrication (FFF). Experimental tests are carried out on PCL‐PVC blends to assess thermo‐mechanical behaviors, morphology, fracture toughness, shape‐memory effects and printability. Macro and microscopic tests reveal that PVC‐PCL compounds are miscible due to high molecular compatibility and strong interaction. This causes extraordinary mechanical properties specially for PVC‐10 wt% PCL. In addition to the desired tensile strength (45 MPa), this material has a completely rubbery behavior at ambient temperature, and its total elongation is more than 81%. In addition, due to the high formability of PVC‐PCL at ambient temperature, it has capability of being programed via different shape‐memory protocols. Programming tests show that PVC‐PCL blends have an excellent shape‐memory effect and result in 100% shape recovery. SEM results prove a high improvement of PVC printability with the addition of 10 wt% PCL. Toughened PVC by PCL is herein added to the materials library of FFF 3D printers and expected to revolutionize applications of PVC compounds in the field of biomedical 3D and 4D printing due to its appropriate thermo‐mechanical properties, supreme printability, and excellent biocompatibility. [ABSTRACT FROM AUTHOR]

Compared to traditional methods, three/four-dimensional (3D/4D) printing technologies allow rapid prototyping and mass customization, which are ideal for preparing nano/microstructures of soft polymer materials. Poly (lactic acid) (PLA) is a biopolymer material widely used in additive manufacturing (AM) because of its biocompatibility and biodegradability. Unfortunately, owing to its intrinsically poor nucleation ability, a PLA product is usually in an amorphous state after industrial processing, leading to some undesirable properties such as a barrier property and low thermal resistance. Crystallization mediation offers a most practical way to improve the properties of PLA products. Herein, we summarize and discuss 3D/4D printing technologies in the processing of PLA nano/microstructures, focusing on crystallization principles and practical applications including bio-inspired structures, flexible electronics and biomedical engineering mainly reported in the last five years. Moreover, the challenges and prospects of 3D/4D printing technologies in the fabrication of high-performance PLA materials nano/microstructures will also be discussed. [ABSTRACT FROM AUTHOR]

Biofragmentable anastomosis ring (BAR) is an ideal sutureless alternative for intestinal connection that is frequently demanded in colonic surgery. However, it is challenging to insert a bulky BAR into the soft and slippery intestine. Here 4D printing of an anastomosis ring with shape memory capability is presented via fused deposition modeling (FDM) 3D printing. The shape memory anastomosis ring can recover from a compressed shape that facilitates the insertion to the permanent shape for connection and supporting. Degradation kinetics is tuned by controlling the blending composition of polylactic acid and poly(lactic‐co‐glycolic acid), so that the device can be excreted after the intestine healing. The shape recovery temperature is adjusted to 50 °C that the human body can withstand for a while. Grid structure and hook lock are designed and printed to guarantee dimension reduction upon programming and stable connection after shape recovery, respectively. A conceptual anastomotic operation shows the advantages and prospects of shape transformation. The 4D printing strategy may promote intestinal anastomosis development and inspire more opportunities for minimally invasive medical surgery. [ABSTRACT FROM AUTHOR]

[Display omitted] • Studying 4D printed-based mechanical metamaterials systematically. • Reviewing multifunctional energy-absorbing and shape-morphing features. • Outlining applications of 4D printed-based mechanical metamaterials. • Discussing multifaceted challenges with proposed solutions. The emergence of mechanical metamaterials from 4D printing has paved the way for developing advanced hierarchical structures with superior multifunctionalities. In particular, 4D-printed mechanical metamaterials exhibit extraordinary mechanical performance by integrating multiphysics stimuli with advanced structures when actuated by external factors, thereby altering their shapes, properties, and functionalities. This critical review offers readers a comprehensive overview of the rapidly growing 4D printing technology for developing novel mechanical metamaterials. It provides essential information about the multifunctionalities of 4D-printed mechanical metamaterials, including energy absorption and shape-morphing behavior in response to physical, chemical, or mechanical stimuli. These capabilities are key to developing smart and intelligent structures for multifunctional applications such as biomedical, photonics, acoustics, energy storage, and thermal insulation. The primary focus of this review is to describe the structural and functional applications of mechanical metamaterials developed through 4D printing. This technology leverages the shape-shifting functions of smart materials in applications such as micro-grippers, soft robots, biomedical devices, and self-deployable structures. Additionally, the review addresses current progress and challenges in the field of 4D-printed mechanical metamaterials. In conclusion, recent developments in 4D-printed mechanical metamaterials could establish a new paradigm for applications in engineering and science. [ABSTRACT FROM AUTHOR]

Belousov–Zhabotinsky (BZ) reactions have been used to investigate periodic spatial patterns due to the oscillatory nature of the reaction. However, these systems have not been confined, nor controlled, in macro‐scaled architectures, making it hard to translate observations to natural behavior. Here, a poly(electrolyte) complex is designed that can be ionically or covalently reinforced to construct 3D geometries with additive manufacturing techniques. Printed geometries varied in shape, size, and angle to investigate spatiotemporal pattern formation in 3D. Size variations correlated to trends in oscillating pattern frequencies, demonstrating a geometry effect on spatial alterations. Overall, the combination of 3D printing techniques with self‐oscillating chemical reactions allows to model, study, and further understand macro‐scale patterns observed in nature. The proposed approach can be used to design smart structure to replicate biological oscillators such as cardiac arrhythmias, neuron signaling, and camouflage skin patterns. [ABSTRACT FROM AUTHOR]

Repairing and regenerating damaged tissues or organs, and restoring their functioning has been the ultimate aim of medical innovations. 'Reviving healthcare' blends tissue engineering with alternative techniques such as hydrogels, which have emerged as vital tools in modern medicine. Additive manufacturing (AM) is a practical manufacturing revolution that uses building strategies like molding as a viable solution for precise hydrogel manufacturing. Recent advances in this technology have led to the successful manufacturing of hydrogels with enhanced reproducibility, accuracy, precision, and ease of fabrication. Hydrogels continue to metamorphose as the vital compatible bio-ink matrix for AM. AM hydrogels have paved the way for complex 3D/4D hydrogels that can be loaded with drugs or cells. Bio-mimicking 3D cell cultures designed via hydrogel-based AM is a groundbreaking in-vivo assessment tool in biomedical trials. This brief review focuses on preparations and applications of additively manufactured hydrogels in the biomedical spectrum, such as targeted drug delivery, 3D-cell culture, numerous regenerative strategies, biosensing, bioprinting, and cancer therapies. Prevalent AM techniques like extrusion, inkjet, digital light processing, and stereo-lithography have been explored with their setup and methodology to yield functional hydrogels. The perspectives, limitations, and the possible prospects of AM hydrogels have been critically examined in this study. [Display omitted] • Precise, functional, and biocompatible 3D/4D hydrogel designing via additive manufacturing. • Exploration of AM-hydrogel impact on bio-medics/printing/medical designing and3D cultures. • Extrusion, inkjet, DLP, and SLA-based futuristic hydrogel designing basics and mechanism. • Tissue regeneration strategy in cartilage, cardiac, and spinal tissues with wound healing. • Targeted drug delivery and cancer therapy-directional cytotoxicity, biosensors application. [ABSTRACT FROM AUTHOR]

3D printed silicones have demonstrated great potential in diverse areas such as soft robots, tissue engineering, flexible sensors and energy dissipation. However, most silicone inks face inevitable curing issue once it is prepared. During the materials extrusion based printing process, the curing-related viscosity change in silicone inks hamper the ink stability and printing controllability, leading to complex relationship among ink properties and printing parameters, as well as printing structures and material properties of final products. Herein, this work presents active mixing of two component silicone ink to realize stable printing, achieving exact and continuous match of ink properties and printing parameters. Using a specially formulated ink containing separate starting components with reactive groups, catalyst and thixotropic agents, this work studies the active mixing process thoroughly for the first time from molecular level to materials performances under various conditions regarding inlet flow rates, impeller rotation speed and component ratios. Besides, cellular silicones with controlled distribution of component ratios and tailored gradient structures are printed, leading to integrated manufacturing of compression performance and shape morphing property. This work will pave way for active mixing and printing of two-component silicones, and provide guidance for other reactive multi-material 3D printing systems. Active mixing of two-component viscoelastic silicone inks is studied, to solve the inevitable curing issue of mixture silicone ink, and to improve printing stability for continuous 3D printing of cellular silicones. Under optimal parameters, good mixing effects are achieved, from molecular distribution to mechanical performances. Furthermore, printed cellular silicones with tunable gradient compositions show adjustable compression and shape-morphing properties. [Display omitted] • Active mixing of two-component viscoelastic silicone inks is studied to improve printing stability for DIW printing of cellular silicones. • Under optimal parameters, good mixing effects are achieved, from molecular distribution to mechanical performances. • Printed cellular silicones with tunable gradient compositions show adjustable compression and shape-morphing properties. [ABSTRACT FROM AUTHOR]

In industries as diverse as automotive, aerospace, medical, energy, construction, electronics, and food, the engineering technology known as 3D printing or additive manufacturing facilitates the fabrication of rapid prototypes and the delivery of customized parts. This article explores recent advancements and emerging trends in 3D printing from a novel multidisciplinary perspective. It also provides a clear overview of the various 3D printing techniques used for producing parts and components in three dimensions. The application of these techniques in bioprinting and an up-to-date comprehensive review of their positive and negative aspects are covered, as well as the variety of materials used, with an emphasis on composites, hybrids, and smart materials. This article also provides an updated overview of 4D bioprinting technology, including biomaterial functions, bioprinting materials, and a targeted approach to various tissue engineering and regenerative medicine (TERM) applications. As a foundation for anticipated developments for TERM applications that could be useful for their successful usage in clinical settings, this article also examines present challenges and obstacles in 4D bioprinting technology. Finally, the article also outlines future regulations that will assist researchers in the manufacture of complex products and in the exploration of potential solutions to technological issues. [ABSTRACT FROM AUTHOR]

Tissue engineering research has undergone to a revolutionary improvement, thanks to technological advancements, such as the introduction of bioprinting technologies. The ability to develop suitable customized biomaterial inks/bioinks, with excellent printability and ability to promote cell proliferation and function, has a deep impact on such improvements. In this context, printing inks based on chitosan and its derivatives have been instrumental. Thus, the current review aims at providing a comprehensive overview on chitosan-based materials as suitable inks for 3D/4D (bio)printing and their applicability in creating advanced drug delivery platforms and tissue engineered constructs. Furthermore, relevant strategies to improve the mechanical and biological performances of this biomaterial are also highlighted. [Display omitted] • Discussion of Bioink formulations based on chitosan and its derivatives. • 3D printed chitosan-based constructs for tissue engineering and drug delivery. • Advanced 4D printed chitosan-based constructs for biomedical applications. [ABSTRACT FROM AUTHOR]

The rise of 3D printing technology has made the personalization of food possible. In this study, peanut protein-polysaccharide semi-interpenetrating networks were constructed to improve the gelling and printing properties of composite hydrogels. The rheological and mechanical test results showed that the storage modulus and fracture stress of peanut protein composite hydrogels increased with increasing carrageenan and gellan gum concentrations. The storage modulus (G′) and hardness of the composite hydrogels with 1.5% polysaccharide addition reached above 104 Pa and 700 g, respectively. The thermal reversibility of both carrageenan and gellan gum gels meant that composite hydrogels could be created as recyclable printable edible inks for 3D food printing. In addition, the composite hydrogels were designed to change color in response to alterations in pH, which meant they could be used in 4D food printing applications, i.e., in situations where the ink changes its attributes sometime after printing. The results of this study should facilitate the rational design and fabrication of plant-based edible inks that can be used for the development of personalized foods with unique properties. [Display omitted] • Peanut protein-polysaccharide semi-interpenetrating network hydrogels were built. • A recyclable food ink for 3D printing based on peanut protein hydrogels was prepared. • Color response of the printed object to pH was realized by adding natural pigment. • This study will contribute to the development of plant protein-based 3D printed food. [ABSTRACT FROM AUTHOR]

Mechanical metamaterials are a class of functional materials with designability and extraordinary mechanical properties. Due to the manufacturing limitation of traditional technology, most of the current research on mechanical metamaterials is limited to theoretical and simulation analysis. In recent years, the rapid development of 3D printing technology has provided an important means for the manufacturing of mechanical metamaterials with complex structures. In addition, the further combination with the 4D printing of smart materials is providing a boost to the development of smart programmable mechanical metamaterials. Here, we outline the recent advances in 3D/4D printing of mechanical metamaterials. First, 3D printing techniques for single-material, multi-material, and composite materials applicable to mechanical metamaterial manufacturing are discussed. Then, the structures and designs of several common mechanical metamaterials in 3D printing are summarized, including the 4D printing of smart programmable mechanical materials, and the applications of 3D/4D printing of mechanical metamaterials are presented. Finally, the future research prospects and challenges of 3D/4D printed mechanical metamaterials are foreseen. [ABSTRACT FROM AUTHOR]

[Display omitted] Progress in three-dimensional (3D) printing of shape memory polymers (SMPs) has produced dynamic and 3D-printed assemblies that can be shaped fast and modified for specific and multifaceted designs. Technology, biochemistry, medicine, computer science and biomaterials are among the areas of specialization, where 3D and four-dimensional (4D) printing techniques have penetrated to herald the next generation of manufacturing processes. Through layer-by-layer addition of diverse materials, 3D printing allows intricate assemblies with high precision. In today's additive manufacturing (AM), 4D printing encapsulates additional magnitude, which is time. Intelligent materials that deform or change color emit an electrical current that becomes bioactive or performs a specific function in response to an external stimulus overlay to manufacture dynamic 3D structures, through a technique known as 4D printing. With this modern dimension, 3D-printed substances can alter their form by themselves, concluding the impact of peripheral stimuli, such as light, heat, electricity and magnetic field, among others. For instance, the cartilage healing and physiological maturation techniques promote bone marrow to differentiate into osteoblasts. SMPs have also been developed as tools and stages for biomedical study. Summarily, this study focuses on a systematic compendious review of 3D and 4D printing techniques and their implications in biomedical techniques. Specific technologies intend to focus on such intelligent materials, and therefore it is essential to modernize the current voxel-based analysis, design methodology and explore effective printable technologies for fabricating organic components. Health professionals will benefit from 4D printing, especially in areas where 3D printing is not available. 4D printing allows for the construction of a three-dimensional building by layering smart material and using computer-operated computer-aided design (CAD) data. It presents a new level of translation over time, in which elements like heat, moisture, and duration affect printed materials. This breakthrough has the potential to make a difference in the health sector, especially when smarter and more sophisticated surgical implants, equipment, and technology become available. 4D printing methods might now be used by medical researchers to improve quality of care. [ABSTRACT FROM AUTHOR]

• Scrutiny of recent advances and trends of PVP in multidisciplinary biomedical applications. • Futuristic 3D and 4D printing based PVP biomedical uses are covered. • Assessments on the PVP based implants developed by electrospinning, electrospraying, 3D/4D printing. • Discussion on broad PVP utilization in regenerative tissue engineering. With emerging technological advances in biomedicine, the scope of futuristic biomaterials has been limited and existing polymers are gaining momentum. Unlike other synthetic polymers, polyvinyl pyrrolidone (PVP) is bioactive, water-soluble, non-toxic, temperature-resistant, pH-stable, biodegradable, and biocompatible. Due to its versatile properties, PVP is explored and widely used in the fabrication of wide biomedical products via electrospinning, 3D/4D printing, and other technologies. PVP owes intrinsic biological and tunable properties with next-generation biomaterials as nanoscaffolds delivering wide therapeutics, supporting material in implants, as a bone spacer, in tissue regeneration, wound healing materials, in diagnostics and many more. Several modifications of PVP are reported to achieve the additional criteria for special functions and additive with other clinically approved polymers to obtain new biomedical products. This article is a literature review on the PVP use in designing multidisciplinary biomedical products via advanced approaches. The review details key research aspects and promising potentials of PVP based nanoscaffolds utilized in several biomedical implants (orthopedic, dental, vaginal, breast), regenerative engineering (neural, cardiac, and pancreatic tissue), ophthalmic, wound healing materials, theranostics and miscellaneous. A special focus on novel PVP biomedical products by emerging, sustainable, cost-effective 3D and 4D printing are highlighted. From a biomedical scientist's viewpoint, this review presents, the current challenges, outlook, and future prospective of PVP in designing bioresorbable devices. [ABSTRACT FROM AUTHOR]

Facile preparation of architectures with precise control of shape deformations are crucial challenges due to the complicated process technique and harsh demands of the active materials. To address, the emerging 3D printing is employed to one‐step build programmable hydrogel architectures composed of only one type of material to perform various complex 3D shape deformations. The basic principle is that the secondary microstructures are introduced in the side of hydrogel strips and result in the bending or twisting deformations due to the asymmetrical swelling. With the merits of freeform design and fabrication, various hydrogel architectures including strips, sheets, and 3D objects are built with stereolithography‐based 3D printing, which realize the complex and controllable shape deformations via the programed microstructures on feature surfaces, such as bending, twisting, and even mimicking plant cirrus or petals. Most importantly, various responsive hydrogels are compatible to the approach, which can thus achieve stimuli‐reversible shape deformations. As proof‐of‐concept, a thermal‐responsive hydrogel gripper is readily realized to perform transportation by thermal‐induced grasping and releasing items. The facile 3D printing approach yet versatile in various hydrogels makes it broad opportunities for soft robotics, tissue engineering, actuators, and other devices where programmable shape deformations are required. [ABSTRACT FROM AUTHOR]