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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]

This study explores the 3D/4D printing of polylactic acid (PLA) composites reinforced with natural particles from mussels PLA (MPLA) and wheat PLA (WPLA) using fused filament fabrication (FFF). The study employs functionally graded (FG) and multi‐material (MM) printing processes emphasizing biodegradable and bio‐derived materials. Shape memory polymer composites (SMPCs) with various MM and FG combinations are printed and examined. The microstructure, mechanical properties, flammability, and shape memory characteristics of these SMPCs are evaluated. The findings demonstrate that incorporating mussel and wheat particles enhances the mechanical performance of PLA, with a reduced burning rate compared to pure PLA samples. A sandwich FG composite structure shows superior strength in compression, tensile, and three‐point bending tests, with WMWFG samples exhibiting a 106% increase in tensile strength compared to WPLA samples. The shape recovery and fixity of the 4D‐printed SMPCs are investigated and WPLA specimens reveal the highest shape recovery ratio of ≈ 93.3% ± 1%. These findings highlight the potential of 4D‐printed SMPCs for diverse applications, spanning shape morphing, human‐material interaction, and mechanical engineering. Additionally, the research contributes to sustainability by promoting reduced material consumption and waste generation, as demonstrated by creating reusable and lightweight objects such as miniature pots, cutlery, holders, grippers, and wrappers. [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]

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.

Additive manufacturing of architected materials, particularly lattice or porous structures, has garnered significant interest in recent years due to its ability to enhance weight-to-strength performance, load-bearing capabilities, and superior energy absorption. Integrating these structures with shape memory alloys (SMAs) introduces unique functionality, enabling them to revert to their original shape after unloading. This paper offers a comprehensive review of the capabilities and challenges associated with additively manufactured architected SMAs. Several examples are presented to illustrate the functional and thermomechanical performance of these structures. Additionally, potential applications are examined, and future trends in this innovative field are explored.

Herein, hybrid triply periodic minimal surfaces (TPMS) metamaterials were structurally designed and additively manufactured via 4D printing using a biomass-derived shape memory polymer. Two TPMS topologies including gyroid and diamond with homogeneous and graded structures were separately generated by adjusting the C parameter. The mechanical performance and deformation behaviour between the uniform and graded structures were compared, and the compressive shaping-recovery cycles were conducted. The results showed that the gyroid (C:0.7→0.4) and diamond (C:0.7→0.4) samples exhibited superior reusability to the uniform counterparts. Subsequently, heterogeneous metamaterials assembled by gyroid and diamond subsections were established and 4D-printed. It was observed that both the yielding and shape recovery were preferred occurring in the gyroid part, while the diamond subsection played a stronger supporting effect. Therefore, the compressive performance and deformation mode could be feasibly tuned by the hybridisation of TPMS, which broadened the functional and sustainable applications in energy absorption, intelligent protection and medical implants.

Poly lactic acid (PLA) is one of the most commonly used bio-derived thermoplastic polymers in 3D and 4D printing applications. The determination of PLA surface properties is of capital importance in 3D/4D printing technology. The surface thermodynamic properties of PLA polymers were determined using the inverse gas chromatography (IGC) technique at infinite dilution. The determination of the retention volume of polar and non-polar molecules adsorbed on the PLA particles filling the column allowed us to obtain the dispersive, polar, and Lewis's acid–base surface properties at different temperatures from 40 °C to 100 °C. The applied surface method was based on our recent model that used the London dispersion equation, the new chromatographic parameter function of the deformation polarizability, and the harmonic mean of the ionization energies of the PLA polymer and organic molecules. The application of this new method led to the determination of the dispersive and polar free surface energy of the adsorption of molecules on the polymeric material, as well as the glass transition and the Lewis acid–base constants. Four interval temperatures were distinguished, showing four zones of variations in the surface properties of PLA as a function of the temperature before and after the glass transition. The acid–base parameters of PLA strongly depend on the temperature. The accurate determination of the dispersive and polar surface physicochemical properties of PLA led to the work of adhesion of the polar organic solvents adsorbed on PLA. These results can be very useful for achieving reliable and functional 3D and 4D printed components. [ABSTRACT FROM AUTHOR]

Super reconstructed foods (SRFs) have characteristics beyond those of real system in terms of nutrition, texture, appearance, and other properties. As 3D/4D food printing technology continues to be improved in recent years, this layered manufacturing/additive manufacturing preparation technology based on food reconstruction has made it possible to continuously develop large‐scale manufacture of SRFs. Compared with the traditional reconstructed foods, SRFs prepared using 3D/4D printing technologies are discussed comprehensively in this review. To meet the requirements of customers in terms of nutrition or other characteristics, multi‐processing technologies are being combined with 3D/4D printing. Aspects of printing inks, product quality parameters, and recent progress in SRFs based on 3D/4D printing are assessed systematically and discussed critically. The potential for 3D/4D printed SRFs and the need for further research and developments in this area are presented and discussed critically. In addition to the natural materials which were initially suitable for 3D/4D printing, other derivative components have already been applied, which include hydrogels, polysaccharide‐based materials, protein‐based materials, and smart materials with distinctive characteristics. SRFs based on 3D/4D printing can retain the characteristics of deconstruction and reconstruction while also exhibiting quality parameters beyond those of the original material systems, such as variable rheological properties, on‐demand texture, essential printability, improved microstructure, improved nutrition, and more appealing appearance. SRFs with 3D/4D printing are already widely used in foods such as simulated foods, staple foods, fermented foods, foods for people with special dietary needs, and foods made from food processingbyproducts. [ABSTRACT FROM AUTHOR]

Abstract 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.

The article discusses the modeling of the use of digital twin technologies (a digital twin) for the task of organizing long-term storage of various types of documents. A digital twin in this respect differs from a digital copy, which has no connection with the real original object. A review of the problem was carried out. We argue that, despite the active use of digital twin technology in various areas, its applications in the area of long-term storage of documents remain limited. At the same time, the task of increasing the durability of documents during long-term storage remains important and largely unresolved. The complexity of solving the problem of long-term storage of documents is considered, and a formal statement of the problem of long-term storage using digital twin technologies is carried out. Destructive factors that affect long-term storage documents and significantly reduce their durability have been identified. A system of indicators has been developed to assess the durability (preservation) of documents. The modeling of the use of digital twin technology in the organization of long-term preservation within the framework of Industry 4.0 was carried out. In the course of modeling, the goals and the strategies of long-term storage were established. Primary mathematical models for controlling destructive factors as well as technological solutions for digital twin long-term storage are proposed. It is assumed that the key part of this technology is the Industrial Internet of Things. The effectiveness of the use of digital twin technologies for solving the problem was assessed. The spheres of application and further ways of research are determined. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) aka three-dimensional (3D) printing has been a well-established and unparalleled technology, which is expanding the boundaries of materials science and is exhibiting an enormous potential to fabricate intricate geometries for healthcare, electronics, and construction sectors. In the contemporary era, the combination of AM technology and stimuli-responsive hydrogels (SRHs) helps to create dynamic and functional structures with extreme accuracy, which are capable of changing their shape, functional, or mechanical properties in response to environmental cues such as humidity, heat, light, pH, magnetic field, electric field, etc. 3D printing of SRHs permits the creation of on-demand dynamically controllable shapes with excellent control over various properties such as self-repair, self-assembly, multi-functionality, etc. These properties accelerate researchers to think of unthinkable applications. Additively manufactured objects have shown excellent potential in applications like tissue engineering, drug delivery, soft robots, sensors, and other biomedical devices. The current review provides recent progress in the 3D printing of SRHs, with more focus on their 3D printing techniques, stimuli mechanisms, shape-morphing behaviors, and their functional applications. Finally, current trends and future roadmap of additively manufactured smart structures for different applications have also been presented, which will be helpful for future research. This review holds great promise for providing fundamental knowledge about SRHs to fabricate structures for diverse applications.

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]

The concept of soft robots has garnered significant attention in recent studies due to their unique capability to interact effectively with the surrounding environment. However, as the number of innovative soft pneumatic actuators (SPAs) continues to rise, integrating traditional sensors becomes challenging due to the complex and unrestricted movements exhibited by SPA during their operation. This article explores the importance of utilising one-shot multi-material 3D printing to integrate soft force and bending sensors into SPAs. It highlights the necessity of a well-tuned and robust low-cost fabrication process to ensure the functionality of these sensors over an extended period. Fused deposition modelling (FDM) offers a cost-effective solution for embedding sensors in soft robots, directly addressing such necessity. Also, a finite element method (FEM) based on the nonlinear hyper-elastic constitutive model equipped with experimental input is developed to precisely predict the deformation and tip force of the actuators measured in experiments. The dynamic mechanical test is conducted to observe and analyse the behaviour and resistance changes of conductive thermoplastic polyurethane (CTPU) and varioShore TPU (VTPU) during a cyclic test. The flexible sensor can detect deformations in SPAs through the application of air pressure. Similarly, the force sensor exhibits the ability to detect grasping objects by detecting changes in resistance. These findings suggest that the resistance change corresponds directly to the magnitude of the mechanical stimuli applied. Thus, the device shows potential for functioning as a resistive sensor for soft actuation. Furthermore, these findings highlight the significant potential of 3D and 4D printing technology in one-shot fabrication of soft sensor-actuator robotic systems, suggesting promising applications in various fields like grippers with sensors and rehabilitation devices. [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]

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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]

Poly lactic acid (PLA) is one of the most commonly used bio-derived thermoplastic polymers in 3D and 4D printing applications. The determination of PLA surface properties is of capital importance in 3D/4D printing technology. The surface thermodynamic properties of PLA polymers were determined using the inverse gas chromatography (IGC) technique at infinite dilution. The determination of the retention volume of polar and non-polar molecules adsorbed on the PLA particles filling the column allowed us to obtain the dispersive, polar, and Lewis’s acid–base surface properties at different temperatures from 40 °C to 100 °C. The applied surface method was based on our recent model that used the London dispersion equation, the new chromatographic parameter function of the deformation polarizability, and the harmonic mean of the ionization energies of the PLA polymer and organic molecules. The application of this new method led to the determination of the dispersive and polar free surface energy of the adsorption of molecules on the polymeric material, as well as the glass transition and the Lewis acid–base constants. Four interval temperatures were distinguished, showing four zones of variations in the surface properties of PLA as a function of the temperature before and after the glass transition. The acid–base parameters of PLA strongly depend on the temperature. The accurate determination of the dispersive and polar surface physicochemical properties of PLA led to the work of adhesion of the polar organic solvents adsorbed on PLA. These results can be very useful for achieving reliable and functional 3D and 4D printed components.

Abstract 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.

Energy absorption and dissipation features of mechanical metamaterials have widespread applications in everyday life, ranging from absorbing shock impacts to mechanical vibrations. This article proposes novel bioinspired friction‐based mechanical metamaterials with a zero Poisson's ratio behavior inspired from parrot's beaks and manufactured additively. The mechanical performances of the corresponding metamaterials are studied at both macro and micro scales by experiments and finite element analysis (FEA). An excellent agreement is observed between the FEA and both microscopic and macroscopic scale experiments, showing the accuracy of the developed digital tool. Performances are compared to traditional triangular lattice metamaterials. Both experimental tests and FEA results demonstrate the following advantages: 1) absorbing and dissipating energy per unit of mass (SEA) at large compressive strains without global buckling; 2) bistable deformation patterns including friction‐based and interlocking mechanisms; 3) reversible deformation patterns after unloading; 4) shape recovery behavior after a heating–cooling process; and 5) the higher elastic modulus of micro metamaterials compared with their macro counterparts. This is the first demonstration of a bioinspired friction‐based design of 3D‐printed mechanical metamaterials that feature absorbing/dissipating energy, stability, and reversibility properties to cater to a wide range of sustainable meta‐cylinders in micro and macro scales. [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]

This research paper investigates the shape memory signatures (SMSs) of SMPs fabricated by two different manufacturing processes, namely Fused Filament Fabricated (FFF) and Injection-molding (IM). The SMSs of each manufacturing route is first investigated by rating the thermophysical and thermodynamic properties of amorphous and semicrystalline-type shape memory polymers. Secondly, the capturing of SMSs is completed by a series of thermomechanical shape programming/recovery cycles on FFF printed specimens, and the results are correlated with the IM-produced samples of similar nature. Furthermore, the thermomechanical cycles are programmed at varying heating rates (1, 2, 3, and 5 °C min−1) to analyze their influence on shape memory behavior and cycling time. Results depict that an increase in induced pre-strain driven by small to large deformations (10% → 25%) in the elastic range leads to maximum shape memory performance and the highest performance was reported while heating at 2 and 3 °C min−1, respectively. Finally, the IM-produced samples showed slightly better shape recovery compared to the 3D-printed samples. The shape memory signatures of 3DP specimens are indeed up to 86% like the ones produced by injection molding, which is mostly governed by the distinct residual stress/strain induced during the two different manufacturing processes. [Display omitted] • Thermophysical and thermodynamic analyses were performed on a semi-crystalline and amorphous type shape memory polymer. • Executed controlled thermomechanical shape memory cycles and analyzed the effects of heating rates (1, 2, 3, and 5 °C.min-1) and peak-strain (10% and 25%) on shape memory performance, such as shape recovery behavior. • Correlated the SMSs with the variability of the fabrication processes, 3D printing, and Injection molding. • Precisely controlled shape programming/recovery cycles enabled higher recovery ratios of 3D printed specimens to their counterpart injection molded. [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]

3D printing (3DP) has emerged in recent years as a form of processing with many exciting aspects. Today, it finds use in the industrial sector as well as among private individuals and small manufacturers, bringing manufacturing closer to end users and helping to bring a multitude of ideas and innovations to life. In this scenario, Chemical Engineering could play an essential role in 3DP, while it can also receive and benefit from many of the characteristics of this technology. This paper aims to highlight those that we consider the most productive meeting points between Chemical Engineering and 3DP, as well as the new techniques and applications that could benefit from this tandem in the future. [Display omitted] • 3DP processes can benefit from knowledge available in many Chemical Engineering topic areas. • The creation of unique and/or complex-shaped objects by 3DP can be of great interest to Chemical Engineering. • The relationship between Chemical Engineering and 3DP is not evident to many chemical engineers. • Including 3DP in the curriculum can enhance students' learning motivation towards different engineering subjects. [ABSTRACT FROM AUTHOR]

The latest developments in smart systems for improved human lives with advanced biomedical devices have evolved out of multi‐disciplinary scientific studies, including medicine, biology, material sciences, design, manufacturing, artificial intelligence, microelectronics, and so forth. The growth of such intelligent systems is primarily possible with innovative materials, which demonstrate the response to various external stimuli like temperature, heat, moisture, light, electromagnetic field, and chemical alteration. Such materials have been recently fabricated using different additive manufacturing techniques to devise personalized unique, complex, and novel structures that can adjust to external conditions over time and are specifically attributed to 4D printing. Novel materials that can further improve such systems continued to be explored and employed. This review paper investigates the additive manufacturing of functional polymer nanocomposites, which offer compliant structures with flexible manufacturing processes with high strength, low cost, and long‐term stability. This study aims to deliver a comprehensive and deep understanding of the latest developments in materials, design, manufacturing, fundamental mechanisms involved, and future possibilities in this area of research. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D/4D printing of novel biodegradable PLA-PBAT blends. • Direct printing by Granule-based FDM printer with low cost. • Achieving fast shape recovery in less than a few seconds (4 s) • Excellent softening of PLA with PBAT resulting in over 200 % elongation. • Achieving excellent thermo-mechanical properties and shape memory effects. One of the major challenges in 4D printed Shape Memory Polymers (SMPs) is their slow response to thermal stimuli. Synthetic carbon fillers have been introduced to address this issue; however, their use comes with environmental concerns. On the other hand, Polylactic Acid (PLA) is commonly used for 3D/4D printing of SMPs, but it requires softening to achieve large deformations. This research paper introduces a sustainable solution through blending PLA with Polybutylene Adipate Terephthalate (PBAT) that not only addresses these challenges but also possesses environmental eco-friendliness due to PBAT's high biodegradability rate. PBAT with weight percentages of 15 %, 30 %, and 45 % is utilized to soften PLA, and their composites are successfully 4D printed. Mechanical properties, shape memory effects, morphology, and thermal behaviors are comprehensively investigated. The results show that blending PLA with 45 % PBAT weight results in excellent features such as 220 % elongation and 93 % shape recovery in just a few seconds. The other two PLA-PBAT blends achieve complete shape recovery in less than 8 s. The PLA-PBAT contains 15 % PBAT, in addition to high strength (40 MPa), has 17 % elongation. This, coupled with the low melting temperature of PBAT, drives the high shape recovery rate. Scanning electron microscopy images finally confirm the high printability of all three blends, with the PLA-PBAT composite containing 30 % PBAT exhibiting the best quality in layer interfaces and the least porosity. [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]

Tissue engineering or tissue reconstruction/repair/regeneration may be considered as a guiding strategy in oral and maxillofacial surgery, as well as in endodontics, orthodontics, periodontics, and daily clinical practice. A wide range of techniques has been developed over the past years, from tissue grafts to the more recent and innovative regenerative procedures. Continuous research in the field of natural and artificial materials and biomaterials, as well as in advanced scaffold design strategies has been carried out. The focus has also been on various growth factors involved in dental tissue repair or reconstruction. Benefiting from the recent literature, this review paper illustrates current innovative strategies and technological approaches in oral and maxillofacial tissue engineering, trying to offer some information regarding the available scientific data and practical applications. After introducing tissue engineering aspects, an overview on additive manufacturing technologies will be provided, with a focus on the applications of superparamagnetic iron oxide nanoparticles in the biomedical field. The potential applications of magnetic fields and magnetic devices on the acceleration of orthodontic tooth movement will be analysed. [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]

Piezoelectricity in native bones has been well recognized as the key factor in bone regeneration. Thus, bio-piezoelectric materials have gained substantial attention in repairing damaged bone by mimicking the tissue’s electrical microenvironment (EM). However, traditional manufacturing strategies still encounter limitations in creating personalized bio-piezoelectric scaffolds, hindering their clinical applications. Three-dimensional (3D)/four-dimensional (4D) printing technology based on the principle of layer-by-layer forming and stacking of discrete materials has demonstrated outstanding advantages in fabricating bio-piezoelectric scaffolds in a more complex-shaped structure. Notably, 4D printing functionality-shifting bio-piezoelectric scaffolds can provide a time-dependent programmable tissue EM in response to external stimuli for bone regeneration. In this review, we first summarize the physicochemical properties of commonly used bio-piezoelectric materials (including polymers, ceramics, and their composites) and representative biological findings for bone regeneration. Then, we discuss the latest research advances in the 3D printing of bio-piezoelectric scaffolds in terms of feedstock selection, printing process, induction strategies, and potential applications. Besides, some related challenges such as feedstock scalability, printing resolution, stress-to-polarization conversion efficiency, and non-invasive induction ability after implantation have been put forward. Finally, we highlight the potential of shape/property/functionality-shifting smart 4D bio-piezoelectric scaffolds in bone tissue engineering (BTE). Taken together, this review emphasizes the appealing utility of 3D/4D printed biological piezoelectric scaffolds as next-generation BTE implants.

Photopolymers are one of the fastest growing 3D printing material classes, despite the lack of diversity in performance or composition. A simple addition of graphite nanopowder is explored for tailoring aliphatic polycarbonate performance and enhancing advanced material properties, targeting the mechanical performance of the norbornene‐containing poly(norbornene trimethyl carbonate) using poly(trimethyl propane allyl ether carbonate) for thermoset formation using thiol‐ene photochemistry. A 30 wt% graphite‐composite photopolymer ink displays shear thinning behavior suitable for pneumatic direct ink write (DIW) printing, along with enhanced elastic modulus (15–542 MPa) and an increase in ultimate strength (2–22 MPa for the composite ink) without significant variation in the glass transition temperature. The composites are further demonstrated as 4D materials including shape memory, conductivity, and recyclability, with this work serving as a guide for designing DIW inks from photopolymer resins. [ABSTRACT FROM AUTHOR]

Thermally triggered active metamaterials with shape memory polymers (SMPs) show greater potential for structural applications with reconfigurability than other programmable structures owing to their temporally stiff condition with shape locking. However, most SMP‐based active metamaterials have not shown complex transformation, such as multi‐modal and asymmetric deformations, because of the lack of an adaptable strategy with reasonable mechanics models. Moreover, conventional SMP has a critical drawback – irreversible transformability, limiting its reconfigurability for active metamaterials. Herein, a thermomechanical tool that allows a single material system to transform with reversible, multi‐modal, and asymmetric deformations is constructed and demonstrated. Using transformation aids (TAs), a localized pre‐stress and a temperature‐dependent reverse stiffness effect to exchange energy with a lattice is conceived. The deformation of a single SMP system whose energy is swapped from TAs by localized pre‐stress and reverse stiffness can transform into reversible, multi‐modal, and asymmetric deformations with shape‐locking. The methods can be used for reconfigurable structures, tuning symmetry, and chirality, especially for active acoustic metamaterials, deployable devices, and biomedical devices. The mechanics‐inspired design approach of local deformation of TA and the interaction with the temperature‐dependent stiffness drop of the lattice open an avenue to the robust design of thermally triggered active metamaterials. [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]

This study proposes a novel and simple fabrication method of magnetic microfibers, employing filament stretching three-dimensional (3D) printing, and demonstrates the capacity of four-dimensional (4D) printing of the proposed magnetic microfibers. A ferromagnetic 3D printing filament is prepared by the mixture of neodymium-iron-boron (NdFeB) and polylactic acid (PLA), and we investigate the characteristics of the ferromagnetic filament by mixing ratio, magnetic properties, mechanical properties, and rheological properties through experiments. By thermal extrusion of the ferromagnetic filament through a 3D printer nozzle, various thicknesses (80-500 μm) and lengths (less than ∼5 cm) of ferromagnetic microfibers are achieved with different printing setups, such as filament extrusion amount and printing speed. The printed ferromagnetic microfibers are magnetized to maintain a permanent magnetic dipole moment, and 4D printing can be achieved by the deformations of the permanently magnetized microfibers under magnetic fields. We observe that the mixing ratio, the thickness, and the length of the magnetized microfibers provide distinct deformation of the microfiber for customization of 4D printings. This study exhibits that the permanently magnetized microfibers have a great potential for smart sensors and actuators. Furthermore, we briefly present an application of our proposed magnetic microfibers for bionic motion actuators with various unique undulating and oscillating motions., Competing Interests: The authors declare no conflicts of interest., (Copyright 2024, Mary Ann Liebert, Inc., publishers.)

Tissue engineering or tissue reconstruction/repair/regeneration may be considered as a guiding strategy in oral and maxillofacial surgery, as well as in endodontics, orthodontics, periodontics, and daily clinical practice. A wide range of techniques has been developed over the past years, from tissue grafts to the more recent and innovative regenerative procedures. Continuous research in the field of natural and artificial materials and biomaterials, as well as in advanced scaffold design strategies has been carried out. The focus has also been on various growth factors involved in dental tissue repair or reconstruction. Benefiting from the recent literature, this review paper illustrates current innovative strategies and technological approaches in oral and maxillofacial tissue engineering, trying to offer some information regarding the available scientific data and practical applications. After introducing tissue engineering aspects, an overview on additive manufacturing technologies will be provided, with a focus on the applications of superparamagnetic iron oxide nanoparticles in the biomedical field. The potential applications of magnetic fields and magnetic devices on the acceleration of orthodontic tooth movement will be analysed.

3D/4D printing of thermosets, composites and hydrogels, lithographic procedures and dental resins are important examples of applications that rely on light-driven polymerization supported on substrates. Adhesion between the polymer and substrate during photopolymerization (and even between printed layers) can restrict the usual polymerization shrinkage, leading to the generation of residual stresses. These residual stresses can result in poor-quality products due to the presence of cracks and occurrence of warpage. In this work, silica nanoparticles were incorporated into photopolymerizable dimethacrylate based networks. These nanoparticles had their surface modified by grafting polymer chains with high mobility at usual room temperatures (low glass transition temperature polymer) and with high affinity towards the polymer matrix in order to test the hypothesis that these high-mobility chains could be helpful in dissipating stress and energy generated during photopolymerization in conditions in which the polymerization shrinkage is restricted. The nanoparticles and composites were analyzed via: electron microscopy (SEM), thermal analysis and mechanical bending tests. The evolution of the monomer-to-polymer conversion during photopolymerization was monitored using real-time infrared (FTIR) spectroscopy. To determine the residual stress generated by the polymerization at restricted contraction conditions, a universal mechanical testing machine was adapted and used. The results showed that silica nanoparticles with grafted high-mobility polymer chains that were able to interpenetrate and interact with the dimethacrylate based networks led to the production of composites having higher mechanical properties and lower polymerization stresses than composites containing only silanized nanoparticles and nanoparticles having immiscible polymer grafts towards the dimethacrylate based network. Results indicate that the modifications of the interface of composites developed in this work can be useful in the formulation of materials with improved mechanical properties and stability regarding polymerization shrinkage and residual stress that can lead to higher-quality products obtained in processes that employ light-driven polymerization supported on substrates or that occur on sequential polymerized layers, such as 3D/4D printing, lithography and in dental applications. [Display omitted] • Residual stress can be created when photopolymerization occurs on rigid substrates. • Residual stress can damage 3D photopolymerized printed parts. • High-mobility chains were grafted on fillers inserted into photopolymerized samples. • Fillers with high-mobility chains were able to reduce residual stress. • Fillers with high-mobility chains can lead to higher-quality printed products. [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]

Cellulose nanocrystals (CNCs) have gained significant attraction from both industrial and academic sectors, thanks to their biodegradability, non-toxicity, and renewability with remarkable mechanical characteristics. Desirable mechanical characteristics of CNCs include high stiffness, high strength, excellent flexibility, and large surface-to-volume ratio. Additionally, the mechanical properties of CNCs can be tailored through chemical modifications for high-end applications including tissue engineering, actuating, and biomedical. Modern manufacturing methods including 3D/4D printing are highly advantageous for developing sophisticated and intricate geometries. This review highlights the major developments of additive manufactured CNCs, which promote sustainable solutions across a wide range of applications. Additionally, this contribution also presents current challenges and future research directions of CNC-based composites developed through 3D/4D printing techniques for myriad engineering sectors including tissue engineering, wound healing, wearable electronics, robotics, and anti-counterfeiting applications. Overall, this review will greatly help research scientists from chemistry, materials, biomedicine, and other disciplines to comprehend the underlying principles, mechanical properties, and applications of additively manufactured CNC-based structures. [Display omitted] • Recent trends of additively manufactured cellulose nanocrystals (CNCs) are illustrated. • 3D/4D printing techniques and stimuli mechanisms applied for CNCs are elucidated. • Novel applications of CNC-based composites are summarized. • Current challenges and future prospects are presented. [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]