Optimization Shape-Memory Situations of a Stimulus Responsive Composite Material.

Four-dimensional (4D) printing technology, as a next-generation additive manufacturing method, enables printed objects to further change their shapes, functionalities, or properties upon exposure to external stimuli. The 4D printing of programmable and deformable materials such as thermo-responsive shape-memory polymers (trSMPs), which possess the ability to change shape by exposure to heat, has attracted particular interest in recent years. Three-dimensional objects based on SMPs have been proposed for various potential applications in different fields, including soft robotics, smart actuators, biomedical and electronics. To enable the manufacturing of complex multifunctional 3D objects, SMPs are often coupled with other functional polymers or fillers during or before the 3D printing process. This review highlights the 4D printing of state-of-the-art multi-component SMP formulations. Commonly used 4D printing technologies such as material extrusion techniques including fused filament fabrication (FFF) and direct ink writing (DIW), as well as vat photopolymerization techniques such as stereolithography (SLA), digital light processing (DLP), and multi-photon polymerization (MPP), are discussed. Different multicomponent SMP systems, their actuation methods, and potential applications of the 3D printed objects are reviewed. Finally, current challenges and prospects for 4D printing technology are summarized.

The existing 3D printing methods exhibit certain fabrication-dependent limitations for printing curved constructs that are relevant for many tissues. Four-dimensional (4D) printing is an emerging technology that is expected to revolutionize the field of tissue engineering and regenerative medicine (TERM). 4D printing is based on 3D printing, featuring the introduction of time as the fourth dimension, in which there is a transition from a 3D printed scaffold to a new, distinct, and stable state, upon the application of one or more stimuli. Here, we present an overview of the current developments of the 4D printing technology for TERM, with a focus on approaches to achieve temporal changes of the shape of the printed constructs that would enable biofabrication of highly complex structures. To this aim, the printing methods, types of stimuli, shape-shifting mechanisms, and cell-incorporation strategies are critically reviewed. Furthermore, the challenges of this very recent biofabrication technology as well as the future research directions are discussed. Our findings show that the most common printing methods so far are stereolithography (SLA) and extrusion bioprinting, followed by fused deposition modelling, while the shape-shifting mechanisms used for TERM applications are shape-memory and differential swelling for 4D printing and 4D bioprinting, respectively. For shape-memory mechanism, there is a high prevalence of synthetic materials, such as polylactic acid (PLA), poly(glycerol dodecanoate) acrylate (PGDA), or polyurethanes. On the other hand, different acrylate combinations of alginate, hyaluronan, or gelatin have been used for differential swelling-based 4D transformations. TERM applications include bone, vascular, and cardiac tissues as the main target of the 4D (bio)printing technology. The field has great potential for further development by considering the combination of multiple stimuli, the use of a wider range of 4D techniques, and the implementation of computational-assisted strategies.

The advancement of four-dimensional (4D) printing has been fueled by the rise in demand for additive manufacturing and the expansion in shape-memory materials. The printing of smart substances that respond to external stimuli is known as 4D printing. 4D printing allows highly controlled shapes to simulate the physiological milieu by adding time dimensions. The 4D printing is suitable with current progress in smart compounds, printers, and its mechanism of action. The 4D printing paradigm, a revolutionary enhancement of 3D printing, was anticipated by various engineering disciplines. Tissue engineering, medicinal, consumer items, aerospace, and organ engineering use 4D printing technology. The current review mainly focuses on the basics of 4D printing and the methods used therein. It also discusses the time-dependent behavior of stimulus-sensitive compounds, which are widely used in 4D printing. In addition, this review highlights material aspects, specifically related to shape-memory polymers, stimuli-responsive materials (classified as physical, chemical, and biological), and modified materials, the backbone of 4D printing technology. Finally, potential applications of 4D printing in the biomedical sector are also discussed with challenges and future perspectives.

Three-dimensional printing technologies are mainly used to build objects with complex shapes and geometry, largely prototypes, and thanks to the possibility of building very thin layers of material with small pores, electrospinning technology allows for the creation of structures with filtration properties, in particular very small particles. The combination of these technologies creates new possibilities for building complex-shape composites that have not been comprehensively tested so far. The article describes the results of research on composites manufactured by combining samples prepared with two 3D printing technologies, Fused Filament Fabrication (FFF) and Photo-Curing of Liquid Polymer Resins (PJM) in combination with electrospinning (ES) technology. The surface morphology of composites manufactured from biocompatible materials was investigated using confocal laser scanning microscopy (CLSM) and contact angle measurements, and chemical composition analysis was studied using Fourier transform infrared spectroscopy (FTIR). This approach to creating composites appears to be an alternative to developing research for filtration applications. The article presents basic research illustrating the quality of composites produced by combining two unconventional technologies: 3D printing and electrospinning (ES). The analysis of the research results showed clear differences in the structure of composites produced with the use of various 3D printing technologies. The CLSM analysis showed a much better orientation of the fibers in the MED610 + PAN/gelatin composite, and the measurement of the contact angle and its indirect interpretation also for this composite allows for the conclusion that it will be characterized by a higher value of adhesion force. Moreover, such composites could be used in the future for the construction of filtering devices and in medical applications.

Compression property and energy absorption capacity of 4D-printed deformable honeycomb structure

Typical techniques for creating synthetic morphing structures suffer from a compromise between quick shape change and geometric complexity. A novel approach is proposed for encoding numerous shapes and forms by magneto-electroactive shape memory polymer composite (SMPC) structures and integrating sustainability with 4D printing (4DP) technology. Electrically driven, remote controllability, and quick reaction are the features of these sustainable composite structures. Low-cost 4D-printed SMPC structures can be programmed remotely at high temperatures to achieve multi-stable shapes and can snap repeatedly between all programmed temporary and permanent configurations. This allows for multiple designs in a single structure without wasting material. The strategy is based on a knowledge of SMPC mechanics, magnetic response, and the manufacturing idea underlying fused deposition modelling (FDM). Iron-filled magnetic polylactic acid (MPLA) and carbon black-filled conductive PLA (CPLA) composite materials are investigated in terms of microstructure properties, composite interface, and mechanical properties. Characterisation studies are carried out to identify how to control the structure with a low magnetic field. The shape morphing of magneto-electroactive SMPC structures is studied. FDM is used to 4D print MPLA and CPLA adaptive structures with 1D/2D-to-2D/3D shapeshifting by the magnetic field. The benefits of switchable multi-stable structures are reducing material waste and effort/energy and increasing efficiency in sectors such as packaging.Graphical

Three-dimensional printing is a rapidly developing area of technology and manufacturing in the field of oral surgery. The aim of this study was comparison of presurgical models made by two different types of three-dimensional (3D) printing technology. Digital reference models were printed 10 times using fused deposition modelling (FDM) and digital light processing (DLP) techniques. All 3D printed models were scanned using a technical scanner. The trueness, linear measurements, and printing time were evaluated. The diagnostic models were compared with the reference models using linear and mean deviation for trueness measurements with computer software. Paired t-tests were performed to compare the two types of 3D printing technology. A P value < 0.05 was considered statistically significant. For FDM printing, all average distances between the reference points were smaller than the corresponding distances measured on the reference model. For the DLP models, the average distances in the three measurements were smaller than the original. Only one average distance measurement was greater. The mean deviation for trueness was 0.1775 mm for the FDM group and 0.0861 mm for the DLP group. Mean printing time for a single model was 517.6 minutes in FDM technology and 285.3 minutes in DLP. This study confirms that presurgical models manufactured with FDM and DLP technologies are usable in oral surgery. Our findings will facilitate clinical decision-making regarding the best 3D printing technology to use when planning a surgical procedure.

This study evaluates the accuracy of drill guides fabricated in medical-grade, biocompatible materials for static, computer-aided implant surgery (sCAIS). The virtually planned drill guides of ten completed patient cases were printed (n = 40) using professional (Material Jetting (MJ)) and consumer-level three-dimensional (3D) printing technologies, namely, Stereolithography (SLA), Fused Filament Fabrication (FFF), and Digital Light Processing (DLP). After printing and post-processing, the drill guides were digitized using an optical scanner. Subsequently, the drill guide’s original (reference) data and the surface scans of the digitized 3D-printed drill guide were superimposed to evaluate their incongruencies. The accuracy of the 3D-printed drill guides was calculated by determining the root mean square (RMS) values. Additionally, cast models of the planned cases were used to check that the drill guides fitted manually. The RMS (mean ± SD) values for the accuracy of 3D-printed drill guides were—MJ (0.09 ± 0.01 mm), SLA (0.12 ± 0.02 mm), FFF (0.18 ± 0.04 mm), and DLP (0.25 ± 0.05 mm). Upon a subjective assessment, all drill guides could be mounted on the cast models without hindrance. The results revealed statistically significant differences (p < 0.01) in all except the MJ- and SLA-printed drill guides. Although the measured differences in accuracy were statistically significant, the deviations were negligible from a clinical point of view. Within the limits of this study, we conclude that consumer-level 3D printers can produce surgical guides with a similar accuracy to a high-end, professional 3D printer with reduced costs.

This study evaluates the three-dimensional (3D) printing materials used in Fused Deposition Modeling (FDM) printing technology. 3D printing technology has been developing strongly, becoming an effective support tool in production and research. The 3D printing process involves many stages, with many parameters affecting the quality and properties of the product, in which 3D printing material is one of many essential factors affecting that process. The study conducts a comprehensive assessment of the most common materials in 3D printing technology to determine the advantages and limitations of precisely five types of materials: Polylactic acid, acrylonitrile butadiene styrene, polyethylene terephthalate glycol-modified, thermoplastic polyurethane, and acrylonitrile styrene acrylate. With 3D printing, parameters such as sintering temperature, printing speed, and layer thickness are kept constant. These parameters are applied equally to all five material samples. The experiment evaluates the tensile strength of materials. The study results provide an overview of the properties and applicability of 3D printing materials, helping to select materials suitable for specific FDM 3D printing technology applications.

Four-dimensional (4D) printing, an evolution of additive manufacturing (AM), integrates stimuli-responsive materials like thermal-induced shape memory polymers (TSMPs) to enable programmable, time-dependent transformations in structures. This review systematically examines recent advancements in TSMPs, 4D printing technologies, and fabrication strategies, emphasizing their interdisciplinary convergence and applications. TSMPs, with their unique phase-separated microstructures, modulus disparity, and tailorable recovery behaviors, form the foundation of 4D-printed systems, enabling innovations in aerospace, healthcare, and soft robotics [1–3, 33–45]. Key printing methods—including fused deposition modeling (FDM), direct ink writing (DIW), PolyJet, stereolithography (SLA), and digital light processing (DLP)—are analyzed for their strengths and limitations. FDM dominates due to cost-effectiveness but faces challenges in resolution and anisotropy [88, 91–93], while SLA and DLP offer high precision and speed but require material optimization [105, 111–115]. Advanced fabrication strategies, such as localized TSMP printing, composite reinforcement with carbon nanotubes or Fe 3O 4 particles, and sacrificial mold templating, expand design possibilities for multi-functional and multi-scale structures [117–120, 140–144]. Despite progress, challenges persist, including environmental sensitivity of TSMPs, interlayer bonding in AM, and dynamic modeling of non-equilibrium thermal responses [74, 77, 146]. Future directions focus on multi-responsive materials, machine learning-driven constitutive models, and sustainable bio-based formulations to address scalability and cyclic durability [31, 77, 147–149]. By bridging material science, computational modeling, and advanced manufacturing, this work provides a roadmap for harnessing 4D-printed TSMPs in real-world applications, from self-deploying biomedical devices to adaptive aerospace systems [28, 85, 137].

4D printing applications in medical field: A brief review

Three‐dimensional (3D) printing technology, virtual reality, and augmented reality technology have been used to help surgeons to complete complex total hip arthroplasty, while their respective shortcomings limit their further application. With the development of technology, mixed reality (MR) technology has been applied to improve the success rate of complicated hip arthroplasty because of its unique advantages. We presented a case of a 59‐year‐old man with an intertrochanteric fracture in the left femur, who had received a prior left hip fusion. After admission to our hospital, a left total hip arthroplasty was performed on the patient using a combination of MR technology and 3D printing technology. Before surgery, 3D reconstruction of a certain bony landmark exposed in the surgical area was first performed. Then a veneer part was designed according to the bony landmark and connected to a reference registration landmark outside the body through a connecting rod. After that, the series of parts were made into a holistic reference registration instrument using 3D printing technology, and the patient's data for bone and surrounding tissue, along with digital 3D information of the reference registration instrument, were imported into the head‐mounted display (HMD). During the operation, the disinfected reference registration instrument was installed on the selected bony landmark, and then the automatic real‐time registration was realized by HMD through recognizing the registration landmark on the reference registration instrument, whereby the patient's virtual bone and other anatomical structures were quickly and accurately superimposed on the real body of the patient. To the best of our knowledge, this is the first report to use MR combined with 3D printing technology in total hip arthroplasty.

Recent developments in three-dimensional (3D) printing technology offer immense potential in fabricating scaffolds and implants for various biomedical applications, especially for bone repair and regeneration. As the availability of autologous bone sources and commercial products is limited and surgical methods do not help in complete regeneration, it is necessary to develop alternative approaches for repairing large segmental bone defects. The 3D printing technology can effectively integrate different types of living cells within a 3D construct made up of conventional micro- or nanoscale biomaterials to create an artificial bone graft capable of regenerating the damaged tissues. This article reviews the developments and applications of 3D printing in bone tissue engineering and highlights the numerous conventional biomaterials and nanomaterials that have been used in the production of 3D-printed scaffolds. A comprehensive overview of the 3D printing methods such as stereolithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), and ink-jet 3D printing, and their technical and clinical applications in bone repair and regeneration has been provided. The review is expected to be useful for readers to gain an insight into the state-of-the-art of 3D printing of bone substitutes and their translational perspectives.

This paper explores the possibility of using different 3d printing methods and materials in the production of polymer molds for injection molding applications. A mold producing a cube was designed using a commercial software. Following the standard 3d printing process, injection molds which could produce a cube were printed using different 3d printing materials and 3d printing technologies. The 3d printing technologies used were Stereolithography (SLA), Polyjet and Fused Filament Fabrication (FFF). A bench-top injection molding machine was used to inject polylactic acid (PLA) in these molds. The quality of the injected parts in terms of dimensional accuracy has been investigated. In some cases, the damage mechanism of the polymer molds has also been observed.

4 - 4D-printed low-voltage electroactive polymers modeling and fabrication