3D-printed Constructs Research Articles

Selection of compositions for additive technologies in construction

Three-dimensional printing is an innovative digital technology and is one of the most significant achievements in the industrial and technological development of modernity. Digital 3D technologies have reached a colossal level of development over a period of about half a century since their invention. Using 3D printing in the construction of low-rise buildings, it becomes possible to implement almost any ideas and achieve the best architectural expressiveness of objects. The aim of this work is to create cement-based compounds that can be used in additive construction methods. A review of the scientific literature on this topic was carried out, the main components of the mixture were identified, and a series of field experiments were conducted. According to the results of the work, the optimal composition for 3D construction printing was determined.

Nacre inspired 3D printing construction for high performance structural member

Inspired by the nacre’s hierarchically assembled structure, the authors tried to use ultra-high ductile cementitious composites (UHDCC) and stack approach to fabricate structure possessing high flexural ductility and load bearing capacity. A series of beams with specially design was constructed, i.e., monolithically cast beams, monolithically stacked beams and hierarchically stacked beams. Four-point bending tests were carried out to explore the effect of hierarchical assembly on load bearing capacity, flexural deformation and flexural toughness. The test results have indicated that the monolithically stacked beams outperform the monolithically cast beams in both deformability and loading bearing capacity, indicating the effectiveness of stack-based construction. Moreover, the setup of connect/separation between layers further improves the flexural ductility of the hierarchically stacked beams, as compared with the monolithically stacked beams. Digital Image Correlation (DIC) observations indicate that the nacreous-like structure of the hierarchically stacked beam helps to trigger crack deflecting and branching between layers and inside matrix, lead to limited slide between layers, thus effectively relieving concentrated strain inside matrix, postponing the emergence of the critical crack and consequently improving the flexural ductility of nacreous-like UHDCC beams.

АНАЛИЗ МИРОВОГО ОПЫТА КОНСТРУИРОВАНИЯ И РАЗРАБОТКА МОБИЛЬНОГО СТРОИТЕЛЬНОГО 3D-ПРИНТЕРА

Introduction: The paper presents a brief overview of current construction 3D printing possibilities and a detailed analysis of a design of a mobile construction 3D printer. The authors analyze advantages, disadvantages and development prospects of the construction method. Based on the analyzed data, they describe the development of a conceptual design for such a printer characterized by the structure built-up of basic modules with a length of 1 m, the possibility of printing in the field without preliminary site preparation, the use of construction wastes as a concrete mix aggregate. The authors highlight that the design can be used both in the system of logistical support of the Russian Federation Armed Forces and for civil purposes to construct various facilities. They conclude that it is reasonable to perform further studies in this area and describe prospects of project development. Methods: In the course of the study, the authors compared and analyzed specifications of construction 3D printers to refine the specifications of the design developed. Results: Based on the analysis and comparison of structures and application fields of analogs, a conceptual design of a mobile construction 3D printer for the Russian Federation Armed Forces was proposed. Discussion: A prototype in scale 1:5 was presented at the International Military-Technical Forum “ARMY-2019” (Popov, 2019).

Кинетика тепловыделения и особенности гидратации модифицированных полимерцементных смесей для строительной 3D-печати

Кинетика тепловыделения и особенности гидратации модифицированных полимерцементных смесей для строительной 3D-печати

Hydrogels with an embossed surface: An all-in-one platform for mass production and culture of human adipose-derived stem cell spheroids

Stem cell spheroids have been studied extensively in organoid culture and therapeutic transplantation. Herein, hydrogels with an embossed surface (HES) were developed as an all-in-one platform that can enable the rapid formation and culture of a large quantity of size-controllable stem cell spheroids. The embossed structure on the hydrogel was adjustable according to the grit designation of the sandpaper. Human adipose-derived stem cells (hADSCs) were rapidly assembled into spheroids on the hydrogel, with their size distribution precisely controlled from 95 ± 6 μm to 181 ± 15 μm depending on surface roughness. The hADSC spheroids prepared from the HES demonstrated expression of stemness markers and differentiation capacity. In addition, HES-based spheroids showed significantly greater VEGF secretion than spheroids grown on a commercially available low-attachment culture plate. Exploiting those advantages, the HES-based spheroids were used for 3D bioprinting, and the spheroids within the 3D-printed construct showed improved retention and VEGF secretion compared to the same 3D structure containing single cell suspension. Collectively, HES would offer a useful platform for mass fabrication and culture of stem cell spheroids with controlled sizes for a variety of biomedical applications.

Ideal scaffold design for total ear reconstruction using a three-dimensional printing technique.

Ear reconstruction using three-dimensional (3D) printing technique has been considered as a good substitute for conventional surgery, because it can provide custom-made 3D framework. However, there are difficulties with its application in clinical use. Researchers have reported 3D scaffolds for ear cartilage regeneration, but the designs of the 3D scaffolds were not appropriate to be used in surgery. Hence, we propose the design of an ideal 3D ear scaffold for use in ear reconstruction surgery. Facial computed tomography (CT) images of the unaffected ear were extracted using a "segmentation" procedure. The selected data were converted to a 3D model and mirrored to create a model of the affected side. The design of 3D model was modified to apply to Nagata's two-stage surgery. Based on the 3D reconstructed model, a 3D scaffold was 3D printed using polycaprolactone. The 3D scaffold closely resembled the real cartilage framework used in current operations in terms of ear anatomy. To account for skin thickness, the 3D scaffold was made 4 mm smaller than the real ear. Furthermore, 2 mm pores were included to allow the implantation of diced cartilage to promote regeneration of the cartilage. 3D printing technology can overcome the limitations of previous auricular reconstruction methods. Further studies are required to achieve a functional and stable substitute for auricular cartilage and to extend the clinical use of the 3D-printed construct. Additionally, the ethical and legal issues regarding the transplantation of 3D-printed constructs and cell culture technologies using human stem cells remain to be solved. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1295-1303, 2019.

PERFORMANCE CHARACTERISTICS OF 3D PRINTING CONSTRUCTION MIXES DEPENDING ON THERMALLYMODIFIED PEAT ADDITIVE

The paper presents the research results on the development of scientifically valid compositions of 3D printing construction mixes with improved performance characteristics. To regulate the physical, mechanical and technological properties of cement-based mixes, thermallymodified peat additive MT-600 is developed. The paper studies the world experience in the construction additive technology field. The experimental results are presented for cement paste and construction mixes with MT-600 additive for 3D printing. It is established that using the proposed fine additive increases the strength of the cement paste at early stages of hardening, which is the determining factor in the formation of building and technical characteristics for 3D printing. The X-ray phase analysis is carried out for the new composition of cement paste modified with MT-600 additive, which allows studying characteristics of the structure and properties of construction mixes during the hardening process.

Particle-bed 3D printing in concrete construction – Possibilities and challenges

This article provides an overview of different particle-bed 3D printing techniques for the production of concrete elements. A classification is proposed which considers the direct production of concrete components, the production of formwork as well as composite components by means of a permanent formwork. Three techniques are considered as relevant for concrete construction, i.e. selective binder activation, selective paste intrusion and binder jetting. Design as well as material aspects are addressed. The underlying physics of fluid infiltration into the particle-bed and its effect on the properties of the hardened material are discussed on the basis of recent research results. Finally, the first applications of particle-bed 3D printing are presented which demonstrate the potential of this technique in concrete construction.

3D printing human induced pluripotent stem cells with novel hydroxypropyl chitin bioink: scalable expansion and uniform aggregation

Human induced pluripotent stem cells (hiPSCs) are more likely to successfully avoid the immunological rejection and ethical problems that are often encountered by human embryonic stem cells in various stem cell studies and applications. To transfer hiPSCs from the laboratory to clinical applications, researchers must obtain sufficient cell numbers. In this study, 3D cell printing was used as a novel method for iPSC scalable expansion. Hydroxypropyl chitin (HPCH), utilized as a new type of bioink, and a set of optimized printing parameters were shown to achieve high cell survival (>90%) after the printing process and high proliferation efficiency (∼32.3 folds) during subsequent 10 d culture. After the culture, high levels of pluripotency maintenance were recognized by both qualitative and quantitative detections. Compared with static suspension culture, hiPSC aggregates formed in 3D-printed constructs showed a higher uniformity in size. Using a novel dual-fluorescent labeling method, hiPSC aggregates in the constructs were found more inclined to form by in situ proliferation rather than multicellular aggregation. This study revealed unique advantages of non-ionic crosslinking bioink material HPCH, including high gel strength and rapid temperature response in hiPSC printing, and achieved primed state hiPSC printing for the first time. Features achieved in this study, such as high cell yield, high pluripotency maintenance and uniform aggregation provide good foundations for further hiPSC studies on 3D micro-tissue differentiation and drug screening.

The study of the structure rebuilding and yield stress of 3D printing geopolymer pastes

For 3D printing construction materials, workability and interlayer force of fresh printing pastes were necessary to ensured extrudability and buildability in the period from extrude to hardened of pastes. The workability and interlayer force of 3 Dimensional printing geopolymer pastes related to its rheological property and more particularly to its structure rebuilding and yield stress. The present study is aimed at investigating structure rebuilding and yield stress of 3 Dimensional printing geopolymer pastes at different Si/Na ratio of alkali activator by rheology method. Results revealed that rheology is an important research method for the extrudability and buildability of 3D printing geopolymer pastes. Structure rebuilding ability (SRE) and fast-growing yield stress of 3 Dimensional printing geopolymer ensured the stability of structure in the period from extrude to hardened of paste. Si/Na ratio of alkali activator has significantly influences on extrudability and buildability of 3D printing geopolymer pastes. High Si/Na ratio of alkali activator decreases the viscosity, yield stress and development rate of fresh pastes. Si/Na ratio of alkali activation significantly influences rate of structure rebuilding of pastes, and low Si/Na ratio of alkali activator exhibited high ability of recovery of pastes.

3D printing of poly(ε-caprolactone)/poly(D,L-lactide-co-glycolide)/hydroxyapatite composite constructs for bone tissue engineering

Abstract

The cost calculation method of construction 3D printing aligned with internet of things

It is controversial that the cost of construction 3D printing is lower than the conventional construction in academic field. The reason is that some scholars have confused attributes between construction 3D printing and traditional construction. The cost calculation of construction 3D printing cannot follow the rules in conventional construction because construction 3D printing was identified as both industrial product and construction product. This paper proposed a new approach to cost calculation of construction 3D printing concerning both the properties of industrial and construction product. The cost elements and calculation methods of onsite and offsite 3D printing were discussed and concluded. The comparison of cost composition among conventional construction, onsite construction 3D printing, and offsite construction 3D printing was presented as well. The paper put forward the idea of cost calculation about industrialized construction, and it solved the problems of cost calculation among different construction technologies.

A hydrophilic coumarin-based polyester for ambient-temperature initiator-free 3D printing: Chemistry, rheology and interface formation

Initiator-free, photocurable, low-toxicity, viscoelastic polymer inks are attractive materials for creating low-modulus 3D-printed elastomeric biomedical constructs. In this work, we describe the synthesis, characterization, and 3D printing/crosslinking of a hydrophilic coumarin-PEG polyester (CPP). The viscoelastic CPP melt can be extruded at room temperature and deposited into layer-by-layer patterns. Upon UV irradiation, the coumarin pendant groups undergo [2 + 2] photocyclization, creating a thermoset network without the use of monomers, photoinitiators or propagating radicals. Voxel-voxel adhesion experiments between crosslinked and uncrosslinked material were performed to examine interfacial dynamics in a native, unperturbed state, and various attempts at 3D printing were made to assess the impact of printing conditions on the ultimate printed structure. Rheological analysis indicates a transition point where elastic behavior overtakes viscous behavior at increasing shear rate. It is hypothesized that this transition point corresponds with changes in interface formation from “sticky” to “bouncy” behavior in voxel-voxel adhesion and 3D printing processes. Tensile-mode dynamic mechanical analysis (DMA) and X-Ray microtomography (microCT) experiments reveal interfacial defect accumulation that results in deterioration of macroscopic structural and mechanical properties.

Study of mineral additives for cement materials for 3D-printing in construction

The present work provides the results of a study of the effect of thermally activated brown coal fly ash from the coal basin in Podmoskovye, microsilica, Crimean shell rock flour and quartz flour on the rheological and physical and mechanical properties of the model system (of the cement mixture) in order to select the most effective mineral components for cement materials for 3D-printing. Optimization of the structure in order to form a dense and tight structure of high-quality concrete on cement binders can be carried out by introducing fine mineral additives of different material composition. In the presence of polycarboxylate plasticizers, such additives allow to regulate the mobility of cement systems at constant W/C ratio. At the same time, the increase in strength characteristics can be achieved both by introducing reaction active additives (microsilica, fly ash, shell rock flour) and components that perform the structural and topological function (shell rock flour, quartz flour). The effectiveness of regional mineral additives for use in cement systems is presented.

3D Bioprinting Stem Cell Derived Tissues.

Stem cells offer tremendous promise for regenerative medicine as they can become a variety of cell types. They also continuously proliferate, providing a renewable source of cells. Recently, it has been found that 3D printing constructs using stem cells, can generate models representing healthy or diseased tissues, as well as substitutes for diseased and damaged tissues. Here, we review the current state of the field of 3D printing stem cell derived tissues. First, we cover 3D printing technologies and discuss the different types of stem cells used for tissue engineering applications. We then detail thepropertiesrequired for the bioinks used when printing viable tissues from stem cells. We give relevant examples of such bioprinted tissues, including adipose tissue, blood vessels, bone, cardiac tissue, cartilage, heart valves, liver, muscle, neural tissue, and pancreas. Finally, we provide future directions for improvingthe current technologies, along with areas of focus for future work to translate these exciting technologies intoclinical applications.

Three dimensional cell printing with sulfated alginate for improved bone morphogenetic protein-2 delivery and osteogenesis in bone tissue engineering

Three-dimensional (3D) cell printing is a unique technique that enables free-form fabrication of cell-laden hydrogel scaffolds with controllable features and interconnected pores for tissue engineering applications. To this end, bioink materials able to offer good printability and favorable cellular interaction are highly required. Herein, we synthesized alginate sulfate, which is a structural mimic of heparin that can strongly bind with growth factors to prolong their activities, and studied its feasibility for cell printing applications. Several bio-inks composed of alginate and alginate-sulfate were studied to characterize their material properties and their utilities in 3D printing. The inclusion of alginate-sulfate in bio-inks (alginate/alginate-sulfate) did not significantly influence their rheological properties and allowed for a good 3D printing processibility with distinct pores and features. Moreover, alginate/alginate-sulfate bio-inks exhibited an improved retention of bone morphogenetic protein 2 in 3D-printed scaffolds. Osteoblastic proliferation and differentiation in vitro were promoted by alginate/alginate-sulfate 3D-printed constructs with an optimal composition of 3% alginate and 2% alginate-sulfate. We envision that bio-inks displaying prolonged interactions with growth factors will be useful for tissue engineering applications including bone regeneration.

Fabrication of Multiple-Layered Hydrogel Scaffolds with Elaborate Structure and Good Mechanical Properties via 3D Printing and Ionic Reinforcement.

A major challenge in three-dimensional (3D) printing of hydrogels is the fabrication of stable constructs with high precision and good mechanical properties and biocompatibility. Existing methods typically feature complicated reinforcement steps or use potentially toxic components, such as photocuring polymers and crosslinking reagents. In this study, we used a thermally sensitive hydrogel, hydroxybutyl chitosan (HBC), for 3D-printing applications. For the first time, we demonstrated that this modified polysaccharide is affected by the specific ion effect. As the salt concentration was increased and stronger kosmotropic anions were used, the lower critical solution temperature of the HBC decreased and the storage modulus was improved, indicating a more hydrophobic structure and stronger molecular chain interactions. On the basis of the thermosensitivity and the ion effects of HBC, a 25-layered hydrogel scaffold with strong mechanical properties and an elaborate structure was prepared via a 3D-printing method and one-step ionic post-treatment. In particular, the scaffold treated with 10% NaCl solution exhibited a tunable elastic modulus of 73.2 kPa to 40 MPa and excellent elastic recovery, as well as biodegradability and cytocompatibility, suggesting the potential for its applications to cartilage tissue repair. By simply controlling the temperature and salt concentrations, this novel approach provides a convenient and green route to improving the structural accuracy and regulating the properties of 3D-printed hydrogel constructs.

Building the Future: How 3D Printing Will Revolutionize the Construction Industry

Plastics EngineeringVolume 74, Issue 3 p. 16-21 3D Printing in Construction Building the Future: How 3D Printing Will Revolutionize the Construction Industry MIT constructed a building in just 14 hours. Can 3D printing shape a unique and prosperous future for construction? Jim Romeo, Jim RomeoSearch for more papers by this author Jim Romeo, Jim RomeoSearch for more papers by this author First published: 01 March 2018 https://doi.org/10.1002/j.1941-9635.2018.tb01853.xCitations: 1AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume74, Issue3March 2018Pages 16-21 RelatedInformation

The Framework of Combining Artificial Intelligence and Construction 3D Printing in Civil Engineering

Construction 3D printing is becoming a significant force driving the transformation of civil engineering industry, but facing many problems for its immaturity. At the same time, the development of artificial intelligence and other advanced technology, especially BIM and virtual reality technology, provides new methods for solving these problems. Based on the defects of construction 3D printing and the advantages of these technology, this paper proposes a framework that combines artificial intelligence with construction 3D printing in five aspects: materials for 3D printing, automation design for 3D printing, digital construction for 3D printing, robots for 3D printing and BIM platform system for 3D printing. BIM platform system associates with the other aspects to work together efficiently during the life cycle of construction.

Predicting Compressive Strength of Recycled Concrete for Construction 3D Printing Based on Statistical Analysis of Various Neural Networks

Construction 3D printing is changing construction industry, but for its immaturity, there are still many problems to be solved. One of the major problems is to study materials for construction 3D printing. Because printed buildings are very different from traditional buildings, there are special requirements for printing materials. Based on environmental and cost considerations, the recycled concrete as printing material is a perfect choice. In order to study and develop the construction 3D printing materials, it is necessary to predict the properties of them. As one of the most effective artificial intelligence algorithms, artificial neural network can deal with multi-parameter and nonlinear problems, and it can provide useful reference to predict the performance of recycled concrete for 3D printing. However, since there are many types and parameters for neural network, it is difficult to select the optimal neural network with excellent prediction performance. In this paper, by comparing different types of neural networks and statistically analyzing the distribution of the root-mean-square error (RMSE) and the coefficient of determination (R2) of these neural networks, we can determine the best performance among four neural networks and finally select the suitable one to predict the performance of 3D printing concrete.