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1 – 10 of over 6000Ker Chin Ang, Kah Fai Leong, Chee Kai Chua and Margam Chandrasekaran
The purpose of this paper is to investigate the mechanical properties and porosity relationships in fused deposition modelling (FDM) fabricated porous structures.
Abstract
Purpose
The purpose of this paper is to investigate the mechanical properties and porosity relationships in fused deposition modelling (FDM) fabricated porous structures.
Design/methodology/approach
Porous structures of numerous build architectures aimed at tissue engineering (TE) application were fabricated using the FDM. The employment of FDM to fabricate these non‐random constructs offers many advantages over conventional scaffold fabrication techniques as patient specific scaffolds with well‐defined architectures and controllable pore sizes can be fabricated accurately and rapidly. There exist several FDM parameters that one needs to specify during the scaffold fabrication process. These parameters, which can be interdependent and exhibit varying effects on scaffold properties, were identified and examined using the design of experiment (DOE) approach. Essentially, the effects of five FDM process parameters, namely air gap, raster width, build orientation, build layer and build profile, on the porosity and mechanical properties of acrylonitrile‐butadienene‐styrene (ABS) scaffold structures with three‐dimensional interconnectivity were investigated in two designed experiments. Statistical analyses of the data were performed and the respective factors that have significant influence on the porosity and mechanical properties of the scaffolds were identified. The relationship between scaffold's mechanical properties and porosity was thereafter established empirically.
Findings
Models of TE scaffolds of numerous build architectures were successfully fabricated using different parameter settings on the FDM. The DOE approach determined air gap and raster width as the most significant parameters in affecting the porosity and mechanical properties of the ABS scaffold structures. The relationship between scaffolds' mechanical properties and porosity was determined to be logarithmic, with the best mechanical properties observed in scaffolds of low porosity.
Originality/value
The paper highlights how the application FDM to tissue scaffold application can overcome most of the limitations encountered in the conventional techniques.
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Abstract
Successes in scaffold guided tissue engineering require scaffolds to have specific macroscopic geometries and internal architectures to provide the needed biological and biophysical functions. Freeform fabrication provides an effective process tool to manufacture many advanced scaffolds with designed properties. This paper reports our recent study on using a novel precision extruding deposition (PED) process technique to directly fabricate cellular poly‐ε_rm;‐caprolactone (PCL) scaffolds. Scaffolds with a controlled pore size of 250 μm and designed structural orientations were fabricated.
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Li Wu, Xinxin Li, Tianmin Guan, Yong Chen and Chunwei Qi
The 3 D bioprinting technology is used to prepare the tissue engineering scaffold with precise structures for the cell proliferation and differentiation.
Abstract
Purpose
The 3 D bioprinting technology is used to prepare the tissue engineering scaffold with precise structures for the cell proliferation and differentiation.
Design/methodology/approach
According to the characteristics of the ideal tissue engineering scaffold, the microstructural design of the tissue engineering scaffold is carried out. The bioprinter is used to fabricate the tissue engineering scaffold with different structures and spacing sizes. Finally, the scaffold with good connectivity is achieved and used to cell PC12 culture.
Findings
The results show that the pore structure with the line spacing of 1 mm was the best for cell culture, and the survival rate of the inoculated cells PC12 is as high as 90%. The influence of the pore shape on the cell survival is not evidence.
Originality/value
This study shows that tissue engineering scaffolds prepared by 3 D bioprinting have graded structure for three-dimensional cell culture, which lays the foundation for the later detection of drug resistance.
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Iman Ghaderi, Amir Hossein Behravesh, Seyyed Kaveh Hedayati, Seyed Alireza Alavinasab Ardebili, Omid Kordi, Ghaus Rizvi and Khodayar Gholivand
This study aims to design and implement a multimaterial system for printing multifunctional specimens suitable for various sectors, with a particular focus on biomedical…
Abstract
Purpose
This study aims to design and implement a multimaterial system for printing multifunctional specimens suitable for various sectors, with a particular focus on biomedical applications such as addressing mandibular bone loss.
Design/methodology/approach
To enhance both the mechanical and biological properties of scaffolds, an automatic multimaterial setup using vat photopolymerization was developed. This setup features a linear system with two resin vats and one ultrasonic cleaning tank, facilitating the integration of diverse materials and structures to optimize scaffold composition. Such versatility allows for the simultaneous achievement of various characteristics in scaffold design.
Findings
The printed multimaterial scaffolds, featuring 20 Wt.% hydroxylapatite (HA) on the interior and poly-L-lactic acid (PLLA) with 1 Wt.% graphene oxide (GO) on the exterior, exhibited favorable mechanical and biological properties at the optimum postcuring and heat-treatment time. Using an edited triply periodic minimal surface (TPMS) lattice structure further enhanced these properties. Various multimaterial specimens were successfully printed and evaluated, showcasing the capability of the setup to ensure functionality, cleanliness and adequate interface bonding. Additionally, a novel Gyroid TPMS scaffold with a nominal porosity of 50% was developed and experimentally validated.
Originality/value
This study demonstrates the successful fabrication of multimaterial components with minimal contaminations and suitable mechanical and biological properties. By combining PLLA-HA and PLLA-GO, this innovative technique holds significant promise for enhancing the effectiveness of regenerative procedures, particularly in the realm of dentistry.
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Fay Rhianna Claybrook, Darren John Southee and Mazher Mohammed
Cushioning is a useful material property applicable for a range of applications from medical devices to personal protective equipment. The current ability to apply cushioning in a…
Abstract
Purpose
Cushioning is a useful material property applicable for a range of applications from medical devices to personal protective equipment. The current ability to apply cushioning in a product context is limited by the appropriateness of available materials, with polyurethane foams being the current gold standard material. The purpose of this study is to investigate additively manufactured flexible printing of scaffold structures as an alternative.
Design/methodology/approach
In this study, this study investigates triply periodic minimal surface (TPMS) structures, including Gyroid, Diamond and Schwarz P formed in thermoplastic polyurethane (TPU), as a possible alternative. Each TPMS structure was fabricated using material extrusion additive manufacturing and evaluated to ASTM mechanical testing standard for polymers. This study focuses attention to TPMS structures fabricated for a fixed unit cell size of 10 mm and examine the compressive properties for changes in the scaffold porosity for samples fabricated in TPU with a shore hardness of 63A and 90A.
Findings
It was discovered that for increased porosity there was a measured reduction in the load required to deform the scaffold. Additionally, a complex relationship between the shore hardness and the stiffness of a structure. It was highlighted that through the adjustment of porosity, the compressive strength required to deform the scaffolds to a point of densification could be controlled and predicted with high repeatability.
Originality/value
The results indicate the ability to tailor the scaffold design parameters using both 63A and 90A TPU material, to mimic the loading properties of common polyurethane foams. The use of these structures indicates a next generation of tailored cushioning using additive manufacturing techniques by tailoring both geometry and porosity to loading and compressive strengths.
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Janet S. Gaffney and Rebecca Jesson
Purpose – The purpose of this chapter is to understand how children expand independence within instructional interactions with their teachers. To do so, the authors re-examine how…
Abstract
Purpose – The purpose of this chapter is to understand how children expand independence within instructional interactions with their teachers. To do so, the authors re-examine how scaffolding is understood and applied.
Approach – First, the authors consult websites and literature used by teachers and academics to examine how the notion of scaffolding is employed and explained. The authors analyze the roles, the intentions, the means, and the timing of scaffolding as used in popular literature to explain and support instruction. The authors then entertain a conceptual shift: What would the scaffolding process look like if learning were conceived as agentive? With this in mind, the authors interrogate descriptions of the tenets and functions of scaffolding to consider the process in relief.
Findings – The authors track the consequences of the inversion of scaffolding onto the understandings of the gradual release of responsibility (GRR) model. Scaffolding is understood as sitting within a GRR model, wherein the learner gradually releases responsibility to a teacher at the point of need. Intersubjectivity remains a basis for the model. A Window for Examining Teaching–Learning Interactions is offered as a frame with which to analyze the theories of both the child and the teacher apparent within scaffolding interactions. An accurate teacher’s theory of the child’s current and changing theories is required for teaching to be honed to invite children to efficiently access personal and contextual resources and to seek assistance when needed within engaging tasks with scope.
Practical Implications – When children are positioned as initiators of their learning, they are able to use their vast repertoire of knowledge of the world, language/s and literacies, and familial, cultural, and community ways of knowing to create, interpret, and engage in tasks. In this agentive view, children are positioned as holding full responsibility at the onset of any task and gradually releasing their responsibility to access support, when needed. Within tasks that are sufficiently wide for engagement at varied entry points, learners are the catalyst of the functions that were formerly initiated by teachers. Teachers invite children to access personal and contextual resources and to seek assistance, as needed, through additional external, contextual resources. This inverted model of scaffolding, that is child-directed rather than teacher-initiated, requires teachers to go beyond theories of teaching and learning and develop a theory of an individual child.
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Neha Choudhary, Chandrachur Ghosh, Varun Sharma, Partha Roy and Pradeep Kumar
The purpose of this paper is to fabricate the scaffolds with different pore architectures using additive manufacturing and analyze its mechanical and biological properties for…
Abstract
Purpose
The purpose of this paper is to fabricate the scaffolds with different pore architectures using additive manufacturing and analyze its mechanical and biological properties for bone tissue engineering applications.
Design/methodology/approach
The polylactic acid (PLA)/composite filament were fabricated through single screw extrusion and scaffolds were printed with four different pore architectures, i.e. circle, square, triangle and parallelogram with fused deposition modelling. Afterwards, scaffolds were coated with hydroxyapatite (HA) using dip coating technique. Various physical and thermo-mechanical tests have been conducted to confirm the feasibility. Furthermore, the biological tests were conducted with MG63 fibroblast cell lines to investigate the biocompatibility of the developed scaffolds.
Findings
The scaffolds were successfully printed with different pore architectures. The pore size of the scaffolds was found to be nearly 1,500 µm, and porosity varied between 53% and 63%. The fabricated circular pore architecture resulted in highest average compression strength of 13.7 MPa and modulus of 525 MPa. The characterizations showed the fidelity of the work. After seven days of cell culture, it was observed that the developed composites were non-toxic and supported cellular activities. The coating of HA made the scaffolds bioactive, showing higher wettability, degradation and high cellular responses.
Originality/value
The research attempts highlight the development of novel biodegradable and biocompatible polymer (PLA)/bioactive ceramic (Al2O3) composite for additive manufacturing with application in the tissue engineering field.
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Abhishek Kansal, Akshay Dvivedi and Pradeep Kumar
The purpose of this study to investigate the organized porous network zinc (OPNZ) scaffolds. Their mechanical characteristics, surface roughness and fracture mechanism were…
Abstract
Purpose
The purpose of this study to investigate the organized porous network zinc (OPNZ) scaffolds. Their mechanical characteristics, surface roughness and fracture mechanism were assessed in relation to their structural properties. The prospects of fused deposition modeling (FDM) for printing metal scaffolds via rapid tooling have also been studied.
Design/methodology/approach
Zn scaffolds with different pore and strut sizes were manufactured via the rapid tooling method. This method is a multistep process that begins with the 3D printing of a polymer template. Later, a paraffin template was obtained from the prepared polymer template. Finally, this paraffin template was used to fabricate the Zn scaffold using microwave sintering. The characterization of prepared Zn samples involved structural characterization, microstructural study, surface roughness testing and compression testing. Moreover, based on the Gibson–Ashby model analysis, the model equations’ constant values were evaluated, which can help in predicting the mechanical properties of Zn scaffolds.
Findings
The scanning electron microscopy study confirmed that the fabricated sample pores were open and interconnected. The X-ray diffraction analysis revealed that the Zn scaffold contained hexagonal closed-packed Zn peaks related to the a-Zn phase, validating that scaffolds were free from contamination and impurity. The range for ultimate compressive strength, compressive modulus and plateau stresses for Zn samples were found to be 6.75–39 MPa, 0.14–3.51 GPa and 1.85–12.6 MPa by adjusting their porosity, which are comparable with the cancellous bones. The average roughness value for the Zn scaffolds was found to be 1.86 µm.
Originality/value
This research work can widen the scope for extrusion-based FDM printers for fabricating biocompatible and biodegradable metal Zn scaffolds. This study also revealed the effects of scaffold structural properties like porosity, pore and strut size effect on their mechanical characteristics in view of tissue engineering applications.
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Apinya Chanthakulchan, Pisut Koomsap, Kampanat Auyson and Pitt Supaphol
– This paper aims to present the development of an electrospinning-based rapid prototyping (ESRP) technique for the fabrication of patterned scaffolds from fine fiber.
Abstract
Purpose
This paper aims to present the development of an electrospinning-based rapid prototyping (ESRP) technique for the fabrication of patterned scaffolds from fine fiber.
Design/methodology/approach
This ESRP technique unifies rapid prototyping (RP) and electrospinning to obtain the ability of RP to create a controllable pattern and of electrospinning to create a continuous fine fiber. The technique follows RP process of fused deposition modeling, but instead of using extrusion process for fiber creation, electrospinning is applied to generate a continuous fiber from a liquid solution. A machine prototype has been constructed and used in the experiments to evaluate the technique.
Findings
Three different lay-down patterns: 0°/90°, 45°/135° and 45° twists were used in the experiments. According to the experimental results, stacks of patterned layers could be created with the ESRP technique, and the fabrication process was repeatable and reproducible. However, the existing machine vibration influenced the fiber size and the ability to control straightness and gap size. Also, incomplete solidification of the fibers prior to being deposited obstructed the control of layer thickness. Improvement on vibration suppression and fiber solidification will strengthen the capability of this ESRP technique.
Research limitations/implications
This research is currently limited to the introduction of the ESRP technique, to the development of the machine prototype, to the demonstration of its capability and to the evaluation of the structural properties of the fabricated patterned scaffolds. Further studies are required for better control of the patterned scaffolds and for investigation of mechanical and biological properties.
Originality/value
This unification of the two processes allows not only the fabrication of controllable patterned scaffolds but also the fabrication of both woven and non-woven layers of fibers to be done on one machine.
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Yan Li, Dichen Li, Bingheng Lu, Dajing Gao and Jack Zhou
The purpose of this paper is to review the current status of additive manufacturing (AM) used for tissue engineering (TE) scaffold. AM processes are identified as an effective…
Abstract
Purpose
The purpose of this paper is to review the current status of additive manufacturing (AM) used for tissue engineering (TE) scaffold. AM processes are identified as an effective method for fabricating geometrically complex objects directly from computer models or three-dimensional digital representations. The use of AM technologies in the field of TE has grown rapidly in the past 10 years.
Design/methodology/approach
The processes, materials, precision, applications of different AM technologies and their modified versions used for TE scaffold are presented. Additionally, future directions of AM used for TE scaffold are also discussed.
Findings
There are two principal routes for the fabrication of scaffolds by AM: direct and indirect routes. According to the working principle, the AM technologies used for TE scaffold can be generally classified into: laser-based; nozzle-based; and hybrid. Although a number of materials and fabrication techniques have been developed, each AM technique is a process based on the unique property of the raw materials applied. The fabrication of TE scaffolds faces a variety of challenges, such as expanding the range of materials, improving precision and adapting to complex scaffold structures.
Originality/value
This review presents the latest research regarding AM used for TE scaffold. The information available in this paper helps researchers, scholars and graduate students to get a quick overview on the recent research of AM used for TE scaffold and identify new research directions for AM in TE.
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