M.M. Savalani, L. Hao, P.M. Dickens, Y. Zhang, K.E. Tanner and R.A. Harris
Hydroxyapatite‐polymer composite materials are being researched for the development of low‐load bearing implants because of their bioactive and osteoconductive properties, while…
Abstract
Purpose
Hydroxyapatite‐polymer composite materials are being researched for the development of low‐load bearing implants because of their bioactive and osteoconductive properties, while avoiding modulus mismatch found in homogenous materials. For the direct production of hydroxyapatite‐polymer composite implants, selective laser sintering (SLS) has been used and various parameters and their effects on the physical properties (micro and macro morphologies) have been investigated. The purpose of this paper is to identify the most influential parameters on the micro and macro pore morphologies of sintered hydroxyapatite‐polymer composites.
Design/methodology/approach
A two‐level full factorial experiment was designed to evaluate the effects of the various processing parameters and their effects on the physical properties, including open porosity, average pore width and the percentage of pores which could enable potential bone regeneration and ingrowth of the sintered parts. The density of the sintered parts was measured by weight and volume; optical microscopy combined with the interception method was used to determine the average pore size and proportion of pores suitable to enable bone regeneration.
Findings
It was found that the effect of build layer thickness was the most influential parameter with respect to physical and pore morphology features. Consequently, it is found that the energy density equation with the layer thickness parameter provides a better estimation of part porosity of composite structures than the energy density equation without the layer thickness parameter. However, further work needs to be conducted to overcome the existing error of variance.
Originality/value
This work is the first step in identifying the most significant SLS parameters and their effects on the porosity, micro and macro pore morphologies of the fabricated parts. This is an important step in the further development of implants which may be required.
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A. Garg, K. Tai and M.M. Savalani
The empirical modelling of major rapid prototyping (RP) processes such as fused deposition modelling (FDM), selective laser sintering (SLS) and stereolithography (SL) has…
Abstract
Purpose
The empirical modelling of major rapid prototyping (RP) processes such as fused deposition modelling (FDM), selective laser sintering (SLS) and stereolithography (SL) has attracted the attention of researchers in view of their contribution to the overall cost of the product. Empirical modelling techniques such as artificial neural network (ANN) and regression analysis have been paid considerable attention. In this paper, a powerful modelling technique using genetic programming (GP) for modelling the FDM process is introduced and the issues related to the empirical modelling of RP processes are discussed. The present work aims to investigate the performance of various potential empirical modelling techniques so that the choice of an appropriate modelling technique for a given RP process can be made. The paper aims to discuss these issues.
Design/methodology/approach
Apart from the study of applications of empirical modelling techniques on RP processes, a multigene GP is applied to predict the compressive strength of a FDM part based on five given input process parameters. The parameter setting for GP is determined using trial and experimental runs. The performance of the GP model is compared to those of neural networks and regression analysis.
Findings
The GP approach provides a model in the form of a mathematical equation reflecting the relationship between the compressive strength and five given input parameters. The performance of ANN is found to be better than those of GP and regression, showing the effectiveness of ANN in predicting the performance characteristics of the FDM part. The GP is able to identify the significant input parameters that comply with those of an earlier study. The distinct advantages of GP as compared to ANN and regression are highlighted. Several vital issues related to the empirical modelling of RP processes are also highlighted in the end.
Originality/value
For the first time, a review of the application of empirical modelling techniques on RP processes is undertaken and a new GP method for modelling the FDM process is introduced. The performance of potential empirical modelling techniques for modelling RP processes is evaluated. This is an important step in modernising the era of empirical modelling of RP processes.
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M. Tarik Arafat, Ian Gibson and Xu Li
This paper aims to review the advances in additive manufactured (AM) scaffolds for bone tissue engineering (TE). A discussion on the state of the art and future trends of bone TE…
Abstract
Purpose
This paper aims to review the advances in additive manufactured (AM) scaffolds for bone tissue engineering (TE). A discussion on the state of the art and future trends of bone TE scaffolds have been done in terms of design, material and different AM technologies.
Design/methodology/approach
Different structural features and materials used for bone TE scaffolds are evaluated along with the discussion on the potential and limitations of different AM scaffolds. The latest research to improve the biocompatibility of the AM scaffolds is also discussed.
Findings
The discussion gives a clear understanding on the recent research trend in bone TE AM scaffolds.
Originality/value
The information available here would be useful for the researchers working on AM scaffolds to get a quick overview on the recent research trends and/or future direction to work on AM bone TE scaffolds.
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Chi Chung Ng, Monica Savalani and Hau Chung Man
Magnesium has been considered as a new generation of bioactive and biodegradable implant for orthopaedic applications because of its prominent properties including superior…
Abstract
Purpose
Magnesium has been considered as a new generation of bioactive and biodegradable implant for orthopaedic applications because of its prominent properties including superior biocompatibility, biodegradability and proper mechanical stiffness. For the direct production of custom biomedical implants, selective laser melting (SLM) has been investigated to fabricate pure magnesium and its resultant properties. The primary objective of this paper is to identify the most appropriate mode of irradiation for the melting of pure magnesium powders due to its reactive properties. This study focuses on investigating the interaction between the laser source and the magnesium powders by varying the SLM parameters of the laser power and scan speed under continuous or pulse mode conditions.
Design/methodology/approach
Single magnesium tracks were fabricated under different processing conditions using SLM, in order to evaluate the effects of processing parameters on the dimension and surface morphology of the achieved parts. The digital images of the tracks were used to analyze the geometrical features in terms of melting width and depth. In addition, scanning electron images were also studied to understanding the selective melting mechanism.
Findings
Magnesium tracks were successfully fabricated using SLM. Results showed that the dimension, surface morphology and the oxygen pick‐up of the laser‐melted tracks are strongly dependent on the mode of irradiation and processing parameters.
Originality/value
This work is a first step towards magnesium fabrication using SLM technique. The experimental results represent an important step in understanding the magnesium under an Nd:YAG laser irradiation, which provides the basis of behavior for follow‐on research and experiments.
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Monica Mahesh Savalani and Jorge Martinez Pizarro
The purpose of this paper is to investigate the effect of preheat and layer thickness in selective laser melting (SLM) of magnesium using pulse mode. Magnesium has been considered…
Abstract
Purpose
The purpose of this paper is to investigate the effect of preheat and layer thickness in selective laser melting (SLM) of magnesium using pulse mode. Magnesium has been considered as a new generation of implant materials which are bioactive and biodegradable for orthopaedic applications.
Design/methodology/approach
To produce optimal single magnesium tracks to compare the effect of layer thickness and preheat, different laser parameters were investigated. The analysis was made based on digital and electronic microscope images and mechanical measurements.
Findings
Improvements in the magnesium tracks due to preheating were successfully achieved. The analysis shows better bonding to the surface. The preheated tracks present an improvement in quality surface: smoother and flatter surfaces are discovered for the low layer thicknesses. When the thickness increases, the surface was disrupted and presented high surface roughness values. These were attributed to the Marangoni convection.
Originality/value
This study continues valuing the fabrication of magnesium with SLM. It shows the improvements of preheat and effect of different layer thicknesses on the part properties.
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I. Gibson, L.K. Cheung, S.P. Chow, W.L. Cheung, S.L. Beh, M. Savalani and S.H. Lee
This paper aims to illustrate a number of instances where RP and associated technology has been successfully used for medical applications.
Abstract
Purpose
This paper aims to illustrate a number of instances where RP and associated technology has been successfully used for medical applications.
Design/methodology/approach
A number of medical case studies are presented, illustrating different uses of RP technology. These studies have been analysed in terms of how the technology has been applied in order to solve related medical problems.
Findings
It was found that RP has been helpful in a number of ways to solve medical problems. However, the technology has numerous limitations that have been analysed in order to establish how the technology should develop in the future.
Practical implications
RP can help solve medical problems, but must evolve if it is to be used more widespread in this field.
Originality/value
This paper has shown a number of new applications for RP, providing a holistic understanding how the technology can solve medical problems. It also identifies a number of ways in which the technology can improve in order to better solve such problems.
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Dario Puppi, Alessandro Pirosa, Andrea Morelli and Federica Chiellini
The purpose of this paper is to describe the fabrication and characterization of poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyexanoate] (PHBHHx) tissue engineering scaffolds with…
Abstract
Purpose
The purpose of this paper is to describe the fabrication and characterization of poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyexanoate] (PHBHHx) tissue engineering scaffolds with anatomical shape and customized porous structure.
Design/methodology/approach
Scaffolds with external shape and size modeled on a critical size segment of a rabbit’s radius model and an internal macrochanneled porous structure were designed and fabricated by means of a computer-aided wet-spinning (CAWS) technique. Morphological, thermal and mechanical characterization were carried out to assess the effect of the fabrication process on material properties and the potential of the PHBHHx scaffolds in comparison with anatomical star poly(e-caprolactone) (*PCL) scaffolds previously validated in vivo.
Findings
The CAWS technique is well suited for the layered manufacturing of anatomical PHBHHx scaffolds with a tailored porous architecture characterized by a longitudinal macrochannel. Morphological analysis showed that the scaffolds were composed by overlapping layers of microfibers with a spongy morphology, forming a 3D interconnected network of pores. Physical-chemical characterization indicated that the used technique did not affect the molecular structure of the processed polymer. Analysis of the compressive and tensile mechanical properties of the scaffolds highlighted the anisotropic behavior of the porous structure and the effect of the macrochannel in enhancing scaffold compressive stiffness. In comparison to the *PCL scaffolds, PHBHHx scaffolds showed higher compressive stiffness and tensile deformability.
Originality/value
This study shows the possibility of using renewable microbial polyester for the fabrication of scaffolds with anatomical shape and internal architecture tailored for in vivo bone regeneration studies.
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G.J. Booysen, L.J. Barnard, M. Truscott and D.J. de Beer
The paper reflects on the development of a medical product using rapid prototyping technologies and customer interaction through a quality function deployment (QFD) approach to…
Abstract
Purpose
The paper reflects on the development of a medical product using rapid prototyping technologies and customer interaction through a quality function deployment (QFD) approach to speed up the process, and to result in customer satisfaction. The purpose of the specific medical product was to develop a device for fixing an Endo‐tracheal (ET) tube in a patient during anaesthesia, as it is common for an ET tube to move and/or become dislodged due to various extraneous reasons. If the tube deviates from the correct position it can cause one or both lungs to collapse, which can be fatal. The paper reviews how the anaesthetist's idea, which was to develop a product that could hold an ET tube in place in a more secure manner than is possible with current technologies, was brought to fruition through customer interaction.
Design/methodology/approach
Using an action‐research approach, the design evolved through series of design concepts, which through customer interaction contributed to a total optimized design. Virtual and physical prototypes, together with silicone mouldings were used as part of the customer interaction.
Findings
As with any new product, some functional parts were needed to conduct tests, which in turn would help to prove the product, and hence, the design. Traditionally this meant the manufacturing of a hard tool and proving of the design through trial and error. Hard tooling allows for some small changes to be made, but if the changes are radical a new tool will have to be designed and manufactured.
Research limitations/implications
Following a developmental approach through the application of various types/stages of prototyping (such as virtual prototypes), revolutionised this process by simplifying and accelerating the development iteration process – it also developed a new version/paradigm of QFD.
Practical implications
Opposed to traditional forms of QFD where customer inputs are gathered through questionnaires, this case study proved that functional models provide an efficient client‐feedback, through constant involvement in the development process, as well as evaluation of the systematic progress.
Originality/value
The case study shows that experts in other disciplines can become involved in the product development process through the availability of functional prototypes, and builds on previous work to introduce a concept of customer interaction with functional prototypes.
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Fangfang Sun, Tianze Wang and Yong Yang
Rapid prototyping (RP) technology is widely used in many fields in recent years. Bone tissue engineering (TE) is an interdisciplinary field involving life sciences, engineering…
Abstract
Purpose
Rapid prototyping (RP) technology is widely used in many fields in recent years. Bone tissue engineering (TE) is an interdisciplinary field involving life sciences, engineering and materials science. Hydroxyapatite (HAp) are similar to natural bone and it has been extensively studied due to its excellent biocompatibility and osteoconductivity. This paper aims to review nanoscaled HAp-based scaffolds with high porosity fabricated by various RP methods for bone regeneration.
Design/methodology/approach
The review focused on the fabrication methods of HAp composite scaffolds through RP techniques. The paper summarized the evaluation of these scaffolds on the basis of their biocompatibility and biodegradability through in vitro and in vivo tests. Finally, a summary and perspectives on this active area of research are provided.
Findings
HAp composite scaffold fabricated by RP methods has been widely used in bone TE and it has been deeply studied by researchers during the past two decades. However, its brittleness and difficulty in processing have largely limited its wide application in TE. Therefore, the formability of HAp combined with biocompatible organic materials and fabrication techniques could be effectively enhanced, and it can be used in bone TE applications finally.
Originality/value
This review paper presented a comprehensive study of the various types of HAp composite scaffold fabricated by RP technologies and introduced their potential application in bone TE, as well as future roadmap and perspective.
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Hui Zhang, Yanling Guo, Kaiyi Jiang, David Bourell, Jian Li and Yueqiang Yu
A new kind of polymer mixture (co-PA-PES) was prepared in different mass ratios, by mixing polyether sulfone hot-melt adhesive (PES-HmA) and copolyamide B249 (PA-B249). This study…
Abstract
Purpose
A new kind of polymer mixture (co-PA-PES) was prepared in different mass ratios, by mixing polyether sulfone hot-melt adhesive (PES-HmA) and copolyamide B249 (PA-B249). This study aims to investigate its characteristics of laser sintering and get the optimal process parameters.
Design/methodology/approach
The effect of mass ratio of co-PA-PES on thermal behavior was analyzed using a simultaneous thermal analyzer, and the density and mechanical properties of sintered parts were tested to evaluate the performance of the polymeric system. Scanning electron microscopy and Fourier transform infrared spectroscopy were performed to characterize the microstructure and binding mechanism of sintered co-PA-PES parts. Specifically, mechanical properties of the mixture with 20 Wt.% PA-B249 were optimized based on a design of experiment methodology, along with the restriction of maximum absorbable laser energy density.
Findings
Liquid phase fusion was considered as the main sintering mechanism for co-PA-PES, and mechanical interlocking was the dominant binding mechanism. The effects of mass ratios of this material on the thermal properties, density and mechanical properties were obtained via data results. Additionally, compared to neat PES-HmA, co-20 Wt.% PA-PES showed a 71.7 per cent increase in tensile strength, 24.4 per cent increase in flexural strength and 102.1per cent increase in impact strength.
Originality/value
This paper proposed a new kind of polymer mixture as the feedstock for laser sintering with the advantages of low price and easy processing. The filler of PA-B249 effectively improved the performance of the polymer mixture, including but not limited to mechanical properties.