M.W. Naing, C.K. Chua, K.F. Leong and Y. Wang
This paper details the derivation of the mathematical formulae of a novel system for designing and fabricating tissue engineering (TE) scaffolds.
Abstract
Purpose
This paper details the derivation of the mathematical formulae of a novel system for designing and fabricating tissue engineering (TE) scaffolds.
Design/methodology/approach
This work combines the unique capability of rapid prototyping (RP) techniques with computer‐aided design (CAD) and imaging software to design and fabricate customised scaffolds that are not only consistent in microstructure but also readily reproducible. The prototype system, called the computer‐aided system for tissue scaffolds (CASTS), has a parametric library of design units which can be assembled into scaffold structures through an in‐house algorithm. An additional module, the slicing routine, has also been added to improve the functionality of the system. To validate the system, scaffolds designed were fabricated using a powder‐based RP technique called selective laser sintering (SLS).
Findings
It is shown that the CASTS can be used to exploit CAD and medical imaging techniques together with RP systems to produce viable scaffolds that can be customised for various applications to suit the needs of individual patients.
Research limitations/implications
Further research is being done to examine the internal microstructure of the scaffolds and to determine the mechanical properties, as well as to study the inter‐relationship between cell proliferation and the pore shapes of the scaffolds.
Originality/value
The crucial role of scaffolds in TE has long been recognised. Successful TE scaffolds should have controllable characteristics such as pore size, porosity, and surface area to volume ratio as well as interconnectivity within the scaffolds. Much work has been carried out to produce such TE scaffolds with varying degrees of success. One major drawback is that the resultant TE scaffolds are not readily reproducible. The potential of CASTS lies in its ability to design and fabricate scaffolds with varying properties through the use of different unit cells and biomaterials to suit different applications.
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EMMANUEL J. YANNAKOUDAKIS and HUSSAIN A. ATTAR‐BASHI
The Subject‐Object Relationship Interface model (SORI) described in this paper is a novel approach that displays many of the structures necessary to map between the conceptual…
Abstract
The Subject‐Object Relationship Interface model (SORI) described in this paper is a novel approach that displays many of the structures necessary to map between the conceptual level and the external level in a database management system, which is an information‐oriented view of data. The model embodies a semantic synthesiser, which is based on an algorithm that maps the syntactic representation of a tuple or a record onto a semantic representation. This is based on table‐driven semantics which are embedded in the database model. The paper introduces a technique for translating tuples into natural language sentences, and discusses a system that has been fully implemented in PROLOG.
Gang Liu, Aino Kianto and Eric Tsui
This meta-analytic study tries to synthesize the mixed relationships between knowledge management technologies (KMT) and organizational performance as well as aims to explore the…
Abstract
Purpose
This meta-analytic study tries to synthesize the mixed relationships between knowledge management technologies (KMT) and organizational performance as well as aims to explore the impacts of contextual elements, such as national culture, economy and industries, on these relationships.
Design/methodology/approach
Findings on various subjects from 40 previous empirical studies were examined using meta-analysis.
Findings
It was found that KMT are positively related to overall organizational performance as well as financial and nonfinancial performance and that the relationship between KMT and financial performance is stronger in developing economies than in developed economies.
Practical implications
It helps practitioners better understand the role of KMT in organizational performance in various contexts and provides practical suggestions for KMT implementation.
Originality/value
As the first meta-analytic study to address the generalizability of KMT–organizational performance relationships, this paper offers an improved understanding of the benefits of KMT. It also expands knowledge about how contextual issues related to national culture, economies and industries affect KMT payoffs.
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Thittikorn Phattanaphibul, Pisut Koomsap, Irwansyah Idram and Suchart Nachaisit
This paper aims to introduce selective vacuum manufacturing (SVM), a powder-based rapid prototyping (RP) technique, and the ongoing development to improve its capability to apply…
Abstract
Purpose
This paper aims to introduce selective vacuum manufacturing (SVM), a powder-based rapid prototyping (RP) technique, and the ongoing development to improve its capability to apply in temporary scaffold fabrication.
Design/methodology/approach
SVM employs a combination of sand casting and powder sintering process to construct a prototype layer by layer. A dense layer of support material is prepared and selectively removed to create a cavity where part material is filled and sintered to form a solid layer. In order for SVM to be considered for scaffold fabrication, besides preparing poly-lactic acid (PLA) for part material, support material preparation and process parameters identification have been studied. Redesigning of SVM machine to be more suitable for the real usage has also been presented.
Findings
Particle size of salt has been controlled, and its suitable composition with flour and water has been determined. Process parameters have been identified to scale down the size of scaffolds to meso-scale and to achieve mechanical requirement. Properties of fabricated scaffolds have been enhanced and can be used for soft tissue applications. A prototype of the medical SVM machine has been constructed and tested. An examination of scaffolds fabricated on this new machine also showed their qualification for soft tissue application.
Research limitations/implications
Further study will be on conducting a direct cytotoxicity test to provide the evidence for tissue growth before the clinical usage, on continuing to scaling down the scaffold size, and on improving SVM to meet the requirement of hard tissue.
Originality/value
This simple, inexpensive RP technique demonstrates its viability for scaffold fabrication.
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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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The purpose of this paper is to propose a method for fabricating tumor vessel phantom and then investigate the thermal dosage profile caused by high‐intensity‐focused ultrasound…
Abstract
Purpose
The purpose of this paper is to propose a method for fabricating tumor vessel phantom and then investigate the thermal dosage profile caused by high‐intensity‐focused ultrasound (HIFU) surgery.
Design/methodology/approach
In this paper, a thermal sensitive powder has been added to silicon‐based gel as a vessel phantom raw material for displaying the thermal dosage profile caused by HIFU. A fused deposition modeling system was used for fabricating the shell casting mold and the vessel arbor mold. The arbor prototype, made of wax, was solidified in the cavity of vessel arbor mold. The vessel phantom object embedded with the arbor prototype was created in the shell mold casting process. The vessel phantom was obtained by immersing the vessel phantom object into hot water (65°C) for melting the vessel arbor prototype. A HIFU experiment has been conducted for verifying the feasibility of displaying the thermal dosage profile of the fabricated vessel phantom. The HIFU experimental parameters including the driving power of HIFU transducer, ultrasound exposure duration and volume flow rate were used for investigating the thermal dosage variation by the perfusion of vessel phantom.
Findings
The properties of fabricated mimicking phantom agree well with those of human tissue. The experimental results show that the proposed method can fabricate the Y‐type vessel phantom. The proposed method has been proved as a promising fabrication process in fabricating the vessel phantom and it displays the thermal dosage profile in HIFU experiment.
Originality/value
The proposed method and the developed experimental apparatus are helpful for pre‐clinical HIFU surgery.
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Chee Kai Chua, Kah Fai Leong, Chu Sing Lim and Trong Thien Vu
The purpose of this paper is to detail the development of a multimedia courseware that enhances the learning of rapid prototyping (RP) among professionals, senior year and…
Abstract
Purpose
The purpose of this paper is to detail the development of a multimedia courseware that enhances the learning of rapid prototyping (RP) among professionals, senior year and graduate students.
Design/methodology/approach
The design and development of the multimedia courseware is based on a “visit a science museum” concept where each topic can be accessed depending on the interests or the needs of users. Factors that influence learning curve such as structure of information, application of visual and auditory components and human‐computer interface are addressed and discussed.
Findings
Instructions using multimedia significantly enhances the education process of RP technology. Methods to produce a good multimedia courseware have been introduced.
Originality/value
This paper describes the latest version of the multimedia courseware which is an accompaniment to the third edition of the book entitled Rapid Prototyping: Principles & Applications published in 2009.
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Florencia Edith Wiria, Kah Fai Leong and Chee Kai Chua
Tissue engineering (TE) involves biological, medical and engineering expertise and a current engineering challenge is to provide good TE scaffolds. These highly porous 3D…
Abstract
Purpose
Tissue engineering (TE) involves biological, medical and engineering expertise and a current engineering challenge is to provide good TE scaffolds. These highly porous 3D scaffolds primarily serve as temporal holding devices for cells that facilitate structural and functional tissue unit formation of the newly transplanted cells. One method used successfully to produce scaffolds is that of rapid prototyping. Selective laser sintering (SLS) is one such versatile method that is able to process many types of polymeric materials and good stability of its products. The purpose of this paper is to present modeling of the heat transfer process, to understand the sintering phenomena that are experienced by powder particles in the SLS powder bed during the sintering process. With the understanding of sintering process obtained through the theoretical modeling, experimental process of biomaterials in SLS could be directed towards the appropriate sintering window, so as not to cause unintentional degradation to the biomaterials.
Design/methodology/approach
SLS uses a laser as a heat source to sinter parts. A theoretical study based on heat transfer phenomena during SLS process was carried out. The study identified the significant biomaterial and laser beam properties that were critical to the sintering result. The material properties were thermal conductivity, thermal diffusivity, surface reflectivity and absorption coefficient.
Findings
The influential laser beam properties were laser power and scan speed, which were machine parameters that can be controlled by users. The identification of the important parameters has ensured that favorable sintering conditions can be achieved.
Research limitations/implications
The selection of biopolymer influences the manner in which energy is absorbed by the powder bed during the SLS process. In this paper, the modeling and investigative work was validated by poly(vinyl alcohol) which is a biomaterial that has been used for many biomedical and pharmaceutical purposes.
Practical implications
The paper can be the foundation for extension to other types of biomaterials including biopolymers, bioceramics and biocomposites.
Originality/value
The formulation of the theory for heat transfer phenomena during the SLS process is of significant value to any studies in using SLS for biomedical applications.
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This paper aims to study the issue of the three-dimensional formation coordinated control for the unmanned autonomous helicopter (UAH) by using the sliding mode disturbance…
Abstract
Purpose
This paper aims to study the issue of the three-dimensional formation coordinated control for the unmanned autonomous helicopter (UAH) by using the sliding mode disturbance observer. Under the designed formation coordinated controller, the desired formation can be maintained and the closed-loop system stability is analyzed by using the Lyapunov theory.
Design/methodology/approach
Considering the unknown time-varying external 10; disturbance in formation flight of UAHs, a sliding mode disturbance observer has been employed to estimate them.
Findings
This work is supported in part by the National Natural Science Foundation of China under Grant 61803207, and in part by the Fundamental Research Funds for the Central Universities under Grant LGZD201806.
Originality/value
A sliding mode disturbance observer has been designed to estimate the unknown time-varying external disturbance in formation flight of UAHs. Aiming at the leading UAH maneuver in three-dimensional space during the formation flight progress, the formation coordinated controller has been proposed based on the output of the disturbance observer to maintain the formation.
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AMM Ahsan, Ruinan Xie and Bashir Khoda
The purpose of this paper is to present a topology-based tissue scaffold design methodology to accurately represent the heterogeneous internal architecture of tissues/organs.
Abstract
Purpose
The purpose of this paper is to present a topology-based tissue scaffold design methodology to accurately represent the heterogeneous internal architecture of tissues/organs.
Design/methodology/approach
An image analysis technique is used that digitizes the topology information contained in medical images of tissues/organs. A weighted topology reconstruction algorithm is implemented to represent the heterogeneity with parametric functions. The parametric functions are then used to map the spatial material distribution following voxelization. The generated chronological information yields hierarchical tool-path points which are directly transferred to the three-dimensional (3D) bio-printer through a proposed generic platform called Application Program Interface (API). This seamless data corridor between design (virtual) and fabrication (physical) ensures the manufacturability of personalized heterogeneous porous scaffold structure without any CAD/STL file.
Findings
The proposed methodology is implemented to verify the effectiveness of the approach and the designed example structures are bio-fabricated with a deposition-based bio-additive manufacturing system. The designed and fabricated heterogeneous structures are evaluated which shows conforming porosity distribution compared to uniform method.
Originality/value
In bio-fabrication process, the generated bio-models with boundary representation (B-rep) or surface tessellation (mesh) do not capture the internal architectural information. This paper provides a design methodology for scaffold structure mimicking the native tissue/organ architecture and direct fabricating the structure without reconstructing the CAD model. Therefore, designing and direct bio-printing the heterogeneous topology of tissue scaffolds from medical images minimize the disparity between the internal architecture of target tissue and its scaffold.