The selection and application of design methodologies for the design of bone tissue scaffolds

Abstract

Research motivation: Bone tissue scaffolds offer a way forward in a strategy to change from tissue replacement to tissue regeneration. Bone tissue scaffolds are a combination of a physical construct, with clearly defined three-dimensional spatial properties, and biological cells. The microstructure of this construct is the bridge between the physicochemical properties of the scaffold and the cellular processes responsible for tissue regeneration. Gap statement: A formal design methodology has yet to be applied for the design of bone tissue scaffolds Aims and objectives: The aim of this research thesis is to select and apply design methods to the design of bone tissue scaffolds. The objectives are: 1. Review the current state of the art in design theory and methodologies for successful applications of design methods 2. Identify which design techniques are currently implemented in bone tissue scaffold design 3. To apply appropriate design methods to the design of bone tissue scaffolds 4. To validate the design outputs via a survey of expert opinion Methodologies: The following design methodologies were applied; Quality Function Deployment (QFD) and Theory of Inventive Problem Solving (TRIZ), an expanded house of quality, three-dimensional relationship technology chart (3DRTC) and Axiomatic Design (AD).Results: The multi-tiered literature review for design methodologies, firstly, identified the above design methods and, secondly, found no reason to exclude them for consideration as design methods for bone tissue scaffolds. The second literature review identified extensive computer-image-based-design as the current most advanced design method in the domain for bone tissue scaffolds. No formal design methods were in use. The first Quality Function Deployment method identified conflicts in the design which were used as inputs into TRIZ to generate potential solutions. The second QFD approach identified an extensive list of design requirements along with target engineering metrics. The three-dimensional relationship technology chart proposed how to organise design requirements into a scaffold design based upon differing scaffold design strategies. In Axiomatic Design, two approaches were followed: the first based upon percolation theory and the second based upon time-dependent behaviour. These models proposed designs at a higher level of abstraction for scaffold designers, rather than the providing the more practical solutions achieved by the QFD and 3DRTC approaches. Validation: The output of the design methodologies were validated by a survey of expert opinion. The responses indicated that both Axiomatic Design and an expanded house of quality tool offered innovation, and enhancement to, the field of bone tissue scaffold design. Conclusion: Formal design methodologies such as Axiomatic Design and Quality Function Deployment provide design solutions which offer innovation, and enhancement to, the field of bone tissue scaffold design.