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The growing interest in scaffold-guided tissue engineering (TE) to guide and support cell proliferation in the repair and replacement of craniofacial and joint defects gave rise to the quest for a precise technique to create such scaffolds. Conventional manual-based fabrication techniques have several limitations such as the lack of reproducibility and precision. Rapid prototyping (RP) has been identified as a promising technique capable of building complex objects with pre-defined macro- and microstructures. The research focussed on the viability of using the selective laser sintering (SLS) RP technique for creating TE scaffolds. A biocomposite blend comprising of polyvinyl alcohol (PVA) and hydroxyapatite (HA) was used in SLS to study the feasibility of the blend to develop scaffolds. The biocomposite blends obtained via spray-drying technique and physical blending were subjected to laser-sintering to produce test specimens. The SLS-fabricated test specimens were characterized using scanning electron microscopy and X-ray diffraction. The test specimens were also tested for bioactivity by immersing the samples in simulated body fluid environment. The results obtained ascertained that SLS-fabricated scaffolds have good potential for TE applications.

Investment casting (IC) has benefited numerous industries as an economical means for mass producing quality near net shape metal parts with high geometric complexity and acceptable tolerances. The economic benefits of IC are limited to mass production. The high costs and long lead-time associated with the development of hard tooling for wax pattern moulding renders IC uneconomical for low-volume production. The outstanding manufacturing capabilities of rapid prototyping (RP) and rapid tooling (RT) technologies (RP&T) are exploited to provide costeffective solutions for low-volume IC runs. RP parts substitute traditional wax patterns for IC or serve as production moulds for wax injection moulding. This paper reviews the application and potential application of state-of-the-art RP&T techniques in IC. The techniques are examined by introducing their concepts, strengths and weaknesses. Related research carried out worldwide by different organisations and academic institutions are discussed. List of AbbreviationsABS Acrylonitrile-butadiene-styrene ACES Accurate clear epoxy solid AIM ACES injection moulding CAM-LEM Computer-aided manufacturing of laminated engineering materials CMB Controlled metal build-up CTE Coefficients of thermal expansion DMD Direct metal deposition DMLS Direct metal laser sintering DSPC Direct shell production casting FDM Fused deposition modelling IC Investment casting LENS Laser engineered net shaping LG Laser generating LOM Laminated object manufacturing LS Laser sintering MJS Multiphase jet solidification MMA Methyl methacrylate MM II Model Maker II PC Polycarbonate POM Precision optical manufacturing PS Polystyrene RIC Rapid investment casting RP Rapid prototyping RP&T Rapid prototyping and tooling RT Rapid tooling RSP Rapid solidification process SDM Shape deposition modelling SGC Solid ground curing SL Stereolithography SLS Selective laser sintering 3D-P 3D printing Background on investment casting (IC) and rapid prototyping (RP)Investment casting (IC), or "lost-wax" casting, is a precision casting process whereby wax patterns are converted into solid metal parts following a multi-step process [1]. IC enables economical mass-production of near net shaped metal parts containing complex geometries and features [2, 3] from a variety of metals, including difficult-to-machine or non-machinable alloys. To produce precision components, the near net shape of castings can reduce machining time and cost to bring components into specifications.

The ability to have precise control over porosity, scaffold shape, and internal pore architecture is critical in tissue engineering. For anchorage-dependent cells, the presence of three-dimensional scaffolds with interconnected pore networks is crucial to aid in the proliferation and reorganization of cells. This research explored the potential of rapid prototyping techniques such as selective laser sintering to fabricate solvent-free porous composite polymeric scaffolds comprising of different blends of poly(ether-ether-ketone) (PEEK) and hydroxyapatite (HA). The architecture of the scaffolds was created with a scaffold library of cellular units and a corresponding algorithm to generate the structure. Test specimens were produced and characterized by varying the weight percentage, starting with 10 wt% HA to 40 wt% HA, of physically mixed PEEK-HA powder blends. Characterization analyses including porosity, microstructure, composition of the scaffolds, bioactivity, and in vitro cell viability of the scaffolds were conducted. The results obtained showed a promising approach in fabricating scaffolds which can produce controlled microarchitecture and higher consistency.