Rapid Manufacturing Techniques Of Metallic, Polymeric And Ceramic Biomaterials

Metallic Biomaterial: One technique for rapid manufacturing of Metallic biomaterial is a Subtractive Rapid Prototyping process called CNC-RP. The geometry of defects can be reverse engineered working from images (CT scans etc), and then accurate fillers can be automatically generated in advanced biomaterials and other bioactive materials. Medical implants are produced from many different biocompatible materials, based on their size, shape, placement in the body, and overall functionality. More specifically, implants used in bone repair and joint replacement have been made from solid and porous stainless steel, ceramics, natural coral, allograft and autograft bone, and different alloys of titanium and cobalt, among others.

There is a challenge in creating accurate shaped implants using biosensitive materials; in particular for those using specialized materials, or naturally occurring materials such as bone or coral. Subtractive Rapid Prototyping (SRP) is particularly well-suited for such a highly customized and material-specific challenge. Rapid prototyping using CNC machining, or CNC-RP (Frank et al. , 2002; Frank, 2007) is a fully functional SRP system that can automatically generate fixture, tooling and setup plans, for creating a part directly from a CAD file. This CNC-RP process is based on a setup strategy whereby a rotating device is used to orient round like stock material that is fixed between two opposing chucks. Rotating the stock using an indexer eliminates the problem of retaining reference coordinates associated with reclamping of a part in a conventional fixture. For each orientation, all visible surfaces are machined and a set of sacrificial supports keep it connected to the uncut ends of the stock material. Once all operations are complete, the supports are severed (sawed or milled) in a final series of operations and the part is removed. Polymeric Biomaterial: The fundamental concept underlying tissue engineering is to combine a scaffold or matrix, with living cells, and/or biologically active molecules to form a tissue engineering construct (TEC) to promote the repair and/or regeneration of tissues.

The scaffold (a cellular solid support structure comprising an interconnected pore network) or matrix (often a hydrogel in which cells can be encapsulated) is expected to perform various functions, including the support of cell colonization, migration, growth and differentiation. External size and shape of the construct are of importance, particularly if it is customized for an individual patient. Besides the physical properties of a scaffold or matrix material (e. g. stiffness, strength, surface chemistry, degradation kinetics), the micro-architecture of the constructs is of great importance for the tissue formation process. In recent years, a number of automated fabrication methods have been employed to create scaffolds with well-defined architectures. These have been classified as rapid prototyping (RP) technologies, solid freeform fabrication (SFF) techniques, or according to the latest ASTM standards, additive manufacturing (AM) techniques.

Together with the development of biomaterials suitable for these techniques, the automated fabrication of scaffolds with tunable, reproducible and mathematically predictable physical properties has become a fast-developing research area. Ceramic Biomaterial: Selective laser sintering (SLS), which is an additive rapid manufacturing technique, it is capable of producing the required product directly and automatically from a 3D computer model representation, have been selected to build implant and scaffold structures using composite materials consisting of a polymer and a bioactive ceramic. Hydroxyapatite (HA), a bioceramic that encourages bone apposition, can be combined with high density polyethylene (HDPE), a biocompatible polymer, to form a material with appropriate stiffness, toughness and bioactivity for use in the body. A miniature SLS system was built to minimize the usage of the expensive experimental material. It was used to determine the CO2 laser sintering operation window of the HA/HDPE composites and to investigate the effect of the process parameters on the surface morphology of the sintered HA/HDPE layer. SLS process deals with powdered materials such as polymers, ceramics, metals and mixed composites. SLS process allows a wide range of materials to be used and it is a building process without the need for supports, which enables its use in a vast range of applications. SLS was initially used to produce of physical models of human anatomy for surgical planning, training and design of customised implants in the medical field such as models of two skulls (Berry et al. 1997).

The potential of SLS for directly fabricating the implants or tissue scaffold has been investigated using Nylon-6 (Das et al. 2003), polycaprolactone (PCL) (Williams et al. 2005), blended HA/polyetheretherketone (PEEK) (Tan et al. 2003) and HA/polyvinyl alcohol (PVA) composites (Chua et al. 2004). SLS process deals with powdered materials such as polymers, ceramics, metals and mixed composites. SLS process allows a wide range of materials to be used and it is a building process without the need for supports, which enables its use in a vast range of applications. SLS was initially used to produce of physical models of human anatomy for surgical planning, training and design of customised implants in the medical field such as models of two skulls (Berry et al. 1997). The potential of SLS for directly fabricating the implants or tissue scaffold has been investigated using Nylon-6 (Das et al. 2003), polycaprolactone (PCL) (Williams et al. 2005), blended HA/polyetheretherketone (PEEK) (Tan et al. 2003) and HA/polyvinyl alcohol (PVA) composites (Chua et al. 2004).