Additive manufacturing (AM) refers to methods that generate three-dimensional structures layer by layer. There is a range of AM technologies each compatible with the specific form of the raw input material that may be in liquid, metal and polymer powder, filament, and sheet form. AM technology particularly lends itself to applications in bioengineering in printing a range of human body parts as well as medical implants. There is a significant global and local effort in the area.
Additive Manufacture is rising in importance globally because parts can be built directly from computer models or from re-engineered components bypassing traditional manufacturing processes such as cutting, milling, and grinding. Benefits include new designs not possible using conventional subtractive technology, dramatic savings in time, materials, energy, and other costs in producing new components, as well as significant reductions in environmental impact, and faster time to market.
RMIT through its Advanced Manufacturing Precinct (AMP) and the Centre for Additive Manufacturing is involved in a number of bioengineering research projects investigating the application of 3D printing technology. One project is set to transform the way we surgically treat bone tumors, and dramatically improve patient and healthcare outcomes. The five-year project, “Just in time implants”, brings together the IMCRC, RMIT University, the University of Technology Sydney, St Vincent’s Hospital Melbourne and global medical technology firm Stryker.
The project combines 3D printing of lattice-based implants, robotic surgery, and advanced manufacturing to create tailored implants for patients with bone cancer. Patient-specific implants, as opposed to traditional orthopedic implants, are derived from the patient’s own CT and MRI scans. The design process typically involves the use of image processing software to segment the patient’s anatomy, identify defects, disease or deformity, preparation of the virtual surgical plan, and design of the implant. The implants are then manufactured by using either a laser or electron beam powder-bed based technology. In this process, a laser or electron beam is used to scan a bed of metal powder based on the computer designed medical implant. As the laser scans the powder it melts it and fuses it to the layer below. Following each layer scan another layer of fresh powder typically 0.03 to 0.05 mm in thickness is deposited and the process repeated until the part is completed.
Lattice structures offer a number of advantages over solid implants. Lattice structures have traditionally been used in orthopedic implants as porous surface coatings on solid implants to enhance secondary fixation through bone on-growth and in-growth. In addition to their superior biological properties, lattice structures also possess unique structural properties making them a superior alternative to solid implants. For example, lattice structures have a high strength to weight compared to solid structures and their design variables can be tailored to enhance biological response as well as static and dynamic mechanical behaviour as demonstrated by RMIT research studies. Illustrated in Figure 1 is an example of a lattice implant designed and manufactured at RMIT AMP in a model bone. This novel approach represents a major shift in the way implants are designed, manufactured, and supplied and could lead to bespoke local manufacturing. The process will expand the surgical options available to patients and surgeons and increase the potential for limb saving surgery and furthermore spinal cord injuries (See Figure 2).
In another project supported by the ARC Training Centre in Additive Biomanufacturing, the RMIT team is using 3D printing to tackle another clinical area: radiation dosimetry. As with bone implants, there is a great potential benefit in the method, largely around the patient specificity offered by additive fabrication. The project involves examining how radiation phantoms – models on which radiation therapy is tested to examine how radiation will be absorbed and scattered by the body’s organs – can be made better using polymer 3D printing. The effort involves close collaboration with Melbourne’s Peter MacCallum Cancer Centre. Radiation phantoms are used where the reaction of tissue to radiation is of interest, including: diagnosis and treatment, studying effects on tissue, minimising health risks from radiation, and using radiation to kill cancerous cells.
Radiation phantoms come in different forms and can represent a patient’s body or a section of their anatomy, but are often simple shapes from an engineering point of view. The more customised and close to reacting like a patient’s actual anatomy, the more effective such phantoms are in clinical applications. 3D printing is being examined systematically to test how 3D printed polymers behave when exposed to radiation. The research being conducted by RMIT University has the potential to better emulate lung and other more complicated tissue types when exposed to radiation.
The work represents another instance of medical technology collaboration between RMIT researchers and PhD students and industry to solve real medical problems and improve delivery of novel health care solutions at lower costs.
About the Author:
Distinguished Professor Milan Brandt is the Technical Director of RMIT’s Advanced Manufacturing Precinct and the Director of RMIT’s Centre for Additive Manufacturing. He is the leading Australian researcher in the area of macro processing with lasers and has conducted work in laser cladding, cutting, drilling, welding, assisted machining, and more recently additive manufacturing. This has resulted in technological achievements, patents, research papers, and commercial products, which have been recognized internationally and nationally in both scientific and industrial circles. He has commercialized the results of his research and also actively promoted the benefits of laser technology to the Australian industry through invited presentations, conference papers, and industry seminars. Professor Brandt initiated and chaired several international conferences and workshops and has extensive links with many international researchers and organizations. He is a Board member and fellow of the Laser Institute of America and honorary fellow of the Welding Technology Institute of Australia.