Thiago Borges, project manager, Medical Device Competence Center, (MDCC), Evonik business line health care, explains why Evonik are ready to support the standard and custom biomaterial and technology requirements of customers for the streamlined development and scale-up of advanced, personalised bioresorbable implant device applications.
Additive manufacturing, commonly referred to as 3D printing, is the process by which a digital model is converted into a three-dimensional physical model via the printing of consecutive layers of material.
For the last three decades, 3D printing has been earmarked as a transformational innovation that can disrupt existing practices across multiple industries. However, it has only been in the last few that 3D printing has become a commercial reality.
Within the medical devices industry, 3D printing technologies have already begun to be utilised across a variety of market segments. 3D printed devices show great potential to generate significant value-based health care outcomes across these and other application areas. For example, the development of an implant device such as a facial plate with patient-specific geometries can dramatically help to accelerate healing, reduce pain and minimise wait times. For clinicians and payers, 3D printing technologies should also help to improve overall levels of productivity and patient satisfaction.
3D-based innovations for implantable medical devices have to date been primarily based around the use of metallic materials. As bioresorbable, biocompatible polymers continue to replace traditional metallic materials these outcomes should only become even more pronounced. This is due to incremental reductions in manufacturing times, and lower surgical costs such as eliminating the need for secondary surgery for implant removal. However, the widespread utilisation of bioresorbable polymers as a preferred material for 3D printed medical device implants will remain difficult to achieve until innovations emerge that can address knowledge gaps such as the impact of various properties, like degradation during the printing process.
There are three main technologies that are most commonly considered for the 3D printing of medical device implants with polymers. Extrusion-based 3D printing which utilises standard pellets and is compliant with multiple materials has a limited print resolution with upfront investment costs, rivaling traditional extrusion equipment. Selective Laser Sintering (SLS), which utilises powder-based materials, allows companies to produce parts with excellent compressive strength, high resolution and the ability to create parts with complex geometries. However, the processes required to attain device parts at sufficient levels of quality can be highly complex.
Fused Deposition Modeling (FDM), which is also referred to as Fused Filament Fabrication (FFF), is another key 3D printing technology for the production of medical implants. This printing process enables the continuous feeding of a filament-based material from a spool through a moving, heated extruder nozzle. There are several advantages in the 3D printing of medical device applications with FDM technologies; the equipment itself is less complex compared to SLS or extrusion-based technologies, it is compliant for use with multiple types of polymer and other materials, and it is highly efficient. With a low melt residence time, parts with complex geometries are also easy to duplicate.
To enable the commercial use of FDM technologies in the production of medical implant devices, it will be of critical importance to develop high molecular weight, implantable, medical-grade filaments that can be manufactured in controlled environments. Such polymers must also be suitable to manufacture patient-specific bioresorbable implants with acceptable part properties and be available in a range of grades on quality spools that are suitable for higher resolution printing. These filament materials must also come from established, trusted suppliers with a record for safety, biocompatibility, performance and supply security to minimise regulatory and scale-up risk.
Resomer filaments
In a search for answers to address such unmet market needs, Evonik has sought to combine its leadership position for biomaterials with new polymer–based 3D printing competencies across various technologies including extrusion-based printing, SLS and FDM.
For more than three decades, Evonik’s Resomer portfolio of bioresorbable polymers has been utilised around the world by medical device companies to enhance various medical implant devices and parenteral controlled release drug products. More than 20 Resomer grades in various compositions such as Polylactide (PLLA), Polylactide co-glycolide (PLGA), Polydioxanone (PDO) and Polycaprolactone (PCL) are available with a range of degradation times and Inherent Viscosities (IV). The portfolio aims to deliver breadth and versatility to match specific device requirements across multiple application areas.
The company has leveraged this existing expertise in the design and synthesis of bioresorbable polymers to develop a new line of Resomer filaments that are suitable for the 3D printing of device parts with FDM technologies.
Resomer filaments are ideal for high resolution 3D printing, with four different grades offered in a 1.75 mm diameter. These PLLA, PLGA, PCL, and PDO-based filament grades feature tight specifications including diameter size and processing temperatures. Degradation times can range from less than six months to greater than three years to match a range of application requirements.
Resomer filaments feature mechanical properties and degradation rate profiles that can be precisely tailored to match the target application. As with other Resomer products, all filament grades undergo hydrolysis degradation in vivo and are eliminated through excretory pathways.
Application area example
The 3D printing of Cranial Maxillo Facial (CMF) plates for use in surgeries for congenital or acquired defects of the skull and facial region represents a significant application opportunity for the use of filament-based bioresorbable polymers and FDM technologies. With mechanical properties including strength, durability, flexibility and the elimination of stress shielding all required, such specialised materials and advanced processes can be leveraged to rapidly and cost-effectively create parts for personalised, high resolution CMF plates that are devoid of defects. Part testing for such devices will still need to be done according to the International Organisation for Standardisation (ISO)/American Society for Testing and Materials (ASTM).
Beyond Resomer filament
In addition to the development and supply of Resomer filaments, Evonik also offers advanced application technology solutions to companies who are seeking to enhance the safety and performance of their bioresorbable implant devices. Evonik’s MDCC in the United States, and application laboratories in Germany and China try to provide customers with a broad range of application services for 3D printing technologies. Evonik also specialises in the development of customised polymers and filaments to match specific application requirements based on specific customer needs.
Summary
While 3D-printing still represents a small fraction of the overall market, industry drivers including a shift to personalised health care, government incentives, reductions in manufacturing time and other technological advances are expected to make this segment increasingly visible and attractive for use over the coming decade.
The convergence of modern 3D printing technologies, including FDM, with a new line of bioresorbable and biocompatible filament-based polymers will enable the development of a new generation of 3D printed implants. These advances will help to improve patient care, accelerate availability of implants for surgeons, and also reduce costs across a broad range of application areas. Evonik is the only known supplier with a full portfolio of granule and filament options for bioresorbable polymers and is therefore well positioned to serve as a supplier and innovation partner for 3D printed device technologies.
A new line of Resomer filaments with a range of material choices and degradation properties that are designed for use across multiple application areas for high resolution printing with FDM technologies are now available for supply.
Evonik has a global network of labs for application technology support, and high-quality Resomer production sites in the United States and Europe.