3D printing, which is also known as additive manufacturing, involves a process in which two-dimensional layers of raw material are joined sequentially to build a rapidly constructed three-dimensional object.
The design and production of products using 3D printing have resulted in reduced material waste, conserved energy, and decreased time to bring products to the market. The capability of 3D printing can provide designers and manufacturers the flexibility of modifying a structural design without needing to alter machinery or tools in a manufacturing process. Such technological advancements have increased the use of 3D printing in the medical device industry.
Applications For 3D-Printed Medical Devices
Whereas some medical devices are 3D-printed from a standard design, other devices are 3D-printed to be patient-specific using imaging data. A digital 3D file, typically from a Magnetic Resonance Image (MRI) or a computer-aided design (CAD) drawing, is used in the development and design of the printed medical device. These patient-matched devices are scaled to consider a patient’s specific anatomical features and internal structures. Contrary to traditional medical device manufacturing, 3D printers provide flexibility in altering a medical device’s thickness, curvature, length, and overall shape while maintaining device performance. The most common medical devices that are produced through the 3D printing process include external prosthetics, dental crowns, orthopedic and cranial implants, and surgical instruments.
Several different technologies can be used in the 3D printing process, which is dependent on the use of the medical device and the functionality of the printer. Unlike conventional, subtractive manufacturing which requires excess material to be cut away, the 3D printing process deposits thin layers of material only where is needed, resulting in about 98% of the raw material being utilized in the final product.
Additive manufacturing technologies include different categories of 3D printers, ranging from inkjet depositing printers to fused layers of powder to sheet lamination systems. Regardless of the printer or material type, the process of 3D printing includes several standard steps. The Food and Drug Administration (FDA) is involved in evaluating the quality of the printing processes and final medical device products. The standardized 3D printing process and the FDA’s technical considerations and guidance are as follows:
Designing the Medical Device
The process begins with a 3D blueprint design, which is specified to validated sizes or matched to a patient’s anatomy. The NIH’s 3D Print Exchange provides a platform in which prototypes can be submitted and clinically reviewed for scientific and medical accuracy per the NIH’s evaluation. The 3D-printable prototypes which meet applicable standards are available and shared on the NIH’s open-source website. The 3D Print Exchange is a public resource that provides a platform for innovation and collaboration; however, submission to the NIH is not an FDA requirement.
The FDA recommends that the minimum possible feature size of a device design be compared with the desired feature size to determine the tolerance of the manufacturing printer, the design parameters, and the design conditions, all of which should be documented. A defined design, including dimension parameters and mechanical limits, must be established before scaling designs for patient-specific medical devices. Clinical staff, device manufacturers, or clinical inputs, including individual measurements, patient imaging, and clinical assessments can contribute to the modification of patient-specific device designs.
The FDA also states that personally identifiable and protected health information (PHI) should be properly managed when device designers are patient-matching devices, which is described in the FDA premarket submissions and postmarket management guidance documents for cybersecurity in medical devices.
Software Workflow and Material Control
The FDA recommends that the software workflow be validated to prevent file conversion errors and compromised device component properties. Once finalized, a file of the standardized formats of the device design and specifications should be documented and archived. Next, the design is converted to a digital file for the printer to read, which informs the printer as to how to divide the layers of the design, where the foundation of the design should be built upon the printing platform, and what material will be used in the process. The printer is also prepared during this time, which may include setting updates and refilling raw material. The material controls, including procedures, requirements, and agreements regarding the material specifications are also confirmed during this time to ensure high-quality and consistent built devices. To ensure consistency of the printed medical devices, the FDA notes that the identity of the materials and/or chemicals, the material supplier, the material specifications, and material certificates of analysis be documented. For designs in which unused raw material can be reused, the FDA recommends a material reuse process be established to monitor for changes in the material and limit the percentage of material reused.
Printing and Post-Processing
While the printing process is automatic, the time-to-completion can vary from minutes to days, which is dependent upon the printer technology, the complexity of the device design, and materials involved.
Following printing completion, medical devices commonly require post-processing steps such as drilling, polishing, sterilization, controlled cooling, or removal of residual debris. According to the FDA, the process and effect of the post-processing steps should be documented, which would identify the mitigation steps implemented to avoid harmful effects from post-processing.
Process Validation and Verification
As outlined above, the process parameters, steps involved before printing, and raw materials utilized all directly impact the quality of a 3D-printed medical device. Following production, some of the device’s component characteristics are verified to meet specifications and functionality requirements. For characteristics that cannot be inspected following production, such as harmful strength tests, processes before validation should be authenticated, monitored, and controlled.
In addition to process validation, the FDA also states that software and test methods must be validated. To validate such processes, monitoring and control methods should be documented, which might include environmental conditions or the status of mechanical elements of the printer. Revalidation may be required for any changes made to the processes or device design, which is detailed throughout several of the FDA’s medical device regulation guidance documents.
The methods and results of device testing are submitted to the FDA to demonstrate safety, effectiveness, and compliance with regulatory requirements according to the medical device’s intended use. While 3D-printed medical devices are generally held to the same regulatory requirements as devices which are manufactured traditionally, each device may also have specific requirements or assessments based on international standards, internal standards, or FDA Guidance documents. For premarket submissions of a 3D-printed medical device, the type and amount of data required for a determination of approval are dependent on the risk profile, intended use, classification, and regulation for that device type.
In summary, the FDA is involved in regulating the manufacturing, packaging, labeling, and importing of 3D-printable medical devices just like their traditionally manufactured counterparts. The FDA continues to evaluate the safety and effectiveness of submissions for new 3D printed medical devices, provide guidance on 3D printing manufacturing recommendations, and consider new applications of 3D printing within the clinical industry.
Many 3D-printed medical devices, such as instrumentation and implants, are commercially available. Research is being conducted to investigate how manufactured living organs could involve 3D printing. In addition to building medical devices, the U.S. Department of Energy is exploring ways that 3D printing can benefit manufacturing processes by reducing waste and decreasing manufacturing steps.
In what clinical settings or industry sectors do you foresee 3D printing advancing?