Effects of post-curing duration on the mechanical properties of complex 3D printed geometrical parts.

This study aims to assess the efficacy of post-curing guidance supplied by 3D printing resin manufacturers. Current guidance applies generically to all geometries with the caveat that post-curing should be extended for 'large' or 'complex' geometries but specific guidance is not provided. Two vat-polymerisation 3D printers (Form3B, Figure 4 Standalone) were used to print test models in 6 biocompatible resins (Pro Black, Med White, Med Amber, Biomed Black, Biomed White, Biomed Amber). The test model is of a complex geometry whilst also housing ISO 527 test specimens in concentric layers. Two separate intervals of curing were applied (100%, 500% stated guidance) creating different curing treatments of the specimens throughout the model. Post processed test models were disassembled and pull testing performed on each of the specimens to assess the mechanical properties. The analysis showed that extending the curing duration had significant effects on the mechanical properties of some materials but not all. The layers of the model had a significant effect except for elongation at break for the Med Amber material. This research demonstrates that generic post-curing guidance regarding UV exposures is not sufficient to achieve homogenous material strength properties for complex geometries. Large variations in mechanical properties throughout the models suggest some material was not fully-cured. This raises a query if such materials as originally marketed as biocompatible are fully cured and therefore safe to use for medical applications involving complex geometries.

Assessment and selection of filler compounds for radiopaque PolyJet multi-material 3D printing for use in clinical settings.

The aim of this research was to assess a selection of radiopaque filler compounds for increasing radiopacity in a resin suitable for Polyjet multi-material 3D printing. A radiopaque resin has potential applications in medicine to produce patient-specific anatomical models with realistic radiological properties, training aids, and skin contacting components such as surgical or procedural guides that require visibility under fluoroscopy. The desirable filler would have a high level of radiopacity under ionising imaging modalities, such as X-ray, CT, fluoroscopy or angiography. Nine potential filler compounds were selected based on atomic number and handling risk: barium sulphate, bismuth oxide, zirconium oxide, strontium oxide, strontium fluoride, strontium carbonate, iodine, niobium oxide and tantalum oxide. The fillers were evaluated using selected criteria. A weighted material selection matrix was developed to prioritise and select a filler for future 3D printing on a multi-material 3D printer. Zirconium oxide was the highest scoring filler compound in the material selection matrix, scoring 4.4 out of a maximum of 5. MED610TM resin doped with zirconium oxide was shown to be UV curable, and when cured is non-toxic, environmentally friendly, and has the ability to display antimicrobial properties. In terms of radiopacity, a sample with thickness 1.5 mm of MED610™ resin doped with 20 wt.% zirconium oxide produced X-ray radiopacity equivalent to 3 mm of aluminium. Zirconium oxide was selected using the material selection matrix. This radiopaque resin can be used to produce anatomical models with accurate radiological properties, training aids or skin contacting devices that require visibility under ionising imaging modalities. The 3D printing validation run successfully demonstrated that the material selection matrix prioritised a filler suitable for radiopaque multi-material 3D printing.

The application of additive manufacturing / 3D printing in ergonomic aspects of product design: A systematic review.

Additive Manufacturing (AM) facilitates product personalization and iterative design, which makes it an ideal technology for ergonomic product development. In this study, a systematic review was conducted of the literature regarding the use of AM in ergonomic-product design, and methodological aspects of the studies were analyzed. A literature search was performed using the keywords "3D print*," "additive manufacturing," "ergonomic*" and "human factors". Included were studies reporting the use of AM specifically in ergonomic design of products/prototypes including the detailing of an ergonomic testing methodology used for evaluation. Forty studies were identified pertaining to the fields of medicine, assistive technology, wearable technology, hand tools, testing devices and others. The most commonly used technology was fused deposition modeling with polylactic acid, but the overall preferred material was acrylonitrile butadiene styrene. Various combinations of objective/subjective and qualitative/quantitative product evaluation methods were used. Based on the findings, recommendations were developed to facilitate the choice of most suitable AM technologies and materials for specific applications in ergonomics.

Three-Dimensional Printing of Medical Devices Used Directly to Treat Patients: A Systematic Review.

Until recently, three-dimensional (3D) printing/additive manufacturing has not been used extensively to create medical devices intended for actual clinical use, primarily on patient safety and regulatory grounds. However, in recent years there have been advances in materials, printers, and experience, leading to increased clinical use. The aim of this study was to perform a structured systematic review of 3D-printed medical devices used directly in patient treatment. A search of 13 databases was performed to identify studies of 3D-printed medical devices, detailing fabrication technology and materials employed, clinical application, and clinical outcome. One hundred and ten papers describing one hundred and forty medical devices were identified and analyzed. A considerable increase was identified in the use of 3D printing to produce medical devices directly for clinical use in the past 3 years. This is dominated by printing of patient-specific implants and surgical guides for use in orthopedics and orthopedic oncology, but there is a trend of increased use across other clinical specialties. The prevailing material/3D-printing technology used were titanium alloy/electron beam melting for implants, and polyamide/selective laser sintering or polylactic acid/fused deposition modeling for surgical guides and instruments. A detailed analysis across medical applications by technology and materials is provided, as well as a commentary regarding regulatory aspects. In general, there is growing familiarity with, and acceptance of, 3D printing in clinical use.

A Radiopaque Nanoparticle-Based Ink Using PolyJet 3D Printing for Medical Applications.

The aim of this study was to develop a 3D printable radiopaque ink and successfully print a finished artifact. Radiopaque 3D printing would be hugely beneficial to improve the visibility of medical devices and implants, as well as allowing more realistic phantoms and calibration aids to be produced. Most 3D printing technologies are polymer based. Polymers are naturally radiolucent, allowing X-rays to pass through, showing up as faint dark gray regions on X-ray detectors, as for soft tissues. During this study, a 3D printable ultraviolet (UV) curable resin containing zirconium oxide (ZrO2) nanoparticles was developed. 5 wt.% ZrO2 was dispersed in a base resin using a high-shear mixer. Particles remained in suspension for 6-8 h at room temperature, allowing time for 3D printing. A model of a hand including radiopaque bones and a test block demonstrating a range of internal radiopaque features were successfully 3D printed. Radiopacity was demonstrated in the 3D-printed models, and there was good dispersion of ZrO2 within the resin matrix. The impregnated resin remained UV curable and viscosity was not compromised. In this study, 3D-printed radiopaque features demonstrated clear radiopacity under X-ray and microcomputed tomography imaging.