Bruno Soares

Additive manufacturing (AM), also known as 3D printing, offers many advantages and, particularly in the medical field, it has stood out for its potential for the manufacture of patient-specific implantable devices. Thus, the unique properties of 3D-printed biocompatible polymers such as Polylactic Acid (PLA) and Polyetheretherketone (PEEK) have made these materials the focus of recent research where new post-processing and joining techniques need to be investigated. This study investigates the weldability of PLA and PEEK 3D-printed plates through stationary shoulder friction stir welding (SS-FSW) with assisted heating. An SS-FSW apparatus was developed to address the challenges of rotating shoulder FSW of thermoplastics, with assisted heating either through the shoulder or through the backing plate, thus minimizing material removal defects in the welds. Successful welds revealed that SS-FSW improves surface quality in both PLA and PEEK welds compared to rotating shoulder tools. Process parameters for PLA welds are investigated using the Taguchi method, emphasizing the importance of lower travel speeds to achieve higher joint efficiencies. In PEEK welds, the heated backing plate proved effective in increasing process heat input and reducing cooldown rates which were associated with higher crystallinity PEEK. Despite these findings, further research is needed to improve the weld strength of SS-FSW with these materials considering aspects like tool design, process stability, and 3D printing parameters. This investigation emphasizes the potential of SS-FSW in the assembly of thermoplastic materials, offering insights into the weldability of additively manufactured biocompatible polymers like PLA and PEEK.

Congenital limb defects occur when a limb does not develop normally during pregnancy. The quality of each person's everyday life is significantly impacted by any of these defects and there is no concrete treatment. 3D modeling and printing, enables the creation and customization of precise virtual and/or physical models, including models of the human anatomy. These technologies provide a novel method of producing new devices with optimized design and production time, improving adaptability, and incorporating functionality. To this end, we propose a method of designing and producing 3D printed assistive devices and we also present an example of an assistive device, done in the 3D Printing Center for Health, as well as its impact on the patient's daily life. With this device, the patient became able to play the guitar and hold a knife, thus helping on these two activities.

Polyetheretherketone (PEEK) is the leading high-performance thermoplastic biomaterial that can be processed through material extrusion (ME) additive manufacturing (AM), also known as three-dimensional (3D) printing, for patient-specific load-bearing implant manufacture. Considering the importance of cyclic loading for load-bearing implant design, this work addresses the high-cycle fatigue behaviour of 3D-printed PEEK. In this work, printed PEEK specimens are cyclically loaded under stress-controlled tension–tension using different stress levels between 75% and 95% of printed PEEK’s tensile strength. The experimental results are used to document 3D-printed PEEK’s fatigue behaviour using Basquin’s power law, which was compared with previous fatigue research on bulk PEEK and other 3D-printing materials. As a pioneering study on its fatigue behaviour, the results from this work show that 3D-printed PEEK exhibits an above-average fatigue strength of 65 MPa, corresponding to about 75% of its tensile strength. Fracture surface analysis suggests that a transition can occur from ductile to brittle fracture with maximum stresses between 85% and 95% of the tensile strength. Evidence of crack propagation features on fracture surfaces under scanning electron microscope (SEM) observation suggests crack initiation in void defects created by printing deposition that propagates longitudinally through line bonding interfaces along layers. Considering this, 3D-printed PEEK’s fatigue behaviour can be strongly related to printing conditions. Further research on the fatigue behaviour of 3D-printed PEEK is necessary to support its use in load-bearing implant applications.

One of the most promising areas for additive manufacturing (AM) adoption is in the healthcare industry, through its ability to produce customized medical devices with personalized fit, feel and functionality. The shift from conventional manufacturing systems to AM implies several changes throughout the medical product’s life cycle phases, from workforce qualification to the relationship with customers. This study investigates the social impact of adopting AM in the medical devices industry. To this end, two case studies related to medical devices were developed: a prosthesis and an orthosis, by applying a social life cycle assessment (S-LCA) methodology. The methodology measures and compares performance and impact of developing, producing, and using the two devices produced by AM, and by conventional processes. The results show how the different stakeholders along the product life cycle stages are affected by the change in the manufacturing technology. Evidence of positive social impacts were found in the ‘Customers’, ‘Local community’ and ‘Society’ stakeholders. A negative social impact was found for the stakeholder ‘Value chain actors’. Furthermore, this study illustrates the suitability of the S-LCA methodology to pinpoint the benefits and negative impacts of AM in each case under study.