A Comparative Study for Material Selection in 3D Printing of Scoliosis Back Brace

Silver Nanoparticles in 3D Printing: A New Frontier in Wound Healing

This review examines the convergence of silver nanoparticles (AgNPs), three-dimensional (3D) printing, and wound healing, focusing on significant advancements in these fields. We explore the unique properties of AgNPs, notably their strong antibacterial efficacy and their potential applications in enhancing wound recovery. Furthermore, the review delves into 3D printing technology, discussing its core principles, various materials employed, and recent innovations. The integration of AgNPs into 3D-printed structures for regenerative medicine is analyzed, emphasizing the benefits of this combined approach and identifying the challenges that must be addressed. This comprehensive overview aims to elucidate the current state of the field and to direct future research toward developing more effective solutions for wound healing.

Examining the Flexural Behavior of Thermoformed 3D-Printed Wrist-Hand Orthoses: Role of Material, Infill Density, and Wear Conditions

This paper examined the mechanical properties of wrist-hand orthoses made from polylactic acid (PLA) and polyethylene terephthalate glycol (PETG), produced through material extrusion with infill densities of 55% and 80%. These orthoses, commonly prescribed for wrist injuries, were 3D-printed flat and subsequently thermoformed to fit the user's hand. Experimental and numerical analyses assessed their mechanical resistance to flexion after typical wear conditions, including moisture and long-term aging, as well as their moldability. Digital Imaging Correlation investigations were performed on PLA and PETG specimens for determining the characteristics required for running numerical analysis of the mechanical behavior of the orthoses. The results indicated that even the orthoses with the lower infill density maintained suitable rigidity for wrist immobilization, despite a decrease in their mechanical properties after over one year of shelf life. PLA orthoses with 55% infill density failed at a mean load of 336 N (before aging) and 215 N (after aging), while PETG orthoses did not break during tests. Interestingly, PLA and PETG orthoses with 55% infill density were less influenced by aging compared to their 80% density counterparts. Additionally, moisture and aging affected the PLA orthoses more, with thermoforming, ongoing curing, and stress relaxation as possible explanations related to PETG behavior. Both materials proved viable for daily use, with PETG offering better flexural resistance but posing greater thermoforming challenges.

Mechanical Properties of Additively Manufactured Polymeric Materials-PLA and PETG-For Biomechanical Applications

The study presented herein concerns the mechanical properties of two common polymers for potential biomedical applications, PLA and PETG, processed through fused filament fabrication (FFF)-Material Extrusion (ME). For the uniaxial tension tests carried out, two printing orientations-XY (Horizontal, H) and YZ (Vertical, V)-were considered according to the general principles for part positioning, coordinates, and orientation typically used in additive manufacturing (AM). In addition, six specimens were tested for each printing orientation and material, providing insights into mechanical properties such as Tensile Strength, Young's Modulus, and Ultimate Strain, suggesting the materials' potential for biomedical applications. The experimental results were then compared with correspondent mechanical properties obtained from the literature for other polymers like ASA, PC, PP, ULTEM 9085, Copolyester, and Nylon. Thereafter, fatigue resistance curves (S-N curves) for PLA and PETG, printed along 45°, were determined at room temperature for a load ratio, R, of 0.2. Scanning electron microscope observations revealed fibre arrangements, compression/adhesion between layers, and fracture zones, shedding light on the failure mechanisms involved in the fatigue crack propagation of such materials and giving design reference values for future applications. In addition, fractographic analyses of the fatigue fracture surfaces were carried out, as well as X-ray Computed Tomography (XCT) and Thermogravimetric (TGA)/Differential Scanning Calorimetric (DSC) tests.

Heat and Moisture Transfer Depending on 3D-Printed Thermoplastic Polyurethane and Ethylene-Vinyl Acetate Foam and the Presence of Holes for 3D Printing Clothing Development

Recently, clothing development 3D printing and the evaluation of its physical characteristics have been explored. However, few studies have tackled thermal comfort, which is a major contributor to the wearers' comfort. Therefore, this study was designed to suggest effective materials and hole sizes for clothing obtained by 3D printing to maintain a comfortable clothing environment. In particular, two main variables, namely five different materials and three-hole sizes, were analyzed. All samples were placed on a hot plate (36 °C), and their surface temperature and humidity were measured for 10 min. The samples with only thermoplastic polyurethane (TPU) achieved the largest temperature change of 3.2~4.8 °C, whereas those with ethylene-vinyl acetate (EVA) foam exhibited the lowest temperature change of -0.1~2.0 °C. Similarly, the samples with only TPU showed the greatest humidity change of -0.7~-5.5%RH. Moreover, the hole size had a larger effect on humidity change than material type. The samples with large holes achieved the largest humidity change of -4.4%RH, whereas the samples without holes had the smallest humidity change of -1.5%RH after 10 min (p < 0.001). Based on these results, various combinations of materials and hole sizes should be considered to fit the purpose of 3D printing clothing.

An Insight into the Characteristics of 3D Printed Polymer Materials for Orthoses Applications: Experimental Study

Knee orthoses assist patients with impaired gait through the amendment of knee abnormalities, restoration of mobility, alleviation of pain, shielding, and immobilization. The inevitable issues with laborious traditional plaster molding procedures for orthoses can be resolved with 3D printing. However, a number of challenges have limited the adoption of 3D printing, the most significant of which is the proper material selection for orthoses. This is so because the material used to make an orthosis affects its strength, adaptability, longevity, weight, moisture response, etc. This study intends to examine the mechanical, physical, and dimensional characteristics of three-dimensional (3D) printing materials (PLA, ABS, PETG, TPU, and PP). The aim of this investigation is to gain knowledge about these materials' potential for usage as knee orthosis materials. Tensile testing, Olympus microscope imaging, water absorption studies, and coordinate measuring machine-based dimension analysis are used to characterize the various 3D printing materials. Based on the investigation, PLA outperforms all other materials in terms of yield strength (25.98 MPa), tensile strength (30.89 MPa), and shrinkage (0.46%). PP is the least water absorbent (0.15%) and most flexible (407.99%); however, it is the most difficult to fabricate using 3D printing. When producing knee orthoses with 3D printing, PLA can be used for the orthosis frame and other structural elements, PLA or ABS for moving parts like hinges, PP for padding, and TPU or PP for the straps. This study provides useful information for scientists and medical professionals who are intrigued about various polymer materials for 3D printing and their effective utilization to fabricate knee orthoses.

From Virtual Reconstruction to Additive Manufacturing: Application of Advanced Technologies for the Integration of a 17th-Century Wooden Ciborium

3D modelling and 3D printing techniques have become increasingly popular in different fields, including cultural heritage. In this field, there are still many challenges to overcome, such as the difficulty of faithfully reproducing complex geometries or finding materials suitable for restoration, due to the limited scientific studies. This work proposes an example of the application of advanced technologies for the reproduction of four missing columns of a 17th century polychrome wooden ciborium. The difficulties of an automatic scan due to its reflective surface (water gilding and estofado decorations) were overcome by creating a 2D manual survey and a subsequent manual 3D redrawing. The CAD model was used to print the missing elements with fused filament fabrication (FFF) in polyethylene terephthalate glycol (PETG), using the following printing parameters: nozzle 0.4 mm, infill 20%, extrusion temperature of PLA 200 °C and of PETG 220 °C, plate temperature 50 °C, printing speed 60 mm/s, layer height 0.2 mm. The conservation and restoration of the ciborium is nearing completion. This study highlights the importance of collaboration between different professionals for the correct design of a restoration, as well as the need to promote scientific research into the development of new high-performance 3D printing materials suitable for conservation.

Additive Manufacturing of Spinal Braces: Evaluation of Production Process and Postural Stability in Patients with Scoliosis

Spinal orthoses produced using additive manufacturing show great potential for obtaining patient-specific solutions in clinical applications, reducing manual operations, time consumption, and material waste. This study was conducted to evaluate the production process of spinal orthoses produced by additive manufacturing, and to test the effects of 3D-printed braces on postural stability in patients with adolescent idiopathic scoliosis and osteogenesis imperfecta. Ten patients were recruited consecutively and were asked to wear a spinal orthosis produced by additive manufacturing for 2 weeks. The four phases of the production process for each brace were evaluated separately on a scale from 0 (not acceptable) to 3 (optimal). Postural stability in the unbraced and the two braced conditions (3D-printed and conventional) was assessed using validated metrics obtained from a wearable inertial sensor. The production process was evaluated as good in four cases, acceptable in five cases, and not acceptable in one case, due to problems in the printing phase. No statistically significant differences were observed in any of the postural balance metrics between the 3D-printed and conventional brace. On the other hand, postural balance metrics improved significantly with both types of braces with respect to the unbraced condition. Spinal orthoses produced with an innovative production process based on digital scans, CAD, and 3D printing are valid alternatives to conventionally produced orthoses, providing equivalent postural stability.