Simulated and Experimental Investigation of Mechanical Properties for Improving Isotropic Fracture Strength of 3D-Printed Capsules

Advancements in diabetic foot insoles: a comprehensive review of design, manufacturing, and performance evaluation

The escalating prevalence of diabetes has accentuated the significance of addressing the associated diabetic foot problem as a major public health concern. Effectively offloading plantar pressure stands out as a crucial factor in preventing diabetic foot complications. This review comprehensively examines the design, manufacturing, and evaluation strategies employed in the development of diabetic foot insoles. Furthermore, it offers innovative insights and guidance for enhancing their performance and facilitating clinical applications. Insoles designed with total contact customization, utilizing softer and highly absorbent materials, as well as incorporating elliptical porous structures or triply periodic minimal surface structures, prove to be more adept at preventing diabetic foot complications. Fused Deposition Modeling is commonly employed for manufacturing; however, due to limitations in printing complex structures, Selective Laser Sintering is recommended for intricate insole designs. Preceding clinical implementation, in silico and in vitro testing methodologies play a crucial role in thoroughly evaluating the pressure-offloading efficacy of these insoles. Future research directions include advancing inverse design through machine learning, exploring topology optimization for lightweight solutions, integrating flexible sensor configurations, and innovating new skin-like materials tailored for diabetic foot insoles. These endeavors aim to further propel the development and effectiveness of diabetic foot management strategies. Future research avenues should explore inverse design methodologies based on machine learning, topology optimization for lightweight structures, the integration of flexible sensors, and the development of novel skin-like materials specifically tailored for diabetic foot insoles. Advancements in these areas hold promise for further enhancing the effectiveness and applicability of diabetic foot prevention measures.

Topology optimization on metamaterial cells for replacement possibility in non-pneumatic tire and the capability of 3D-printing

One of the applications of mechanical metamaterials is in car tires, as a non-pneumatic tire (NPT). Therefore, to find a suitable cell to replace the pneumatic part of the tire, three different solution methods were used, including topology optimization of the cubic unit cell, cylindrical unit cell, and fatigue testing cylindrical sample (FTCS). First, to find the mechanical properties, a tensile test was conducted for materials made of polylactic acid (PLA) and then, the optimization was done based on the weight and overhang control for the possibility of manufacturing with 3D printers, as constraints, besides, the objective of minimum compliance. In the optimization of the cubic unit cell, the sample with a minimum remaining weight of 35% was selected as the optimal sample. However, for the cylindrical unit cell, a sample with a weight limit of 20% was the most optimal state. In contrast, in the FTCS optimization, a specimen with lower remaining weight equal to 60% of the initial weight was selected. After obtaining the answer, five cells in the FTCS and two mentioned cells were evaluated under compressive testing. The samples were also subjected to bending fatigue loadings. The results demonstrated that cellular structures with 15% of lower weight than the optimized samples had the same fatigue lifetime. In the compressive test, the line slope of the specimens with cellular structures in the elastic region of the force-displacement diagram was reduced by 37%, compared to the completely solid samples. However, the weight of these samples decreased by 59%. Furthermore, the fracture surface was also investigated by field-emission scanning electron microscopy. It was observed that a weak connection between the layers was the cause of failure.

Development of 3D-Printed Self-Healing Capsules with a Separate Membrane and Investigation of Mechanical Properties for Improving Fracture Strength

Studies on self-healing capsules embedded in cement composites to heal such cracks have recently been actively researched in order to improve the dimensional stability of concrete structures. In particular, capsule studies were mainly conducted to separately inject reactive healing solutions into different capsules. However, with this method, there is an important limitation in that the probability of self-healing is greatly reduced because the two healing solutions must meet and react. Therefore, we propose three-dimensional (3D) printer-based self-healing capsules with a membrane structure that allows two healing solutions to be injected into one capsule. Among many 3D printing methods, we used the fusion deposition modeling (FDM) to design, analyze, and produce new self-healing capsules, which are widely used due to their low cost, precise manufacturing, and high-speed. However, polylactic lactic acid (PLA) extruded in the FDM has low adhesion energy between stacked layers, which causes different fracture strengths depending on the direction of the applied load and the subsequent performance degradation of the capsule. Therefore, the isotropic fracture characteristics of the newly proposed four types of separated membrane capsules were analyzed using finite element method analysis. Additionally, capsules were produced using the FDM method, and the compression test was conducted by applying force in the x, y, and z directions. The isotropic fracture strength was also analyzed using the relative standard deviation (RSD) parameter. As a result, the proposed separated membrane capsule showed that the RSD of isotropic fracture strength over all directions fell to about 18% compared to other capsules.

Overview and Comparison of PLA Filaments Commercially Available in Europe for FFF Technology

This study presents a comprehensive techno-economic analysis of PLA materials for fused filament fabrication (FFF) from eight European manufacturers. The comparison involved rigorous experimental assessments of the mechanical properties, dimensional accuracy, and print quality using standardized methods and equipment such as tensile and CT testing. What makes this study unique is the consistent methodology applied, considering factors such as material color, printing temperature, printing orientation, filament diameter, and printer selection, to ensure meaningful and reliable results. Contrary to the common belief that a higher price implies better quality, the study revealed that the second cheapest PLA material achieved the best overall performance within the methodology employed. The study also confirmed certain observations, such as the influence of printing orientation and geometry on dimensional accuracy and mechanical properties, as well as the significant disparities between manufacturer-provided values and actual measured mechanical properties, highlighting the importance of experimental verification. Hence, the findings of this study hold value not only for the scientific community but also for hobbyist printers and beginners in the 3D printing realm seeking guidance in material selection for their projects. Furthermore, the methodology employed in this research can be adapted for evaluating a broad range of other 3D printing materials.

3D printed TPMS structural PLA/GO scaffold: Process parameter optimization, porous structure, mechanical and biological properties

Bone scaffolds should have good biocompatibility and mechanical and biological properties, which are primarily by the material design, porous structure, and preparation process. In this study, we proposed polylactic acid (PLA) as the base material, graphene oxide (GO) as an enhancing filler, triply periodic minimal surface (TPMS) as a porous structure, and fused deposition modeling (FDM) 3D printing as a preparation technology to develop a TPMS structural PLA/GO scaffold and evaluate their porous structures, mechanical properties, and biological properties towards bone tissue engineering. Firstly, the influence of the FDM 3D printing process parameters on the forming quality and mechanical properties of PLA was studied by orthogonal experimental design, based on which the process parameters were optimized. Then, GO was composited with PLA, and PLA/GO nanocomposites were prepared by FDM. The mechanical tests showed that GO can effectively improve the tensile and compression strength of PLA; only by adding 0.1% GO the tensile and compression modulus was increased by 35.6% and 35.8%, respectively. Then, TPMS structural (Schwarz-P, Gyroid) scaffold models were designed and TPMS structural PLA/0.1%GO nanocomposite scaffolds were prepared by FDM. The compression test showed that the TPMS structural scaffolds had higher compression strength than the Grid structure; This was owing to the fact that the continuous curved structure of TMPS alleviated stress concentration and had a more uniform stress bearing. Moreover, cell culture indicated bone marrow stromal cells (BMSCs) showed better adhesion, proliferation, and osteogenic differentiation behaviors on the TPMS structural scaffolds as the continuous surface structure of TPMS had better connectivity and larger specific surface area. These results suggest that the TPMS structural PLA/GO scaffold has potential application in bone repair. This article suggests the feasibility of co-designing the material, structure, and technology for achieving the good comprehensive performance of polymer bone scaffolds.

The Analysis of Mechanical Properties and Geometric Accuracy in Specimens Printed in Material Jetting Technology

The purpose of this research was to analyze polymer materials based on mechanical properties and geometrical parameters, such as the smallest material deviations and the best printing texture after three-dimensional (3D) printing in two methods of Material Jetting technology: PolyJet and MultiJet. This study covers checks for Vero Plus, Rigur, Durus, ABS, and VisiJet M2R-WT materials. Thirty flat specimens were printed both for 0 and 90 raster orientations. Specimen scans were superimposed on the 3D model from CAD software. Each of them was tested, paying attention to the accuracy and the layer thickness effect of printed components. Then, all specimens were subjected to tensile tests. The obtained data-Young's modulus and Poisson's ratio-were compared using statistical methods, focusing on the two most important parameters: the isotropy of the printed material in two directions and the characteristics close to linear. It was found that unitary surface deviation with general dimensional accuracy equal to ±0.1 mm was the common feature of printed models. Some small areas had lower accuracy depending on the material and printer device. Rigur material obtained the highest mechanical properties. Dimensional accuracy in Material Jetting technology as a function of layer parameters such as layer thickness and raster orientation was checked. The materials were checked in terms of relative isotropy and linearity. Additionally, similarities and differences between PolyJet and MultiJet methods were covered.

Strategies To Modify the Surface and Bulk Properties of 3D-Printed Solid Scaffolds for Tissue Engineering Applications

3D printing is one of the effective scaffold fabrication techniques that emerged in the 21st century that has the potential to revolutionize the field of tissue engineering. The solid scaffolds developed by 3D printing are still one of the most sought-after approaches for developing hard-tissue regeneration and repair. However, applications of these solid scaffolds get limited due to their poor surface and bulk properties, which play a significant role in tissue integration, loadbearing, antimicrobial/antifouling properties, and others. As a result, several efforts have been directed to modify the surface and bulk of these solid scaffolds. These modifications have significantly improved the adoption of 3D-printed solid scaffolds and devices in the healthcare industry. Nevertheless, the in vivo implant applications of these 3D-printed solid scaffolds/devices are still under development. They require attention in terms of their surface/bulk properties, which dictate their functionality. Therefore, in the current review, we have discussed different 3D-printing parameters that facilitate the fabrication of solid scaffolds/devices with different properties. Further, changes in the bulk properties through material and microstructure modification are also being discussed. After that, we deliberated on the techniques that modify the surfaces through chemical and material modifications. The computational approaches for the bulk modification of these 3D-printed materials are also mentioned, focusing on tissue engineering. We have also briefly discussed the application of these solid scaffolds/devices in tissue engineering. Eventually, the review is concluded with an analysis of the choice of surface/bulk modification based on the intended application in tissue engineering.

Various Substitute Aggregate Materials for Sustainable Concrete

Concrete is one of the most widely used structural construction materials and has significantly influenced industrial development [...].

A novel workflow to fabricate a patient-specific 3D printed accommodative foot orthosis with personalized latticed metamaterial

Patients with diabetes mellitus are at elevated risk for secondary complications that result in lower extremity amputations. Standard of care to prevent these complications involves prescribing custom accommodative insoles that use inefficient and outdated fabrication processes including milling and hand carving. A new thrust of custom 3D printed insoles has shown promise in producing corrective insoles but has not explored accommodative diabetic insoles. Our novel contribution is a metamaterial design application that allows the insole stiffness to vary regionally following patient-specific plantar pressure measurements. We presented a novel workflow to fabricate custom 3D printed elastomeric insoles, a testing method to evaluate the durability, shear stiffness, and compressive stiffness of insole material samples, and a case study to demonstrate how the novel 3D printed insoles performed clinically. Our 3D printed insoles results showed a matched or improved durability, a reduced shear stiffness, and a reduction in plantar pressure in clinical case study compared to standard of care insoles.