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Three-dimensional bioprinting (3D bioprinting) is used for repairing and regenerating living tissues due to its ease of use, cost-effectiveness and high precision in fabricating. Owing to their high biocompatibility, natural hydrogels are widely used as scaffold materials in bioprinting. However, the mechanical properties and low printability of hydrogels present a challenge. This study aims to introduce a composite hydrogel that exhibits excellent mechanical, biological and printability properties simultaneously.

Alginate (Alg), carboxymethyl cellulose (CMC) and nanohydroxyapatite (nHA) as suitable materials for 3D printing were used. Effect of material content and pre-crosslinking on various properties of these materials were investigated. Both quantitative and qualitative experiments were conducted to validate the biomaterial ink’s printability, its rheological characteristics, as well as its biological and mechanical properties.

Based on the analysis of the obtained experimental results from all mentioned tests, a hydrogel with a composition of 4% Alg, 2% CMC and 2% nHA with the pre-crosslinking process was selected as the preferred option. The results demonstrated that the selected material has good cell adhesion, wettability, degradation rate and 93% cell viability. Furthermore, compared to the composition of 4% Alg–2% CMC, the chosen material exhibited a 52% improvement in printability and a 55% improvement in compressive modulus.

A significant challenge in the field of 3D bioprinting is the development of scaffolds that possesses optimal mechanical, biological and printability characteristics simultaneously, essential for attaining tissue-like properties. Hence, this paper explores a novel nanocomposite hydrogel that demonstrates promising outcomes across all these aspects simultaneously.

In this study, two postprocessing techniques, namely, conventional burnishing (CB) and ultrasonic-assisted burnishing (UAB), were applied to improve the fatigue behavior of 316 L stainless steel fabricated through selective laser melting (SLM). The effects of these processes on surface roughness, porosity, microhardness and fatigue performance were experimentally investigated. The purpose of this study is to evaluate the feasibility and effectiveness of ultrasonic-assisted burnishing as a preferred post-processing technique for enhancing the fatigue performance of additively manufactured components.

All samples were subjected to a sandblasting process. Next, the samples were divided into three distinct groups. The first group (as-Built) did not undergo any additional postprocessing, apart from sandblasting. The second group was treated with CB, while the third group was treated with ultrasonic-assisted burnishing. Finally, all samples were evaluated based on their surface roughness, porosity, microhardness and fatigue performance.

The results revealed that the initial mean surface roughness (Ra) of the as-built sample was 11.438 µm. However, after undergoing CB and UAB treatments, the surface roughness decreased to 1.629 and 0.278 µm, respectively. Notably, the UAB process proved more effective in eliminating near-surface pores and improving the microhardness of the samples compared to the CB process. Furthermore, the fatigue life of the as-built sample, initially at 66,000 cycles, experienced a slight improvement after CB treatment, reaching 347,000 cycles. However, the UAB process significantly enhanced the fatigue life of the samples, extending it to 620,000 cycles.

After reviewing the literature, it can be concluded that UAB will exceed the capabilities of CB in terms of enhancing the surface roughness and, subsequently, the fatigue performance of additive manufactured (AM) metals. However, the actual impact of the UAB process on the fatigue life of AM products has not yet been thoroughly researched. Therefore, in this study, this paper used the burnishing process to enhance the fatigue life of 316 L stainless steel produced through the SLM process.

This paper aims to study the elasto-dynamic behavior of additively manufactured metallic lattice implants and compare them with human lower-body bone. This work is a step toward producing implants with high similarity of material properties to bone by developing a dynamic design approach.

A suitable topology was selected and admissible design space was established. Implants were fabricated by selective laser melting. Material dynamics, including elastic modulus, damping and natural frequency, were analyzed with experimental and finite element method methodology.

Generally, porosity improves dynamic properties up to an optimum point, which depends on printability, that is, ∼70%. Regarding elastic modulus and natural frequency, it is possible to achieve enough similarity with bone. But, considering damping, the similarity is <23% and <12% with dry and fresh bone, respectively. Damping and strain rate sensitivity increase with porosity. The natural frequency decreases with porosity. Bone ingrowth into lattice implants improves damping substantially while increasing elastic modulus.

Designers, dominantly had quasi-static approach, which considered only elastic modulus. But, the human body is a dynamic structure and experiences dynamic loads; meanwhile, bone, with its damping and natural frequency, regulates dynamic events like shock absorption and elastic wave filtering. Importantly, bone cells sense no load in quasi-static loading and must receive impact loads near their natural frequencies and special accelerations to conduct optimum mechanotransduction. So, it is necessary to develop a dynamic strategy which is comprehensive and describes bone duties.