Selective Laser Sintering Technology Research Articles

Walnut shell/phenolic resin carbon electrodes via laser sintering and KOH activation

Currently, the application of 3D-printed biomass-based carbon electrodes is hindered by their suboptimal performance. This study utilizes walnut shell powder as a carbon source and employs Selective Laser Sintering (SLS) technology for the efficient 3D printing of a double-helix carbon precursor. High-performance biomass-based carbon electrodes are prepared through carbonization and KOH activation. Comparative studies on the microstructure and electrochemical performance of the carbonized and activated samples were conducted. Experimental results demonstrate that KOH activation significantly enhances the microstructure of the carbon electrodes, leading to marked improvements in their electrochemical performance. During desalination experiments, the carbon electrodes exhibited excellent ion removal efficiency, with a maximum conductivity reduction rate of 0.2 μS/cm·min, confirming their feasibility in seawater desalination applications. This research validates the potential of walnut shell biomass for the preparation of 3D-printed carbon electrodes, addressing bottlenecks in traditional carbon electrode manufacturing processes while promoting efficient biomass utilization and environmental protection.

Experimental and Simulation Study of Fiber-Reinforced and Foam-Filled Anti-Tetrachiral and Re-Entrant Structures

Negative Poisson's ratio (NPR) honeycomb structures exhibit excellent properties, including resistance to compression, impact resistance, and energy absorption. To better study NPR structures, this paper investigates two different methods to enhance the mechanical properties and energy absorption capabilities of re-entrant and anti-tetrachiral structures. Fiber reinforcement and polyurethane foam filling methods were used to address material enhancement issues, aiming to achieve structures with high specific energy absorption. Specimens were fabricated using selective laser sintering technology with three different material configurations, including nylon, carbon fiber-reinforced nylon, and glass fiber-reinforced nylon, for comparative analysis. Additionally, some specimens were filled with polyurethane foam. Quasi-static compression tests indicated that both glass fiber-reinforced nylon and foam filling significantly improved the material's stiffness, initial peak stress, and energy absorption, although the "auxetic" effect was weakened. Subsequently, finite element methods were used to simulate the deformation modes and mechanical properties of the two NPR structures, and the numerical results showed good agreement with the experimental results.

Study on the fabrication and mechanical properties of SiCp/SiC gradient lattice structure based on selective laser sintering technology

ABSTRACT Conventional uniform lattice structures are subject to non-uniform loads or concentrated loads alternating back and forth during service, which can no longer meet the refinement requirements. In this paper, SiCp/SiC gradient lattice structures are prepared by selective laser sintering (SLS) technology and polymer impregnation pyrolysis (PIP) process, and compression standard specimens with different tilt angles are prepared according to the structural model by changing the printing direction, to analyze the influence of the anisotropic properties of the materials due to the SLS molding technology on the load-bearing behaviour of the core rod, and to further study the mechanical properties of the gradient lattice structures and the Failure behaviour. The results show that: with the increase of the angle of printing direction, the compression performance of the densification specimen decreases gradually; the compression strength of the gradient lattice structure is 13.95 MPa. During compression, the core rods with tilt angles of 60° and 75° mainly exhibit shear failure and crushing failure, respectively. The theoretical and simulated compression strengths were 16.08 and 16.32 MPa, respectively. This paper provides a new insight into the research and application of gradient lattice structures.

3D-Printed Shape Memory and Piezoelectric Bifunctional Thermoplastic Polyurethane/Polyvinylidene Fluoride Porous Composite Scaffold for Bone Regeneration.

Physical stimulations such as mechanical and electric stimulation can continuously work on bone defect locations to maintain and enhance cell activity, and it has become a hotspot for research in the field of bone repair. Herein, bifunctional porous composite scaffolds with shape memory and piezoelectric functions were fabricated using thermoplastic polyurethane (TPU) and poly(vinylidene fluoride) through triply periodic minimal surfaces design and selective laser sintering technology. Thereinto, the shape fixity ratio and recovery ratio of the composite scaffold reached 98.6% and 81.2%, respectively, showing excellent shape memory functions. More importantly, its piezoelectric coefficient (d33 = 2.47 pC/N) is close to the piezoelectric constant of bone tissue (d33 = 0.7-2.3 pC/N), and the voltage released during the compression process can reach 0.5 V. Furthermore, cyclic compression experiments showed that the strength of composite scaffold was up to 8.3 times compared with the TPU scaffold. Besides, the composite scaffold showed excellent cytocompatibility. In conclusion, the composite scaffold is expected to continuously generate mechanical and electric stimulation due to shape memory and piezoelectric function, respectively, which provide an effective strategy for bone repair.

A Chemotherapy-Photothermal synergistic system in bifunctional bone Scaffold: Tumor therapy and bone repair

Bone defect repair and tumor recurrence are the main challenges in the postoperative treatment of bone tumors. The incorporation of zoledronate (ZOL) into scaffolds presents a promising approach, attributed to its osteogenic and anti-tumor properties. However, there are still some unfavorable factors that make it difficult to eradicate tumor cells at the surgical site, including drug rapid release, the insufficient anti-tumor efficacy of ZOL and the multidrug resistance of chemotherapy. Herein, a novel nano drug delivery platform mesoporous silicon-coated graphene oxide (GO/MSN) and ZOL loaded nanoparticle (GO/MSN-ZOL) were developed. Then PLLA/ GO/MSN-ZOL scaffold that integrates photothermal therapy (PTT) and chemotherapy was fabricated using poly (L-lactic acid) as raw materials by selective laser sintering (SLS) technology. The GO not only imparted scaffold with photothermal properties for localized tumor cell ablation but also significantly enhanced its anti-tumor efficacy through synergistic effects in combination with chemotherapy. The mesoporous structure and large specific surface area of MSN contribute to the sustained release of ZOL. Additionally, GO could promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), which in combine with ZOL’s osteoclast inhibition, enhances the bone repair capacity. This study offers a straightforward and promising strategy for treating tumor-related bone defects.

Effect of shape and thermal conductivity of microstructured capillary-porous coatings on heat transfer during evaporation and boiling in thin horizontal liquid layers

Investigation results on heat transfer during evaporation and boiling in thin horizontal liquid layers on 2D modulated capillary-porous coatings with a sinusoidal profile in a wide range of relative pressures and layer heights are presented in this paper. Coatings were made on a 3D laser printer using the technology of additive selective laser sintering (SLS). One coating was made of bronze with a modulation wavelength equal to the Laplace constant of the working fluid and two coatings were made of stainless steel and bronze with a doubled wavelength. The experimental data obtained on the coatings were compared with each other and with the values obtained by evaporation and boiling of n-dodecane on a smooth surface under the same conditions. It is shown that in the region of low relative pressures in liquid layers with a height less than the Laplace constant, heat transfer intensification achieved on a sample made of a material with low thermal conductivity (stainless steel) was five times higher as compared to a smooth surface. In the range of relative pressures, when nucleate boiling was observed in the layers, the temperature difference reached on the bronze coatings was approximately 3–4 times less than on a smooth surface. The temperature difference for the stainless steel coating changed little with an increase in the heat flux. In pre-crisis conditions, the temperature difference during boiling on the stainless steel coating was less than on the bronze coatings in the entire range of relative pressures and layer heights. The highest critical heat fluxes were obtained on a bronze coating with a modulation wavelength equal to the Laplace constant.

3D-printing of Fe–Ni bimetallic particles and their application in removal of arsenic from water

Arsenic is a hazardous element found in water sources, and removing it is crucial for ensuring a safe environment and water quality. Iron-based metal oxides efficiently remove arsenic; however, their small particle sizes make separation from water difficult after arsenic removal. Furthermore, the growing global issue of polymer waste further complicates environmental concerns. Combining three-dimensional (3D) printing and adsorption technology by incorporating nanosized functional materials into supporting polymers offers a potential solution to address both challenges. In this study, we developed a 3D-printed adsorption material through the incorporation of synthesized Fe–Ni bimetallic particles into a supporting polymer using selective laser sintering (SLS) technology. This adsorbent's properties were examined through scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and zeta potential. Furthermore, its performance in removing As(III) and As(V), even at trace levels, was assessed under varied conditions. The 3D-printed adsorbent demonstrated excellent removal of As(III) at pH 6, and As(V) at pH 4, lowering their concentration below 10 μg/L, thereby adhering to the limit established by the World Health Organization (WHO). Both As(III) and As(V) fitted the Freundlich isotherm and pseudo-second-order model, suggesting potential heterogeneous and chemisorption processes. FT-IR indicated that the exchange of the –OH group of Fe–OH with oxyanions of As(III) and As(V) could be the adsorption mechanism. Additionally, thermodynamic evaluation unveiled an endothermic and non-spontaneous adsorption reaction. The 3D-printed adsorbent exhibited excellent reusability across recurring adsorption cycles. The combination of SLS 3D printing with Fe–Ni bimetallic particles produces structures that retain their functionality in removing both arsenic species present in water. This indicates the potential of the 3D-printed adsorbent for effective treatment of arsenic-contaminated water, offering remedies to challenges like handling small particle sizes, mitigating polymer waste, and addressing environmental concerns.

Briefing: Selective laser sintering technology to print walnut shell/phenolic resin new biomass-based porous electrode

In this paper, porous carbon electrodes were prepared by using walnut shell and phenolic resin as matrix materials, combined with selective laser sintering (SLS) technology and carbonization process. The effects of different ratios and temperatures on the macroscopic morphology, graphitization degree, electrical conductivity and pore structure of the carbonized parts were investigated. The results show that the lower proportion of walnut shell and the higher carbonization temperature increase the degree of graphitization. High temperature has a significant effect on the conductivity. The conductivity at 1000 °C is 7.5197 S·cm−1, which is 752 % higher than that at 600 °C, while the conductivity at 30 % walnut shell content is only 75.4 % higher than that at 50 %. This study provides a new reference for the preparation of carbon electrodes with complex shape and structure by biomass consumables.

A novel process study of biomass-based graphene-enriched body based on selective laser sintering technology

Laser-induced graphene (LIG) on natural wood is a novel method for producing porous graphene composite materials with low cost and high efficiency. However, the three-dimensional (3D) fabrication of biomass-derived LIG remains challenging, restricting its applications in various domains. This paper introduces a “SCG” (sintering, carbonization and grapheneization) preparation strategy, which integrates selective laser sintering and multiple laser processes to achieve rapid fabrication of graphene-enriched structures from natural biomass materials with complex shapes. The experiment demonstrates that the sintering necks are preserved during the carbonization and graphitization process, maintaining the original interlocking state of the upper and lower layers. The laser power and irradiation times for producing porous graphene have an optimal range, beyond which the quality of the synthesized graphene deteriorates. This study validates the effectiveness of this method and investigates the optimal process parameters and application directions. This method not only offers a 3D fabrication technique for biomass-derived LIG for the first time, but also enables 3D printing of biomass carbon electrodes, which have the benefits of wide applicability, no need for activators, low cost, and high efficiency.

Optimization of a tetrahedron compliant spherical joint via computer-aided engineering tools

This article focuses on enhancing the range of motion (ROM) of the Tetra II joint, a spherical compliant joint consisting of three internally interconnected tetrahedron-shaped elements that achieve motion through elastic deformation. Despite its excellent precision, this specific design is constrained in terms of ROM due to internal contacts among the tetrahedral elements. To overcome this limitation, this study utilizes a computer-aided engineering (CAE) framework to optimize the configuration of the Tetra II joint and enhance its ROM. The resultant optimized joint, referred to as Tetra III, is subsequently compared to Tetra II in terms of both ROM and center shift. Finite element models (FEM) are employed to validate the optimization results and examine how various tetrahedron-shaped geometries impact the joint’s performance. The newly optimized joint exhibits a significantly higher ROM compared to the previous version, while maintaining excellent precision and overall smaller dimensions. Finally, to demonstrate its manufacturability, the Tetra III joint is produced using selective laser sintering (SLS) technology, with Duraform PA serving as the construction material. The successful fabrication serves as a demonstrative example of the improved design of the Tetra III joint.

Mechanical Testing of Selective-Laser-Sintered Polyamide PA2200 Details: Analysis of Tensile Properties via Finite Element Method and Machine Learning Approaches.

This study delves into the mechanical characteristics of polyamide PA2200 components crafted using selective laser sintering (SLS) technology. Our primary objective is to analyze the tensile behavior of the components printed at various orientations, showing its response to diverse loading conditions. Finite element method (FEM) modeling was employed to analyze the tensile behavior of these details. The time determined for breaking the detail is 9 s. In addition we forecast key properties, such as tensile behavior and strength, using machine learning (ML) techniques, and the best models are for predicting relative elongation are KNeighborsRegressor and SVR.

Process Study of Selective Laser Sintering of PS/GF/HGM Composites.

To address the issues of insufficient strength and poor precision in polystyrene forming parts during the selective laser sintering process, a ternary composite of polystyrene/glass fiber/hollow glass microbeads was prepared through co-modification by incorporating glass fiber and hollow glass microbeads into polystyrene using a mechanical mixing method. The bending strength and dimensional accuracy of the sintered composites were investigated by conducting an orthogonal test and analysis of variance to study the effects of laser power, scanning speed, scanning spacing, and delamination thickness. The process parameters were optimized and selected to determine the optimal combination. The results demonstrated that when considering bending strength and Z-dimensional accuracy as evaluation criteria for terpolymer sintered parts, the optimum process parameters are as follows: laser power of 24 W, scanning speed of 1600 mm/s, scanning spacing of 0.24 mm, and delamination thickness of 0.22 mm. Under these optimal process parameters, the bending strength of sintered parts reaches 6.12 MPa with a relative error in the Z-dimension of only 0.87%. The bending strength of pure polystyrene sintered parts is enhanced by 15.69% under the same conditions, while the relative error in the Z-dimension is reduced by 63.45%. It improves the forming strength and precision of polystyrene in the selective laser sintering process and achieves the effect of enhancement and modification, which provides a reference and a new direction for exploring polystyrene-based high-performance composites and expands the application scope of selective laser sintering technology.

Innovative Approaches to 3D Printing of PA12 Forearm Orthoses: A Comprehensive Analysis of Mechanical Properties and Production Efficiency.

This research paper aims to explore the mechanical characteristics of polyamide PA12 (PA12) as a 3D material printed utilizing Selective Laser Sintering (SLS) and HP MultiJet Fusion (HP MJF) technologies in order to design and manufacture forearm orthoses. The study assessed the flowability of the materials used and compared the mechanical performance of PA12 with each other using tensile, flexure, and impact tests in five different fabrication orientations: X, Y, Z, tilted 45° XZ, and tilted 45° YZ. The results of the study provide, firstly-the data for testing the quality of the applied polyamide powder blend and, secondly-the data for the design of the orthosis geometry from the aspect of its strength parameters and the safety of construction. The mechanical parameters of SLS specimens had less variation than MJF specimens in a given orientation. The difference in tensile strength between the 3D printing technologies tested was 1.8%, and flexural strength was 4.7%. A process analysis of the forearm orthoses revealed that the HP MJF 5200 system had a higher weekly production capacity than the EOS P396 in a production variance based on obtaining maximum strength parameters and a variance based on maximizing economic efficiency. The results suggest that medical device manufacturers can use additive manufacturing technologies to produce prototypes and small-batch parts for medical applications. This paper pioneers using 3D printing technology with Powder Bed Fusion (PBF) methods in designing and manufacturing forearm orthoses as a low- to medium-volume product. The applied solution addresses the problem of medical device manufacturers with regard to the analysis of production costs and mechanical properties when using 3D printing for certified medical devices.

A bidirectional quasi-zero stiffness metamaterial for impact attenuation

A reusable bidirectional quasi-zero stiffness metamaterial (BQZS-MM) with quasi-zero stiffness zones under compressive and tensile loads is proposed, which can be employed for bidirectional kinetic energy absorption and impact attenuation. The BQZS-MM is characterized by the parallel connection of positive stiffness components and negative stiffness components to generate the BQZS. At the unit level, the bidirectional BQZS characteristics are analyzed theoretically and validated by simulations. The research further discusses the span and amplitude of the quasi-zero stiffness zone with structural parameters and serial-parallel mechanisms. The effect of quasi-zero stiffness zone’ span and amplitude on dynamic performance is investigated. The physical prototypes are manufactured by selective laser sintering technology. The BQZS and reusability characteristics of BQZS-MM are examined by three repeated tensile and compressive tests. In comparison to existing metamaterials with bidirectional negative stiffness in one principal direction, under compressive and tensile loads, energy absorption, specific energy absorption, energy density, and crushing force efficiency of BQZS-MM have been significantly improved. During dynamic analysis, BQZS-MM attenuates bidirectional response acceleration peaks and achieves bidirectional impact attenuation. However, existing metamaterial with unidirectional quasi-zero stiffness can only achieve unidirectional impact attenuation. The BQZS-MM features novel BQZS mechanical characteristics, serving as a guide for creating brand-new buffer energy absorbers.

PH-Responsive nanoplatform synergistic gas/photothermal therapy to eliminate biofilms in poly(L-lactic acid) scaffolds.

To date, implant-associated infection is still a significant clinical challenge, which cannot be effectively eliminated by single therapies due to the formation of microbial biofilms. Herein, a pH-responsive nanoplatform was constructed via the in situ growth of zinc sulfide (ZnS) nanoparticles on the surface of Ti3C2 MXene nanosheets, which was subsequently introduced in poly(L-lactic acid) (PLLA) to prepare a composite bone scaffold via selective laser sintering technology. In the acidic biofilm microenvironment, the degradation of ZnS released hydrogen sulfide (H2S) gas to eliminate the biofilm extracellular DNA (eDNA), thus destroying the compactness of the biofilm. Then, the bacterial biofilm became sensitive to hyperthermia, which could be further destroyed under near-infrared light irradiation due to the excellent photothermal property of MXene, finally achieving gas/photothermal synergistic antibiofilm and efficient sterilization. The results showed that the synergistic gas/photothermal therapy for the composite scaffold not only evidently inhibited the formation of biofilms, but also effectively eradicated the eDNA of the already-formed biofilms and killed 90.4% of E. coli and 84.2% of S. aureus under near infrared light irradiation compared with single gas or photothermal therapy. In addition, the composite scaffold promoted the proliferation and osteogenic differentiation of mouse bone marrow mesenchymal stem cells. Thus, the designed scaffold with excellent biofilm elimination and osteogenesis ability has great potential as an alternative treatment for implant-associated bone infections.

Establishment of an Animal Model of Dog Bite Injuries.

Nowadays dog bite is becoming a world public health problem. Therefore, the study aimed to develop a dog bite animal model that is helpful to solve these problems. In this study, the skull of an adult dog was scanned. The three-dimensional model of the dog maxillofacial bones and dentition was built by MIMICS. Next, the model was printed with Co-Cr alloy by using selective laser sintering technology to develop the dog bite simulation pliers. Then, to simulate dog bite to most, the maximum bite force of the pliers was measured and actions contained in dog bite process was analyzed. Afterwards, according to action analysis results, rabbits were bitten by the prepared instrument in actions that simulate dog's bite. Finally, the reproducibility and controllability of this animal model of dog bite injuries was validated in an in vivo study. The results showed a reliable animal model of dog bite injuries has been developed in this study. The sites and severities of the injuries could be adjusted as the operator wishes and the animal model of dog bite injuries was highly repeatable. This study also indicates the feasibility of using digital technology in establishing animal bite models.

Additive Manufactured Parts Produced Using Selective Laser Sintering Technology: Comparison between Porosity of Pure and Blended Polymers.

For different manufacturing processes, porosity occurs in parts made using selective laser sintering (SLS) technology, representing one of the weakest points of materials produced with these processes. Even though there are different studies involving many polymeric materials employed via SLS, and different manuscripts in the literature that discuss the porosity occurrence in pure or blended polymers, to date, no researcher has reported a systematic and exhaustive comparison of the porosity percentage. A direct comparison of the available data may prove pivotal in advancing our understanding within the field of additively manufactured polymers. This work aims to collect and compare the results obtained by researchers who have studied SLS's applicability to different amorphous or semi-crystalline polymers and pure or blended materials. In particular, the porosity values obtained by different researchers are compared, and tables are provided that show, for each material, the process parameters and the measured porosity values.

Application of Additive Manufacturing Technology for Chair Parts Connections

Additive manufacturing (AM) is a potential technology to be applied for replacing wood joints in the furniture industry. Overall, 3D-printed connectors have a lot of advantages in chair construction: the possibility of improving the design by using colored materials and new concepts with no limits of shape and size, avoiding the use of synthetic materials such as adhesives and finishing materials. The present research shows the results of the research conducted on 3D-printed connectors for a chair leg-stretchers joint. Larch (Larix decidua Mill.) wood was used for chair components and selective laser sintering (SLS) technology was employed for the 3D-printing connector designed to assemble the chair elements. Diagonal tensile and compression tests were performed on the L-type joints with 3D-printed connectors and the bending moments were determined and compared to the results obtained after testing the leg-stretchers mortise–tenon joints made of larch wood, taken as a reference. Micrograph investigation was finally performed on the broken areas of the 3D-printed connectors as a result of mechanical testing failures. The results show that the SLS printing technology applied to build the connector does not ensure enough strength to the assembly, and changes in printing parameters are needed for further research, in terms of laser power and scan speed.

Comparative evaluation of osseointegration of new percutaneous implants made of Ti Grade 4 ultrafine‑grained alloy

Introduction It has been shown that titanium implants with a structured surface provide an increased rate of osseointegration what makes their application quite promising.The purpose of this work was to conduct a comparative evaluation of the efficiency of osseointegration of new percutaneous implants for prosthetics made of ultrafine-grained Ti Grade 4 alloy.Materials and methods The study was carried out on 12 male rabbits of the Soviet Chinchilla breed. Six rabbits of the control group had implants made of Ti6Al4V powder using selective laser sintering technology that were osseointegrated into the tibia, 6 rabbits of the experimental group had implants made of Ti Grade 4 by equal channel angular pressing. The formation of the "bone-implant" block was examined 26 weeks after the implantation.Results Histologically, after 26 weeks of the experiment, porous changes, enlargement of the Haversian canals, and pronounced osteoclastic resorption were not detected in the animals of the experimental group throughout the stump in the compact plate. Around the implant, a bony case repeating the bone shape was formed, represented by lamellar bone tissue. Using X-ray electron probe microanalysis, it was found that in the substrate formed on the surface of the implant in rabbits of the experimental group, there was significantly more calcium in all areas over the implant relative to the animals of the control group. In the control group, relative to the experimental group, an increased level of C-reactive protein in blood serum was retained longer. Complications and significant clinical and laboratory abnormalities were not found in both groups during the entire experiment.Discussion Our data are consistent with the results of other experimental studies, which unambiguously noted that titanium implants with a structured surface show increased osseointegration characteristics in comparative studies relative to implants without modification of the structure of the material of the threaded surface. The absence of complications and undesirable reactions of the animal organism also indicates the acceptable safety of the tested products.Conclusion Osseointegration of a percutaneous implant that has a mixed nanocrystalline and ultrafine-grained structure was more effective than the reference implant. This makes the use of such implant promising for solving clinical problems in prosthetics.

Preparation of Graphite/Ferrite/Resin‐Based Composite High‐Efficiency Wave‐Absorbing Materials by Selective Laser Sintering

Herein, graphite/Fe3O4/resin‐based composite absorbers are prepared by selective laser sintering (SLS) and vacuum impregnation of epoxy resin. The effects of different graphite–Fe3O4 powder compositions on the absorbing and mechanical properties of the composites are investigated. The results show that with the increase of Fe3O4 content, the absorption performance of the composites first increases and then decreases, and the absorption peak gradually moves from high frequency (12–18 GHz) to low frequency (2–8 GHz). The bending strength of composites decreases with the increasing of Fe3O4 content. When the mass ratio of graphite–Fe3O4 is 4:3, the wave absorption performance is the best, the minimum reflection loss is −54.8 dB, the effective absorption bandwidth is 2.8 GHz (8.72–11.52 GHz), and the bending strength is 11 MPa, which is 9 times higher than that of SLS plain billets. This is because the increase of the Fe3O4 content in the hybrid powder increases the number of heterogeneous interfaces, but decreases the number of holes inside the composite, which affects the number of microwave reflections inside the material, resulting in different wave absorption and mechanical properties. The graphite/ferrite/resin matrix composites prepared by SLS technology achieve the synergy of lightweight, high strength, and good wave absorption properties.