Optimal Printing Research Articles

3D vat photopolymerization printing of hydrophilic silicone-based microfluidic devices and the effect of cellulose nanocrystals as additives for improved printing accuracy

The lack of an ideal silicone-based ink material with optimal printability has significantly limited the potential to fabricate silicone-based microfluidic devices via 3D vat photopolymerization (VPP) printing. Oftentimes, photoabsorbers are incorporated into the ink material for better control of the photocuring depth in order to avoid excessive curing of unwanted parts. However, the search for a suitable photoabsorber without staining the ink material remains challenging due to the need to retain the clear interface in the final printed product. Herein, we present the fabrication of highly precise and transparent microfluidic devices using hydrophilic silicone-based ink via 3D VPP printing upon photocuring depth adjustment with cellulose nanocrystals (CNC). With the optimal CNC content, the ink material demonstrates enhanced printing accuracy with highly precise replication of channel patterns consisting of near zero deviation in width dimension down to 100 µm. Moreover, the addition of optimal CNC content exhibits no distinct final color and has no negative impact on the pre-gel viscosity and the gel point of the developed ink material. Moving on, the printed devices exhibit excellent fluid manipulation with various solvents for up to 24 hours, with incubation temperature up to 100ºC for 5 hours, and with a continuous flow rate up to 20 mL/min. The sustainable hydrophilicity, good organic solvent resistance, and excellent biocompatibility properties of the printed material further eliminate the need for additional surface modification to suit its application with either organic solvents or biological cells. To the best of our knowledge, the approach to tuning the photocuring depth of ink material with CNC is not widely reported. Besides, the successful fabrication of a highly detailed, neutral-colored, and highly functional hydrophilic silicone-based microfluidic device via 3D VPP printing upon the incorporation of CNC introduces a new avenue in terms of printing material and fabrication method for the mass production of microfluidic devices.

Determination of optimum printing direction of the polycarbonate parts produced by additive manufacturing

In this study, the effect of printing direction on the tensile properties of polycarbonate (PC) parts produced using a 3D printer was investigated. A total of 9 samples were produced with printing directions of 0°, 45° and 90° with infill density of 20%. Tensile tests were carried out to determine the maximum tensile strength (UTS) of the samples. As a result of the research, it was determined that the samples produced in the same direction as the tensile direction (0° printing direction) had the highest strength values; on the other hand, samples produced in the 90° printing direction have the lowest strength values. While the ultimate tensile strength values for samples produced in 0° printing direction were measured respectively as 22.4 MPa, 21.6 MPa and 20.7 MPa; as 7.1 MPa, 9.1 MPa and 9.2 MPa in 45° printing direction; it was determined as 7.2 MPa, 5.4 MPa and 5.8 MPa in the 90° printing direction. In addition, UTS/mass ratios were calculated by measuring the mass of the samples after the tensile test. According to the results obtained, samples in the 0° printing direction have the highest UTS/mass ratio compared to other printing directions, making them the most durable option for applications requiring lightweight structures. Tensile samples produced in FDM were analyzed with the finite element method (FEM) and analysis results were found to be equivalent to physical tests. This study contributes to examination of the influence of 3D printing direction, especially exposed to tensile, on material properties, and provides important information for the production of lightweight and high strength PC components in industries such as medicine, aerospace and automotive.

Printing GelMA bioinks: a strategy for buildingin vitromodel to study nanoparticle-based minocycline release and cellular protection under oxidative stress.

Owing to its thermoresponsive and photocrosslinking characteristics, gelatin methacryloyl (GelMA)-based biomaterials have gained widespread usage as a novel and promising bioink for three-dimensional bioprinting and diverse biomedical applications. However, the flow behaviors of GelMA during the sol-gel transition, which are dependent on time and temperature, present significant challenges in printing thick scaffolds while maintaining high printability and cell viability. Moreover, the tunable properties and photocrosslinking capabilities of GelMA underscore its potential for localized drug delivery applications. Previous research has demonstrated the successful incorporation of minocycline (MH) into GelMA scaffolds for therapeutic applications. However, achieving a prolonged and sustained release of concentrated MH remains a challenge, primarily due to its small molecular size. The primary aim of this study is to investigate an optimal extrusion printing method for GelMA bioink in extrusion bioprinting, emphasizing its flow behaviors that are influenced by time and temperature. Additionally, this research seeks to explore the potential of GelMA bioink as a carrier for the sustained release of MH, specifically targeting cellular protection against oxidative stress. The material properties of GelMA were assessed and further optimization of the printing process was conducted considering both printability and cell survival. To achieve sustained drug release within GelMA, the study employed a mechanism using metal ion mediation to facilitate the interaction between MH, dextran sulfate (DS), and magnesium, leading to the formation of nanoparticle complexes (MH-DS). Furthermore, a GelMA-basedin vitromodel was developed in order to investigate the cellular protective properties of MH against oxidative stress. The experimental results revealed that the printability and cell viability of GelMA are significantly influenced by the printing duration, nozzle temperature, and GelMA concentrations. Optimal printing conditions were identified based on a thorough assessment of both printability and cell viability. Scaffolds printed under these optimal conditions exhibited exceptional printability and sustained high cell viability. Notably, it was found that lower GelMA concentrations reduced the initial burst release of MH from the MH-dextran sulfate (MH-DS) complexes, thus favoring more controlled, sustained release profiles. Additionally, MH released under these conditions significantly enhanced fibroblast viability in anin vitromodel simulating oxidative stress.

Optimization of 3D Printing Parameters for Alumina Ceramic Based on the Orthogonal Test.

In this paper, an alumina ink with good rheological properties was successfully prepared using pseudoboehmite as the main component, nitric acid as the colloidal solvent, and sesbania powder as the lubricant. The impact of nine different ink formulations, namely, Ink1 to Ink9, on the printability and rheological features of the ink was investigated. Consequently, it was found that Ink3 with 5 wt % nitric acid and 5 wt % sesbania powder exhibited the most favorable formability. This ink was utilized to fabricate alumina samples with direct ink writing (DIW) three-dimensional (3D) printing technology. The printed alumina samples were characterized using an automatic Brunauer-Emmett-Teller, X-ray diffractometer, Fourier transform infrared spectroscopy, and scanning electron microscope. To obtain the optimal printing parameters, a three-factor and three-level orthogonal test was designed to research the influences of different 3D printing parameters (filling ratio, nozzle diameter, and layer thickness) on the specific surface area, pore characteristics (size and volume), and radial crushing strength of the alumina specimens. The primary and secondary orders of the effects on the radial crushing strength and pore structure were determined through analysis of the experimental data. The experimental results showed that the alumina sample with a filling ratio of 80%, nozzle diameter of 0.6 mm, and layer thickness of 0.3 mm was found to have better strength of 48.07 ± 9.53 N/mm and specific surface area of 185.7315 m2/g. This study provides a theoretical base for the preparation of alumina carriers by DIW 3D printing.

Nanofibrous polyelectrolyte complex incorporated BSA-alginate composite bioink for 3D bioprinting of bone mimicking constructs

Although several bioinks have been developed for 3D bioprinting applications, the lack of optimal printability, mechanical properties, and adequate cell response has limited their practical applicability. Therefore, this work reports the development of a composite bioink consisting of bovine serum albumin (BSA), alginate, and self-assembled nanofibrous polyelectrolyte complex aggregates of gelatin and chitosan (PEC-GC). The nanofibrous PEC-GC aggregates were prepared and incorporated into the bioink in varying concentrations (0 % to 3 %). The bioink samples were bioprinted and crosslinked post-printing by calcium chloride. The average nanofiber diameter of PEC-GC was 62 ± 15 nm. It was demonstrated that PEC-GC improves the printability and cellular adhesion of the developed bioink and modulates the swelling ratio, degradation rate, and mechanical properties of the fabricated scaffold. The in vitro results revealed that the bioink with 2 % PEC-GC had the best post-printing cell viability of the encapsulated MG63 osteosarcoma cells and well oragnized stress fibers, indicating enhanced cell adhesion. The cell viability was >90 %, as observed from the MTT assay. The composite bioink also showed osteogenic potential, as confirmed by the estimation of alkaline phosphatase activity and collagen synthesis assay. This study successfully fabricated a high-shape fidelity bioink with potential in bone tissue engineering.

Carboxymethylcellulose-induced depletion attraction to stabilize high internal phase Pickering emulsions for the elderly: 3D printing and β-carotene delivery

In this study, a carboxymethylcellulose (CMC) induced depletion attraction was developed to stabilize high internal phase Pickering emulsions (HIPPEs) as age-friendly 3D printing inks. The results demonstrated that depletion force induced the adsorption of yolk particles at the droplet interface and the formation of osmotic droplet clusters, thereby increasing the stability of HIPPEs. In addition, the rheological properties and nutrient delivery properties of HIPPEs could be adjusted by the mass ratio of yolk/CMC. The HIPPEs stabilized at yolk/CMC mass ratio 20:7.5 showed optimal printability, viscoelastic, structural recovery, and swallowability. HIPPEs have been applied to 3D printing, International Dysphagia Dietary Standardization Initiative (IDDSI) test, and in vitro digestive simulation in the elderly, indicating their attractive appearance, safe swallowability, and enhanced bioaccessibility of β-carotene. Our work provides new ideas for developing age-friendly foods with plasticity and nutrient delivery capacity by depletion attraction stabilizing HIPPEs.

Near-Room-Temperature Detection of Aromatic Compounds with Inkjet-Printed Plasticized Polymer Composites.

Chemiresistive gas sensors composed of a thermoplastic polymer matrix and conductive fillers offer various advantages for detecting volatile organic compounds (VOCs), including low power consumption due to near-room-temperature operation, high sensitivity, and inherent selectivity toward VOCs. However, such sensors have a slow response time as the polymer matrix often has a glass transition temperature (Tg) higher than the sensor operating temperature slowing the analyte diffusion to/from the polymer. A plasticizer lowers polymer Tg to match the sensor operation temperature, reducing its response time. In this study, the effect of a plasticizer diethylene glycol dibenzoate (DEGDB) on the sensing properties of polystyrene (PS)-carbon black (CB) composite is investigated to obtain sensors with a fast response time and high sensitivity to VOCs. The sensors are fabricated via drop-on-demand inkjet printing, providing a high degree of control over the sensory film morphology and reproducibility. A design-of-experiment (DoE) approach is adopted to find the optimum ink and print parameters with a minimum number of experiments. As a result, sensors with 30 times faster response time and 25 times higher effective sensitivity are obtained while operating near room temperature (27 °C). Furthermore, the sensors show high sensitivity toward aromatic hydrocarbons (toluene, benzene, and ethylbenzene), with a sub-10 ppm limit of detection (LoD) and a negligible sensitivity toward humidity. Our results show the potential of PS-DEGDB-CB composite as a selective and cost-effective sensory material compatible with large-scale manufacturing techniques for selective near-room-temperature detection of toxic VOCs.

Suitability of Gelatin Methacrylate and Hydroxyapatite Hydrogels for 3D-Bioprinted Bone Tissue.

Complex bone defects are challenging to treat. Autografting is the gold standard for regenerating bone defects; however, its limitations include donor-site morbidity and increased surgical complexity. Advancements in 3D bioprinting (3DBP) offer a promising alternative for viable bone grafts. In this experiment, gels composed of varying levels of gelatin methacrylate (GelMA) and hydroxyapatite (HA) and gelatin concentrations are explored. The objective was to increase the hydroxyapatite content and find the upper limit before the printability was compromised and determine its effect on the mechanical properties and cell viability. Design of Experiments (DoE) was used to design 13 hydrogel bioinks of various GelMA/HA concentrations. These bioinks were assessed in terms of their pipettability and equilibrium modulus. An optimal bioink was designed using the DoE data to produce the greatest stiffness while still being pipettable. Three bioinks, one with the DoE-designed maximal stiffness, one with the experimentally defined maximal stiffness, and a literature-based control, were then printed using a 3D bioprinter and assessed for print fidelity. The resulting hydrogels were combined with human bone-marrow-derived mesenchymal stromal cells (hMSCs) and evaluated for cell viability. The DoE ANOVA analysis indicated that the augmented three-level factorial design model used was a good fit (p < 0.0001). Using the model, DoE correctly predicted that a composite hydrogel consisting of 12.3% GelMA, 15.7% HA, and 2% gelatin would produce the maximum equilibrium modulus while still being pipettable. The hydrogel with the most optimal print fidelity was 10% GelMA, 2% HA, and 5% gelatin. There were no significant differences in the cell viability within the hydrogels from day 2 to day 7 (p > 0.05). There was, however, a significantly lower cell viability in the gel composed of 12.3% GelMA, 15.7% HA, and 2% gelatin compared to the other gels with a lower HA concentration (p < 0.05), showing that a higher HA content or print pressure may be cytotoxic within hydrogels. Extrusion-based 3DBP offers significant advantages for bone-tissue implants due to its high customizability. This study demonstrates that it is possible to create printable bone-like grafts from GelMA and HA with an increased HA content, favorable mechanical properties (145 kPa), and a greater than 80% cell viability.

Magnetic printing characteristics of burst signals by using double magnet master media

In this study, the magnetic printing characteristics of burst signals with double magnet master (DMM) media, which consists of hard and soft magnet patterns corresponding to the burst signals, onto energy-assisted magnetic recording (EAMR) media was investigated by the micromagnetic simulation. For comparison, the magnetic printing characteristics with the conventional master media, which includes only soft magnet patterns, was also calculated. The magnetic film patterns of each master media transfer automatic-gain-control (AGC) and burst parts to the recording medium. The burst signals was amplitude AB-burst patterns, which consists of the repeated pattern region and blank area without burst patterns. Two possible master media structures of DMM media were considered, which are herein called positive- and negative- DMM media. By utilizing the positive-DMM, which spatially divides soft magnets, the AGC and the burst signals can be clearly printed, comparing with the conventional master media. While the negative-DMM is insufficient to print burst signals because the blank area without burst patterns has some non-recorded clusters. Thus, the positive-DMM are feasible for the magnetic printing of burst signals. The clear printing onto EAMR media is expected to be obtained by the optimum non-magnetic separator thickness and the optimum printing field. Therefore, the magnetic printing with positive DMM master is promising onto EAMR media.

Eco-friendly 3D Printing Mortar with Low Cement Content: Investigation on Printability and Mechanical Properties

The conventional approach to achieving optimal printability and buildability in 3D printing mortar relies heavily on cement, which is both costly and environmentally detrimental due to substantial carbon emissions from its production. This study aims to mitigate these issues by investigating the viability of slag as a partial substitute for cement, with the goal of developing an eco-friendly alternative. The newly formulated mortar, featuring a 30% reduction in cement content (from 830 to 581 kg/m3) and the inclusion of 0.10% micro-fibers, exhibits properties comparable to conventional 3D printing mortar. The research is structured into two parts: Part 1 focuses on determining the optimal fiber content, while Part 2 delves into the investigation of fiber-reinforced mortar with reduced cement content for 3D printing. Criteria were established to ensure mortar flow at 115%, initial printable time below 60 minutes, and 7-day compressive strength exceeding 28 MPa. Part 1 results indicate that a fiber content of 0.1% by volume meets the specified requirements. In Part 2, it was observed that increasing the slag replacement percentage extended the initial printable time and time gap. However, even at a 30% replacement rate, the initial printable time remained within the acceptable range, partially attributed to the presence of fibers in the mix. Additionally, higher slag content led to increased flow and reduced filament height in the mixes. Notably, all formulations surpassed the 7-day compressive strength threshold. These findings underscore the potential of slag as a sustainable alternative to cement in 3D printing fiber-reinforced mortar, offering promising prospects for environmentally friendly construction practices. Doi: 10.28991/CEJ-2024-010-03-010 Full Text: PDF

ОПТИМИЗАЦИЯ РЕЖИМА 3-D ПЕЧАТИ ТУРБИННОЙ МЕШАЛКИ ДЛЯ ДИСПЕРГИРОВАНИЯ РАСТВОРОВ ПОЛИМЕРНЫХ КОМПОЗИТОВ

The design of the turbine stirrer is characterized by a rather complex shape of working surfaces and during its manufacture by traditional methods unique molds are required for each type of stirrer, increased material and labor costs are required. The use of 3D printing allows you to obtain products with a complex surface configuration, with minimal costs and which do not require subsequent machining. Analysis was carried out and selection of 3D printing type and material of turbine stirrer intended for mixing of elastomeric nanocomposite solutions components was carried out. FDM (Fused Deposition Modeling) is the most suitable type of 3D printing for solving design and technological problems in the manufacture of turbine stirrers. Plastics of the brands ABS, PLA and PETG have become very widespread in this type of 3D printing. The highest mechanical properties, chemical resistance and the lowest price of the materials under consideration are PETG plastic, which was chosen for the manufacture of a turbine stirrer designed to mix and disperse solutions of elastomeric nanocomposites. An active experiment was implemented according to the В2 plan. The samples are PETG plastic plates printed on a Flying Bear Ghost 5 3D printer. The main mode parameters of 3D printing by FDM type, which determine the strength of samples and printing performance, are: the number of concentric lines that make up the wall of the printed product and the line width. A regression model of the dependence of strength of samples made of PETG plastic on the number and width of lines in 3D printing was obtained. The optimal 3D printing mode of the turbine stirrer is set, providing high strength of the product and performance of the technology.

High-precision digital light processing (DLP) printing of microstructures for microfluidics applications based on a machine learning approach

ABSTRACT Digital light processing (DLP) is renowned for its precision, but the challenge lies in the identification of optimal print parameters to minimise print errors and enhance overall print accuracy. This study introduces a groundbreaking approach by integrating 'Random Forest' (RF) models with DLP printing to construct a predictive model for printing errors to achieve unparalleled precision. We conducted experiments using common commercial resins to print, resulting in a comprehensive dataset of 690 experimental datasets. Consequently, we validated this approach by fabricating Y-type microfluidic structures with a minimum feature size printing of 2 µm and herringbone mixer structures with feature sizes of 21.2 µm. We successfully controlled the average print error below 2.3 µm. The 'RF' model was also extended from the printing of microfluidics (2.5D) to complex spatial three-dimensional (3D) Triple-Periodic Minimal Surface (TPMS) structures. We have successfully achieved the printing of TPMS-Gyroid and TPMS-Diamond structures with a minimum feature size of 20 µm, while the printing errors were all kept within 1.5 µm. This study underscores the generalizability and immense potential of integrating machine learning techniques with high-precision DLP printing, offering valuable insights for future research in the realm of high-precision and expeditious 3D printing.

Effects of Shot Peening and Electropolishing Treatment on the Properties of Additively and Conventionally Manufactured Ti6Al4V Alloy: A Review.

This literature review indicates that the basic microstructure of Ti6Al4V is bimodal, consisting of two phases, namely α + β, and it occurs after fabrication using conventional methods such as casting, plastic forming or machining processes. The fabrication of components via an additive manufacturing process significantly changes the microstructure and properties of Ti6Al4V. Due to the rapid heat exchange during heat treatment, the bimodal microstructure transforms into a lamellar microstructure, which consists of two phases: α' + β. Despite the application of optimum printing parameters, 3D printed products exhibit typical surface defects and discontinuities, and in turn, surface finishing using shot peening is recommended. A literature review signalizes that shot peening and electropolishing processes positively impact the corrosion behavior, the mechanical properties and the condition of the surface layer of conventionally manufactured titanium alloy. On the other hand, there is a lack of studies combining shot peening and electropolishing in one hybrid process for additively manufactured titanium alloys, which could synthesize the benefits of both processes. Therefore, this review paper clarifies the effects of shot peening and electropolishing treatment on the properties of both additively and conventionally manufactured Ti6Al4V alloys and shows the effect process on the microstructure and properties of Ti6Al4V titanium alloy.

Physiological cell bioprinting density in human bone-derived cell-laden scaffolds enhances matrix mineralization rate and stiffness under dynamic loading.

Human organotypic bone models are an emerging technology that replicate bone physiology and mechanobiology for comprehensive in vitro experimentation over prolonged periods of time. Recently, we introduced a mineralized bone model based on 3D bioprinted cell-laden alginate-gelatin-graphene oxide hydrogels cultured under dynamic loading using commercially available human mesenchymal stem cells. In the present study, we created cell-laden scaffolds from primary human osteoblasts isolated from surgical waste material and investigated the effects of a previously reported optimal cell printing density (5 × 106 cells/mL bioink) vs. a higher physiological cell density (10 × 106 cells/mL bioink). We studied mineral formation, scaffold stiffness, and cell morphology over a 10-week period to determine culture conditions for primary human bone cells in this microenvironment. For analysis, the human bone-derived cell-laden scaffolds underwent multiscale assessment at specific timepoints. High cell viability was observed in both groups after bioprinting (>90%) and after 2 weeks of daily mechanical loading (>85%). Bioprinting at a higher cell density resulted in faster mineral formation rates, higher mineral densities and remarkably a 10-fold increase in stiffness compared to a modest 2-fold increase in the lower printing density group. In addition, physiological cell bioprinting densities positively impacted cell spreading and formation of dendritic interconnections. We conclude that our methodology of processing patient-specific human bone cells, subsequent biofabrication and dynamic culturing reliably affords mineralized cell-laden scaffolds. In the future, in vitro systems based on patient-derived cells could be applied to study the individual phenotype of bone disorders such as osteogenesis imperfecta and aid clinical decision making.

Inkjet-Printed Dielectric Layer for the Enhancement of Electrowetting Display Devices.

Electrowetting with a dielectric layer is commonly preferred in practical applications. However, its potential is often limited by factors like the properties of the dielectric layer and its breakdown, along with the complexity of the deposition method. Fortunately, advancements in 3D inkjet printing offer a more adaptable solution for making patterned functional layers. In this study, we used a negative photoresist (HN-1901) to create a new dielectric layer for an electrowetting display on a 3-inch ITO glass using a Dimatix DMP-2580 inkjet printer. The resulting devices performed better due to their enhanced resistance to dielectric breakdown. We meticulously investigated the physical properties of the photoresist material and printer settings to achieve optimal printing. We also controlled the uniformity of the dielectric layer by adjusting ink drop spacing. Compared to traditional electrowetting display devices, those with inkjet-printed dielectric layers showed significantly fewer defects like bubbles and electrode corrosion. They maintained an outstanding response time and breakdown resistance, operating at an open voltage of 20 V. Remarkably, these devices achieved faster response times of ton 22.3 ms and toff 14.2 ms, surpassing the performance of the standard device.

Autonomous Output‐Oriented Aerosol Jet Printing Enabled by Hybrid Machine Learning

AbstractAdditive manufacturing (AM) is rapidly revolutionizing modern manufacturing with recent progress in advanced printing methods and improved properties of printed materials. However, traditional AM methods are limited by their input‐oriented nature, which demands tedious trial‐and‐error tuning of printing parameters to achieve desired output properties. Here, an output‐oriented artificial intelligence‐integrated AM (AIAM) method is reported that enables an user to specify desired output properties while the printer autonomously discovers the optimal input printing parameters by integrating hybrid machine learning models and in situ measurements. Based on a predictive mapping between the input printing parameters and the output properties of interests established with &lt;20 experiments designed by active learning, inverse design tasks are performed to intelligently generate the printing parameter settings that lead to desired outcomes using reinforcement learning. This method is demonstrated by autonomous aerosol jet printing (AJP) of conductive polymer films and achieving user‐defined electrical resistances with an ultralow error of 3.7%. The AIAM method, with its output‐oriented nature, holds the potential to significantly improve the autonomy, predictability, efficiency, and accessibility of the AM processes, which will unlock new possibilities in the autonomous and intelligent printing of a broad range of functional materials and devices.

26. BIOPRINTING VASCULAR GRAFTS WITHOUT SUPPORT MATERIAL: A COMPARISON BETWEEN NEW AND COMMERCIAL HYDROGEL

Abstract Introduction Currently, the demand for personalized vascular grafts is increasing and bioprinting techniques emerge as a promising approach for its development. The aim is to comparatively evaluate the performance of a Gelatin/Gellan Gum/Alginate hydrogel and a commercial bioink to produce bioprinted vascular grafts without support material. Methods Two hydrogels were employed in this study: a custom-made Gelatin/Gellan Gum/Alginate (8:3:0.5 %w/v) and a commercial bioink (Cellink Bioink) consisting of 5% alginate with nanocellulose. Three experiments were conducted to assess their performance. The first experiment involved diluting the commercial hydrogel in PBS at a 1:10 ratio. The second experiment applied the commercial hydrogel without dilution, while the third experiment utilized the custom-made hydrogel without dilution. Optimal printing conditions were established for both hydrogels, with the Cellink bioink set to 37 °C, 10 kPa, and 7 mm/s, and the Gelatin/Gellan Gum/Alginate hydrogel set to 50 °C, 45 kPa, and 9 mm/s. For each hydrogel, three grafts were printed, each with dimensions of 15 mm height, 500 μm wall-thickness, and a 6 mm inner diameter. The physical characteristics of these grafts were subsequently measured using an optical microscope. Results Results showed differences between the three experiments. Vascular grafts produced with Gelatin/Gellan Gum/Alginate hydrogel present a wall-thickness and an inner diameter of 553±150 μm and 5.33±0.24 mm, respectively. In contrast, the commercial bioink from Cellink failed to facilitate the production of vascular grafts, as it fully collapsed at layer 17 out of 37. Conclusion The Gelatin/Gellan Gum/Alginate hydrogel proves to be effective in bioprinting vascular grafts, demonstrating both adequate accuracy and structural stability. Notably, it distinguishes itself from commercial bioinks by not necessitating additional sacrificial materials in the process.

Performance enhancement of 3D‐printed carbon fiber‐reinforced nylon 6 composites

AbstractThe inherent defects of the layer‐by‐layer manufacturing process limit the mechanical performance of 3D‐printed composite parts. This paper explores a process optimization method for continuous fiber composites 3D printing to improve the mechanical performance of 3D‐printed CF/PA6 (Carbon Fiber/Nylon 6) parts. First, the effects of printing temperature, printing speed, layer thickness, and side step on the mechanical performance of 3D‐printed CF/PA6 were studied by conducting variable parameter printing experiments. All optimal printing parameters for CF/PA6 were obtained, and their impact mechanisms were analyzed. Second, the coupling effect of temperature and pressure of post‐processing reduced the internal voids of 3D‐printed CF/PA6 and improved its mechanical properties. The influence mechanism of the coupling effect of temperature and pressure was summarized, and the optimal post‐processing parameters applicable to CF/PA6 were obtained. Based on the above process optimization, the fiber volume content of the printed CF/PA6 reached 41.05%, and the bending strength and elastic modulus reached 651.54 MPa and 79.08 GPa, which were 209.05% and 179.53% higher than those before optimization. Moreover, the tensile strength and elastic modulus reached 730 MPa and 29.23GPa, which were 98.10% and 81.10% higher than those before optimization. The experimental results give a positive validation of the effectiveness and feasibility of the proposed methodology.Highlights The effects of printing temperature, printing speed, layer thickness, and side step on the mechanical properties of 3D‐printed CF/PA6 were investigated. The optimal printing parameters applicable to CF/PA6 were obtained and their influence mechanisms were analyzed. The effects of the heat press processing method on the internal voids and mechanical properties of 3D‐printed CF/PA6 were investigated, and the optimal post‐processing parameters applicable to CF/PA6 were obtained. The study resulted in optimal printing parameters and post‐processing parameters for 3D printing CF/PA6, which greatly enhanced its tensile and flexural strength and modulus.

Determination of optimal 3D printing modes for composite parts for reaching the set design-engineering parameters

This paper discusses properties of various 3D printing materials, namely, plastics, including polyamides, along with composite or engineering plastics with inclusions of carbon fiber and fiberglass. We selected an optimal sample printing mode and carried out experiments, following which we determined maximal loads for test composite materials, and linear shrinkage. As the result, we determined an optimal 3D printing mode for various structures of composite material parts with the purpose to reach the set design-engineering parameters.

Preparation and efficacy verification of three-dimensional printed partitioned multi-effect precision-care gel facial mask.

A partition multi-effect precision-care gel facial mask conforming to facial skin characteristics was prepared using three-dimensional (3D) printing technology. First, the hydrogel matrix and humectant of a 3D-printed gel for facial masks were screened, and three 3D-printed gels of arbutin, hexapeptide, and salicylic acid were prepared with whitening, wrinkle removal, and oil control functions, respectively. Skin irritation tests were performed on the gels. Physicochemical properties such as pH, heat and cold tolerance were evaluated. The efficacy of three 3D-printed gels was assessed by measuring melanin value, wrinkle depression score, and oil secretion. Finally, the facial mask model design and printing parameters were studied, and a partition multi-effect precision-care gel facial mask was printed in line with facial skin characteristics. For the 3D-printed facial mask, the gel prescription with 2% hydroxyethyl cellulose gel as matrix and 7% glycerol as humectant was the best. The prepared 3D-printed gel did not irritate the human skin, and its physicochemical properties met the Chinese facial mask industry standard (QB/T2872-2017). We showed that three types of 3D-printed gels containing arbutin, hexapeptide, and salicylic acid could be applied to the corresponding parts of the face to solve different problems, such as facial skin dullness, wrinkles, and oil secretion. Therefore, according to facial physiological characteristics, the facial mask model was designed for the forehead and nasolabial fold, which needs to be anti-wrinkled; the cheek, which needs to be whitened; and the nose and chin, which need oil control. The optimal printing parameters were 0.26 mm nozzle diameter, 90 mm/s printing speed, 30% filling density, 140% wire extrusion ratio, and 0.25 mm layer height. Different skin care effects can be achieved using a three-nozzle printer to print arbutin, hexapeptide, or salicylic acid gel on the mask's forehead and nasolabial fold, cheek, and nose and chin, respectively. The 3D-printed partition multi-effect care gel facial mask prepared according to the skin features of different parts of the face can overcome the problem of the single skincare effect of the mass-produced facial masks.