Printing Properties Research Articles

Precision 4D Printing of Multifunctional Olive Oil‐Based Acrylate Photo‐resin for Biomedical Applications

AbstractSince the advent of 3D printing technology, a significant effort has been made to develop new 3D printable materials. Despite the recent progress in the field of 3D printing, the limited availability of photoactive resins has motivated continuous research endeavors to develop novel photoresins with multifunctional capabilities. Herein a biobased photoresin derived is reported from modified olive oil, designed for high‐resolution solvent‐free 4D printing with multifunctional capabilities. The physicochemical properties of the printed polymers are fine‐tuned using acrylic acid as a diluent cum comonomer. The mechanical properties of the printed polymers are similar to various soft tissues, such as ligaments, articular cartilage, and soft collagenous bone, showcasing its potential for soft tissue engineering applications. While the excellent temperature‐responsive shape memory 4D attributes coupled with exceptional antimicrobial properties toward gram‐negative and gram‐positive bacteria highlight the multifunctional nature of the printed polymers. Moreover, the printed polymers exhibited outstanding hemocompatibility and good cytocompatibility toward mouse fibroblast cells, suggesting their potential soft tissue engineering applications. In sum, the newly developed biobased resin can be employed to minimize the environmental impact of additive manufacturing while being competitive with existing fossil‐based photoresins, thereby meeting the growing demand for advanced photoresins with superior high‐resolution printing and smart properties for biomedical applications.

Stereolithography Printing and Mechanical Properties of Polyethylene Glycol Diacrylate/Hexagonal Boron Nitride Ceramic Composites

To enhance the mechanical properties of bioceramic composite bone scaffolds, a composite paste of polyethylene glycol diacrylate (PEGDA) and hexagonal boron nitride (h‐BN) with a solid content of up to 42 wt% was developed in this study. The part was produced using stereolithography (SLA). The SLA printing parameters and material ratios of the paste were optimized through a homogeneous design and mechanical property tests. The results indicate that the single‐line curing width of the PEGDA/h‐BN paste in the XY plane ranged from 172 to 209 μm, while the curing depth of a single layer along the Z‐axis ranged from 99 to 154 μm. Laser power was identified as the primary factor influencing both the width and depth of curing. The compressive strength of the printed sample of PEGDA/h‐BN ceramic composite paste was measured at 222.4 ± 5.6 MPa, which is 61 times greater than the compressive strength of a pure PEGDA structure and comparable to that of cortical bone (100‐230 MPa). Finally, the superior biocompatibility of PEGDA/h‐BN ceramics was confirmed through cytotoxicity experiments. Consequently, PEGDA/h‐BN ceramic composites meet the mechanical properties and biocompatibility requirements necessary for bone tissue applications, indicating promising potential in the field of bone tissue engineering.

Effect of aminolysis treatment on self-healing properties and printing potentialities of banana peel and edible wax based biodegradable film

Cellulose-based materials are a viable alternative to petroleum-based sources; however, the practical applicability of cellulose films is severely limited by their poor hydrophobicity. This study explores the development of hydrophobic films with self-healing properties through the incorporation of natural wax into a cellulose matrix. Different formulations of films were developed varying the concentration of glycerol (0 % to 3.5 % v/v) and aminolysis treatment. Printability property, rubbing, acid, and water resistance property of the film were also evaluated. The self-healing efficiency of the films varied from around 30 % to 80 % based on variations in glycerol and aminolysis treatment provided. Aminolysis-treated films showed enhanced self-healing properties (Self-healing efficiency ~77 %) compared to the control films. The films were characterized for their physical, mechanical, barrier, and thermal properties and it was found that 1.5 % had superior properties compared to other compositions. Printability properties showed that aminolysis-treated films had better wetting properties (WCA ~ 74.46°) with a peak tact force of 8.1 N. This signifies aminolysis-treated films had better ink absorption and adhesion properties, which confirms the printability nature of the films. This study highlights the potential applications of biodegradable self-healing based film, applications with a scope of resolving environmental problems by replacing petrochemical plastics.

A new path planning strategy driven by geometric features and tensile properties for 3D printing of continuous fiber reinforced thermoplastic composites

Three-dimensional (3D) printing technology for continuous fiber reinforced thermoplastic composites (C-FRTP), capable of rapid manufacturing of lightweight components with intricate geometric features, has emerged as one of the most promising technologies in the field of advanced composite manufacturing. Path planning is a crucial step for determining the fabrication quality of C-FRTP components. This study proposed a new 3D printing path planning strategy driven by the geometric features and tensile properties of C-FRTP components. The strategy employed the properties of the Euler graph to generate the continuous full-field filling paths, ensuring the geometric features of the target components. The intersections were scattered along the printing path to enhance the tensile strength. The feasibility and advantages of the new path planning strategy were validated by comparative experiments with different printing paths. The results indicated that the new strategy not only achieved the geometric features of the target components but significantly enhanced their tensile strength. Using the printing path generated by the new path planning strategy, the tensile strength of specimens featuring mounting holes reached 349.4 MPa, which was only about 4.1 % lower than the tensile strength of continuous fibers at straight paths. Compared to the existing contour-parallel path, the new strategy in this work improved the tensile properties by about 40.9 %. The new path planning strategy proposed in this study shows great potential to design and fabricate C-FRTP components with enhanced mechanical properties for practical applications.

Hybrid Screen Printable Electrolyte for Large‐Scale Flexible Electrochromic Display Production

AbstractThis study presents the development of a novel screen printable quasi‐solid polymer electrolyte (p‐QSPE) for Electrochromic Displays (ECDs) applications. p‐QSPE is composed of three key components: polyvinylidene fluoride (PVDF), a high‐dielectric constant polymer that ensures high ionic conductivity in solid‐state; glyceril propoxy triacrylate (GPTA), a UV‐cross‐linkable monomer that provides structure and durability for overprinting; titanium dioxide (TiO₂) nanoparticles, which modulate the electrolyte's rheological properties for screen printing; reducing the solvent (PC:EC) content to only 35.90 wt.%. Electrochemical Impedance Spectroscopy (EIS) revealed that this well‐designed formulation achieved an ionic conductivity of 1.17 × 10−3 S cm−1 at room temperature, surpassing the threshold required for commercial applications. Moreover, p‐QSPE facilitated the production of fully screen printed ECDs in an industrial printing line, streamlining their production process and achieving an optimal balance between printability, overprint resilience, and device performance. Operational tests for the ECDs showed fast switching times (<6 s for t90 and <2 s for t75) across a wide temperature range (−20 °C to 80 °C). Additionally, the electrolyte demonstrated low charge consumption (2.10 ± 0.11 mC cm−2) and a lifespan exceeding 10 000 cycles. These results highlight the potential of p‐QSPE as a screen printable, high‐performance electrolyte, capable of advancing ECD manufacturing by enabling the production of fully screen‐printed, performing ECDs.

A novel colored chitosan-modified polystyrene composite dye nanospheres with enhanced coloring properties for binder-free printing

The limited utilization rate of dyes for coloring coupled with the consumption of large quantities of chemical reagents, can result in acute environmental pollution and waste of resources. Herein, in accordance with the electrostatic attraction between electropositivity of chitosan and anionic dyes, a novel type of chitosan-modified cationic polystyrene nanospheres (PSCS) was creatively synthesized, which can be innovatively employed as a special carrier with an adsorption capacity of up to 197.4mg/g for acid dyes. Consequently, a exclusive pigment identified as colored chitosan-modified polystyrene composite dye nanospheres (PSCS(AR9)) was procured. Simultaneously, the binder-free printing was accomplished by leveraging the intrinsic self-curing property of PSCS(AR9) for screen printing of textiles. Additionally, printed fabrics with PSCS(AR9) exhibited superb darkening effect (the K/S value can be increased by 2 times.) in conjunction with significantly improved hand feel in contrast with the conventional printed fabrics. The last but not least, the rubbing fastness of the printed fabrics using PSCS(AR9) can meet demand of the practical application. Therefore, this work may provide an innovative insight for constructing a new type of environmentally friendly and depth-enhanced printed textile.

Structural build-up of 3D printed earth by drying

In recent years, the potential of earth materials in construction has emerged as a sustainable pathway, offering environmental benefits compared to traditional methods. When used in raw form, earth materials can be recycled at the end of a building life, reducing construction waste. In parallel, integrating additive manufacturing into the architecture, engineering, and construction (AEC) sector has brought about a shift in construction dynamics, combining efficiency with precision. This paper bridges the study of 3D printing with earth-based fresh mortars, emphasising the capabilities of the “Forced Layer Drying” (FLD) technique in the additive manufacturing process to increase the mechanical performance of the printing mortar.This paper begins by defining the requisite rheological properties for successful 3D printing. A chosen material for this paper is speswhite kaolin. An instrumental aspect of our research is exploring an established model for the drying rate of saturated porous media, such as earth and concrete, and its application to predict the evaporation rate of saturated earth-based mortar in 3D printing with forced drying conditions. The Wind-Tunnel experiment was conducted to validate this model, examining the interplay of airflow speed and temperature on the evaporation rate. Further deepening this study, the soil water content and undrained shear strength are correlated, specifically based on models derived from oedometer geotechnical standard tests. This facilitated a comprehensive understanding of porous earth-based materials in various moisture scenarios. Our findings confirm that airflow, temperature, and the geometry of the printed object play instrumental roles in affecting evaporation rate, consequent mechanical performance, and structural build-up of the material. The paper wraps up by offering insights into the practical application of 3D printing using earth-based mortars, with a special focus on FLD technique.

Vat photopolymerization for thermal energy storage applications using encapsulated phase change material suspended in photocurable resin

A novel approach to additively manufacture latent heat thermal energy storage heat exchangers through the development of microencapsulated phase change material (MEPCM) suspensions in photocurable resin for vat photopolymerization (VPP) 3D printing is presented. Using MEPCM addresses the leakage risks that have typically been associated with PCMs and subsequently makes the particulates a suitable additive for VPP 3D printing. In the current study, VPP was employed to fabricate functional composites with varying MEPCM mass fractions for thermal, rheological, microstructure, and chemical characterization. Microstructure visualization was conducted to assess the overall distribution of MEPCM within the 3D printed samples and to confirm the structural integrity of the encapsulated particles after printing. The influence of the base resin viscosity was explored by investigating two photocurable resins with different viscosities—a high-tensile UV photopolymer and an ABS-like resin—during the printing process. Thermal properties, such as latent heat of fusion, phase-change temperature, thermal conductivity, and decomposition temperature of the 3D printed samples were determined. Rheology was used to observe the effect of varying shear rates on the MEPCM-resin mixtures to identify the optimal viscoelastic properties for VPP 3D printing. It was determined that the ABS-like resin was able to contain a larger amount of PCM (40 wt%) while maintaining printability due to the lower viscosity of the corresponding pure resin. The 40 wt% MEPCM composite exhibited an average viscosity of 18,817 cPs, a maximum latent heat of fusion of 54.12 kJ/kg, and a 12.4 % reduction in thermal conductivity compared to the pure polymer.

A novel route to 3D printable protein-based HIPEs developed with shiitake oil

Tuning protein-based Pickering high internal phase emulsions (HIPEs) into 3D printing inks is promising in the food fields. Currently, the correlation between the changes in oil phase composition and the regulation of protein-based HIPEs 3D printing performance is still unclear. In this study, spiking the shiitake oil (ranging from 0 to 60 %) into the soybean oil phase of HIPEs can enhance their rheological properties and induce the formation of 3D printable HIPEs. The rheological tests showed that the yield stress and viscosity of the HIPEs respectively increased from 81.8 ± 4.84 Pa to 309 ± 16.3 Pa and from 409 to 1.74 Pa.s to 1762–2.93 Pa.s with increasing the shiitake oil concentration (0 % to 60 %) in the oil phase. In this study, the spontaneous interaction between phenolic compounds in shiitake oil and interfacial casein promoted the aggregation of protein, which led to the formation of casein cross-linking network in emulsion droplets, thus realizing the self-supporting and printing fidelity required for 3D printing. These findings provide a new perspective for enhancing the 3D printing properties of protein-based HIPEs.

Precision 3D printing of chitosan-bioactive glass inks: Rheological optimization for enhanced shape fidelity in tissue engineering scaffolds

3D printing technology in tissue engineering applications provides several advantages for scaffold development, especially with natural materials, such as chitosan, which provides a biomimetic environment for cellular growth. However, chitosan hydrogel-based inks still show poor printing fidelity. In this article, we overcame this challenge by incorporating bioactive glasses (BG) nanoparticles (up to 5 wt%) into the chitosan hydrogel. The resulting inks were characterized by rheological tests, while their processability was evaluated through measurements of shape fidelity. An indirect cytotoxicity assay was also conducted to evaluate the cell viability of the printed scaffolds. The results indicated that adding BG nanoparticles to the chitosan-based ink modified its rheological properties and improved its shape-fidelity during 3D printing, which we suggest are consequences of hydrogen bonds established between the glass and the chitosan chains. Also, cytotoxicity assessment demonstrated that the resulting scaffold exhibits high cell viability. In conclusion, the proposed composite ink has optimized rheological properties for 3D printing and is promising for applications in tissue engineering.

3D Printing of Thermally Responsive Shape Memory Liquid Crystalline Epoxy Networks.

A two-component liquid crystalline epoxy network (LCEN) with shape memory behavior was developed and evaluated as a candidate material for 3D printing. The cure kinetics of the uncured material and the shape memory properties of the cured LCEN were investigated by using parallel plate rheology and dynamic mechanical analysis, respectively. A commercially available fumed silica additive was introduced to the neat, uncured material to improve the rheological properties for 3D printing. The addition of fumed silica was found to increase the yield stress, shear-thinning behavior, and toughness of the uncured epoxy ink. Polarized light microscopy, differential scanning calorimetry, and wide-angle X-ray scattering measurements between the neat and additive-modified LCEN suggested a reduction in liquid crystalline alignment in the modified LCEN, owing to interactions between crystalline domains and fumed silica, which in turn influenced the mechanical behavior. Overall, the additive was found to be successful in preserving the shape memory properties of LCEN while improving its printability.

Coaxial bioprinting of a stentable and endothelialized human coronary artery-sized in vitro model.

Atherosclerosis accounts for two-thirds of deaths attributed to cardiovascular diseases, which continue to be the leading cause of mortality. Current clinical management strategies for atherosclerosis, such as angioplasty with stenting, face numerous challenges, including restenosis and late thrombosis. Smart stents, integrated with sensors that can monitor cardiovascular health in real-time, are being developed to overcome these limitations. This development necessitates rigorous preclinical trials on either animal models or in vitro models. Despite efforts being made, a suitable human-scale in vitro model compatible with a cardiovascular stent has remained elusive. To address this need, this study utilizes an in-bath bioprinting method to create a human-scale, freestanding in vitro model compatible with cardiovascular stents. Using a coaxial nozzle, a tubular structure of human coronary artery (HCA) size is bioprinted with a collagen-based bioink, ensuring good biocompatibility and suitable rheological properties for printing. We precisely replicated the dimensions of the HCA, including its internal diameter and wall thickness, and simulated the vascular barrier functionality. To simplify post-processing, a pumpless perfusion bioreactor is fabricated to culture a HCA-sized model, eliminating the need for a peristaltic pump and enabling scalability for high-throughput production. This model is expected to accelerate stent development in the future.

Fabrication and characterization of starch-based bigels under phase control: Structural, physicochemical and 3D printing properties

Edible bigels are being developed to replace plastic fats in the food industry due to their ability to form semi-solids with controllable properties. In this study, biopolymer hydrogels were formed using modified corn starch with chitosan, betaine, and vanillin, whereas oleogels were formed from insect wax in soybean oil. The impact of varying the hydrogel-to-oleogel ratio on the properties of bigels was then examined. The rheological, oil-binding capacity (OBC), water-oil distribution, structural, and 3D printing characteristics of the bigels were evaluated. Higher hydrogel-to-oleogel ratios resulted in improved rheological properties of bigels. Hydrogen bonding, electrostatic interactions, and covalent Schiff base bonds played an important role in the formation and properties of the hydrogels. In contrast, the mechanical strength of the oleogels was mainly attributed to van der Waals attraction between the insect wax crystals. The optimized bigels had good OBC and mechanical strength. Furthermore, increasing the hydrogel-to-oleogel ratio induced a transition from W/O to O/W type structure in the bigels. A study of the potential application of the bigels as edible inks showed that bigels with a high hydrogel-to-oleogel ratio had better 3D printing characteristics. The findings of this study suggest that bigels can be successfully used as solid fat substitutes.

Advanced MXene/Graphene Oxide/Lignosulfonate Inks for 3D Printing Thick Electrodes with Vertically Aligned Pores to Dually Boost Mass Loading and Areal Capacitance

AbstractDirect ink writing 3D printing, using ink extrusion, promises to transform conventional 2D thin electrodes into 3D thick architectures for high‐performance supercapacitors. However, formulating 3D printing inks and designing 3D architectures for electrodes remain challenges. In this work, a novel MXene/graphene oxide/lignosulfonate (MGL) ink with excellent rheological properties is developed for 3D printing MGL thick electrodes with vertically aligned architectures. The MGL ink exhibited excellent shear‐thinning properties for smooth 3D printing and shape retention after printing. The 3D‐printed MGL thick electrode, with a thickness of up to 4 mm, achieved a breakthrough mass loading of 72.1 mg cm−2, resulting in an extremely high areal capacitance of 8.6 F cm−2 that is 9.6 times greater than the value observed for the bulk MGL electrode (0.9 F cm−2). Additionally, supercapacitors using the 3D MGL electrode achieved an energy density of 505.3 µWh cm−2, significantly surpassing the value for bulk MGL electrode (52.8 µWh cm−2). This enhancement is attributed to the efficient design of the electrodes, where vertically aligned pores in the 3D MGL electrode enhanced ion transfer and reaction kinetics. This study demonstrates an innovative approach for formulating inks and provides guidance for designing 3D thick electrodes with rapid ion transport and excellent electrochemical performance.

IR-spectroscopic analysis of interaction with multi-layer paper and cardboard containing synthetic fibers with printing inks

An IR spectroscopic analysis of the printing and technical properties of new types of multilayer packaging paper and cardboard containing waste polyacrylonitrile fiber and their interaction with printing inks was carried out. The preference for using multilayer composite paper and cardboard for the printing and paper industries is shown. It has been established that the tensile strength of paper does not depend on the strength of individual components, but on the strength of the paper structure formed during its production. When the paper contained 20% waste modified polyacrylonitrile, maximum optical density was achieved with a minimum thickness of the ink layer, that is, saturated prints were obtained with minimal consumption of printing ink.

Assessment on the influence of FDM process parameters on the mechanical properties of PLA samples

Abstract The manufacturing of functional parts from the fused deposition modeling 3D printer is limited due to poor mechanical properties, low surface finish, and huge production time. During 3D printing of prototypes, the time consumption of printing and mechanical properties of the model is directly proportional. The fused deposition modeling process parameters significantly impact the quality of printed parts. The prime objective of this research is to optimize the process parameters of a 3D printing machine (wall thickness, infill percentage, infill pattern, and infill speed) using polylactic acid material to enhance the mechanical properties with less printing time of the 3D printing model. The ultimate tensile strength and elongation of the 3D printed samples are used to evaluate the mechanical properties of the various slicing process parameters as per the standards. From the results, it is evident that the mechanical properties of the 3D printed materials increased significantly. The magnitude of ultimate tensile strength is reported as 39.972 MPa with a printing time of 28 min. From close observation, it is evident that lower infill speeds with gyroid infill pattern produce the highest ultimate tensile strength of all combinations. Also, optimal results are derived at higher wall thickness and higher infill percentage. In addition to that, finite element analysis was carried out for different infill percentages of the specimen to validate the actual result.

3D Printing and Biodegradable Polymers

Abstract 3D printing technology has a wide range of applications in many industries, including automotive, aerospace, biomedical, electronics and packaging, requiring different types of filaments to be used in producing 3D printed objects. The most commonly used materials are metals, ceramics, composites and plastics of which the latter are most available. Since it is necessary to reduce pollution caused by waste from conventional petroleum-based plastics, biodegradable polymers made from renewable resources or produced synthetically have gained in importance recently. Polylactic acid, poly(butylene succinate), thermoplastic starch, poly(butylene adipate co-terephthalate) and polycaprolactone are well-known representatives of this group of materials. They possess desirable properties for 3D printing which make them promising materials in many areas of applications.

Enhancement of micron fish bone on gelling and 3D printing properties of Northern pike (Esox lucius) low-salt surimi

Micron fish bone (MFB) is an ideal food material for low-salt surimi gel. The gel properties and the 3D printing performance quality of Esox lucius surimi involved by MFB at various additions were investigated. The MFB promoted the unfolding of the surimi protein structure, catalyzed the covalent cross-linking within or between protein molecules, and boosted the formation of the surimi gel. MFB can be embedded into the gel network, increasing the strength of the gel network structure, making the surimi gel more self-supporting, and improving the thermal stability of the 3D-printed surimi gel products. The results showed that 4.0 g/100 g MFB could sustain the printing accuracy (95.22%), reduce the shrinkage rate and cooking loss rate (7.39% and 11.31%), maintain the shape stability, improve the whiteness value and water holding capacity (80.12% and 68.92%), enhance the gel strength (444.07 g cm), and improve the texture of the 3D printing product. The 4.0 g/100 g MFB also increased the hydrogen bond content and the P21 value (the peak area ratio of the bound water) and shaped a denser mesh structure with smaller pores inside the surimi gel printed samples. This study could encourage the high-value applications of MFB and supply guidance for the subsequent progression of low-salt surimi products.

Co-regulation of gelatin content and Hofmeister effect on 3D-printed high internal phase emulsion gel characteristics for resveratrol delivery

The study investigated the influence of gelatin (GE) content and the Hofmeister effect on the physicochemical, rheological, and printing properties of high internal phase emulsion (HIPE) gels. Incremental GE content introduced more triple helix structures (junction zones) in the continuous phase of HIPE. By soaking in a sodium citrate (Na3Cit)-glycerol-water solution, polymer chain bundling, hydrophobic interactions, and abundant hydrogen bonds between GE and glycerol further increased, achieving a more compact crosslinking density and internal network. The optimized HIPE-GE-Cit3- gel with 1.5 wt% GE displayed improved shape retention, generating smoother and firmer gels with enhanced freezing and heat resistance. Its excellent mechanical strength and viscoelasticity can resist large deformations and maintain reversible structures. HIPE-GE gel with 1.5 wt% GE demonstrated satisfactory printing suitability with clear outlines, favorable visual aesthetics, and minimal dimensional deviation. This post-soaking (Hofmeister effect) also eliminated rough surfaces and visible layered lines, improved mechanical properties and more elastic networks. The printed HIPE-GE1.5-Cit3- gel with higher rigidity and elasticity impeding molecular release, protected encapsulated resveratrol against degradation, especially from heat, and enhanced the release rate in the small intestine, achieving sustained release. This work produced customizable HIPE gels by 3D printing with multiple advantages to develop personalized nutraceutical carriers with high-temperature tolerance.

3D-Printed Interfacially Jammed Emulsion Aerogels.

3D printing ultralightweight porous structures using direct ink writing (DIW) while maintaining their mechanical robustness is highly challenging. This difficulty is amplified when low ink concentrations are used to create complex geometries. Herein, this shortfall was addressed by interfacially jammed emulsion gels. The gel emerged from the electrostatic interaction among synergized nanomaterials (graphene oxide (GO) and cellulose nanocrystals (CNCs)) in the aqueous phase and a ligand in the oil phase. This interaction led to the jamming of the nanoparticles and the creation of stable emulsion gels. The formed interfacial assemblies were further treated by post-jamming ionic cross-linking with NaHCO3, which dictated the emulsion gels' rheological characteristics, enhancing the ink's viscoelastic properties for high-resolution 3D printing. The customizable emulsion system allows control over porosity from the macro- to the micro-scale and generates complex geometries with desired compositions. By manipulating post-annealing processes and varying concentrations, it is possible to achieve aerogels that feature a remarkably low density (∼2.63 mg/cm3) and adjustable mechanical robustness (elastic modulus of 0.45 MPa). Additionally, this method allows for producing aerogels with flexible or stiff characteristics as required, alongside the capability to tailor specific electromagnetic shielding effectiveness (ranging from 6791 to 19615 dB cm2/g), showcasing the technique's versatility and engineerability.