Printing Ink Research Articles

Directly Printable, Non‐Smearable and Stretchable Conductive Ink Enabled by Liquid Metal Microparticles Interstitially Engineered in Highly Entangled Elastomeric Matrix

AbstractLiquid metal or liquid metal microparticles (LMP) based conductive inks, though promising for fabrication of circuits for use in soft and stretchable electronics, are constrained by a few drawbacks such as need for encapsulation, need for sintering to induce conductivity, and smearing. To address these issues, herein, a stretchable conductive composite ink is developed by combining LMPs with carbon black (CB) in highly entangled polysiloxane elastomer. LMP‐dispersed elastomer lacks conductivity because of its non‐percolated network, however, the CB can interconnect LMPs to act as a bridge, thereby imparting conductivity to the elastomer. Due to presence of fluidic LMPs, the LMPs‐dispersed elastomer lies in soft regime with initial conductivity of 5.6 S m−1, aided by the presence of CB in the interstitial spaces between the LMPs. The highly entangled molecular network of the encapsulating elastomer endows the resulting composite with high stretchability (≈286%) and softness (0.648 MPa) and its long pot life enables rheological modulation of the ink to achieve pressure‐driven direct printed non‐smearing traces. The LMPs‐based conductive ink developed in this work is expected to be further utilized in the fabrication of soft robotics and electronic skin and integrated into electronic modules by facile direct 3D printing.

A MULTI-ANALYTICAL INVESTIGATION OF AN IRANIAN LITHOGRAPHY BOOK FROM THE QAJAR PERIOD

The lithography books of Iran, despite their historical importance, have received relatively little attention. This study aims to comprehensively examine an Iranian lithography book from the Qajar period titled Hayat al-Qolub, to identify its materials. The paper pulp, sizing, inks and leather of the bookbinding were analyzed through various methods, including staining tests for identifying paper pulp, light microscopy, FTIR, Raman spectroscopy, Micro-spectrophotometry, multi-band imaging, SEM-EDS and LC-MS. The findings suggest that the book was made of rag paper composed of linen and cotton fibers, while animal glue and gypsum were used for paper sizing and filling, respectively. Carbon black was used as black printing ink and cochineal was used for red ink. The leather cover of the book was made of goat skin that was tanned with gallotannins and unhaired with lime. Evidence of the use of liming in the unhairing process was also observed in this leather. This research enhances our understanding of paper and bookmaking techniques of the Qajar period in Iran.

Recent Development in Edible Inks for Food Printing and Packaging Applications: A Review

Recent Development in Edible Inks for Food Printing and Packaging Applications: A Review

Transcription of Customized Circularly Polarized Luminescence from Enantiomeric Metal–Organic Framework to Carbon Dots

AbstractChiral carbon dots (CDs) with circularly polarized luminescence (CPL) are one of the most dynamic areas of modern science. However, the design, preparation, and ambiguity mechanism of solid‐state CPL‐active CDs remains a formidable challenge. Herein, for the first time, CDs with customized chiroptical activities in the solid state, especially CPL, are transcribed from chiral metal–organic framework (CMOFs) via a bottle‐around‐ship strategy. Within these CMOFs⊃CDs assemblies, CDs inherited the chirality of the host CMOFs through host–guest interactions, which is revealed by density functional theory (DFT) simulations and experimental results, and amplified the luminescence dissymmetry factor (glum) by effective artificial chiral light‐harvesting systems. Impressively, CMOFs⊃CDs in pairs generated color‐tunable CPL and white CPL with chromaticity coordinates of (0.32, 0.32). Furthermore, benefiting from excellent processability, as luminescent coatings and 3D printing inks, a white circularly polarized light‐emitting diode, and an extended 3D model “light bulb” featuring white CPL are successfully fabricated, respectively. This strategy paves a new avenue for the synthesis and advanced application of solid‐state CPL‐active CDs‐based materials.

Studies on cytocompatibility of human dermal fibroblasts on carbon nanofiber nanoparticle-containing bioprinted constructs

Functional nanocomposite-based printable inks impart strength, mechanical stability, and bioactivity to the printed matrix due to the presence of nanomaterials or nanostructures. Carbonaceous nanomaterials are known to improve the electrical conductivity, osteoconductivity, mechanical, and thermal properties of printed materials. In the current work, we have incorporated carbon nanofiber nanoparticles (CNF NPs) into methacrylated gelatin (GelMA) to investigate whether the resulting nanocomposite printable ink constructs (GelMA-CNF NPs) promote cell proliferation. Two kinds of printable constructs, cell-laden bioink and biomaterial ink, were prepared by incorporating various concentrations of CNF NPs (50, 100, and 150 µg/mL). The CNF NPs improved the mechanical strength and dielectric properties of the printed constructs. The in vitro cell line studies using normal human dermal fibroblasts (nHDF) demonstrated that CNF NPs are involved in cell-material interaction without affecting cellular morphology. Though the presence of NPs did not affect cellular viability on the initial days of treatment, it caused cytotoxicity to the cells on days 4 and 7 of the treatment. A significant level of cytotoxicity was observed in the highly CNF-concentrated bioink scaffolds (100 and 150 µg/mL). The unfavorable outcomes of the current work necessitate further study of employing functionalized CNF NPs to achieve enhanced cell proliferation in GelMA-CNF NPs-based bioprinted constructs and advance the application of skin tissue regeneration.Graphical abstract

Optimization of the interfacial properties between mechanically and electrochemically treated aluminium and nano-modified coatings for printed outdoor applications

The aim of this research was to analyze the interfacial properties between the surfaces of mechanically and electrochemically treated aluminium substrates and the printed coatings modified by the addition of silicon dioxide (SiO2) and titanium dioxide (TiO2) nanoparticles. The nanoparticles were added to the printing inks in various concentrations with the scope to optimize the interface properties of the prints for outdoor applications. The surface, as well as the structural and mechanical properties of the printed coatings were evaluated. Various methods were employed to measure and analyze the surface and interfacial properties of aluminium and coatings. Surface microphotographs and the roughness of the treated aluminium substrates were examined, the surface free energy of the aluminium and the coatings as well as the adhesion properties were calculated, and the thickness and optical density of the coatings were measured. Considering that the treated aluminium samples prepared for this research had quite textured and different surfaces, the contact angles used for the calculation of surface free energy were calculated with and without Wenzel model to obtain detailed information about the interactions between the surface of aluminium samples and the printed modified coatings. The results showed that the type of treatment of aluminium substrates as well as the modification of the printing inks have a significant influence on the adhesion and surface properties of the coatings considered. Furthermore, the results demonstrated that the produced nano-modified coatings can be used as printed coatings or as customized primers for applying various types of inks and coatings.

Development, characterization and underling mechanism of 3D printable quinoa protein emulsion gels by incorporating of different polysaccharides for curcumin delivery

Emulsion gels stabilized by food-grade polymers such as proteins and polysaccharides are edible 3D food printing inks with various applications in food industry. In this study, 3D printable quinoa protein emulsion gels with four polysaccharides incorporated were fabricated to delivery curcumin. The effect of inulin (INU), fucoidan (FU), dextran sulfate (DS), and sodium alginate (SA) on the microstructure, rheological properties, and 3D printing performance of quinoa protein emulsion gels were all investigated. The results showed that the incorporation of four polysaccharides promoted formation of tightly packed oil droplets within gel networks, along with enhanced hardness, water holding capacity, freeze-thaw stability and decreased swelling ratio of the QP emulsion gel. All samples exhibited shear thinning behavior and polysaccharides increased viscoelasticity of QP emulsion gel. The hydrophobic interactions and disulfide bond are the main chemical molecular force of emulsion gels, INU significantly increased the hydrogen bonds interactions, and anionic polysaccharide (FU, DS, and SA) significantly increased the electrostatic interactions. QP-INU exerted best printing performance as identified by preferable self-supporting capability and high line printing accuracy. The addition of polysaccharides improved the encapsulation efficiency of curcumin in QP emulsion gel. In vitro release property showed that FU increased the bioavailability of curcumin, DS and SA decreased bioavailability of curcumin with delayed digestion rate. This study demonstrated the potential of utilizing polysaccharides to improve the flexibility of QP emulsion gel for 3D printing functional food.

Low-temperature DLP 3D printing of low-concentration collagen methacryloyl for the fabrication of durable and bioactive personalized scaffolds

Digital Light Processing (DLP) bioprinting has revolutionized tissue engineering and regenerative medicine with its speed and precision. Although commonly used in DLP printing, Gelatin Methacrylate (GelMA) lacks the mechanical strength and complex biological signaling of collagen, owing to the absence of collagen’s unique triple helix structure. However, collagen faces challenges such as denaturation at high temperatures and aggregation at neutral pH, limiting its use as a bioink. Herein, we present for the first time the development of a low-temperature DLP 3D printing technique using low-concentration Collagen Methacryloyl (ColMA) for fabricating durable and bioactive personalized scaffolds. Our study shows that pH significantly influences ColMA printing, with pH 3 producing low-concentration scaffolds that exhibit enhanced mechanical properties, minimal swelling, and prolonged resistance to enzymatic hydrolysis compared to high-concentration GelMA scaffolds, while low-concentration GelMA cannot be printed independently. ColMA scaffolds notably boost the proliferation, adhesion, migration, and differentiation of human foreskin fibroblasts. In vivo rat model tests demonstrate that ColMA scaffolds reduce inflammation, enhance collagen deposition, and accelerate epidermal regeneration. This method offers a robust solution for low-temperature DLP 3D printing of collagen ink, facilitating the creation of personalized scaffolds with superior bioactivity and representing a significant advancement in tissue engineering applications.

Anti-counterfeiting labels with controllable and anti-interference coding information based on core–shell Ag@SiO2 nanomaterials for ink printing

The core–shell structured Ag@SiO2 nanomaterial integrated with surface-enhanced Raman scattering (SERS) spectroscopy promises a critical application in anti-counterfeiting. Security labels have been fabricated based on Ag@SiO2 embedded with Raman reporters. The Ag@SiO2 nanomaterial shows good stability and excellent anti-interference property for anti-counterfeiting. Multiple kinds of Raman probe molecules have been anchored in the Ag@SiO2 labels to provide specific and abundant encoding information. The flexible encoding security information could be controlled conveniently by adjusting probe molecules, which not only enrich the SERS information but also improve the level of anti-counterfeiting. Furthermore, the Ag@SiO2 shown excellent stability in organic solvent, and successfully used in ink for the anti-counterfeiting application.

Tailoring texture and functionality of vegetable protein meat analogues through 3D printed porous structures

This study presents a comprehensive 3D printing process for plant-based meat alternatives, covering ink formulation, printing, and final product characterization. Traditionally, achieving desired food properties requires extensive exploration of ink components. Here, we demonstrate the potential of manipulating processing parameters instead of ink composition. Two structures were printed, differing only in extrusion temperature. The printed structures exhibited a dimensional accuracy slightly below 100%. We investigated their behavior through simulated food production cycles, including freezing, thawing, dehydration, and rehydration. Rheological measurements revealed that protein denaturation caused a 20% increase in viscosity. Temperature-induced protein denaturation allowed to produce 3D printed samples with a fine porous structure, with pore sizes ranging from 50 to 450 μm. Mechanical characterization showed that a single printing parameter (extrusion temperature) significantly impacts the final product mechanical properties, with an increase of about 50% in the maximum stress for denatured samples after rehydration. This novel approach simplifies 3D-printed protein-based food production, establishing a link between processing parameters and the final product mechanical behavior.

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.

3D inkjet printing of hybrid electroactive ink based on molecularly imprinted polymers for lipopolysaccharides detection

A hybrid electroactive ink based on molecularly imprinted polymer (MIP) hollow microparticles, zinc oxide nanoparticles (ZnO NPs) and conductive carbon paste (CP) is reported herein for the first time. The MIP/ZnO NPs/CP and corresponding non-imprinted NIP/ZnONPs/CP modified inks were screen-printed on plastic substrates via 3D inkjet technology to cover around 40 working screen-printed carbon electrodes (SPCE) pieces in a single batch. The custom-made electrochemical MIP/ZnONPs/CP@SPCE sensor was designed for the detection of bacterial endotoxins, i.e., lipopolysaccharides (LPS), derived from Pseudomonas aeruginosa. Hollow MIP silica microparticles with specific properties for 3D printing application, in terms of granulation and morphology, were synthesized via sol-gel method using tetraethyl orthosilicate and (3-aminopropyl) triethoxysilane as monomers. Following the structural and morphological characterization of microparticles, the evaluation of template rebinding indicated a clear specificity of MIPs for LPS compared to the NIPs. Hybrid MIP/ZnONPs/CP and NIP/ZnONPs/CP inks were characterized using morphological and structural methods, which confirmed a viscosity of 25.000 mPa.s, a granulation of <20 µm, and a solid powder content of <27 %, as well as a homogenous incorporation of MIP particles and ZnONPs in the conductive CP. Finally, the electrochemical evaluation of the modified MIP/ZnONPs/CP@SPCE sensor revealed a good sensitivity to LPS molecules in PBS at pH 7.4, in the linear working range 1 - 100 µM, where a 0.058 µM limit of detection (LOD) and a response time less than or equal to 1 min were determined. The selectivity of the MIP/ZnONPs/CP@SPCE sensor towards LPS from Salmonella enterica and Escherichia coli was also assessed, highlighting a clear difference between these structural resembling species.

Exploring puffed rice as a novel ink for 3D food printing: Rheological characterization and printability analysis

This study introduces a novel approach by using puffed rice (PR) as a sustainable and innovative ink for 3D food printing. Due to gelatinization and dextrinization, PR saw notable water absorption and solubility gains, with a modest viscosity uptick from 39.2 to 49.9 RVU, sharply contrasting Native rice (NR)'s jump from 128.9 to 167.8 RVU, emphasizing PR's minimal retrogradation. Gelatinized rice (GR) demonstrates similar stability in viscosity changes as PR, yet it requires more water and extended processing times for gelatinization. Conversely, PR's puffing process, which eliminates the need for water, offers quicker preparation and notable environmental benefits. Rheological analysis at 25% PR concentration reveals an optimal balance of viscosity (η, 897.4 Pa s), yield stress (τy, 2471.3 Pa), and flow stress (τf, 1509.2 Pa), demonstrating superior viscoelastic properties that facilitate enhanced printability and shape fidelity. Texture Profile Analysis outcomes reveals that PR significantly enhances key textural properties including hardness, adhesiveness, and springiness at this specific concentration. These findings highlight PR's potential as an eco-friendly and efficient ink choice for 3D-printed food products, providing enhanced performance and sustainability compared to GR and NR.

All-printed MXene/WS2-based flexible humidity sensor for multi-scenario applications

As non-contact sensing, non-invasive medical diagnostics and environmental humidity monitoring technologies advance, the demand for high-performance humidity sensors is becoming increasingly apparent. Ti3C2Tx MXene is an attractive humidity-sensitive candidate due to its excellent chemical activity and hydrophilic surface. However, achieving fast responsiveness and high sensitivity of dynamic changes in humidity is still challenging. Herein, this work introduced a WS2-modified Ti3C2Tx MXene composite material as humidity sensing material with superior sensing performance. Then sodium carboxymethyl cellulose solution was added to the Ti3C2Tx MXene/WS2 composite material to adjust viscosity of the composite material, enabling the formulation of printable humidity-sensitive ink. Utilizing screen-printing technology, a mass-producible humidity sensor (CMXW2) was successfully fabricated. Experimental results show that the sensor has short response and recovery times of 4.65 s/1.33 s in the relative humidity of 11–97 % with a high humidity response of 1707 % and excellent mechanical properties. The efficacy of the humidity sensor for skin moisture monitoring, real-time respiration monitoring, and non-contact switch was also evaluated. The successful demonstration of multi-scenario applications using the CMXW2 humidity sensor opens up new possibilities and applications in the fields of smart healthcare and non-contact sensing.

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.

One-step solvothermal synthesis of nitrogen-doped carbon dots with efficient red emission from conjugated perylene for multiple applications

Despite its significance for applications related to plant growth, the development of carbon dots (CDs) with bright red emissions still faces multiple obstacles. Herein, red emission hydrophobic carbon dots (RH-CDs) featuring one emission peak centered at 594 nm and a shoulder emission peak at 630 nm with a quantum yield of 34 % and a wide full width at half maximum (FWHM) of 100 nm (580 nm–680 nm) were synthesized by adopting large conjugated perylene anhydride and aromatic amine precursors under solvothermal conditions. Density functional theory calculations support the method of using larger conjugated systems and higher graphite N doping to increase red emissions from CDs. With a post-surface functionalization strategy, polyvinylpyrrolidone (PVP)-modified RH-CDs (QY = 12 %) were utilized as an anti-counterfeiting ink for information printing. Moreover, both blue-red light-emitting diodes (LEDs) and light conversion poly (methyl methacrylate) (PMMA)-CDs film were fabricated with emission spectra that are consistent with the absorption spectra of plants, suggesting that the prepared RH-CDs may have widespread application potential as a stable fluorescent material in plant growth.

Study of quality indicators of gravure imprints obtained with fluorescent ink

The peculiarities of the decoration of gravure imprints on cardboard using fluorescent inks are considered. The influence of the number of fluorescent impurities added to gravure printing ink on the optical indicators of printed image quality, particularly optical density, and gloss, is investigated. Increasing the number of fluorescent impurities added to the ink from 10 to 30% helps to increase the gloss on imprints from 2 to 15 units. Conducted thermogravimetric studies show the resistance of fluorescent imprints to the influence of temperatures during drying in the printing process. The topography of the surface of the substrates and its influence on the quality of imprints is studied. Conducted electron microscopic studies of imprints obtained with inks with different amounts of fluorescent impurities show their uniform distribution on the surface of the substrate. Studies of the fluorescence spectra of the ink and the imprints formed by it confirm the phenomenon of an increase in the intensity of the glow of printed images. The studies confirm the well-known influence of substrate roughness on the smoothness of gravure imprints. It is established that the absence of significant macro irregularities on the surface of Koppargloss FBB cardboard is due to the presence of two coating layers. Analysis of the surface profiles of FBB cardboard shows that its roughness parameter (Ra = 0.424 μm) is three times smaller compared to Incada Silk С GC1 cardboard (the roughness parameter Ra = 1.28 μm), with a single-layer coating. Such a pattern is also preserved on the imprints, which is reflected in their quality accordingly. Studies show that for imprints on GC1 cardboard, the average ΔE value is 2.23, for imprints on FBB cardboard, the average ΔE value is 3.71, which is due to the presence of double coating. The factors that can influence the process of fluorescence of printed images are outlined. The technological characteristics of inks for gravure printing on packaging are described.

High performance pixelated quantum dots array on Micro-LED by inkjet printing

Micro-LED display has risen to prominence in research and industry, distinguished by their numerous advantages. Quantum dots (QDs) film, serving as color conversion layers (CCLs) for Micro-LED, are considered a leading candidate for the next generation of displays, owing to their low power consumption and broad color gamut. Inkjet printing stands out as a feasible approach for crafting QDs CCLs. The essence of the process hinges on attaining a printed QDs film that boasts both uniformity and high-precision QDs array. However, the unstable printing of QDs ink significantly impacts the surface morphology of QDs arrays and the display performance of Micro-LEDs. Therefore, elucidating the mechanism behind the unstable printing of QDs in inkjet printing and fabricating QDs is of paramount importance. In this study, through the simulation of unstable printing with conventional QDs ink, we identified nozzle blockage and the rapid evaporation of low-boiling-point ink as the primary causes of unstable printing. This leads to aggregation and deposition of QDs, obstructing the nozzle and altering the fluid path. A novel binary organic composite ink was employed to print the QDs array on the substrate with ultra-stability, achieving a high yield and greatly reduced coffee-ring effect Micro-LED full-color display.

ADDITIVE MANUFACTURING OF SYNTHETIC RUBBER INK WITH HIGH SOLID CONTENT REINFORCED BY NETWORKED SILICA

ABSTRACT Silica is a reinforcing filler commonly used in the production of environmentally friendly tires, because tires reinforced with silica have lower rolling resistance that translates into reduced energy consumption and improved fuel economy. However, achieving the optimal dispersion of silica within the rubber matrix is crucial for maximizing its reinforcing effects. In this study, a three-dimensionally networked silica (NS) was introduced in various amounts to rubber inks to improve their tensile strength and increase miscibility to enable their use in additive manufacturing. The results show that synthetic rubber ink with a high content of SBR (90%) and reinforced by NS possesses adequate viscosity for use in the direct ink write (DIW) process. NS was confirmed to have an impact on the rheological properties and printability of the rubber ink as well as improve the tensile strength of the printed parts. Different formulations were tested to study and facilitate the vulcanization process and identify the optimal curing conditions as well as the print parameters to use in DIW printing. The successful printing and vulcanization of various printed structures demonstrate the potential for using the developed printable ink in additive manufacturing. This study opens up new possibilities for creating rubber products (such as tire treads) with adequate flexibility and high tensile strength.

Polycaprolactone strengthening gelatin/nano-hydroxyapatite composite biomaterial inks for potential application in extrusion-based 3D printing bone scaffolds

Extrusion-based three-dimensional (3D) printing of gelatin (Gel) is crucial for fabricating bone tissue engineering scaffolds via additive manufacturing. However, the thermal instability of Gel remains a persistent challenge, as it tends to collapse at mild temperatures. Current approaches often involve simply mixing Gel particles with various materials, resulting in biomaterial inks that lack uniformity and have inconsistent degradation characteristics. In this study, acetic acid was used to dissolve Gel and polycaprolactone (PCL) separately, producing homogeneous Gel/PCL dispersions with optimal pre-treatment performance. These dispersions were then combined and hybridized with nano-hydroxyapatite (n-HA) to create a composite printing ink. By evaluating the printability of the ink, the optimal conditions were identified: a n-HA concentration of 50% (w/w), a printing temperature of 10–15 ℃, a printing pressure of 2.5 bar, and a printing speed of 7 mm/s. The resulting biomaterial inks, with a composition of 25% Gel, 25% PCL, and 50% n-HA, demonstrated excellent printability and stability, along with significantly enhanced mechanical properties. As a result, 3D scaffolds with high printability and shape fidelity can be printed at room temperature, followed by deep freezing at -80 ℃ and cross-linking with vanillin. The Gel-based composite scaffolds demonstrated excellent biocompatibility, cell adhesion, cell viability and nano-hydroxyapatite absorption in vitro. Additionally, in vivo experiments revealed that the bioactive scaffold biodegraded during implantation and significantly promoted bone regeneration at the defect site. This provides a promising strategy for treating bone defects in clinical setting. In conclusion, the Gel/PCL/n-HA biomaterial inks presented here offer an innovative solution for extrusion bioprinting in the field of bone tissue engineering.Graphical