Effects of Viscosity and Surface Tension of a Reactive Dye Ink on Droplet Formation

Xanthan gum ink based on Lycium ruthenicum anthocyanin as an indicator of color change for monitoring freshness of cold fresh meat

The continuous development of intelligent food packaging has led to an increased focus on using freshness-indicating inks, which could provide a high level of quality control and consumer experience. This study aimed to further promote the application of xanthan gum ink in food freshness indication by optimizing its performance in screen printing. A novel freshness-indicating ink was prepared using Lycium ruthenicum anthocyanin (LRA) as the core indicator, glucose as the pigment carrier, soybean oil as the linker, and xanthan gum (XG) as the thickener. Scanning electron microscopy (SEM) demonstrated that the ink was uniformly distributed on paper using screen printing. Rheological and particle size analyses revealed that the incorporation of XG significantly enhanced the interaction force between droplets in the ink system. Further tests on viscosity, fineness, and initial dryness indicated that XG, a natural microbial polysaccharide with excellent stability, could effectively improve the flowability of the ink. Specifically, at a 0.3 % XG content, the ink exhibited a unimodal particle size distribution with an average particle size of 851.02 nm and a zeta potential of -27 mV. This indicated the ink system was stable and uniform, with optimal rheological properties and printing suitability. Furthermore, the printed freshness indication labels exhibited a significant change in color as the freshness of the refrigerated meat changed. This study develops a natural and safe method for monitoring the freshness of refrigerated meat and provides an optimized idea for applying indicator inks.

Inkjet printing quality improvement research progress: A review

Inkjet printing is a prevalent printing technology that finds extensive applications in diverse fields, including mechanical manufacturing and flexible electronics. Enhancing the quality of inkjet printing has consistently piqued significant interest, with the goal of attaining superior printing resolution, precise color reproduction, and finer image details. This article begins with an overview of the current advancements in inkjet printing, elaborating on four key principles and technologies of inkjet printing. Subsequently, the article delves into the application and research progress related to enhancing inkjet printing quality across various fields. This exploration is structured around four perspectives: printing equipment, substrates, ink properties, and emerging printing technologies. Significant enhancements in inkjet printing quality, resulting in improved image details and color reproduction effects, can be attained by optimizing ink formulations, refining inkjet head design, and selecting suitable substrates and surface treatment methods. To conclude, this article addresses and summarizes future technological advancements aimed at enhancing inkjet printing quality.

Three-Dimensional Printing of Hydrogels for Flexible Sensors: A Review

The remarkable flexibility and heightened sensitivity of flexible sensors have drawn significant attention, setting them apart from traditional sensor technology. Within this domain, hydrogels-3D crosslinked networks of hydrophilic polymers-emerge as a leading material for the new generation of flexible sensors, thanks to their unique material properties. These include structural versatility, which imparts traits like adhesiveness and self-healing capabilities. Traditional templating-based methods fall short of tailor-made applications in crafting flexible sensors. In contrast, 3D printing technology stands out with its superior fabrication precision, cost-effectiveness, and satisfactory production efficiency, making it a more suitable approach than templating-based strategies. This review spotlights the latest hydrogel-based flexible sensors developed through 3D printing. It begins by categorizing hydrogels and outlining various 3D-printing techniques. It then focuses on a range of flexible sensors-including those for strain, pressure, pH, temperature, and biosensors-detailing their fabrication methods and applications. Furthermore, it explores the sensing mechanisms and concludes with an analysis of existing challenges and prospects for future research breakthroughs in this field.

The Evaluation and Exploration of Piezoelectric Parameter Optimization for Droplet Ejection in Binder Jet 3D Printing Drugs

Since the first three-dimensional (3D) printed drug was approved by the Food and Drug Administration in 2015, there has been a growing interest in using binder jet 3D printing (BJ-3DP) technology for pharmaceuticals. However, most studies are still at an exploratory stage, lacking micromechanism research, such as the droplet ejection mechanism, the effect of printhead piezoelectric parameters on inkjet smoothness and preparation formability. In this study, based on the inkjet printing and observation platform, the Epson I3200-A1 piezoelectric printhead matched to the self-developed BJ-3DP was selected to analyze the droplet ejection state of self-developed ink at the microlevel with different piezoelectric pulse parameters. The results showed that there was a stable inkjet state with an inkjet pulse width of 3.5 μs, an ink supply pulse width of 4.5 μs, and a jet frequency in the range of 5000-19,000 Hz, ensuring both better droplet pattern and print accuracy, as well as high ejection efficiency. In conclusion, we performed a systematic evaluation of the inkjet behavior under different piezoelectric pulse parameters and provided a good idea and case study for the optimization of printhead piezoelectric parameters when BJ-3DP technology was used in pharmaceuticals.

Development of Binder-Free Pigment Inks for Direct Inkjet Printing on Cotton Fabric without Pretreatment

Inkjet printing technology is widely used in the textile digital printing application today though the current technology still requires pretreatment and postwashing procedures before and after printing. Additional chemical treatment generates a large amount of wastewater and complicates the process. Among the many potential approaches for reducing chemical waste, pigments with self-dispersing capability were prepared and formulated into binder-free inkjet inks that require no pretreatment or after-washing process when printing cotton fabrics. The new self-dispersing pigment inks were tested and evaluated on cotton fabrics. The distribution of particles was between 122.2 and 188.5 nm, and inks have excellent storage capability. Printed fabrics' light fastness and acid/alkali resistance are about grade 5, and printed cotton's washing and rubbing fastness are above grade 3. The mechanism and performance of ink drops were investigated by LF-NMR and ink-drop observation methods. This work provides a possible solution for reducing wastewater in the textile industry.

Fast-speed, Highly Sensitive, Flexible Humidity Sensors Based on a Printable Composite of Carbon Nanotubes and Hydrophilic Polymers

Carbon nanotubes (CNTs) are a promising material for humidity sensors and wearable electronics due to their solution capability, good flexibility, and high conductivity. However, the performance of CNT-based humidity sensors is limited by their low sensitivity and slow response. Herein CNTs and hydrophilic polymers were mixed to form a composite. The hydrophilicity of the polymers and the network structure of the CNTs empowered the humidity sensors with a high response of 171% and a fast response/recovery time of 23 s/10 s. Owing to the sticky and flexible polymers, the humidity sensors showed strong adhesion to the PET substrate and exhibited outstanding bending durability. Furthermore, the flexible humidity sensor was applied to monitor human breathing and detect finger movements and handshaking.

Fabrication of Chitosan-Loaded Multifunctional Wool Fabric for Reactive Dye Digital Inkjet Printing by Schiff Base Reaction

Improving the development of high-value multifunctional wool fabrics was essential to satisfy diverse needs. Considering the various characteristics of chitosan macromolecules, herein, a padding-cross-linking process was adopted and then multifunctional wool fabrics with outstanding printing effects, shrink resistance, and antibacterial properties were fabricated. The test results showed that chitosan macromolecules loaded successfully on the wool fiber surface by Schiff base reaction. Wool fabrics changed from hydrophobic to hydrophilic due to the existence of chitosan macromolecules. The color strength (K/S value) of the reactive dye inkjet-printed wool fabric was greatly increased from 20.48 to 26.6. The area shrinkage of final samples was 2.53%, which was exceedingly lower than that of the original wool (10.96%). Moreover, the chitosan macromolecules with reactive amino groups endowed wool fabrics with certain antibacterial properties against E. coli and S. aureus. Generally, this study provided guidance for manufacturing multifunctional digital inkjet-printed wool products in mass production.

Prediction of Newtonian Droplet Breaking Time from a Capillary at Low Weber Numbers

Droplet formation and growth processes have numerous scientific and industrial applications. Experimental and numerical studies on the formation, growth, and breaking of droplet are carried out in present work. The numerical results are in good agreement with the experiment. This work focused on the effect of different Weber numbers (We) on the droplet breaking time. The results show when We < 0.05, the length and volume of the droplet increase, and the breaking time decreases rapidly. The resultant force acting on the main droplet suddenly drops around the critical breaking time. The difference rate between the time t _n (when the resultant force is zero) and the breaking time t _b is less than 8.49%. For the dimensional analysis of the numerical results, a prediction formula of breaking time on the Weber number is modeled as aWe ^b + c for We < 0.5.

Insights into coloration enhancement of mercerized cotton fabric on reactive dye digital inkjet printing

Mercerization can improve the utilization rate of dyes in the dyeing process, and reduce the discharge of washing wastewater. However, the effect and mechanism of mercerization is not clear on digital inkjet printing of cotton fabric. In this work, two kinds of cotton fabrics (original and mercerized) were used for reactive dye digital inkjet printing, and the color improvement mechanism of caustic soda mercerization was investigated. It was found that the crystallinity of cotton fibre was adjusted from 73.9% to 58.5% by caustic mercerization, and the breaking strength did not decrease compared with original cotton fibre. Thus, the accessible reactive hydroxyl groups and the wettability were enhanced for treated cotton fibres, which promoted the inks' wick into the fibres. Interestingly, the penetration of ink droplets between the yarns and fibres after caustic mercerization was decreased, thus the dyes mainly gathered on the surface of cotton fabric. The cotton fibres' cross section structure changed from flat oval to round, which increased the contact area between reactive dyes and fibres. At a certain amount of ink, the optimal K/S value of 23.47 was achieved for treated cotton fabrics, which was higher than that of untreated cotton fabrics (17.15). Meanwhile, the printed fabrics displayed good washing fastness, rubbing fastness and glossiness. This work has important theoretical guiding significance for producing high quality mercerized cotton fabric digital printing products and reducing printing wastewater discharge.

Mercerization can control the crystallinity of cotton fiber, promote the absorption of ink droplets' wick into the fiber and inhibit ink droplets from penetrating the back of fabric. Therefore, the printing quality was extremely enhanced.

Controllable Droplet Ejection of Multiple Reagents through Focused Acoustic Beams

Acoustic droplet ejection (ADE) technology has revolutionized fluid handling with its contactless and fast fluid transfer. For precise droplet ejection and stable droplet coalescence at the target substrates for further detection, the input power of the ADE system needs to be adjusted. Currently, the existing power control method depends on scanning the source fluid wells one by one, which cannot afford precise and highly efficient droplet velocity adjustment, and the complicated operation caused by the repeated power evaluation processes for thousands of fluid transfers will waste much time. We propose a new method, which realizes the controllable ejection of multiple reagents by analyzing the effect of the product of kinematic viscosity and surface tension of the reagents on the droplet initial velocity. The experimental results obtained by ejecting dimethyl sulfoxide coincide well with the predicted results, and the relative error in the droplet initial velocity is mostly less than 8%. On the basis of the input power prediction method proposed in this paper, the ADE system is successfully constructed for continuous dispensing of polystyrene microspheres as cell surrogates, which provided an advanced liquid handling solution for research in biochemistry and other fields.

Inkjet-Printed Electron Transport Layers for Perovskite Solar Cells

Inkjet printing emerged as an alternative deposition method to spin coating in the field of perovskite solar cells (PSCs) with the potential of scalable, low-cost, and no-waste manufacturing. In this study, the materials TiO₂, SrTiO₃, and SnO₂ were inkjet-printed as electron transport layers (ETLs), and the PSC performance based on these ETLs was optimized by adjusting the ink preparation methods and printing processes. For the mesoporous ETLs inkjet-printed from TiO₂ and SrTiO₃ nanoparticle inks, the selection of solvents for dispersing nanoparticles was found to be important and a cosolvent system is beneficial for the film formation. Meanwhile, to overcome the low current density and severe hysteresis in SrTiO₃-based devices, mixed mesoporous SrTiO₃/TiO₂ ETLs were also investigated. In addition, inkjet-printed SnO₂ thin films were fabricated by using a cosolvent system and the effect of the SnO₂ ink concentrations on the device performance was investigated. In comparison with PSCs based on TiO₂ and SrTiO₃ ETLs, the SnO₂-based devices offer an optimal power conversion efficiency (PCE) of 17.37% in combination with a low hysteresis. This work expands the range of suitable ETL materials for inkjet-printed PSCs and promotes the commercial applications of inkjet printing techniques in PSC manufacturing.

Effects of alkanolamine solvents on the aggregation states of reactive dyes in concentrated solutions and the properties of the solutions

The aggregation of dyes is a common phenomenon in solutions, particularly concentrated solutions, which seriously affects the dyeing and printing processes. In this study, the effects of alkylamine solvents on the reactive dye aggregation behavior in highly concentrated solutions was studied. Typical cases were conducted with two slightly toxic and environmentally friendly solvents, namely diethanolamine (DEA) and triethanolamine (TEA), and two reactive dyes, namely C. I. Reactive Red 218 (R-218) and C. I. Reactive Orange 13 (O-13). Aggregation states were studied by ultraviolet-visible (UV-Vis) absorption spectroscopy, Gaussian-peak-fitting method and fluorescence spectroscopy. The results showed that both the additives DEA and TEA could reduce the dye aggregation because the solvents, DEA and TEA, can break the iceberg structure and allow easy entry of the molecules into the dye aggregates. Also, the disaggregation caused by DEA was higher as compared with TEA, which may be caused by the weaker hydrogen bond and the relatively smaller steric hindrance effects of DEA. The schematic of disaggregation between R-218 and DEA was also discussed. For R-218, the dimers were disaggregated to monomer, while the higher-ordered aggregates were disaggregated to trimers and dimers for O-13. Moreover, physical properties such as viscosity and surface tension of the solutions were measured. This investigation is instructive for the further dyeing progress with organic bases in the textile industries.

Influences of Polymer-Surfactant Interaction on the Drop Formation Process: An Experimental Study

The interaction between polymer and surfactant molecules affects the physical properties of liquids, which could be of great importance in an abundance of processes related to drop formation. Polymer and surfactant concentration is a factor that dramatically impacts the shape of molecular networks formed in the fluid bulk and the characteristics of a forming drop. In this study, the deformation and detachment of aqueous carboxymethyl cellulose (CMC) solutions' drops containing different concentrations of sodium dodecyl sulfate (SDS) are studied experimentally. Our purpose is to determine the effects of CMC and SDS concentrations on the parameters related to the formation process, including drop length, minimum neck thickness, and formation time. Our results clearly show that the increment of the SDS amount at a constant low CMC concentration increases the drop detachment length and results in a slower thinning process. However, at higher CMC concentrations, the drop limiting length reaches a maximum, indicating the effects of disintegration of molecular structures as the SDS amount exceeds the critical concentration. Moreover, the drop formation time is found to decrease with the increment of the SDS concentration, which could be attributed to the reduction of dynamic interfacial tension.

Effect of Polyol Molecular Structure on Fluidity, Surface Tension, and Printed Pattern Sharpness of Disperse Dye Inks

In the present study, density functional theory (DFT) has been used in simulating and calculating the molecular geometries of differently structured polyols (within a water phase), as well as the weak interactions between these polyols and the water molecules. Furthermore, low field nuclear magnetic resonance (LF-NMR) has been used in studying the transverse relaxation times of different polyols, in addition to their (20.00 wt %) fluidity in an aqueous environment. Moreover, the influence of polyols, with different molecular structures, on the ink fluidity, was also explored. A bubble pressure tensiometer was also used to characterize the surface tension of the aqueous polyol (20.00 wt %) solution, the sodium dodecyl sulfate (SDS, 0.50 wt %) solution, and the ink. This was made to clarify the influence of polyol and SDS on the surface tension of ink. In addition, the particle size, zeta potential, pH value, viscosity, and rheological properties of the ink, were also investigated. The resulting data showed that polyols have certain effects on the particle size, stability, and viscosity of the ink. The jetting performances of different polyol inks were, under certain conditions of the inkjet drive waveform, also explored. The results showed that the fluidity, viscosity, and surface tension of the ink will render a certain influence on the inkjet performances. The prepared polyol ink was thereafter used for polyester fabric printing, and the contour sharpness and color fastness of the printed fabric were accordingly evaluated. The data showed that the increase in ink viscosity, and decrease in fluidity, promote the improvement in contour sharpness. In addition, the printed fabric demonstrated an excellent color fastness.

Syntheses of Silver Nanowires Ink and Printable Flexible Transparent Conductive Film: A Review

Nowadays, flexible transparent conductive film (FTCF) is one of the important components of many flexible electronic devices. Due to comprehensive performances on optoelectronics, FTCF based on silver nanowires (AgNWs) networks have received great attention and are expected to be a new generation of transparent conductive film materials. Due to its simple process, printed electronic technology is now an important technology for the rapid production of low-cost and high-quality flexible electronic devices. AgNWs-based FTCF fabricated by using printed electronic technology is considered to be the most promising process. Here, the preparation and performance of AgNW ink are introduced. The current printing technologies are described, including gravure printing, screen printing and inkjet printing. In addition, the latest methods to improve the conductivity, adhesion, and stability of AgNWs-based FTCF are introduced. Finally, the applications of AgNWs-based FTCF in solar cells, transparent film heaters, optoelectronic devices, touch panel, and sensors are introduced in detail. Therefore, combining various printing technologies with AgNWs ink may provide more opportunities for the development of flexible electronic devices in the future.