Color Printing Research Articles

Nanograting-Based Dynamic Structural Colors Using Heterogeneous Materials.

Dynamic structural colors can change in response to different environmental stimuli. This ability remains effective even when the size of the species responsible for the structural color is reduced to a few micrometers, providing a promising sensing mechanism for solving microenvironmental sensing problems in micro-robotics and microfluidics. However, the lack of dynamic structural colors that can encode rapidly, easily integrate, and accurately reflect changes in physical quantities hinders their use in microscale sensing applications. Herein, we present a 2.5-dimensional dynamic structural color based on nanogratings of heterogeneous materials, which were obtained by interweaving a pH-responsive hydrogel with an IP-L photoresist. Transverse gratings printed with pH-responsive hydrogels elongated the period of longitudinal grating in the swollen state, resulting in pH-tuned structural colors at a 45° incidence. Moreover, the patterned encoding and array printing of dynamic structural colors were achieved using grayscale stripe images to accurately encode the periods and heights of the nanogrid structures. Overall, dynamic structural color networks exhibit promising potential for applications in information encryption and in situ sensing for microfluidic chips.

Microcavity-assisted multi-resonant metasurfaces enabling versatile wavefront engineering

Metasurfaces have exhibited exceptional proficiency in precisely modulating light properties within narrow wavelength spectra. However, there is a growing demand for multi-resonant metasurfaces capable of wavefront engineering across broad spectral ranges. In this study, we introduce a microcavity-assisted multi-resonant metasurface platform that integrates subwavelength meta-atoms with a specially designed distributed Bragg reflector (DBR) substrate. This platform enables the simultaneous excitation of various resonant modes within the metasurface, resulting in multiple high-Q resonances spanning from the visible to the near-infrared (NIR) regions. The developed metasurface generates up to 15 high-Q resonant peaks across the visible-NIR spectrum, achieving a maximum efficiency of 81% (70.7%) in simulation (experiment) with an average efficiency of 76.6% (54.5%) and a standard deviation of 4.1% (11.1%). Additionally, we demonstrate the versatility of the multi-resonant metasurface in amplitude, phase, and wavefront modulations at peak wavelengths. By integrating structural color printing and vectorial holographic imaging, our proposed metasurface platform shows potential for applications in optical displays and encryption. This work paves the way for the development of next-generation multi-resonant metasurfaces with broad-ranging applications in photonics and beyond.

Enhanced color density from high-viscosity inkjet inks

AbstractInkjet printing inks are typically limited to low viscosities, employing highly dilute inks with low pigment loading compared with inks for other printing processes. This reduces color intensity, limits productivity, and requires higher drying energy. This study compares standard-viscosity graphic inkjet inks (~13 mPa.s shear viscosity) with higher-viscosity inkjet inks (~60 mPa.s), traditionally considered outside the normal jetting range, for print outcomes on corrugated cardboard with both white coated and brown uncoated liners. Higher-viscosity inks imparted greater color density to the print; this was assessed as being due to both the inherently higher viscosity of the ink reducing penetration into the substrate and the higher pigment loading capable of being contained within these inks. While standard-viscosity inks tended to plateau in color intensity as ink coverage was increased, higher-viscosity inks could increase in intensity throughout the entire coverage range on coated white liner. This effect was dependent on the substrate, with the coated white liner exhibiting up to a 67% increase in maximum color density but the uncoated brown liner showing up to a 13% increase. It is envisaged that wider adoption of higher-viscosity inks can increase both color intensity and printing speed, thus making inkjet more competitive with conventional printing processes.

High-resolution, high-speed, chromotropic color printing based on fs-laser-induced gold/graphene HSFL

High-resolution, high-speed, chromotropic color printing based on fs-laser-induced gold/graphene HSFL

Filaments for 3D Printing of Iridescent Structural Colors

Filaments for 3D Printing of Iridescent Structural Colors

Laser Control of Specular and Diffuse Reflectance of Thin Aluminum Film-Isolator-Metal Structures for Anti-Counterfeiting and Plasmonic Color Applications

Plasmonic structural color originates from the scattering and absorption of visible light by metallic nanostructures. Stacks consisting of thin, disordered semicontinuous metal films are attractive plasmonic color media, as they can be mass-produced using industry-proven physical vapor deposition techniques. These films are comprised of random nano-island structures of various sizes and shapes resonating at different wavelengths. When irradiated with short-pulse lasers, the nanostructures are locally restructured, and their optical response is altered in a spectrally selective manner. Therefore, various colors are obtained. We demonstrate the generation of structural plasmonic colors through femtosecond laser modification of a thin aluminum film–isolator–metal mirror (TAFIM) structure. Laser-induced structuring of TAFIM’s top aluminum film significantly alters the sample’s specular and diffuse reflectance depending on the fluence value and the number of times a region is scanned. A “negative image” effect is possible, where a dark field observation mode image is a negative of a bright field mode image. This effect is visible using an optical microscope, the naked eye, and a digital camera. The use of self-passivating aluminum results in a long-lasting, non-fading coloration effect. The reported technique could be used in anti-counterfeiting and security applications, as well as in plasmonic color printing and macroscopic and microscopic marking for personalized fine arts and aesthetic products such as jewelry.

Color detection of printing based on improved superpixel segmentation algorithm

We propose an improved superpixel segmentation algorithm based on visual saliency and color entropy for online color detection in printed products. This method addresses the issues of low accuracy and slow speed in detecting color deviations in print quality control. The improved superpixel segmentation algorithm consists of three main steps: Firstly, simulating human visual perception to obtain visually salient regions of the image, thereby achieving region-based superpixel segmentation. Secondly, adaptively determining the superpixel size within the salient regions using color information entropy. Finally, the superpixel segmentation method is optimized using hue angle distance based on chromaticity, ultimately achieving a region-based adaptive superpixel segmentation algorithm. Color detection of printed products compares the color mean values of post-printing images under the same superpixel labels, outputting labels with color deviations to identify areas of color differences. The experimental results show that the improved superpixel algorithm introduces color phase distance with better segmentation accuracy, and combines it with human visual perception to better reproduce the color information of printed materials. Using the method described in this article for printing color quality inspection can reduce data computation, quickly detect and mark color difference areas, and provide the degree of color deviation.

Modifying Cotton Fabric Properties by Controlling HPMC Viscosity Grade to Limit Ink Spreading and Penetration.

In cotton fabric inkjet printing, the spreading and penetration of the ink seriously damage printing resolution and color strength. In this study, hydroxypropyl methyl cellulose (HPMC) with varying viscosity grades (6, 30, 100, 400, and 4000 mPa·s) were used for fabric pretreatment to reduce the ink spreading and penetration. The results indicated that HPMC with a high viscosity grade enhanced the ability of pretreatment paste to form a continuous HPMC film on the fiber surface. A continuous film could greatly increase the hydrophobicity of the fabric, thereby restricting the spreading and penetration of ink. Meanwhile, ink migration was also limited by the paste connected to the fibers and the swelling of the film, which was more significant at higher HPMC viscosity grades. However, the increase of the HPMC viscosity grade was not conducive to dye fixation. Additionally, HPMC with a viscosity grade of 100 mPa·s was considered a reasonable choice, which could improve printing resolution and color strength in industrial applications. This research provides a new approach for optimizing pretreatment paste to achieve high-quality printed products.

Localized Surface Plasmon Resonances of AgAl Alloy Nanoparticles Self-Organized by Annealing of Ag/Al Bilayer Films

Plasmonic applications have traditionally relied on noble metals such as gold (Au) and silver (Ag) for their excellent plasmonic performance in the visible and near-infrared spectrum. However, these metals are costly, scarce, and have limitations such as low stability (Ag) and interband transition losses, which restrict their spectral range. To address these issues, alternative plasmonic materials have been explored. One such material is aluminum (Al), which is inexpensive, abundant, and exhibits remarkable plasmonic properties in the UV region as well as wide tunability. Al is also compatible with complementary metal–oxide semiconductor (CMOS) fabrication processes and is very stable due to its ultrathin native oxide layer. Alloying different metals can combine their advantageous properties, resulting in enhanced tunable optical characteristics. This study investigates the LSPR properties of AgAl alloy nanoparticles grown after the annealing of precursor AgAl bilayer films. Interestingly, LSPRs were also observed in some cases for the as-deposited bilayers. The experimental results were complemented with simulations conducted via the rigorous coupled-wave analysis (RCWA) method. The investigated materials could be potentially useful for applications in energy harvesting or color printing.

The influence of raw material changes on gamut colour volume of a matt ceramic glaze

This study aims to investigate the relationship between digital printing colour performance and the raw materials used in a matt glaze. Inkjet technology has enhanced the decorative properties of ceramic tiles in production. Improving the colour perception of the glaze is possible by optimizing the raw materials in the glaze, which results in less ink usage and thus lower costs. Investigation of the colour performance of glazes is possible by determining the L* a* b* values of the colours as well as the gamut colour volumes. Colour of the samples were evaluated by spectrophotometer and i1 profiler. Gamut volume was calculated by 3D CIE chromaticity diagrams of ICC profiles. It was observed that the colour saturation was higher in the samples where the pigment was homogeneously distributed in the glaze microstructure. SiO2 particles not embedded in the glass structure observed in the glaze microstructure disrupt the colour intensity. The low sphere temperature value of the composition made with wollastonite enabled the SiO2 particles to be embedded in the glaze. When wollastonite was used instead of dolomite as the source of calcium oxide in mat glaze, the colour gamut volume reached its highest value (11262), consequently increasing colour saturation. Conversely, the lowest colour gamut volume (6475) was obtained when dolomite was used instead of wollastonite.

Color Generation and Polarization-Sensitive Encryption by Laser Writing on Plasmonic Reflector Arrays.

Plasmonic color printing presents a sustainable solution for vibrant and durable color reproduction by leveraging the light-manipulating properties of nanostructures. However, the fabrication of plasmonic nanostructures has posed challenges, hindering widespread adoption. In this paper, we introduce plasmonic reflector arrays (PRAs) composed of three layers─Ag nanoparticles (NPs), an Al2O3 spacer, and an Ag reflector─deposited via physical vapor deposition (PVD). By employing nanosecond and femtosecond laser writing techniques, we manipulate the surface morphology of silver nanoparticles on PRAs, resulting in a diverse range of structural colors that are both polarization-insensitive and polarization-sensitive. Furthermore, we demonstrate the versatility of nanosecond laser writing in creating intricate patterns on PRAs. Additionally, we propose a novel two-step method combining nanosecond and femtosecond laser processing to embed QR code patterns into PRAs, showcasing their potential for secure data encryption and transmission. This research underscores the promising applications of PRAs in advanced color printing and secure optical data encoding.

Operando Colorations from Real-Time Growth of 3D-Printed Nanoarchitectures.

While artificial 3D nanostructures can generate precise and flexible coloration, their real-time color changes during 3D nanoprinting remain unexplored owingto the inherent challenges of in situ transient measurements and observations. In this study, a 3D-printing system which supports the operando observation/measurement of the color dynamics of subwavelength metallic nanoarchitectures fabricated in real time is developed and evaluated. During 3D printing, the dimensions and geometries of the 3D nanostructures grow over time, producing a large library of optical spectra associated with real-time color changes. Only a timer is needed to define the expected colors from a single 3D print run. Fin-like nanostructures are used to toggle colors based on the polarization effect and produce color gradients. Based on structural coloration, nanoarchitectures are designed and printed to animate desired color patterns. Moreover, the resulting color dynamics can also serve as an operando identifier for real-time structural information during 3D nanoprinting. A single print run enables the efficient creation of a comprehensive library of desired colorations owing to the flexibility in time-dependent controllability and 3D geometries at the subwavelength scale. 3D nanoprinted plasmonic structures exhibiting time-varying colorations (4D printing of colors) uniquely redefines the coloring stategy,offering considerable potential for numerousapplications.

Tunable and Non-Invasive Printing of Transmissive Interference Colors with 2D Material Inks.

Interference colors hold significant importance in optics and arts. Current methods for printing interference colors entail complex procedures and large-scale printing systems for the scarcity of inks that exhibit both sensitivity and tunability to external fields. The production of highly transparent inks capable of rendering transmissive colors has presented ongoing challenges. Here, a type of paramagnetic ink based on 2D materials that exhibit polychrome in one magnetic field is invented. By precisely manipulating the doping ratio of magnetic elements within titanate nanosheets, the magneto-optical sensitivity named Cotton-Mouton coefficient is engineerable from 728 to a record high value of 3272 m-1 T-2, with negligible influence on its intrinsic wide optical bandgap. Combined with the sensitive and controllable magneto-responsiveness of the ink, modulate and non-invasively print transmissive interference colors using small permanent magnets are precised. This work paves the way for preparing transmissive interference colors in an energy-saving and damage-free manner, which can expand its use in widespread areas.

Diatom Cribellum-Inspired Hierarchical Metamaterials: Unifying Perfect Absorption Toward Subwavelength Color Printing.

Diatom exoskeletons, known as frustules, exhibit a unique multilayer structure that has attracted considerable attention across interdisciplinary research fields as a source of biomorphic inspiration. These frustules possess a hierarchical porous structure, ranging from millimeter-scale foramen pores to nanometer-scale cribellum pores. In this study, this natural template for nanopattern design is leveraged to showcase metamaterials that integrates perfect absorption and subwavelength color printing. The cribellum-inspired hierarchical nanopatterns, organized in a hexagonal unit cell with a periodicity of 300nm, are realized through a single-step electron beam lithography process. By employing numerical models, it is uncovered that an additional induced collective dipole mode is the key mechanism responsible for achieving outstanding performance in absorption, reaching up to 99%. Analysis of the hierarchical organization reveals that variations in nanoparticle diameter and inter-unit-cell distance lead to shifts and broadening of the resonance peaks. It is also demonstrated that the hierarchical nanopatterns are capable of color reproduction with high uniformity and fidelity, serving as hexagonal pixels for high-resolution color printing. These cribellum-inspired metamaterials offer a novel approach to multifunctional metamaterial design, presenting aesthetic potential applications in the development of robotics and wearable electronic devices, such as smart skin or surface coatings integrated with energy harvesting functionalities.

Single‐Pulse‐Driven Frame Printing of Chromatic Pixels in Lithium Niobate Crystal

AbstractHighly efficient and programmable writing of multidimensional optical data is of great value for next‐generation high‐throughput information technologies but has been rarely achieved. Here, a one‐step frame printing of chromatic pixels in lithium niobate crystal by using a single ultrafast laser pulse is reported. In this strategy, a phase superposition‐based spatial light modulation strategy is applied to split a single ultrafast laser pulse into multiple son pulses with designated optical properties and spatial distribution patterns. It is demonstrated that these son pulses allow for massively creating micro‐amorphous phase transition zones with on‐demand structural features that can modulate the intrinsic birefringence of the crystal matrix and generate wavelength‐selective interference in the visible band to form pixel‐level chromatic patterns, namely, single‐pulse‐driven frame color printing. The created chromatic pixels can be encoded into computer‐recognizable data arrays to play a role in high‐efficiency multidimensional information recording. The presented approach enables fast and programmable information batch writing in 3D space and can serve as a versatile tool boosting next‐generation information optics.

Utilization of Acacia auriculiformis tannins as a biomordant material for fabrics in the natural dyeing process using the ecoprint technique

The ecoprint coloring techniques has the disadvantage that they fade easily. so a mordant is needed which functions as a color binder between the media and natural dyes so that they do not fade easily. Research was conducted to analyze the effect of acacia tannin compounds on color fastness. Tracing the chemical content in acacia bark powder was carried out by phytochemical screening methods. The stages of making ecoprint include mordanting. pattern and color printing and fixation. The results of phytochemical screening showed that acacia bark powder contains flavonoids. tannins. alkaloids. glycosides and triterpenoids. The yield of acacia tannins obtained from the extraction results was 22.47% with a tannin content of 19.61%. The ΔE value obtained in the color fading test against fabric washing produces a small (ΔE = 1-3). medium (ΔE = 3-6) and large (ΔE > 6) effects. Color coloring tests on fabric ironing produced little effect (ΔE=1-3). Based on the tests carried out. acacia tannins can be used as mordant materials.

Detection of Fake Currency Using Machine Learning

Counterfeiting of currency is a growing problem due to advancements in color printing technology, impacting economies worldwide. Fake money is often used for criminal activities, including terrorism. Research indicates that developing countries, like India, are particularly affected. One solution proposed involves analyzing the image of counterfeit currency through pre-processing steps such as converting from RGB to grayscale. This approach aims to tackle the issue of counterfeit currency circulation effectively. After converting the text, the image is divided into sections, its characteristics are assessed, relationships are identified, and a decision is made to determine if the image is authentic or counterfeit. Counterfeit currency continues to be a notable problem. Financial institutions and other establishments have the necessary resources to confirm the legitimacy of money. However, the average person does not have access to such equipment, making it essential to have counterfeit money detection software that can be used by anyone. This study achieves a maximum accuracy of 81% when analyzing 50 Indian currency notes with a denomination of 2000 rupees. This initiative offers a comprehensive overview of a counterfeit detection system that is accessible to the general public. The proposed system uses image processing to distinguish real currency from counterfeit money. The entire software has been developed using the Python programming language. Key Words: Fake Currency, Counterfeit, Denomination, Python, Machine Learning,

Empirical BRDF model for goniochromatic materials and soft proofing with reflective inks.

The commonly used analytic bidirectional reflectance distribution functions (BRDFs) do not model goniochromatism, that is, angle-dependent material color. The material color is usually defined by a diffuse reflectance spectrum or RGB vector and a specular part based on a spectral complex index of refraction. Extension of the commonly used BRDFs based on wave theory can help model goniochromatism, but this comes at the cost of significant added model complexity. We measured the goniochromatism of structual color pigments used for additive color printing and found that we can fit the observed spectral angular dependence of the bidirectional reflectance using a simple modification of the standard microfacet BRDF model. All we need to describe the goniochromatism is an empirically-based spectral parameter, which we use in our model together with a specular reflectance spectrum instead of the spectral complex index of refraction. We demonstrate the ability of our model to fit the measured reflectance of red, green, and blue commercial structural color pigments. Our BRDF model enables straightforward implementation of a shader for interactive preview of 3D objects with printed spatially and angularly varying texture.

Between Kochel and Kalmunz. Early plein airs by Gabriele Munter at the school "Phalanx" by Vasily Kandinsky.

The subject of the study of the proposed article is the early plein-air works of the German expressionist artist Gabriele Munter, later a member of the Blue Horseman art association, a student and friend of Vasily Kandinsky. The authors of the article aim to review and introduce into scientific circulation a number of Munter's sketches created by her during summer trips to the plein air in 1902-1903 to the Alpine towns of Kochel and Kalmunz with the Munich art school "Phalanx", headed by Kandinsky. The article also examines the picturesque plein-air works by Kandinsky, created by him in the same years there, in Bavaria - mainly landscapes and sketches of figures in the landscape. The authors of the study see as their task to trace the influence of Kandinsky's artistic manner and his role as a teacher on the formation of a Munter painter. The research methodology includes formal stylistic, comparative methods of art criticism analysis, as well as a comprehensive historical and biographical approach. The relevance of the study is due to its scientific novelty: the authors of the article for the first time in Russian-language art history literature describe the pre-expressionist works of Munter during the period of joint plein-airs with Kandinsky, trace the formation of her artistic vision and picturesque manner, the influence of Kandinsky on her formation. The development of the impressionistic technique common to Munter and Kandinsky in the early 1900s, according to the authors of the article, is combined with individual searches for expressiveness of form and color. The first experiments of plein-air oil painting in a special "spatula technique" under the guidance of Kandinsky were accompanied by the successful search for Munter in the field of graphics, mastering the technique of printing color woodcuts. The authors of the article come to the conclusion that the formation of the original manner of Munter was equally influenced by both pictorial emancipation through sketching practice in oil, as well as their own experiences in drawing and engraving.

Study of color degradation in package prints: Analyzing kinetics with principal component analysis

AbstractColor degradation is a pressing issue in various fields like food and medicine packaging, as well as printed materials, leading to a loss or distortion of vital information. Therefore, understanding how the color of package prints evolves over time is essential for product quality assessment and effective product life cycle management. This study focuses on investigating color changes in prints on blister foils, widely used in the medicine and packaging industries. To assess fading characteristics, samples printed via the gravure process have been exposed to a Xenon Test Chamber (B‐SUN). Spectrophotometric measurements of the prints have been conducted using a spectroradiometer, and the data have been analyzed using principal component analysis (PCA). The fading nature of cyan and black prints aligns with Type IV, while magenta and yellow prints correspond to Type II, as described by Giles. Notably, cyan and black inks demonstrated resistance toward fading at the end of the exposure, with a minor exception. The investigation involved curve fitting, revealing a consistent first‐order kinetic model governing fading rates throughout the exposure time. High R2 values (0.96–0.99) and low root means square error values (0.02–0.08) are observed across all cases. While color fading involves diverse kinetics, the fading rate consistently adheres to a singular first‐order kinetic path. The study highlights that yellow ink is most sensitive to light, followed by magenta ink. These findings offer valuable insights for optimizing packaging materials and ensuring product quality in industries reliant on printed materials. By mitigating color degradation, manufacturers can enhance the longevity and appeal of their products, reinforcing consumer trust and satisfaction. Furthermore, the effective utilization of PCA as a data analysis tool offers a valuable approach for future investigations in color science and related fields.