Ink jet technology has advantages such as high-resolution and a multicolor printing capability and has a good potential for computer-based three-dimensional (3D) fabrication. The authors have developed an ink jet 3D bioprinter to manufacture biologically viable 3D structures using living cells. They have developed an effective method for the fabrication of 3D hydrogel structures by using ink jet technology with a liquid aqueous gelating medium, which is essential in fabricating 3D structures with living cells. In the present study, they evaluated the feasibility of the ink jet approach for digital 3D biofabrication, analyzing the microgel beads produced by the ink jet droplets. The ink jet droplets of sodium alginate solution, which were ejected into CaCl₂ solution, gelled to form microgel beads. The resulting beads were analyzed by means of image-based particle analysis to show that homogeneously sized microgel beads were effectively produced. Ink jet 3D biofabrication has a high potential for effective digital fabrication with such homogeneous microgel beads and will provide promising approaches for sophisticated computer assisted tissue engineering.

Spot colors are widely used in commercial, product, or packaging printing to obtain a colorful appearance. With the combination of the right software, inks, and media, an ink jet printer can be treated as a digital proofer for spot color printing, providing significant time and cost savings compared to conventional procedures for jobs approval for printing technologies with master image carrier, such as rotogravure, flexography, or offset lithography. An Epson StylusPro 4000 digital printer combined with commercially available raster imaging processors (RIPs) and its own printer drivers were tested and compared. Custom ICC profiles were generated for each print combination, using the gravure production substrate and a manufacturer recommended proofing paper (Epson premium semimatte photopaper). Certain popular Pantone colors and a set of custom spot colors used in gravure decorative laminates industry was investigated and the quality of spot color reproduction was evaluated in terms of the color difference (ΔE^*_ab) in L*a*b color space. The results show that all tested print combinations have higher ΔE^*_ab values in highly saturated spot colors, regardless of which printer control software is used. Digital printers employing extended color sets, such as Pantone Hexachrome might be required to reproduce these highly saturated colors. The results also suggested that usage of third party RIP software results in better spot color reproduction. Users can proof spot colors printing via RIPs, if good color matching is considered crucial.

To obtain high quality color images on plain papers using ink jet printing, the authors studied a new marking technology, named "double-component liquid system (DCLS)." The DCLS technology, which uses an ink set comprising pigment inks and treatment liquid, is a design concept that achieves high speed and high image quality by utilizing pigment agglomeration and vehicle penetration. The authors found that optical density and drying time can be described by the increase in viscosity of the ink-treatment liquid combination on admixture, which simulates sequential application of these components to the substrate. They compared various agglomerating agents (organic amine, multivalent metal salt, and organic acid) in treatment liquid by this measuring method and found that both high speed and high image quality could be achieved at the same time regardless of the types of agglomerating agents. Organic acids were found to demonstrate relatively high performance. The functional mechanism of organic acids can generally be explained by pH, and it was possible to control DCLS behavior by acid dissociation constant (pKa), neutralization of organic acid, and molar concentration in treatment liquid. DCLS ink set showed high-speed drying performance of 0.6 s or less (equivalent of 100 ppm or higher) and high image quality (optical density of 1.3 or more) at the same time on a variety of plain papers without using a heater.

In digital halftone technology, dot reproducibility is an important factor because our perception and recognition of an image depend on the characteristics of the printed dot. Halftone dot size variations reproduced by typical printing technologies, such as electrophotography, offset, and flexography, were investigated to determine their dot reproducibility. The investigation found that offset, flexography, and electrophotography can produce halftone dot sizes with a percentage coefficient of variation (%CV) at 8.88, 19.64, and 13.93 consecutively in the highlight image areas (small dot size), while the %CV of halftone dot size variations tend to decrease when the dot size increases in the midtone and shadow image areas. The perception of simulated halftone dot size variations was then studied experimentally under set observation distance and halftone frequency conditions in order to analyze the relation between human perception and halftone dot size variations. It was determined that human perception detects nonuniform halftone image dot patterns when the %CV of the halftone dot size variation is greater than 6.72.

Text and line attributes are an integral part of print quality. In this article the authors study artifacts introduced by the electrophotographic process that make text and thin lines with high colorant content appear blurred. The authors characterize the amount of blurriness of a specific print engine by measuring edge transition widths and correlate their results with previous psychophysical studies regarding perception of blur to determine the acceptable limits of the printer's performance. They propose a memory efficient algorithm that requires minimal modifications to the printer engine architecture to attain those limits. They demonstrate that the proposed solution outperforms the currently implemented solution in terms of color and texture preservation.

The objective of this article is to investigate the effect of counter magnet configuration of an interactive touchdown developing system on the behavior of the brushes using the discrete element method. The shape of the magnetic brush, its shearing force acting on a development roll, or the electric potential distribution were analyzed. The magnetic brushes in the nip were crowded when the counter magnet was installed in the development roll. Their velocities also fluctuated; the brushes were pulled into the nip and returned to only a slight degree. The shearing force increases in the presence of the counter magnet because the stiffness of the magnetic brush became high, owing to the strong magnetic field. In the experimental work the toner mass adhered onto the development roll under the uninstalled condition was much larger than that with the counter magnet installed because of the reduced shearing force. The electric potential distributions around the nip also fluctuated in the presence of multiple magnetic brushes. The adhered toner mass was found to be affected by not only the shearing force but also this fluctuation of the electric field.

The authors present a new approach for modeling toner transfer in xerographic printing. Our formalism combines a new three-dimensional (3D) stochastic fiber network model of paper, a 3D model of electrostatic, and contact adhesion forces acting on toner particles in xerographic printing. Our modeling platform allows the authors to study the relative importance of paper surface and mass density variations in establishing the electrostatic and contact adhesion forces crucial in controlling toner transfer efficiency during xerography. Simulations of xerographic printing are used to show that state of compression of the paper surface in the print nip is critical in controlling the distribution of toner onto paper. This is quantified by showing how the paper surface controls the distribution of both the electrostatic and contact adhesion forces that draw toner to paper. In contrast, paper formation, a traditional index of paper quality in the paper industry, is found to play a negligible role as a predictive measure of print uniformity in xerographic printing. Our simulation results are validated against new xerographic printing experiments of black toner onto laboratory handsheets.

The purpose of this study is to determine whether there is any correlation between subjective and objective artwork reproduction assessment when using different printing technologies. The investigations are based on reproductions of works of art, which belong to the traditional tonal system of visual representation, characterized by the brightness range of the dominant hue from a certain part of the spectrum. This system appeared in the period of the late Renaissance. Today it is often used for expressing volume in graphic media. As a method for assessing the quality of the reproductions, instrumental measurement and visual evaluation were used. The visual study included formal/methodological characteristics of the artwork. Based on the results, a correlation between objective and subjective approaches has been shown. The results demonstrate that the best quality of color lightness is produced with conventional offset printing and an amplitude modulation screen. These results can be applied in the reproduction of images employing this tonal system of visual representation.