Results 1 - 10 of 445
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[en] Four-dimensional (4D) bioprinting of cell-laden constructs with programmable shape-morphing structures has gained increasing attention in the field of biofabrication and tissue engineering. Currently, most of the widely used materials for 4D printing, including N-isopropylacrylamide-based polymers, are not commonly used in bioinks for cell-laden bioprinting. Herein, we propose a facile approach to create cell-laden constructs with near-infrared (NIR)-triggered shape morphing using bioinks based on alginate (the most widely used bioink for cell-laden bioprinting). Three-dimensional (3D) printed bilayered scaffolds with orthogonal structures using concentrated alginate/polydopamine (PDA) inks (14–18 wt%) showed a change in folded shape during NIR-induced dehydration. The deformation angle of the scaffold could be controlled by laser power, irradiation time and the designed patterns of the printed alginate/PDA struts in scaffolds. Then, 3D printed biphasic scaffolds consisting of alginate/PDA and cell-laden hydrogels exhibited programmable shape change under NIR stimulation. Scaffolds were able to maintain their deformed structures, and the printed cells in hydrogels retained high viability during culture in medium for at least 14 days. The biocompatible and commonly used hydrogel bioinks, NIR-triggered shape-morphing structures and maintenance of the deformed shape in the medium give this facile approach great potential for application in the field of 4D bioprinting and 4D biofabrication of artificial tissues and organs. (paper)
[en] The automatic reproduction of images with edible materials is a new method used lately to decorate cakes. An important component of this technology is the ink. The paper presents the results obtained by using different physical methods for analysis of some jet printing inks types. The analysed inks were the Canon inks and edible inks from Thailand. The main considered methods were the spectrocolourymetrical, rheological, electrochemical. Choosing as a chromatic standard the Canon inks and for the physicochemical properties the edible inks from Thailand, it was prepared a yellow edible printing ink which was characterized by same methods
[en] Silicone elastomers have broad versatility within a variety of potential advanced materials applications, such as soft robotics, biomedical devices, and metamaterials. Furthermore, a series of custom 3D printable silicone inks with tunable stiffness is developed, formulated, and characterized. The silicone inks exhibit excellent rheological behavior for 3D printing, as observed from the printing of porous structures with controlled architectures. Here, the capability to tune the stiffness of printable silicone materials via careful control over the chemistry, network formation, and crosslink density of the ink formulations in order to overcome the challenging interplay between ink development, post-processing, material properties, and performance is demonstrated.
[en] The printing quality delivered by a drop-on-demand inkjet printhead is severely affected by the residual oscillations in an ink channel and the cross-talk between neighboring ink channels. For a single ink channel, our earlier contribution shows that the actuation pulse can be designed, using a physical model, to effectively damp the residual oscillations. It is not always possible to obtain a good physical model for a single ink channel. A physical model for a multi-input multi-output (MIMO) inkjet printhead is made even more sophisticated by the presence of the cross-talk effect. This paper proposes a system identification-based approach to build a MIMO model for an inkjet printhead. Additionally, the identified MIMO model is used to design new actuation pulses to effectively minimize the residual oscillations and the cross-talk. Using simulation and experimental results, we demonstrate the efficacy of the proposed method. (paper)
[en] This paper asserts that shear force plays an important role in the printing mechanism of gravure offset line printing. To that end, a theoretical printing model showing shear force dependence on the printing angle is proposed. The decrement of the internal angle between the printing direction and the pattern-line direction increases shear force, thereby enhancing the amount of transferred ink in the off stage. A printing experiment using pattern-line widths of 80 µm and 20 µm shows the angle dependence of the line width, thickness and amount of transferred ink, reflecting the effect of shear force. The effect of the internal angle on cross-sectional differences in lines with a width of 20 µm and with angle variation is greater than that in lines with a width of 80 µm, which corresponds with the theoretical prediction that shear force has greater influence on a narrower line. The strong correlation between the experimental data and the theoretical model supports the validation of the theoretical model
[en] The novel fluorescent dyes based on diketopyrrolopyrrole materials were developed as a basic component for use in inkjet ink formulations. N-substituted DPP derivatives of ethyl formate and ethyl acetate (symmetric and asymmetric) were synthesized and characterized. Then, quantum chemical calculations were performed to investigate the observed changes in the photophysical properties of synthesized materials. Photophysical investigations of fluorescence dyes in various solvents and the effect of solvatochromism and the solubility of dyes in inkjet inks and solid state emission of dyes were used to select symmetric and asymmetric derivatives for application in inkjet formulation. In addition, the inkjet ink based on the symmetric N-substituted DPP derivatives of N,N-diethylformate and ethyl acetate was formulated. Inkjet inks were printed on polymeric substrate and their fluorescence were studied. The solubility of the asymmetric N-ethyl acetate dye in ink formulation was lower than symmetric derivatives due to stronger inter-particle interactions. From photophysical features of printed substrate, the final formulation based on symmetric ethyl acetate dye was performed for further investigation. The effect of concentration on the intensity of emission and also on the color properties (Lab) of formulation was studied. The optimum dye concentration of symmetric N,N-diethylacetate dye with highest fluorescent intensity was 0.3wt% in ink formulation. Finally, the symmetric ethyl acetate dyes formulation for security inkjet ink was performed.
[en] Printed electronics is a rapidly developing field where many components can already be manufactured on flexible substrates by printing or by other high speed manufacturing methods. However, the functionality of even the most inexpensive microcontroller or other integrated circuit is, at the present time and for the foreseeable future, out of reach by means of fully printed components. Therefore, it is of interest to investigate hybrid printed electronics, where regular electrical components are mounted on flexible substrates to achieve high functionality at a low cost. Moreover, the use of paper as a substrate for printed electronics is of growing interest because it is an environmentally friendly and renewable material and is, additionally, the main material used for many packages in which electronics functionalities could be integrated. One of the challenges for such hybrid printed electronics is the mounting of the components and the interconnection between layers on flexible substrates with printed conductive tracks that should provide as low a resistance as possible while still being able to be used in a high speed manufacturing process. In this article, several conductive adhesives are evaluated as well as soldering for mounting surface mounted components on a paper circuit board with ink-jet printed tracks and, in addition, a double sided Arduino compatible circuit board is manufactured and programmed. (paper)
[en] The fabrication process and the operation characteristics of a fully roll-to-roll printed resistive write-once-read-many memory on a flexible substrate are presented. The low-voltage (<10 V) write operation of the memories from a high resistivity ‘0’ state to a low resistivity ‘1’ state is based on the rapid electrical sintering of bits containing silver nanoparticles. The bit ink is formulated by mixing two commercially available silver nanoparticle inks in order to tune the initial square resistance of the bits and to create a self-organized network of percolating paths. The electrical performance of the memories, including read and write characteristics, is described and the long-term stability of the less stable ‘0’ state is studied in different environmental conditions. The memories can find use in low-cost mass printing applications. (paper)