Suitable properties of ink to create inkjet-printed surface-directed microchannels that utilize the pinning effect of a triple line on a rough surface

If microfluidic devices can be directly produced using printing techniques, the combination of microfluidics and printing techniques for other applications, such as printed electronics, will make all-printed highly-functionalized microfluidic devices possible. Therefore, we have made efforts to develop a technique for producing microfluidic devices using an inkjet printer. The microchannels that could be created using this technique were a kind of surface-directed channels that utilize the pinning effect of a triple line on a rough surface. In this study, we focused on what were the required properties of the printer ink during the wetting and drying processes of the ink. As a result, one of the properties required during the wetting process was that the advancing contact angle of the ink should be smaller than a certain value, which depended on the average volume of the ink drops ejected from the printhead and the number of drops per unit area. The receding contact angle should be smaller than about one third of each advancing angle. In addition, during the drying process, a small amount of surfactant added to the ink played a critical role in order to leave a continuous stain of the ink. As an application of this inkjet-printed channel, we also created a device for mixing aqueous solutions.     

Printing of NiO-YSZ nanocomposites: From continuous synthesis to inkjet deposition

Water-based inks, containing nanometric NiO and YSZ particles in 66/34 vol. % ratio, are produced by colloidal stabilization of a binary dispersion obtained via continuous hydrothermal synthesis at supercritical conditions, i.e. 280 bar and 400 °C. The method yields single-crystal particles with diameter ≤ 10 nm for both phases in a single-step process, achieving a highly mixed composite. Two different approaches are applied to formulate inks printable with piezoelectric printheads, i.e. an electrostatic and an electrosteric stabilization path. The use of an electrosteric dispersant results in colloids with superior stability > 200 days, more uniform thin films and finely nanostructured porous cermet films with thickness below 500 nm, after reducing NiO to Ni. Particles coarsening to 50–150 nm is obtained at 1000 °C, accompanied by a shrinkage of ca. 43% in thickness without the formation of cracks or delamination of the zirconia substrates.     

Inkjet-printed Ag@SDC core-shell nanoparticles as a high-performance cathode for low-temperature solid oxide fuel cells

This work demonstrates the superior thermostability of silver-based nanoparticle cathodes under continuous solid oxide fuel cell operation by coating the samarium-doped ceria (SDC) thin shell over silver nanoparticles. The Ag-core/SDC-shell (Ag@SDC) nanoparticles prepared by solvothermal synthesis (Ag core diameter = 48 nm; average SDC shell thickness = 2–5 nm) is inkjet-printed on electrolyte substrates as a thin film cathode. The Ag@SDC film survives the 48-h thermal annealing and its most porosities remain visibly un-agglomerated. The results of fuel cell current stability test show that the cell using the Ag@SDC nanoparticle cathode have only 3% of current degradation after 25 h, which is remarkably lower than that of the cell using the bare Ag nanoparticle cathode (96.1%). In addition, the electrochemical performance of the bare silver cathode in oxygen reduction reaction has significantly improved because of the enhanced surface oxygen adsorption/dissociation process provided by the SDC thin shell.     

Positive direct-mask stereolithography with multiple-layer exposure: layered fabrication with stair step reduction

In this paper, we explain a new stereolithography involving the separate use of liquid photoinitiator and a base resin (photopolymer resin without photoinitiator). First, the base resin is supplied as a layer, and then a mask pattern is drawn onto the surface with photoinitiator by inkjet printing. When the surface is exposed to a UV lamp, only the pattern drawn with the photoinitiator is cured. In this process, the photoinitiator acts as a positive mask. Also, the idea of multiple-layer exposure, which may enable stair step reduction and fabrication time reduction, is introduced. The proposed idea and method are implemented in an experimental stereolithography system and some experiments are conducted using the system. As a result, the effectiveness and feasibility of the idea and method are confirmed.     

采用水基前驱溶液喷墨印刷制备光催化活性TiO2薄膜

摘译 近年来,作为一种高能量带隙半导体,二氧化钛(TiO2)由于在紫外光照射下具有良好的光催化活性,已引起科研人员的广泛关注.由于TiO2无色透明,具有广泛的应用前景,如薄的TiO2涂层可用于创建自清洁、防雾、超亲水表面.同时,也能用于太阳能电池等光电子行业. 化学溶液沉积法因具有相对简单的大面积生产工艺,且较低的制膜成本和高可用性,成为TiO2薄膜制备常用的方法之一.针对另一种TiO2制备方法,即溶胶凝胶法,大量研究文献主要关注乙醇的水解控制.然而,工业需求鼓励开发水基前驱设计.其难度在于钛醇盐与水的高反应性.在有机介质中,加入少量的水往往导致水解.因此,需要采用络合剂作为稳定剂,阻止纯水中的水解反应和避免由此产生的产物沉淀.     

Excimer laser processing of inkjet-printed and sputter-deposited transparent conducting SnO2:Sb for flexible electronics

The feasibility of low-temperature fabrication of transparent electrode elements from thin films of antimony-doped tin oxide (SnO₂:Sb, ATO) has been investigated via inkjet printing, rf magnetron sputtering and post-deposition excimer laser processing. Laser processing of thin films on both glass and plastic substrates was performed using a Lambda Physik 305i excimer laser, with fluences in the range 20-100 mJ cm^− 2 reducing sheet resistance from as-deposited values by up to 3 orders of magnitude. This is consistent with TEM analysis of the films that shows a densification of the upper 200 nm of laser-processed regions.     

Evaluation of jet performance in drop-on-demand (DOD) inkjet printing

Inkjet printing has been widely used in many applications and has been studied for many years. However, there are not many systematic researches on the mechanism of jet formation, nor is there any reliable platform that enables us to evaluate jet performance. In this study, an approach to practically evaluate the jet stability of the dropon-demand (DOD) inkjet printing has been proposed, based on which the transient behavior of the DOD drop formation has been studied experimentally for Newtonian liquids with a range of different viscosities (1.0–11 cp) but of a comparable surface tension. For more viscous liquids, the rate of the jet retraction after a pinch-off from the nozzle was found to increase as the thread motion became more sharp and conical as a result of the shape effect. The break-up time of the jet also increased because the rate of capillary wave propagation was lower for more viscous liquids. The jet stability graph, which can be drawn in terms of jet retraction and break-up time, was employed to characterize the jetting stability, and the degree of satellite drop generation was quantitatively evaluated by two critical jet speeds. The effect of an electric pulse imposed on a piezoelectric plate inside the printhead was also studied. The single-peak electric pulse was used in this experiment for simple analysis, and the jet speed variation was measured under different operating conditions. Both the optimal dwell time and the maximum stable jetting frequency were affected by viscosity and they were explained in terms of the propagation theory.     

Microstructure and electrical properties of high power laser thermal annealing on inkjet-printed Ag films

In this work, a high power continuous-wave (CW) Nd:YAG laser was used for thermal treatment of inkjet-printed Ag films - resulting in the elimination of organic additives (dispersant, binder, and organic solvent) in the Ag ink and annealing of Ag nano-particles. By optimizing laser parameters such as laser power and defocusing value, the laser energy can be totally converted into heat energy, which is used for thermal treatment of inkjet-printed Ag films. This results in the microstructure and the resistivity of the films to be controlled. We investigated the thermal diffusion mechanisms during laser annealing and the resulting microstructures. The impact of high power laser annealing on microstructures and electrical characteristics of inkjet-printed Ag films was compared to those of the films annealed by a conventional furnace annealing. Focused ion beam (FIB) channeling images show that the laser annealed Ag films have large columnar grains and a dense void-free structure, while furnace annealed films have much smaller grains and exhibit void formation. As a result, the laser annealed films have better electrical properties (low resistivity) compared to furnace annealed samples.     

The inkjet printing process for Lyocell and cotton fibres. Part 1: The significance of pre-treatment chemicals and their relationship with colour strength, absorbed dye fixation and ink penetration

A statistical study of the outcome of inkjet printing, using a reactive dye based ink, on three cellulosic fabrics, namley Lyocell (standard Tencel and Tencel A100) and cotton, pre-treated with urea, migration inhibitor, penetration agent and alkali is reported. Colour strength (as Integ value), absorbed dye fixation and ink penetration were analysed as main responses. A full factorial design method was applied to study the effect of the level of each ingredient in the pre-treatment formulation on the responses, together with the steaming time used for dye fixation. The interactions between variables were also evaluated. The statistically significant variables were determined for each response and contour plots constructed for the most significant interactions to assess where the optimum responses might be achieved.