Preparation of PDOT:PSS Transparent Conductive Film Using Ink-Jet Printing

Flexible devices produced using organic materials have attracted the attention of many researchers. Important components of these flexible devices include transparent electrodes, which transmit visible light and possess conductivity. The present study improved the characteristics of a transparent conductive film that was made of poly(3, 4 ethylenedioxythiophene):poly(styrenesul-fonate) (PEDOT:PSS), an organic conductive material, and that had been prepared using ink-jet printing. To improve the resistance value and visible light transmittance of the film, the film substrate was first cleaned with ultraviolet/ozone treatment, and then the film was annealed after it was deposited on the substrate and dipped into a polar solvent. Consequently, the resistance value of the thin film decreased. However, the surface state of the film changed according to the treatment method and affected its visible light transmittance. Thus, the surface state of the film substrate, the annealing temperature after film deposition, and the dipping treatment with a polar solvent influenced the characteristics of a thin film.

Characteristics Improvement of PEDOT:PSS Transparent Conductive Film Prepared by Ink-Jet Printing

Recently, a high-performance and low-priced transparent conductive film has been expected to be developed because flexible devices produced using organic materials have been actively studied. An indium tin oxide (ITO) thin film, which has been generally used as a material for a transparent conductive film, has problems, such as fragility to bending stress and depletion of the resource. The present study used poly(3, 4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS), an organic electroconductive material, and examined the improvement in the resistance value and visible light transmittance of a transparent conductive film produced using the ink-jet method. In previous studies, we reported that, to improve the resistance value and visible light transmittance of a thin film, it was effective to clean the film substrate with ultraviolet/ozone (UV/O3) treatment, anneal the film after it was deposited on the substance, and dip the annealed film into a polar solvent. Focusing on the thin film processing between printing operations, the present study improved resistance value and visible light transmittance by examining both the application methods of a polar solvent and the annealing time between printing operations. As a result, the resistance value and visible light transmittance of a PEDOT:PSS thin film were 390.4 Ω and 86.6%, respectively. This film was obtained by applying a polar solvent and performing annealing for 30 min between printing operations. The printing was performed three times.

Application of nonlinear color matching model to four-color ink-jet printing

Through discussing the color matching technology and its application in printing industry the conventional approaches commonly used in color matching, and the difficulties in color matching, a nonlinear color matching model based on two step learning is established by finding a linear model by learning pure color data first and then a nonlinear modification model by learning mixed color data. Nonlinear multiple regression is used to fit the parameters of the modification model. Nonlinear modification function is discovered by BACON system by learning mixture data. Experiment results indicate that nonlinear color conversion by two step learning can further improve the accuracy when it is used for straightforward conversion from RGB to CMYK. An improved separation model based on GCR concept is proposed to solve the problem of gray balance and it can be used for three to four color conversion as well. The method proposed has better learning ability and faster printing speed than other historical approaches when it is applied to four color ink jet printing.

The Effect of Silica Particle Size on the Performance of Color Ink-jet Printing Paper

In this paper,the effects of four sorts of silica with the particle size range of 4～10μm on coated paper properties and printing performance were studied.The results showed that the smaller particle size silica can provide the coated paper with higher density and contrast, better definition and good printing performance.

Formation of Photosensitizing Crystalline C₆₀Particles by Ink-Jet Method

The crystalline fullerene C60 particles were formed and immobilized on poly(dimethylsiloxane) (PDMS) substrates under the various discharge conditions by an ink-jet method, and investigated for the reactive oxygen species (ROS) generation property under visible light irradiation. The particles were synthesized by discharging a toluene solution dissolved C60 and poly(methyl methacrylate) (PMMA) with the ink-jet spotting system. The ROS generation was evaluated by comparisons of the fluorescence intensities measured for the formed particles under green laser irradiation and in a dark room using fluorescent dyes, 2’,7’-dichlorofluorescein diacetate and dihydroethidium. The results of transmission electron microscope (TEM) observation showed that the formed particles consisted of crystalline C60. The optimal ink-jet discharge conditions for synthesizing the particles to generate more ROS were found. In the case of the optimal conditions, the structure in which the needle-like particles were three-dimensionally formed was confirmed. The surface area of the crystalline C60 particles was calculated using the SEM observation results, and it was suggested that when the needle-like finer particles were three-dimensionally formed under the optimal conditions, increasing the surface area lead to an increase in the ROS generation amount.

Combinatorial Optimization of Ba/Fe-cordierite Solid Solution （Ba0.05Fe0.1Mg）2Al4Si5O18 for High Infrared Radiance Materials

A combinatorial chemistry method was employed to screen the Ba2＋ and Fe3＋ incorporated into cordierite structure （Ba0.05Fe0.1Mg）2A14Si5018 for exploring of high infrared radiance materials. A series of square-type sample array that consists of 7×7 compositions was syn- thesized by ink-jetting nitrate solutions into micro-reactor wells in a ceramic plate and then heat-treated at high temperatures. X-ray diffraction and infrared thermograph were used to analyze the effects of Ba2＋/Fe3＋ incorporating on the lattice distortion of cordierite and resultant changes in infrared radiance properties. Based on the results of X-ray phase analy- sis and radiance measurement of the scale-up prepared samples, the optimal Ba2＋ and Fe3＋ co-adding amount was determined to be 5%Ba2＋ plus 10%Fe3＋. Moreover, the infrared emissivity of the optimal composition at 100 ℃ was found to be higher than 0.8 in a wide wavelength range of 5-24μm. The research work demonstrates a promising application of Ba2＋/Fe3＋ cordierite solid solution as a kind of infrared heating materials for energy saving.

Electronic Absorption Spectra of Copper(Ⅱ) Sulphophthalocyanine and Aggregation of the Dye in Aqueous Solution

Aggregation behavior of C.I.Direct Blue 86 was discussed using analyses of its UV-Vis spectra.The experiment results show that the dye molecules are inclined to aggregate in aqueous solution.Even in a very dilute solution of 0.050μmol/L,A618/A659 =1.2398,showing that the dye monomers still coexist with its dimers.The strong aggregation trend may cause dye precipitates at a higher concentration,which is an important factor that should be considered in producing a formula of ink-jet inks containing the dye as a colorant.

Plasma Nitriding-Assisted Printing of Stainless Steel Punches for Micro-piercing Process

MEMS （micro-electric-mechanical-system） required for miniature, thin mechanical parts as a structural member; e.g., the miniature pumping system consisted of ten to twelve thin metallic plates before joining. At present, those thin shaped sheets were fabricated by the chemical etching. Their geometric inaccuracy as well as long leading time often became an engineering issue. Micro-piercing process was expected to make mass production of thin sheet products with complex and accurate geometry for much shorter leading time once the die for this micro-piercing was built in. In the present paper, a new plasma nitriding-assisted printing was proposed as an automatic production line to fabricate the micro-piercing punch. After preparation of CAD-data of the punch head, its two dimensional geometry was ink-jet printed directly on the AISI420 stainless steel die-substrate. The unprinted surface area was only plasma nitrided at 693 K for 14.4 ks to transform this two dimensional micro-pattern to the three dimensional hardness distribution in the AISI420 substrate. Through the mechanical removal of ink-jet printed area, the flat punch head with sharp edge comers was fabricated in much shorter duration time than the end-milling. SEM-EDX, surface profiling measurement as well as micro-hardness testing were employed to describe each step in the above plasma printing. The thin MEMS stainless steel part with a micro-pendulum as well as three S-letter shaped springs was taken for an example to describe this automatic production procedure of plasma printing from the CAD data mining to the micro-piercing punch finishing.

Full-color quantum dots active matrix display fabricated by ink-jet printing

Making full-color active matrix display based on quantum dot light emitting diodes(AM-QLEDs) via ink-jet printing is attractive in display industry due to QLEDs' wide color gamut and their potential manufacturing advantages of large screen size and low cost. The challenges for realizing AM-QLED display are how to achieve high quality films through ink-jet printing, multi-color patterning, electroluminescence(EL) color purity, and high efficiency. Herein, a 2-inch diagonal full-color AM-QLEDs display with pixel density of 120 pixels per inch(PPI) fabricated by ink-jet printing technique is presented. Driven by a metal oxide TFT(MOTFT) back-panel, the display exhibits a maximum brightness of 400 cd m.2, and a color gamut of 109%(NTSC 1931). The red, green, and blue(RGB) monochrome QLEDs passive matrix panels fabricated by ink-jet printing technique have a current efficiency(CE) of 2.5, 13.9, and 0.30 cd A.1, respectively. To the best of our knowledge, the efficiencies are the highest among passive matrix QLEDs panels made by ink-jet printing technique. The ink-jet printed QDs films show good thickness uniformity due to high viscosity and low volatility of the printable inks, and no cross-contamination between adjacent pixels resulting from the hydrophobic pixel defining layer.

Ionic liquid passivated black phosphorus for stabilized compliant electronics

Black phosphorus(BP)is an attractive material for two-dimensional(2D)electronics and optoelectronics given its direct optical band gap in the bulk.However,the vulnerability of BP to oxygen and moisture under ambient conditions has been a significant impediment for the adoption of this material towards practical applications.This vulnerability has also curtailed the development of additively manufactured,solution processed,ink-jet printed BP devices,which are cost-effective alternatives to lithographically patterned rigid electronics and optoelectronics based on silicon.In this work,we have fabricated stable BP electronic devices on flexible and compliant substrates using low-cost,additive manufacturing techniques with ink-jet printing through scalable chemical exfoliation routes.To address the stability issues with BP,ionic liquids(ILs)were used as a passivation layer on the surface of the BP to minimize oxidative degradation.The enhanced stability of BP was inferred through Raman spectroscopy and scanning probe microscopy techniques,where no observable changes in the A^(1)_(g)and A^(2)_(g)Raman vibrational modes were observed with time for the BP films passivated with ILs over a period of 168 h under ambient conditions.On the other hand,a blue-shift in these Raman modes was evident for unpassivated samples.Atomic probe microscopy measurements clearly revealed the difference in the surface characteristics through localized regions of degradation that intensified with time,which was clearly absent in IL/BP samples.The stability measurements were also conducted in electronic device platforms for IL coated BP devices,where the temperature T dependence of the I_(ds)-V_(ds)characteristic was measured from T~5.4 to 335 K.Prototypical demonstrations of stabilized ILs/BP devices at ambient printed on flexible polyimide substrates were also made.The irradiation with broadband radiation appears to have a significant influence on the electrical behavior of BP,evident through the variation of photocurrent with temperature.Overall,our study shows that by engineering the exfoliation chemistry of BP with the use of ILs,highly concentrated BP inks can be additively manufactured,that present remarkable opportunities for the large-area integration of BP in printed and flexible electronics using low-cost,scalable approaches benefiting from the direct bandgap characteristics of BP in the bulk.

Preparation of P(St-NMA)microsphere inks and their application in photonic crystal patterns with brilliant structural colors

Patterned photonic crystals with structural colors on textile substrates have attracted a special attention due to the great advantages in application,which currently become a research hot-spot.This study utilized an ink-jet printing technology to prepare high-quality photonic crystal patterns with structural colors on polyester substrates.The self-assembly temperature of poly(styrene-N-methylol acrylamide)(P(St-NMA))microspheres set to construct photonic crystals were deeply optimized.Moreover,the structural colors of prepared photonic crystal patterns were characterized and evaluated.When the mass fraction of P(St-NMA)microspheres was 1.0 wt.%,the pH value ranged from 5 to 7,and the surface tension was in the range of 63.79 to 71.20 mN/m,inks could present the best print performance.At 60°C,prepared P(St-NMA)microsphere inks were good for printing to obtain patterned photonic crystals with regular arrangement and beautiful structural colors.Specifically,photonic crystals with different colors could be constructed by regulating the diameter of microspheres in inks,and prepared structural colors exhibited distinct iridescent phenomenon.The present results could provide a theoretical basis for the industrial realization of patterned photonic crystals by ink-jet printing technology.

Solid Freeforming and Combinatorial Research

A view of manufacturing processes is presented in which five distinct categories are defined as casting, deformation, machining, joining, and solid freeforming. Solid freeforming is essentially biomimetic and shares problems of morphogenesis with natural processes. Our team in University of London has been exploring three mechanisms of solid freeforming. In dry powder deposition and direct ink-jet printing, the emphasis has turned to the problem of delivering a complex shape in which the three dimensional spatial arrangement of composition is delivered from the design file. In extrusion freeforming, the aim is to control microstructure at hierarchical levels also from the design file. The quest for 3-D functional gradients is satisfied by acoustic and ultrasonic dispensing and mixing of powders so that each layer can be patterned. These methods could be extended to deliver the complex patterns demanded by left-handed microwave metamaterials. Dry powder deposition and direct ink-jet printing are turning towards combinatorial methods in which multiple sample libraries are used to accelerate discovery. In turn, this paves the way for ‘autonomous research machines’ which steer their own search refinements in response to our requests for new materials. In this way, solid freeforming used for sample preparation can give an ‘arm’ to an intelligent machine so that it can conduct its own experimentation and learning; an idea that originated with Alan Turing in the late 1940s.