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Polyelectrolytes are water-soluble polymers having repeat units carrying electrolyte groups. As polyionic molecules having like charge units, they are self-repelling with a rod-like conformation in solution. Inkjet applications of polyelectrolytes include particle dispersing, surface modification, and multilayer structures. This work investigates the physical properties of low molecular weight sodium polyacrylate (NaPA) and poly-diallyl dimethyl ammonium chloride (polyDADMAC) polyelectrolyte solutions in the water–ethanol mixture in relation to their behavior in inkjet deposition. In rotational rheometry measurements, the solutions are found to behave in a Newtonian fashion once the effects of experimental artifacts are taken into account. The range of NaPA concentrations that could be studied was limited to 1 wt./wt. % by the poor solubility of NaPA in the presence of ethanol, and at these concentrations, the addition of NaPA to the solvent did not have a significant effect on the jetting behavior. PolyDADMAC had good solubility, and concentrations up to 10 wt./wt. % were studied and jetted successfully. While an increase in polyelectrolyte concentration resulted in a slow increase in ink viscosity, this was not found to have a significant effect on the required jetting voltage or maximum stable jetting frequency, though drop detachment and satellite droplet formation times were found to increase. As a practical limitation of polyDADMAC inks, solvent evaporation was found to lead to idle nozzles becoming non-jetting, with the allowed idle time decreasing rapidly as ink polyDADMAC concentration increased. This non-jetting behavior is likely due to residence time at the nozzle exit leading to the local surface tension and/or viscosity increase, differing from the bulk ink properties. [ABSTRACT FROM AUTHOR]

Conductivity of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) strongly depends on the film morphology, which can be altered by the presence of polyelectrolytes. Aqueous dispersion of PEDOT:PSS was studied with anionic sodium polyacrylate (PA) and cationic poly(dimethyldiallylammonium chloride) (pDADMAC) polyelectrolytes that are typically used in papermaking as retention aids and dispersing agents in the paper pigment coating formulations. Spin-coated PEDOT:PSS films on a PA coated glass formed non-uniform layers with lowered conductivity compared to the reference PEDOT:PSS films on a clean glass substrate. On contrary, spin-coated PEDOT:PSS on a pDADMAC coated glass formed uniform layers with good conductivity. These results point out the importance of surface chemistry when using renewable and recyclable paper-based substrates with the PEDOT:PSS films. [ABSTRACT FROM AUTHOR]

A multilayer coated paper substrate, combining barrier and printability properties was manufactured utilizing a pilot-scale slide curtain coating technique. The coating structure consists of a thin mineral pigment layer coated on top of a barrier layer. The surface properties, i.e. smoothness and surface porosity, were adjusted by the choice of calendering parameters. The influence of surface properties on the fine line printability and conductivity of inkjet-printed silver lines was studied. Surface roughness played a significant role when printing narrow lines, increasing the risk of defects and discontinuities, whereas for wider lines the influence of surface roughness was less critical. A smooth, calendered surface resulted in finer line definition, i.e. less edge raggedness. Dimensional stability and its influence on substrate surface properties as well as on the functionality of conductive tracks and transistors were studied by exposure to high/low humidity cycles. The barrier layer of the multilayer coated paper reduced the dimensional changes and surface roughness increase caused by humidity and helped maintain the conductivity of the printed tracks. Functionality of a printed transistor during a short, one hour humidity cycle was maintained, but a longer exposure to humidity destroyed the non-encapsulated transistor. [ABSTRACT FROM AUTHOR]

Abstract: Printability of functional inks on multilayer curtain coated substrates was investigated. The inks represent those commonly used to produce solution processable electronic devices, such as organic transistors. The substrate, which combines sufficient barrier and printability properties for printed functional devices, was manufactured utilizing high speed curtain coating technique. The coating structure consists of a mineral pigment layer coated on top of a barrier layer. The combination of the two layers allows for controlling the absorption of ink solvents. By adjusting the thickness, porosity and surface energy of the top-coating the printability can be tuned for various functional inks. Focus was set on printing conducting silver and carbon inks, both with nano- and micrometer sized particles, as well as printing of an organic semiconductor, poly(3-hexylthiophene). The pore volume in the top-coating determined the spreading of the micrometer sized silver ink as well as the amount semiconductor per area required, whereas the pore size was the determining factor regarding penetration of the nano-sized silver ink. As a proof of concept hygroscopic insulator field effect transistors were printed on the multi-layer curtain coated paper using a custom-built roll to roll hybrid printer. [Copyright &y& Elsevier]

Abstract: In this study, the influence of different surface characteristics of dispersion-coated barrier layers on top layer coatability is examined. The barrier layer consisted of platy pigments, such as talc and kaolin, combined with different amounts and types of latexes. Coating of the top coat was carried out using the reverse gravure technique in which a dispersion consisting of mineral pigments and latex is applied under slight pressure onto the barrier-coated substrate. Wettability and coatability were measured as a function of surface energy and surface roughness of the barrier layer and the surface tension of the top coat dispersion. Plasma and corona surface treatments were used to increase the surface energy and wettability without affecting the surface topography. The most important aspect for predicting the coatability was the wettability, especially the water contact angle, because the top coat is an aqueous suspension. Decreasing the surface tension of the top coat dispersion also improved the coatability, whereas roughness had only a minor effect. [Copyright &y& Elsevier]

Abstract: A recyclable multilayer coated fiber-based substrate combining sufficient barrier and printability properties for printed functional devices was developed using reel-to-reel techniques. The substrate consists of a mineral pigment layer coated on top of a barrier latex layer. The pigment layer allows controlled absorption of ink solvents. By adjusting the thickness and porosity of the top coating the printability can be tuned for various functional inks. As a proof of concept a hygroscopic insulator field effect transistor (HIFET) was successfully printed on the multilayer-coated paper. [Copyright &y& Elsevier]

Analytical devices made of inherently porous material can provide platforms for sensor applications in point-of-care medical diagnostics and environmental monitoring. However, separation and concentration of analytes on such devices has received limited attention. Neither have porous coatings, with their potential high surface area for chromatographic separation, in such devices been studied in detail. This study investigates inkjet printed polyelectrolyte patterns on such a coating as a possible method for concentration and separation of cationic and anionic compounds through surface charge interaction. Both anionic (sodium polyacrylate) and cationic (poly(diallyldimethylammonium chloride)) polyelectrolytes were printed on a custom designed porous pigment coating, having fine internal particle pore structure to ensure high surface contact with analytical samples. Printed polyelectrolyte patterns were poorly visible under visible or ultraviolet light. In a proof of principle test, a controllable degree of separation of three anionic dyes (amaranth, tartrazine and uranine) from aqueous solution passing through a printed cationic polyelectrolyte region was observed. Separation of the two tested cationic dyes (crystal violet and methylene blue) on printed anionic polyelectrolyte regions could not be evaluated effectively with the set-up, since the dyes were too strongly arrested by the anionic micro-fibrillated cellulose binder in the pigment coating. The weakly cationic/zwitterionic dye rhodamine B was shown to remain free to pass in solution through either cationic or anionic printed polyelectrolyte regions. The principles illustrated can provide a basis for enhancing detection on certain analytical device designs. [ABSTRACT FROM AUTHOR]

Abstract: Wetting and printing properties of recently developed smooth multilayer coated papers suitable for printed functionality have been investigated. Spreading of a semiconducting polymer poly(3-hexylthiophene) (P3HT) dissolved in ortho-dichlorobenzene (o-DCB) was studied both by contact angle measurements (macro-scale drop) and inkjet printing experiments (micro-scale droplet). In addition, film formation and final print quality of inkjetted P3HT was analyzed by topographical, chemical and optical characterization. Results were compared to reference substrates, poly(ethylene terephthalate) (PET) plastic and atomically flat mica. Wetting rate of the macro-scale drop was strongly influenced by the magnitude of surface extremes (asperties). Maximal spreading of inkjet droplets was affected by roughness, surface energy, pore volume and geometry of the substrate. Both the film formation of successive printings and the final film quality were comparable for the paper substrates and the PET film. Therefore the multilayer coated paper can be used instead of plastic films to reduce environmental impact. For example, low-cost disposable electronics can thus be made recyclable. [ABSTRACT FROM AUTHOR]

Printed, self-contained sensor designs based on capillary transport and microfluidic principles form a major part of current research in printed functionality. Previous work into such designs has mainly focused on cellulosic papers as base substrates. In this study, novel findings are presented employing alternative custom-designed functional pigment coated substrates, locally functionalised by inkjet printed polyelectrolytes, to separate or transport anionic or cationic molecules by surface chemistry tailoring. Both anionised and cationised coatings are tested and found to transport similarly charged model colorants successfully, while separating those of opposite charge, with the extent of separation depending on colorant concentration. Furthermore, surface chemistry reversal by cationic (polyethyleneimine, polyDADMAC) and anionic (carboxymethyl cellulose) polyelectrolyte inks is demonstrated as a complementary method for analyte separation or concentration. However, the deposition of the polyelectrolyte ink itself was found to affect the cationised coating by solubilising and re-depositing coating components, while the printed polyethyleneimine was found to be partially dissolved and transported by water elution, suggesting limited adsorption under tested conditions. [ABSTRACT FROM AUTHOR]

Abstract: Cytochrome P450 (CYP) is a superfamily of enzymes in charge of elimination of the majority of clinically used drugs and other xenobiotics. This study focuses on the development of a rapid microfluidic lateral flow assay to study human phase I metabolism reactions mediated by CYP2A6 isoenzyme, the major detoxification route for many known carcinogens and drugs, with coumarin 7‐hydroxylation, as the prototype model reaction. Assay fabrication utilizes custom‐designed porous functionalized calcium carbonate (FCC) coatings and inkjet‐printed fluid barriers. All materials used are novel and carefully chosen to preserve biocompatibility. The design comprises separate zones for reaction, separation and detection, and an absorbent pad to keep the assay wet for extended periods (up to 10 min) even when heated to physiological temperature. The concept enables CYP assays to be made at lower cost than conventional well‐plate assays, while providing increased selectivity at equally high speed, owing to the possibility for simultaneous chromatographic separation of the reaction products from the reactants on the FCC coating. The developed concept provides a viable rapid prediction of the interaction risks related to metabolic clearance of drugs and other xenobiotics, and exemplifies a novel coating technology illustrating the opportunity to broaden application functionality. [ABSTRACT FROM AUTHOR]

A solution-based fabrication of flexible and light-weight light-emitting devices on paper substrates is reported. Two different types of paper substrates are coated with a surface-emitting light-emitting electrochemical cell (LEC) device: a multilayer-coated specialty paper with an intermediate surface roughness of 0.4 μm and a low-end and low-cost copy paper with a large surface roughness of 5 μm. The entire device fabrication is executed using a handheld airbrush, and it is notable that all of the constituent layers are deposited from solution under ambient air. The top-emitting paper-LECs are highly flexible, and display a uniform light emission with a luminance of 200 cd m−2 at a current conversion efficacy of 1.4 cd A−1. [ABSTRACT FROM AUTHOR]

This work describes the development of a stable dispersion which is suitable for roll-to-roll printing of a film exhibiting hydrogen sulfide (H 2 S) gas sensing functionality. The dispersions are made from copper chloride in combination with either citric acid or citric acid and polyaniline (PANI). Aqueous PANI dispersions together with copper chloride (CC) have been shown to have H 2 S sensing properties, but the dispersion gets unstable with the addition of CC within a pH range from 5 to 8. In this study, a mixture of CC and citric acid (CA) was optimized for printability as well as for sensitivity towards H 2 S gas. Furthermore the stability of an aqueous PANI dispersion was studied after the addition of CC or a CC–CA mixture as a function of pH. The stable dispersions were printed on top of flexographically printed interdigitated silver electrodes and their sensitivity towards 10 ppm H 2 S was verified by following the change in resistance. The printed films were characterized by atomic force microscope (AFM), time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and conductometry. The sensors showed almost a three orders of magnitude change in resistance upon exposure to 10 ppm H 2 S at ambient conditions. [ABSTRACT FROM AUTHOR]

A new class of biofriendly ionogels produced by gelation of microcellulose thin films with tailored 1-ethyl-3-methylimidazolium methylphosphonate ionic liquids are demonstrated. The cellulose ionogels show promising properties for application in flexible electronics, such as transparency, flexibility, transferability, and high specific capacitances of 5 to 15 μF cm−2. They can be laminated onto any substrate such as multilayer-coated paper and act as high capacitance dielectrics for inorganic (spray-coated ZnO and colloidal ZnO nanorods) and organic (poly[3-hexylthiophene], P3HT) electrolyte-gated field-effect transistors (FETs), that operate at very low voltages (<2 V). Field-effect mobilities in ionogel-gated spray-coated ZnO FETs reach 75 cm2 V−1 s−1 and a typical increase of mobility with decreasing specific capacitance of the ionogel is observed. Solution-processed, colloidal ZnO nanorods and laminated cellulose ionogels enable the fabrication of the first electrolyte-gated, flexible circuits on paper, which operate at bending radii down to 1.1 mm. [ABSTRACT FROM AUTHOR]

Abstract: Sintering of printed metal nanoparticles can be made not only by conventional heating, but also by, e.g., electrical, microwave, plasma, laser and flash lamp annealing. We demonstrate sintering by using low-cost incandescent lamps as an effective way of obtaining highly conductive contacts of two types of ink-jet printed metal-nanoparticle inks on paper; both alkanethiol protected gold nanoparticles and a commercially available silver nanoparticle ink. This low-cost roll-to-roll compatible sintering process is especially suitable on paper substrates because of the high diffuse reflectance, relatively high thermal stability and low thermal conductivity of paper. A volume resistivity of around 10μΩcm was achieved of the inkjetted silver nanoparticles within 15s of exposure to an IR lamp, which corresponds to a conductivity of 10–20% of that of bulk silver. Too long exposure time and too high intensity, however, lead to darkening of the paper fibers. Both the crack formation and the coffee ring effect of the inkjet printed gold nanoparticles were, furthermore, found to be reduced on paper as compared to glass or plastic substrates. [Copyright &y& Elsevier]

Abstract: Electrodeposition of poly(3,4-ethylenedioxythiophene) doped with chloride (PEDOT-Cl) on a paper substrate is demonstrated. A fully printed silver/polyaniline (Ag/PANI) layer-by-layer structure on a pigment coated paper acted as a working electrode, on which a layer of PEDOT-Cl was galvanostatically grown in an electrochemical cell. The deposited PEDOT-Cl appeared as a dark-blue circular area on a green Ag/PANI electrode. The electrodeposition was further confirmed by chemical and topographical analyses. The results demonstrate the potential of low-cost paper substrates and roll-to-roll mass-manufacturing methods in electrochemical applications. [ABSTRACT FROM AUTHOR]