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Teekkarikylä, Finland

Sarfraz J.,Abo Akademi University | Tobjork D.,Abo Akademi University | Osterbacka R.,Abo Akademi University | Osterbacka R.,Center for Functional Materials | Linden M.,University of Ulm
Proceedings of IEEE Sensors

Drop-casted deprotonated Emeraldine base (poly)aniline (PANI) - copper chloride films on paper substrates containing ink-jet printed silver electrodes have been prepared and are shown to be promising low-cost gas-sensors for H2S at room temperature. These films showed large changes in the conductivity (three to four orders of magnitude) upon exposure to low concentrations of H 2S (10ppm) due to the formation of CuS and concurrent protonation of PANI. This large response of the sensor can be explained by the relatively large roughness and porosity of the paper substrate. Furthermore, the minimum resistances are low enough to allow LED lamps to be switched on using a low-voltage battery, thus serving as a proof-of-concept for mass-produced H 2S-sensors for, for example, the food packaging industry. © 2011 IEEE. Source

Bober P.,Process Chemistry Center | Bober P.,Czech Institute of Macromolecular Chemical | Liu J.,Process Chemistry Center | Mikkonen K.S.,University of Helsinki | And 8 more authors.

In this work, flexible and free-standing composite films of nanofibrillated cellulose/polypyrrole (NFC/PPy) and NFC/PPy-silver nanoparticles (NFC/PPy-Ag) have been synthesized for the first time via in situ one-step chemical polymerization and applied in potential biomedical applications. Incorporation of NFC into PPy significantly improved its film formation ability resulting in composite materials with good mechanical and electrical properties. It is shown that the NFC/PPy-Ag composite films have strong inhibition effect against the growth of Gram-positive bacteria, e.g., Staphylococcus aureus. The electrical conductivity and strong antimicrobial activity makes it possible to use the silver composites in various applications aimed at biomedical treatments and diagnostics. Additionally, we report here the structural and morphological characterization of the composite materials with Fourier-transform infrared spectroscopy, atomic force microscopy, and scanning and transmission electron microscopy techniques. © 2014 American Chemical Society. Source

Pykonen M.,Center for Functional Materials | Johansson K.,Ytkemiska Institutet AB | Bollstrom R.,Center for Functional Materials | Fardim P.,Abo Akademi University | Toivakka M.,Center for Functional Materials
Industrial and Engineering Chemistry Research

SocietyFluorocarbon, organosilicon, and hydrocarbon plasma coatings were used to modify the surface of permeable pigment-coated paper, and their impact on UV-varnish absorption was investigated. According to mercury porosimetry results, the plasma coatings had no influence on the porous structure of the paper. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) results showed characteristic surface chemical compositions for each plasma coating. The fluorocarbon plasma coating increased the UV-varnish contact angles significantly, whereas the hydrocarbon plasma coating had no clear influence. When the UV varnish was applied with a flexography unit including nip pressure, the role of surface chemical composition seemed to become minimal. The viscosity of the UV varnish was shown to impact the absorption rate with and without external pressure. © 2010 American Chemical. Source

Bollstrom R.,Center for Functional Materials | Bollstrom R.,Abo Akademi University | Tobjork D.,Center for Functional Materials | Tobjork D.,Abo Akademi University | And 10 more authors.
Chemical Engineering and Processing: Process Intensification

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. © 2012 Elsevier B.V. Source

Bollstrom R.,Center for Functional Materials | Bollstrom R.,Abo Akademi University | Pettersson F.,Center for Functional Materials | Pettersson F.,Abo Akademi University | And 7 more authors.

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. © 2014 IOP Publishing Ltd. Source

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