Plasma treatment is a commonly used technology to modify the wetting behavior of polymer films in the production process for, e.g., printed electronics. As the effect of the plasma treatment decreases in time, the so-called "aging effect", it is important to gain knowledge on how this effect impacts the wetting behavior of commonly used polymers in order to be able to optimize production processing times. In this article the authors study the wetting behavior of polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polycarbonate (PC), fluorinated ethylene propylene (FEP) and polyimide (PI) polymer films after plasma treatment in time. The plasma treatment was performed using a novel maskless DBD plasma patterning technology, i.e., Plasma Printing, at atmospheric pressure under nitrogen atmosphere. After treatment, the samples were stored at room temperature at 30%-40% relative humidity for up to one month. An increase in wettability is measured for all polymers directly after Plasma Printing. The major increase in wettability occurs after a small number of treatments, e.g., low energy density. More treatments show no further beneficial gain in wettability. The increase in wettability is mainly due to an increase in the polar part of the surface energy, which can probably be attributed to chemical modification of the surface of the investigated polymers. With the exception of FEP, during storage of the plasma treated polymers, the wettability partially declines in the first five days, after which it stabilizes to approximately 50% of its original state. The wettability of FEP shows little decline during storage. As the storage time between production steps is mostly under two days, Plasma Printing shows good promise as a pre-treatment step in the production of printed electronics. d c 2013 Society for Imaging Science and Technology.
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In manufacturing of organic electronics, inkjet printing as an alternative technique for depositing materials is becoming increasingly important. Aside to the ink formulations challenges, improving the resolution of the printed patterns is a major goal. In this study we will discuss a newly developed technique to selectively modify the substrate surface energy using plasma treatment as a means to achieve this goal. First, we look at the effects of the μPlasma treatment on the surface energy for a selection of plastic films. Second, we investigated the effects of the μPlasma treatment on the wetting behaviour of inkjet printed droplets to determine the resolution of the μPlasma printing technique. We found that the surface energy for all tested films increased significantly reaching a maximum after 3-5 repetitions. Subsequently the surface energy decreased in the following 8-10 days after treatment, finally stabilizing at a surface energy roughly halfway between the surface energy of the untreated film and the maximum obtained surface energy. When μPlasma printing lines, an improved wetting abillity of inkjet printed materials on the plasma treated areas was found. The minimal achieved μPlasma printed line was found to be 1 mm wide. For future application it is important to increase the resolution of the plasma print process. This is crucial for combining plasma treatment with inkjet print technology as a means to obtain higher print resolutions.
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With a market demand for low cost, easy to produce, flexible and portable applications in healthcare, energy, biomedical or electronics markets, large research programs are initiated to develop new technologies to provide this demand with new innovative ideas. One of these fast developing technologies is organic printed electronics. As the term printed electronics implies, functional materials are printed via, e.g. inkjet, flexo or gravure printing techniques, on to a substrate material. Applications are, among others, organic light emitting diodes (OLED), sensors and Lab-on-a-chip devices. For all these applications, in some way, the interaction of fluids with the substrate is of great importance. The most used substrate materials for these low-cost devices are (coated) paper or plastic. Plastic substrates have a relatively low surface energy which frequently leads to poor wetting and/or poor adhesion of the fluids on the substrates during printing and/ or post-processing. Plasma technology has had a long history in treating materials in order to improve wetting or promote adhesion. The µPlasma patterning tool described in this thesis combines a digital inkjet printing platform with an atmospheric dielectric barrier discharge plasma tool. Thus enabling selective and local plasma treatment, at atmospheric pressure, of substrates without the use of any masking materials. In this thesis, we show that dependent on the gas composition the substrate surface can either be functionalized, thus increasing its surface energy, or material can be deposited on the surface, lowering its surface energy. Through XPS and ATR-FTIR analysis of the treated (polymer) substrate surfaces, chemical modification of the surface structure was confirmed. The chemical modification and wetting properties of the treated substrates remained present for at least one month after storage. Localized changes in wettability through µPlasma patterning were obtained with a resolution of 300µm. Next to the control of wettability of an ink on a substrate in printed electronics is the interaction of ink droplets with themselves of importance. In printing applications, coalescence of droplets is standard practice as consecutive droplets are printed onto, or close to each other. Understanding the behaviour of these droplets upon coalescence is therefore important, especially when the ink droplets are of different composition and/or volume. For droplets of equal volume, it was found that dye transport across the coalescence bridge could be fully described by diffusion only. This is as expected, as due to the droplet symmetry on either side of the bridge, the convective flows towards the bridge are of equal size but opposite in direction. For droplets of unequal volume, the symmetry across the bridge is no longer present. Experimental analysis of these merging droplets show that in the early stages of coalescence a convective flow from the small to large droplet is present. Also, a smaller convective flow of shorter duration from the large into the small droplet was identified. The origin of this flow might be due to the presence of vortices along the interface of the bridge, due to the strong transverse flow to open the bridge. To conclude, three potential applications were showcased. In the first application we used µPlasma patterning to create hydrophilic patterns on hydrophobic dodecyl-trichlorosilane (DTS) covered glass. Capillaries for a Lab-on-a-chip device were successfully created by placing two µPlasma patterned glass slides on top of each other separated by scotch tape. In the second application we showcased the production of a RFID tag via inkjet printing. Functional RFID-tags on paper were created via inkjet printing of silver nanoparticle ink connected to an integrated circuit. The optimal operating frequency of the produced tags is in the range of 860-865 MHz, making them usable for the European market, although the small working range of 1 m needs further improvement. Lastly, we showed the production of a chemresistor based gas sensor. In house synthesised polyemeraldine salt (PANi) was coated by hand on top of inkjet printed silver electrodes. The sensor proved to be equally sensitive to ethanol and water vapour, reducing its selectivity in detecting changes in gas composition.
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This project is part of an interdisciplinary and international collaboration bringing together experts in nanomaterials, sensor technology, and engineering from the University of Technology of Troyes (UTT, France), Eindhoven University of Technology (TU/e, The Netherlands) and Hanze University of Applied Sciences (HUAS, The Netherlands). It presents an innovative, integrated approach including design, fabrication, characterization, and integration of flexible sensors dedicated to wind turbine blade monitoring, aiming to advance smart monitoring and renewable energy research. The sensor will be developed using functional polymer films decorated with conductive nanoparticles. A novel manufacturing approach will be applied, combining additive manufacturing techniques with the colloidal deposition of silver or gold nanoparticles.
In vele industrieën zoals in de scheepsbouw, luchtvaart en infrastructuur worden metaalsoorten veelvuldig toegepast omdat het een sterk en gemakkelijk te verwerken materiaal is. Nadelig is dat het materiaal bij buitentoepassing corrodeert. Daarom wordt er veelal gebruik maakt van een oppervlaktebehandeling zoals een verfsysteem of coating. Traditionele coatings bevatten vaak schadelijke stoffen zoals conserveringsstoffen, chromaat-zouten of Chroom-6 om infecties en oxidatieprocessen te verminderen en de levensduur van het materiaal te verlengen. Daarnaast zijn veel coatings op aardolie gebaseerd en kunnen microplastics door verwering vrijkomen. Milieuvriendelijke en duurzamere beschermingssystemen zouden een mijlpaal zijn in de metaalindustrie. De schimmel Aureobasidium pullulans wordt in combinatie met lijnzaadolie inmiddels al succesvol toegepast voor het beschermen van hout en kan door zijn aanmaak van pullulaan of andere extracellulaire polymere stoffen (EPS) mogelijk een grote rol spelen in de zoektocht naar milieuvriendelijke en duurzame beschermingssystemen voor metaal. In onderzoek is aangetoond dat de extracellulaire polymere stof pullulaan in staat is om corrosie op metaal sterk te verminderen. Het nadeel is echter dat pullulaan wateroplosbaar is. Het doel van dit missie-gedreven onderzoek is om een fermentatieproces te ontwikkelen waarbij geschikte en watervaste biopolymeren voor de bescherming van metaal worden geproduceerd door de schimmel A. pullulans. Door een nieuw fermentatieproces kan de productie van deze EPS gestimuleerd worden. Met een beschermingssysteem van A. pullulans, EPS en lijnzaadolie kunnen de corroderende factoren als vocht en zuurstof worden verminderd. Daarnaast kan de productie van melanine door A. pullulans een rol spelen in de bescherming tegen UV-licht waardoor gepolymeriseerd lijnzaadolie langer stabiel blijft. Deze onderdelen zullen een dergelijke oppervlaktebehandeling voor metaal geschikt maken voor buiten toepassing en geven meer toegevoegde waarde aan het product.
