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Thin inkjet-printed tracks of silver nanoparticles have previously been observed to show a non-reversible decrease in resistance when exposed to a high degree of relative humidity and thus providing sensor functionality with a memory effect. This paper provides a more in-depth explanation of the observed humidity sensor effect that originates from inkjet-printed silver nanoparticle sensors on a paper substrate. It is shown that the geometry of the sensor has a large effect on the sensor's initial resistance, and therefore also on the sensor's resistive dynamic range. The importance of the sensor geometry is believed to be due to the amount of solvent from the ink interacting with the coating of the paper substrate, which in turn enables the diffusion of salts from the paper coating into the ink and thus affecting the silver ink. [ABSTRACT FROM PUBLISHER]

Abstract: This paper reports sintering condition effect on an ink-jet printed conductive pattern of silver ink made on a cellulose paper. To fabricate the conductive pattern on the cellulose paper, silver ink is ink-jet printed and the influence of sintering temperature and time is investigated in terms of electrical resistivity and morphology by using scanning electron microscope and atomic force microscope. Two-level baking process composed of soft baking and hard baking is found to be effective for silver nanoparticle network. The sintering temperature and time are strongly associated with the conductivity of the ink-jet printed pattern. [Copyright &y& Elsevier]

The lifetime of a power transformer is typically defined by the lifetime of the cellulose insulation in the transformer. As the paper ages, there is a reduction in its mechanical strength properties. Dakin [1] was the first to show that the temperaturerelated chemical changes to the paper followed an Arrhenius relationship. The Arrhenius relationship shows, for example, life can be decreased to half for every 6 to 7°C rise in temperature in the hot spot temperature range of 80 to 100°C; the doubling rate can range from 5.9 to 9.7°C in the 80 to 180°C range [2]. It has also been long understood that the aging of cellulose is influenced by the amount of oxygen or water in the paper and the surrounding insulating medium [3], [4]. Paper and pressboard consist mainly of cellulose fibers composed of a polymeric chain of cellulose, which is formed from D-glucose monomers. The reduction in mechanical strength described above is due to splitting of the cellulose polymer by the action of oxygen, water, temperature, and likely acids. The number of D-glucose monomers in the cellulose fiber is termed the degree of polymerization (DP). New oil-impregnated cellulose typically has 1,000 to 1,100 individual monomers in the cellulose polymer. The DP of cellulose at its traditionally accepted end of life is 150 to 200. This article will first provide a review of data from aging studies performed on cellulose (both Kraft paper and pressboard) impregnated separately in mineral oil and BIOTEMP (ABB, USA), a high oleic sunflower based fluid. Next, possible mechanisms that explain the differences in aging behavior will be discussed. The article concludes with recommendations for new temperature limits for BIOTEMP-impregnated transformers in comparison with mineral-oil-impregnated transformers. [ABSTRACT FROM PUBLISHER]