625 www.MaterialsViews.com wileyonlinelibrary.com . IntroductionPaper is a cheap, ubiquitous, and biofriendly material that is used as a fl exible substrate for many applications in daily life. Modern methods of pulp and paper processing have also substantially reduced the energy consumption associated with paper production. [ 1 ] Hence, using paper as a substrate for lowcost, printable, and fl exible electronics has been an attractive goal for some time. [2][3][4][5][6][7] The absorbency and roughness of ordinary paper make it a challenging substrate compared to smooth but more expensive and non-biodegradable plastic sheets, such as polyethylene terephthalate (PET) and polyimide (PI). However, these issues may be overcome by using a recently developed multilayer-coating structure [ 8 ] which holds great potential for applications in fl exible electronics. [ 9,10 ] Furthermore, special micro-and nanocellulose papers, which are transparent and have a much smoother surface than regular paper and a low thermal expansion coeffi cient, have attracted considerable attention recently as substrates for circuits [11][12][13][14][15] and actuators [ 16,17 ] In general, paper is seen as a renewable, biofriendly material whose value and utility is increased substantially by adding extra functionalities such as energy storage and (opto-)electronic circuits. [ 18 ] In order to build electronic circuits on paper, suitable electrode materials, semiconductors and dielectrics are required, which should ideally reproduce the advantageous properties of the paper, e.g., biodegradability, low cost, and fl exibility, while maintaining high performance. They should not only be compatible with paper in terms of their mechanical, thermal, and adhesion properties, but should also be processable in the same way. High temperature and vacuum processes are therefore less suitable. One crucial component of an electronic circuit containing many thin-fi lm fi eld-effect transistors (FETs) is the gate dielectric, which determines to a large degree the operating voltage and switching speed. High capacitance dielectrics are ideal for lowvoltage FETs. [ 19 ] However, most polymeric printable dielectrics (e.g., Cytop, PMMA, PVA) result in relatively low capacitances and are not particularly compatible with paper substrates, while high-permittivity inorganic dielectrics (e.g., Al 2 O 3 or HfO 2 ) require vacuum deposition or sputtering. Here we introduce a new class of cellulose-based ionogels as high capacitance gate dielectrics for electrolyte-gated FETs on paper. These ionogels are produced from microcellulose thin fi lms and tailor-made methylphosphonate ionic liquids, which result in fl exible, transferable, and high capacitance dielectrics, that match the advantageous properties of paper while allowing for low-voltage (<2 V) operation of solution-processed inorganic and organic FETs.Electrolyte-gating has recently emerged as a promising method to obtain low voltage, high performance FETs with solution-processed organic, inorganic, or colloidal se...

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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.