In recent years, Paper-based materials have witnessed increasing interest, both from academia and industry, as a renewable, low-cost and non-toxic ‘green’ material for the design of “high-tech” devices, such as microfluidic papers or paper-materials used in microelectronic applications. Despite low-cost and well-established technologies to produce paper in large scale, the material offers a number of interesting features, such as high surface area, and tunable porosity. The latter properties lay the foundation, in particular, for the use of paper in microfluidic applications, where paper can achieve a pump-less laminar fluid-flow in a channel. Often several chemical steps are necessary to design such channels, which can limit the control over channel-definition, and intrinsic paper-properties (porosity etc.). In this paper, we introduce a novel method in order to tailor the chemical properties of paper sheets in a simple process, where only one polymer coat is used to modify paper fibers, and by simple polymeranalogous reactions, this polymer coating can be switched from hydrophobic to hydrophilic surface properties. For this instance, we focus on photo-reactive polyvinyl acetate as a functional coating that can be applied onto various substrates from solution by dip-coating or doctor blading. These copolymers can easily be synthesized using free radical copolymerization and offer uncomplicated photo-chemically induced surface-attachment and network generation properties by direct C-C bond formation via UV excitation of benzophenone moieties, which have been incorporated into the copolymer in desired ratios. Additionally, the hydrophobic polyvinyl acetate can be converted into hydrophilic polyvinyl alcohol by simple and fast ester hydrolysis in alkaline methanolic sodium hydroxide solution. This change in surface chemistry allows direct micro structuring of a substrate surface into non-wetting and wetting domains and ultimately the fabrication of microfluidic structures or channels on a substrate by spatially resolved application of methanolic sodium hydroxide solution via inkjet printing.

Tailoring barrier-properties of paper substrates using fiber-immobilized polyvinyl acetate copolymer

249th National Meeting (2015)

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