Printed platforms for paper-based analytical applications

Paper-based analytical technologies enable quantitative and rapid analysisof analytes from various application areas including healthcare,environmental monitoring and food safety. Because paper is a planar,flexible and light weight substrate, the devices can be transported anddisposed easily. Diagnostic devices are especially valuable in resourcelimitedenvironments where diagnosis as well as monitoring of therapycan be made even without electricity by using e.g. colorimetric assays. Onthe other hand, platforms including printed electrodes can be coupled withhand-held readers. They enable electrochemical detection with improvedreliability, sensitivity and selectivity compared with colorimetric assays.In this thesis, different roll-to-roll compatible printing technologies wereutilized for the fabrication of low-cost paper-based sensor platforms.The platforms intended for colorimetric assays and microfluidics werefabricated by patterning the paper substrates with hydrophobic vinylsubstituted polydimethylsiloxane (PDMS) -based ink. Depending on thebarrier properties of the substrate, the ink either penetrates into the paperstructure creating e.g. microfluidic channel structures or remains on thesurface creating a 2D analog of a microplate. The printed PDMS can becured by a roll-ro-roll compatible infrared (IR) sintering method. Theperformance of these platforms was studied by printing glucose oxidase-based ink on the PDMS-free reaction areas. The subsequent applicationof the glucose analyte changed the colour of the white reaction area topurple with the colour density and intensity depending on theconcentration of the glucose solution.Printed electrochemical cell platforms were fabricated on paper substrateswith appropriate barrier properties by inkjet-printing metal nanoparticlebased inks and by IR sintering them into conducting electrodes. PrintedPDMS arrays were used for directing the liquid analyte onto thepredetermined spots on the electrodes. Various electrochemicalmeasurements were carried out both with the bare electrodes andelectrodes functionalized with e.g. self assembled monolayers.Electrochemical glucose sensor was selected as a proof-of-concept deviceto demonstrate the potential of the printed electronic platforms.