Paper-based planar reaction arrays for printed diagnostics

A reaction plate mimicking the working principle of a conventional three-dimensional microplate was printed on various hydrophilic paper substrates. Planar well patterns with high wetting/non-wetting contrast were formed using hydrophobic polydimethylsiloxane (PDMS) based ink with fast curing time, which enables truly low cost roll-to-roll fabrication. The formation and functionality of the printed reaction arrays were verified by two proof-of-concept demonstrations. Firstly a colorimetric glucose sensor, based on an enzymatic reaction sequence involving glucose oxidase, was screen-printed on the reaction plate. A detection limit of 0.1 mg/mL and a fairly linear sensor response was obtained on a logarithmic scale. Secondly, the employment of the reaction plate for electrical applications was demonstrated by modulating the resistance of a drop-casted polyaniline film as a function of pH.