A fabrication technique for paper-based analytical devices via two-sided patterning with thermal-transfer printer and laminator

In this study, we propose a novel technique for fabricating paper-based analytical devices (PADs) using a wax-based thermal-transfer printer and a thermal laminator, which allows prototyping and roll-to-roll mass production of PADs without utilizing widely used conventional wax printers. This fabrication scheme involves two-sided patterning to form hydrophobic barriers and an ink ribbon that contains sufficient wax content to form hydrophobic barriers without undesirable components or additives. First, a thermal-transfer printer forms positive patterns on the ink ribbon for the front and back sides of the device design. Subsequently, a laminator performs the two-sided thermal transfer of the patterns from the ink ribbon to a paper substrate and the thermal formation of hydrophobic barriers for channels. The hydrophobicity of the prepared ink is similar to that of ink used in wax printers and exhibits excellent stability in organic solvents and surfactants. Hydrophobic barriers and channels were successfully formed using various paper substrates typically used for PADs. The two-sided scheme allows the formation of 3D channels, including vertical paths in a single paper substrate. The utility of the proposed fabrication technique was demonstrated using a dip-type 3D PAD for sensing glucose.