Paper-based analytical devices (PADs), firstly introduced in 2007, are attractive for point-of-care testing (POCT) due to being low-cost, easy-to-handle, portable and disposable, while requiring only small sample volumes. They are typically made of unmodified hydrophilic paper areas enclosed by hydrophobic barriers. Applications have been demonstrated for various analytes including proteins and nucleic acids in biological sample solutions.<br/><br/>There are several types of detection techniques of PADs. Colorimetry is the simplest among them and provides multiple options such as text-based, distance-based as well as color intensity-based readout. Regarding practical use, distance-based PADs (dPADs) are the most advanced method because of intuitive and calibration-free readout. However, their biggest challenge lies in long assay times, ca. 20 to 40 minutes for a single assay. To achieve rapid analysis, flow control, especially acceleration of liquid flow, is important. To our best knowledge, no work addressing tailor-made flow control for dPADs has been reported.<br/><br/>This study introduces centrifugal flow control for dPADs. By combining an ultra low-cost DVD player with a microcomputer, i.e. Arduino, signal detection within 1 minute is achieved not only due to rapid flow, but also rapid liquid drying at high disc rotation speed. A one-dollar DVD pickup unit was used and programmed as a rotational device using Arduino. Paper-based “discs” were fabricated as follows. Hydrophobic barriers were created by wax printing followed by heating. Printed devices were then laminated with a polymer film. Elaborate studies on flow speed parameters were performed by comparison of different filter papers, DVD motor angular velocities and positions of inlet areas. We found that rapid rotation enabled quick evaporation of liquids on paper microchannels. In addition, we noticed that fiber directions of the paper substrate negligibly affected the flow behaviour under centrifugal force.

Microfluidic paper-based analytical devices (microPADs) with DVD player: Centrifugally assisted flow acceleration for rapid distance readout assays

2019 Fall National Meeting

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