Characterizing effects of humidity and channel size on imbibition in paper-based microfluidic channels

Paper-based microfluidic devices have gained an increasing amount of interest over the last few years. As such devices continue advancing toward more complex and sophisticated functions, obtaining accurate and consistent fluid imbibition under different conditions will become increasingly important. This study presents a series of controlled imbibition experiments investigating effects of relative humidity and channel width in paper-based microfluidic channels. The obtained imbibition data highlighted the importance in accounting for the effects of these design and environmental parameters. Additionally, fitting of the experimental data to three relevant imbibition models revealed evaporation, not water saturation, to be the main mechanism of the observed relative humidity effect. The current study has created a library of paper-specific, imbibition-related properties for commonly used filter and chromatography papers for the first time. Collectively, the presented imbibition data and the discovered relationships are expected to help researchers design more precise and reproducible paper-based microfluidic devices.