We present a rapid (<10 s), cost-effective, unique single-step method for fabricating paper-based devices without necessitating any expensive instrumentation, simply by deploying correction pens that are otherwise commonly used for masking typos in printed or written matters. The marked regions formed by deposits from the correction pen demonstrate ubiquitous flow resistances to typical aqueous solutions and organic solvents in the transverse direction, resulting in a preferential bulk flow along the axial direction of the paper channels ‘fabricated’ in the process. Considering the simplicity and cost-effectiveness of this platform, it is deemed to be ideal for (bio) chemical sensing and point-of-care diagnostics in resource-limited settings.
We present a high resolution, ultra-frugal printing of paper microfluidic
devices using in-house paraffin formulation on a simple filter paper. The patterns
printed using an office inkjet printer formed a selective hydrophobic barrier of
4 ± 1 µm thickness with a hydrophilic channel width of 275 µm. These printed patterns
effectively confine common aqueous solutions and solvents, which was verified by solvent
compatibility studies. SEM analysis reveals that the solvent confinement is due to pore
blockage in the filter paper. The fabricated paper-based device was validated for
qualitative assessment of Candida albicans
(pathogenic fungi) by using a combination of L-proline β-naphthylamide as the substrate
and cinnamaldehyde as an indicator. Our studies reveal that the pathogenic fungi can be
detected within 10 min with the limit of detection (LOD) of
0.86 × 106 cfu/mL. Owing to its simplicity, this facile
method shows high potential and can be scaled up for developing robust paper-based
devices for biomarker detection in resource-limited settings.
Graphic abstract
Urinary tract infections (UTIs) make up a significant proportion of the global burden of disease in vulnerable groups and tend to substantially impair the quality of life of those affected, making timely detection of UTIs a priority for public health. However, economic and societal barriers drastically reduce accessibility of traditional lab-based testing methods for critical patient groups in low-resource areas, negatively affecting their overall healthcare outcomes. As a result, cellulose-based materials such as paper and thread have garnered significant interest among researchers as substrates for so-called frugal analytical devices which leverage the material’s portability and adaptability for facile and reproducible diagnoses of UTIs. Although the field may be only in its infancy, strategies aimed at commercial penetration can appreciably increase access to more healthcare options for at-risk people. In this review, we catalogue recent advances in devices that use cellulose-based materials as the primary housing or medium for UTI detection and chart out trends in the field. We also explore different modalities employed for detection, with particular emphasis on their ability to be ported onto discreet casings such as sanitary products.
Graphical abstract
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