2.

Comparison of lateral flow and vertical flow with illustrations of VF-μPADs in POCT. (A) Illustration of the shorter fluid path in VF-μPADs, enabling rapid fluid transfer through vertically stacked layers. This arrangement reduces assay time. Reproduced with permission from ref (). Available under a CC-BY license. Copyright 2021 MDPI. (B) Difference in color signal uniformity between LF-μPADs and VF-μPADs depending on flow direction. Reproduced with permission from ref (). Copyright 2019 American Chemical Society. (C) Effect of flow direction on assay performance. Schematic representation illustrating fluid division into two streams directed into the control and test zones, effectively mitigating the hook effect through vertical flow. Reproduced with permission from ref (). Copyright 2013 Royal Society of Chemistry. (D) Multiplexing in VF-μPADs achieved by folding and unfolding patterned paper with photoresist. This design allows simultaneous detection of multiple analytes within a compact device. Reproduced with permission from ref (). Copyright 2011 American Chemical Society. (E) Blood separation in VF-μPADs using a filtration layer. Reproduced with permission from ref (). Copyright 2012 American Chemical Society. (F) Fluid control in VF-μPADs using multiple functional layers. Reproduced with permission from ref (). Copyright 2017 Elsevier B.V.