Abstract

Paper substrates, with their inherent capillary-driven forces, eliminate the need for external power sources typically required by microfluidic biochips. However, conventional lateral flow (LF) systems face limitations, including non-specific adsorption, uneven molecular distribution, and restricted flexibility for multiplexed detection. In this work, we developed a novel vertical-flow paper-tape (VFPT) integrated device. By engineering a gradient pore-size paper substrate and replacing pre-patterned channels with gravity-driven flow, this innovation achieves size-selective molecular transport while doubling the effective transport distance. Its roll-to-roll fabrication process enables scalable, low-cost production with customizable detection capabilities. As a proof of concept, the VFPT device demonstrated detection limits of 200 copies/mL for HIV and HBV and 600 copies/mL for HCV, comparable to PCR and superior to traditional paper-based systems. Validation with 203 blinded clinical plasma samples revealed sensitivity and specificity exceeding 90.9%. This innovative platform offers a user-friendly, accurate, and cost-effective solution for clinical diagnostics and resource-limited settings.