Programmed sample delivery on a pressurized paper

Abstract

This paper reports a method to control the fluid flow in paper-based microfluidic devices simply by pressing over the channel surface of paper, thereby decreasing the pore size and permeability of a non-woven polypropylene sheet. As a result, fluid resistance is increased in the pressed region and causes flow rate to decrease. We characterize the decrease of flow rate with respect to different amounts of pressure applied, and up to 740% decrease in flow velocity was achieved. In addition, we demonstrate flow rate control in a Y-shaped merging paper and sequential delivery of multiple color dyes in a three-branched paper. Furthermore, sequential delivery of multiple fluid samples is performed to demonstrate its application in multi-step colorimetric immunoassay, which shows a 4.3-fold signal increase via enhancement step. V C 2014 AIP Publishing LLC.

A quantitative model for lateral flow assays

“…Thus, the analyte flux can be adjusted by varying the location of the detection line (distance x L ), which is known to have a significant impact on assay sensitivity. Nevertheless, as changing x L also influences both the amount of sample required and the assay time, other strategies to control the fluid front velocity are being explored as well (Jahanshahi-Anbuhi et al 2012;Shin et al 2014;Elizalde et al 2015;Choi et al 2016). …”

Wax-Printed Fluidic Time Delays for Automating Multi-Step Assays in Paper-Based Microfluidic Devices (MicroPADs)

“…However, these techniques have a limited range of fluid control [6,31,34]. While there are many additional methods of passive fluid control in microPADs (e.g., fluidic diodes, delay shunts, altering pore size, ionogel passive pumps, laser direct writing, sucrose delays, chemical modifications, dissolvable/erodible bridges) [6,11,[36][37][38][39][40][41][42][43][44][45][46], all of these have significant limitations, such as the extensive use of additional fabrication materials or equipment beyond what is required for wax printing (e.g., laser cutters, plastic sheets, or adhesives) [39,40,44,45], use of reagents that could impact downstream assays (e.g., sugars, polymers, or surfactants) [11,38,42,43,46], or the use of techniques not compatible with high-volume fabrication [36,37,41].…”

Recent Advances of Fluid Manipulation Technologies in Microfluidic Paper-Based Analytical Devices (μPADs) toward Multi-Step Assays

“…The methods using the structural change of paper or a combination of various kinds of papers and attaching additional materials have been frequently applied in μPADs. These methods have a principle that adjusts the flow rate by reducing the pore size and cross-sectional area on the paper by applying pressure to the paper [67][68][69]. If the pore size and cross-sectional area are reduced, the fluid resistance increases and, consequently, the flow rate decreases.…”