Capillary flow control in lateral flow assays via delaminating timers

Abstract

Lateral flow assays (LFAs) use capillary flow of liquids for simple detection of analytes. While useful for spontaneously wicking samples, the capillary flow inherently limits performing complex reactions that require timely application of multiple solutions. Here, we introduce a technique to control capillary flow on paper by imprinting roadblocks on the flow path with water-insoluble ink and using the gradual formation of a void between a wetted paper and a sheath polymer tape to create timers. Timers are drawn at strategic nodes to hold the capillary flow for a desired period and thereby enable multiple liquids to be introduced into multistep chemical reactions following a programmed sequence. Using our technique, we developed (i) an LFA with built-in signal amplification to detect human chorionic gonadotropin with an order of magnitude higher sensitivity than the conventional assay and (ii) a device to extract DNA from bodily fluids without relying on laboratory instruments.

Point-of-Care Toolkit for Multiplex Molecular Diagnosis of SARS-CoV-2 and Influenza A and B Viruses

“…The capillary flow on a laminated paper can be controlled by drawing patterns on the paper with two water-insoluble inks with different levels of hydrophobicity. 38 The region patterned with a more hydrophobic ink (Sharpie metallic permanent marker) is permanently tethered to the sheath tape with no void formation, acting as channel boundaries to guide the flow. The region patterned with the less hydrophobic ink (Sharpie ultra fine point marker) eventually separates from the sheath tape when wetted, leaving the void to be formed at the interface between the patterned region and the tape.…”

“…The capillary flow on a laminated paper can be controlled by drawing patterns on the paper with two water-insoluble inks with different levels of hydrophobicity . The region patterned with a more hydrophobic ink (Sharpie metallic permanent marker) is permanently tethered to the sheath tape with no void formation, acting as channel boundaries to guide the flow.…”

Assessment of Urinary Biomarkers for Infectious Diseases Using Lateral Flow Assays: A Comprehensive Overview

“…By modifying the geometry, the timers at strategic nodes could introduce different reagents into the reaction, with optimum incubation times in between, and perform complex assays which were not possible with traditional LFAs. 94 In another research, an additional element known as the stacking pad was configured between the conjugation and test pads with a view to extend the antigen/antibody interaction and enhance the strip sensitivity. LFAs are extremely simple and convenient to handle, with no requirement for any professional skills.…”

Lateral flow immunoassay for small-molecules detection in phytoproducts: a review

“…Hence, the sample is applied either into the sample loading opening of the cassette or by directly dipping the sample pad of the strip into the sample solution. The liquid flows through the strip mainly by capillary force [ 44 ]. The direction of the flow is the origin of the assay name since the liquid flows laterally through the other compartment when the cassette is provided.…”

“… [ 29 ] Rhein Anthraquinone Rheum officinale [ 42 ] Kwakhurin Isoflavonoids Pueraria mirifica [ 102 ] Higenamine Benzyltetrahydroisoquinoline alkaloid Aconitum carmichaelii, Asarum heterotrophies, Nandina domestica [ 34 ] Amarogentin Secoiiridoid glycoside Swertia spp., Gentiana spp. [ 46 ] Colchicine Alkaloid Colchicum autumnale [ 44 ] …”