Controlling Capillary Flow Rate on Lateral Flow Test Substrates by Tape.

Zhiqing Xiao,Yuqian Yang,Weijin Guo,Xingwei Zhang

doi:10.3390/mi12050562

Abstract

Controlling capillary flow rate of sample liquid is of high interest for lateral flow tests, since the flow rate can affect the dissolution and mixing of the immunoreagents and the efficiency of immunoreactions. Here we develop a facile method to adjust the capillary flow rate on lateral flow test substrates by using tape to cover the surface of substrates. We test this method on the traditional lateral flow test substrate—nitrocellulose and a novel lateral flow test substrate—synthetic paper, which is a porous media made by interlocked off-stoichiometry thiol-ene (OSTE) micropillars. We found that after the surface was covered by tape, the average flow rate decreased to 61% of the original flow rate on nitrocellulose, while the average flow rate increased to at least 320% of the original flow rate on synthetic paper. More interesting, besides the increase of flow rate, the volume capacity of synthetic paper also increases after covered by tape. Furthermore, we investigated the influence of length and position of tape on the capillary flow rate for nitrocellulose. A longer tape will lead to a smaller flow rate. The influence of tape of same length on the flow rate is bigger when the tape is placed closer to the loading pad. These results can help in the flow rate control on lateral flow test substrates, and potentially improve the performance of lateral flow tests.

Highlights

Lateral flow tests utilize capillary force to pump the sample liquid
We found that for nitrocellulose, the flow rate decreased to 61% of the original value after the surface was covered by tape, while for synthetic paper the flow rate increased to at least 320% of the original value after the surface was taped
The pore size of nitrocellulose was below 10 μm, and the dimension of nitrocellulose test strips was 144 μm × 4 mm × 40 mm, the pore size of synthetic paper was between 50 μm and 100 μm, and the dimension of synthetic paper test strips was 100 μm × 4 mm × 40 mm

Summary

Introduction

Lateral flow tests utilize capillary force to pump the sample liquid. Sample liquid will flow through the conjugate pad, and reach test line and control line. During this process, sample liquid will dissolve the immunoreagents on the conjugate pad and mix with them. The mixture will react with the antibodies on the test line and control line. Sample flow rate will affect the efficiency of all these steps including dissolution, mixing and reaction. The liquid flow on a porous lateral flow test strip follows the Washburn

Methods

Results

Conclusion