Influence of Geometry and Surrounding Conditions on Fluid Flow in Paper-Based Devices.

Noosheen Walji,Brendan D Macdonald

doi:10.3390/mi7050073

Abstract

Fluid flow behaviour in paper is of increasing interest due to the advantages and expanding use of microfluidic paper-based analytical devices (known as µPADs). Applications are expanding from those which often have low sample fluid volumes, such as diagnostic testing, to those with an abundance of sample fluid, such as water quality testing. The rapid development of enhanced features in μPADs, along with a need for increased sensitivity and specificity in the embedded chemistry requires understanding the passively-driven fluid motion in paper to enable precise control and consistency of the devices. It is particularly important to understand the influence of parameters associated with larger fluid volumes and to quantify their impact. Here, we experimentally investigate the impacts of several properties during imbibition in paper, including geometry (larger width and length) and the surrounding conditions (humidity and temperature) using abundant fluid reservoirs. Fluid flow velocity in paper was found to vary with temperature and width, but not with length of the paper strip and humidity for the conditions we tested. We observed substantial post-wetting flow for paper strips in contact with a large fluid reservoir.

Highlights

Microfluidic paper-based analytical devices are a versatile technology capable of facilitating a variety of complex detection and diagnostic processes [1,2,3]
Processing and analyzing small fluid volumes is critical in many fields, in diagnostics, due to the availability of low fluid volumes and convenience associated with collecting small volumes of fluid, such as finger prick collection of blood samples. μPADs have been developed for a number of diagnostic analytical tests including infectious diseases [4,5,6], and cancer detection and investigation [7]. μPADs can be used for testing where larger fluid volumes are available as evidenced by the widespread application of μPADs for pregnancy testing using urine samples, and recently there has been a trend towards using μPADs in applications where an abundance of fluid is available, such as environmental testing, for water quality testing
Results and Discussion levels, the paper machine direction, and the dimensions of the paper strips including strip length and Experiments were conducted to study the influence of the surrounding temperature and strip width on the wicking behaviour of fluid in a paper strip fed from a large fluid reservoir

Summary

Introduction

Microfluidic paper-based analytical devices (μPADs) are a versatile technology capable of facilitating a variety of complex detection and diagnostic processes [1,2,3]. ΜPADs have been developed for a number of diagnostic analytical tests including infectious diseases [4,5,6], and cancer detection and investigation [7]. The availability of larger fluid volumes makes it possible to process more fluid through the devices, for example in cases where greater concentration may be desired; the μPADs can be designed with larger sizes and fed from large reservoirs, which can influence the fluid flow behaviour during wicking. To design μPADs capable of exploiting larger fluid volumes we require an understanding of how the parameters associated with larger fluid volumes, such as larger geometry and fluid reservoirs, influence the fluid flow behaviour

Methods

Results

Conclusion