Abstract

A 3D Printed Lightbox for Enhancing Nitrate Detection in the Field Using Microfluidic Paper-Based Devices

Amer Charbaji, PhD Holder, University of Rhode Island

Paper-based microfluidic devices have demonstrated their capabilities of detecting low concentrations of analytes of interest in a variety of applications such as environmental monitoring, healthcare, food safety and have also found many other miscellaneous uses such as in portable fuel cells. The majority of these devices use colorimetric detection and can deliver qualitative or quantitative results at the point of care and without the need of specialized equipment for analysis. In general, paper-based microfluidic devices are made up of several different sections and may include portions that allow proper fluid manipulation and control. These devices have the advantage of being inexpensive, simple, portable and easy to use and allow sample flow across the different sections of the device without the need for a pump. This results in device miniaturization and cost savings which make them suitable for use by citizen scientists to help in collecting a large amount of data for analysis and decision making by policy makers. This also allows oceanographers and marine scientists to better choose locations from which they will collect their water samples in the field to send back to the lab for further analysis. Nitrate is the most stable form of nitrogen in oxygenated environments and the continuous measurement of its concentration in natural water bodies or in sources used for drinking water is of great importance to make sure that there isn’t any alarming increase. Recent advancements in paper-based technology allowed the enhanced detection of nitrate in water samples. Desktop scanners provide a simple and inexpensive method for capturing the colorimetric signal produced in the detection zone of paper-based devices; however, these scanners are not practical for use in the field. Previous work has shown that capturing the color produced by the Griess assay using a desktop scanner and analyzing its green component yields the best limits of detection and quantification. This can be attributed to the fact that green is the complimentary color of the visible pinkish red azo dye produced by the Griess reaction since the highest absorbance or light occurs at a wavelength that corresponds to that of visible green light. In this study, we build on our previous work and develop a 3D printed lightbox that utilize LEDs to deliver a portable imaging device. The LEDs emit green light with a wavelength that spans the range 495 to 555 nm for use with paper-based microfluidic devices utilizing the Griess assay for nitrate or nitrite detection in the field.