Many nucleic acid tests (NATs) rely on a DNA amplification step as the detection mechanism for pathogens, viral load, and so on.  Usually, DNA concentration is measured using a spectrophotometric instrument that costs tens of thousands of dollars.  In this paper, Heather Whitehead used an inexpensive dye that binds to DNA and a cell phone to measure the concentration of double stranded DNA in the same concentration range commonly used to analyze NAT results. The color of Nile Blue dye shifts from blue to blue-purple to blue  as it binds to DNA.  While it's been known for many years that Nile Blue dye changes color when it binds to DNA, and that property has been used to develop instrumental assays, Heather figured out that by using different concentrations of the Nile Blue dye and monitoring the red, green, and blue channel intensities, the concentration of double stranded DNA can be measured with an error of less than 10 ug/ml.  

Link is coming....