Microaxicave colour analysis system for fluoride concentration using a smartphone

Abstract

People in northern China use underground water as their major water source. The fluoride in the water is threatening the health of the people. We demonstrate a fluoride concentration measurement method using a smartphone and microaxicave grating. The hue–value relation of the image captured by the smartphone and the results of a commercial spectrophotometer show great consistency, which indicates that the resolution of fluoride concentration of our system approaches 80 μg L⁻¹. We also use a rigorous coupled-wave analysis (RCWA) method, to calculate the diffractive efficiency of the microaxicave and it shows better performance than some commercial gratings in diffractive efficiency. Our fluoride detection system does not need any additional power or light supply and has a volume of 264 cm³ and a weight of 140 g, which can bring great convenience to fluoride detection in rural areas.