Real-time measurement of human salivary cortisol for the assessment of psychological stress using a smartphone

We present a simple smartphone-based measurement system consisting of a smartphone, a holder, and a lateral flow immune strip. The smartphone camera and light source were used to read the colorimetric signal from the lateral flow assay. A smartphone application was written and installed onto the smartphone. Various concentrations of cortisol were successfully measured using the images captured by the smartphone. Measurement of human salivary cortisol was then demonstrated using the lateral flow assay and the quantitative analysis was validated with the smartphone. The system was further evaluated using human saliva, demonstrating an accurate and reproducible platform for rapid and point-of-care quantification of cortisol using a smartphone-based measurement system.