Fig. 7
From: Challenges in paper-based fluorogenic optical sensing with smartphones
(reproduced from [88] with permission, © 2017 Royal Society of Chemistry)
Smartphone attachment utilizing the onboard “white” LED flash as a light source, using pulse excitation to address the paper's autofluorescence, for detecting human chorionic gonadotropin (hCG) on LFA strip: a smartphone's flash is turned on for short excitation; b flash is turned off showing luminescence imaging