Paper Microfluidic Detection of Salmonella Using a Smart Phone

We describe a novel demonstration of latex immunoagglutination assay in a paper microfluidics format and subsequent Mie scatter detection using the smart phone’s flash and digital camera as optical sensing platform. The background noise was eliminated through careful optimization of Mie scatter parameters: the diameter of latex beads, surfactant concentration, the angle of scatter detection, etc. The detection limit was 10 CFU/mL for Salmonella typhimurium using the paper microfluidics and smart phone. This method can be used for any field deployable assays (demonstrated for foodborne pathogens here; can be used for medical, veterinary, and environmental diagnostics) and is low-cost, easy-to-use, near-real-time and handheld.