developed for the detection of Salmonella and E. coli. The latter device was specifically used to detect E. coli in seven field water samples from Tucson, Arizona. Antibody-conjugated polystyrene particles were loaded in the middle of the microfluidic channel, after the sample inlet. Immunoagglutination occurs when samples containing Salmonella or E. coli, respectively, come into contact with these particles. The amount of immunoagglutination can be correlated with increased Mie scattering of light, which was detected with a specialized smartphone application under ambient light. Paper-based microfluidics has also been used to detect pesticides in food products, such as apple juice and milk. A recent design used piezoelectric inkjet printing to imprint paper with the enzyme acetylcholinesterase (AChE) and the substrate indophenyl acetate (IPA), and this paper-based microfluidic device was used to detect organophosphate pesticides (AChE inhibitors) via a decrease in blue-purple color. This device is distinguished by its use of bioactive paper instead of compartments with pre-stored reagents, and it was demonstrated to have good long-term stability, making it ideal for field use. A more recent paper-based microfluidic design utilized a sensor, consisting of fluorescently labeled single-stranded DNA (ssDNA) coupled with graphene oxide, on its surface to simultaneously detect heavy metals and antibiotics in food products. Heavy metals increased fluorescence intensity, whereas antibiotics decreased fluorescence intensity. Recently, paper-based devices have become very attractive for making inexpensive, disposable and convenient analytical devices for the determination of reactive phosphate in water. These devices utilize the molybdenum blue protocol for phosphate detection. References Microfluidics