We present a low-cost lab on a smartphone (LOS) platform for rapid and in-situ monitoring of fecal indicator bacteria (FIB) such as Escherichia coli (E. coli) to examine the presence and concentration levels of fecal contamination in environmental waters. To realize the LOS, three main components, a plasmonic-enhanced optoelectrowetting (OEW) device, a transparent heater, and a smartphone, are compactly assembled for on-chip water quality monitoring through loop-mediated isothermal amplification (LAMP) assays. The LOS integration with the OEW device enables pumpless and tubeless droplet manipulations for on-chip water sample preparation using a plasmonic-enhanced OEW technology. The integration with a transparent heater provides isothermal heating at 65 degrees C, where low-cost, portable LAMP assays are conveniently implemented on the LOS platform. Finally, a smartphone is used as an integrated optical detector to take digital images of target water samples during the LAMP reaction, while a time-dependent red-green-blue (RGB) analysis is performed for quantitative and accurate colorimetric study using a smartphone's image processing app. Experimentally, we have successfully demonstrated on-chip sample processing of water samples spiked with E. coli DNA and LAMP mixtures, and conducted in-situ isothermal LAMP amplifications of E. coli DNA, while obtaining the LAMP test results within 30 min, followed by an accurate time-dependent colorimetric assessment. The LOS platform truly offers a low-cost, portable, and fully integrated system for rapid, on-site detection for the presence of FIB and their associated pathogens in environmental water without the need for sophisticated laboratory equipment or skilled personnel.
