Lab on a smartphone (LOS): A smartphone-integrated, plasmonic-enhanced optoelectrowetting (OEW) platform for on-chip water quality monitoring through LAMP assays
Si Kuan Thio, Sung Woo Bae, Sung-Yong Park
Abstract
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 °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.