A Portable Handheld Microfluidic Colorimetric Device for the Detection of Organophosphorus Pesticides

The increasing usage of organophosphorus pesticides (OPs) has posed a public concern. To tackle these concerns, we developed a portable microfluidic device with integrated electronics and the Internet of Things (IoT) capabilities for rapid and on-site OP residue detection. Malathion, chlorpyrifos, dimethoate, and a mix of eight pesticides were chosen for device calibration owing to their wide usage in agriculture. The developed device works on the colorimetric principle and consists of an optoelectronic circuit comprising an LED-photodiode detection unit, a transimpedance amplifier unit, a microcontroller (MC), and a filter circuit. The miniaturized device is powered using a 9-V power supply and housed in a 3-D-printed enclosure. A PDMS-based microfluidic chip was developed for facilitating the molybdenum-based chemical reaction with split and recombine and spiral micromixers for mixing. The device could detect pesticides within the maximum residual limits as reported by international food standards with a limit of detection (LoD) for malathion, chlorpyrifos, dimethoate, and OP mix found to be 2.35, 0.20, 0.63, and 0.07 ppm, respectively. The findings substantiated that the developed rapid, low-cost point-of-care testing (POCT) device is an integrated solution for the nondestructive detection of OP residues in citrus fruits and vegetables, thus exploring the arenas of POCT devices for various food safety applications in limited resource settings.