Simple microfluidic device for simultaneous extraction and detection of microplastics in water using DC electrical signal

Abstract

In this paper, we used DC electrophoretic force and electrical resistance measurement between two microwires in a microchannel to respectively extract and detect 1–10 μm polystyrene microplastics in water at 5–100 ppm concentration range. Ex situ microplastic detection methods like visual recognition and optical spectroscopy are expensive, time-consuming, and labor-intensive, highlighting the need for on-site rapid detection and quantification technologies. While micro-electro-fluidic devices have been introduced, they require advanced microfabrication and expensive signal processing instruments, while being prone to blockage with larger microplastics, limiting their point-of-need applications. We developed a simple wide PDMS channel equipped with two copper microwire electrodes, orthogonal to the flow direction and connected to a DC sourcemeter, for electrical resistance-based sensing of polystyrene microplastics in water. Electrical resistance between the two microwires was associated with microplastics’ size and concentration, following their electrophoretic accumulation around the positive electrode. A positive correlation was found between microplastic concentration and reduction in the normalized resistance. Reducing the flow rate strengthened the extraction and detection of larger microplastics. In the future, the sensor will be tested for other types of microplastics in real samples and can be integrated into a handheld device for low cost and on-site microplastic detection.