Title : Low-cost, flexible, and portable sensors manufacturing for microplastic monitoring in aqueous environment
Microplastics (MPs) pollution, particularly in fresh and marine ecosystems, have become a growing environmental problem and concerns. MPs not only have a ubiquitous presence but also serve as carriers of other contaminants due to its adsorption capacity such as heavy metals and pharmaceutical compounds. Despite the ubiquity of MPs, the ability to characterize MPs in the environment is challenged by the scarcity of technologies for rapidly and precisely identifying and quantification of MPs. Although guidelines have been established for the collection and preparation of MPs samples, the methods of MPs analysis are highly variable and provide data with a broad range of data content and quality. In addition, existing quantification methods tend to lack flexibility and transferability as well as the capacity for continuous in situ monitoring is often prohibitively expensive.
This project aims to explore methods for the flexible, simple, and cost-effective printing sensors based on nanomaterials (Silver nanoparticles- Ag NPs and Carbon nanotubes - CNTs) through capacitance and impedance measurements to detect and quantify MPs either by sampling and/or, preferably, in situ monitoring. For that purpose, procedures for optimized CNTs and Ag NPs inks will be presented, and the resulting products will be characterized for morphological (Scanning Electron Microscopy-SEM, Transmission Electron Microscope -TEM), chemical (Energy-dispersive X-ray spectroscopy - EDS, X-ray Diffraction – XRD and Raman spectroscopy) and physical properties (electrical properties: electrical conductivity, Seebeck effect).
Impedance spectroscopy will be applied to infer the electrical properties of particles directly in a liquid medium using a micrometric interdigital configuration. Measurements were carried out in 5 different configurations fabricated by screen printed technique on a PET substrate and using the optimized prepared nanomaterial inks. Different electrode thickness and electrode gap settings were tested. It was found that capacitive sensors with a higher number of interdigitated legs presented the greatest sensitivities. A series of microplastic (Polystyrene) solutions with concentrations of 0.1, 0.2, 0.4, 0.6, 0.8 and 1 g/L with 1-50 µm size was prepared in ultrapure water. The impedance spectroscopy was characterized in the range between 20 Hz until 3 MHz. The comparison between the influence of the Ag NPs and CNTs will be discussed, namely the role of CNTs MPs adsorption. At the end it will be presented future trends where this method could be applied for MPs detection.