Top and bottom microelectrode glass slide sandwiches a channel made of adhesive tape and packed with reduced graphene oxide to make a new non-planar interdigitated microfluidic device. Novel device integration allows packing of any transducer material at room temperature with no instrument. Electrical impedance spectroscopy signal is stable over long times, fits an equivalent circuit with well-defined circuit elements. Flow visualization concurs that electric double-layer signal shifts to high frequency due to disruption of the diffusive process from increased convective flow. Charge transfer resistance appears at higher frequencies making the device rapid with high signal to noise ratio.

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Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are human-made chemicals with high chemical resistance and thermal stability. The extremely stable fluoro-carbon (F-C) skeletons enable PFAS molecules can exist stably in nature especially in the water sources for a long time concerning thermal, chemical, and biodegradation. Perfluorooctanoic acid (PFOA) is one of the most dominant environmental contributors, and its half-life in water has been estimated to be longer than 92 years. Therefore, the monitoring of PFOA level in the water source is needed. It is reported that Zirconium (Zr) based metal-organic frameworks (MOFs) have shown considerable affinity to PFOA molecules. In addition, electrochemical impedance spectroscopy (EIS) as a rapid and sensitive detection method (based on measuring the impedance changes at the electrode/solution interface) is perhaps the most frequently used technique in the investigation of affinity-based transducers. In the pursuit of building a highly efficient screening sensor to PFOA molecules. In this work, the application of Zr based MOF in NP-μFEC as a combined sensing platform to PFOA molecules is conducted. Here, the NP-μFEC is our group proposed new impedance sensing platform with enhanced, three-dimensional distributed electric field. To validate the feasibility of Zr based MOF packed NP-μFEC’s sensing performance. The work is conducted with a ranging concentration of PFOA (in 0.1X PBS) from 150 to 10 ng/L. We finally find that the proposed combination of Zr based MOF and NP-μFEC can show an excellent response to the PFOA molecules, which offers a detection limit lower than the established US Environmental Protection Agency (EPA)'s water contamination level (70 ng/L).

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