Ultra-sensitive and rapid detection of perfluorooctanesulfonic acid by a capacitive molecularly-imprinted-polymer sensor integrated with AC electrokinetic acceleration

Abstract

The development of point-of-use sensors capable of rapidly detecting per- and polyfluoroalkyl substances (PFAS) is crucial for real-time monitoring and effective management of PFAS contamination in the aquatic environment. Addressing current limitations in existing techniques for sensitive in-field analysis, this work employs a multifaceted approach to develop a rapid, ultra-sensitive, and single-step sensing platform for perfluorooctanesulfonic acid (PFOS). The approach integrates self-referencing interfacial capacitance sensing with microfluidic enrichment by AC electrothermal (ACET) effect. A molecular imprinted polymer (MIP) on gold interdigitated microelectrode chip is employed as a robust recognition element for the affinity-based capture of PFOS. A predetermined AC signal applied to the sensor will not only accelerate PFOS molecules towards the sensing surface for binding, but also track the interfacial capacitance change during binding, enabling real-time detection with extremely high sensitivity. The resulting single-step and rapid assay demonstrates detection as low as 0.5 fg/L (5×10−7 ppt) in 10 s, a linear range of 0.5–500 fg/L (5×10−7–5×10−4 ppt), and high selectivity (105:1) in Phosphate-buffered saline (PBS) media against other PFAS compounds including perfluorooctanoic acid (PFOA). The success of this work will potentially provide a routine PFOS monitoring test for drinking water.