A new fluidic MEMS-based mercury ion sensor for water sources

Mercury detection is essential for ensuring the safety and environmental responsibility of clean energy technologies. This sensor can be used to detect mercury in water sources to remove the toxic pollutant from water effectively. Our proposed sensor addresses this demand by accurately detecting mercury ions through its mass-sensitive properties. The novelty of this sensor stems from two key aspects: first, the incorporation of a highly mercury-sensitive gold layer on the active area to enhance its capabilities and specificity to mercury ions; and second, its unique integration with a digital microfluidic system without any pump and microchannel. This system is fully compatible with microelectromechanical systems (MEMS) technology and can be used in conjunction with, or as part of, clean energy systems. This integration is crucial as it facilitates the delivery of deionized water droplets containing mercury ions to the sensing area. The sensor employs comb-drive electrodes to actuate its resonator in an in-plane mode, which causes its surfaces to slide parallel to the liquid interface. This leads to the mass and stiffness changes in the central resonator and consequently, a measurable frequency shift. Finite element analysis of the mechanical behavior of the sensor demonstrated a quality factor of 651 at a resonance frequency of 351.96 kHz for the resonator. Furthermore, the sensor exhibits a high sensitivity of approximately 105 Hz/ppb, highlighting its potential for trace mercury detection.