Abstract: Due to the growing concerns over heavy metal contamination and its adverse effects on environmental and public health, we propose a novel approach for non-contact detection of heavy metals, integrating microwave technology with bacterial inhibition sensing. Our sensor platform integrates a split ring resonator (SRR) with Escherichia coli immobilized on an agar plate, which is positioned near the SRR. It allows real-time monitoring of bacterial physiological changes in response to varying heavy metal concentrations. With a sensitivity of 0.2 dB/(μg∕mL), the sensor demonstrates over 95% inhibition of bacterial growth at 5 μg∕mL cadmium chloride (CdCl2) salt concentration, yielding a detection limit of 0.51 μg∕mL. This detection limit is 3–4 orders of magnitude lower than that reported for microwave-based biosensors in the literature. Additionally, its cleanroom-free, cost-effective fabrication, with a production cost of less than $5, and reusability make it suitable for widespread adoption. We validate our sensor for determining Cd2+ concentrations in environmental water by comparing its performance against the standard method, atomic absorption spectroscopy (AAS). Cadmium salts spiked at a concentration of 3 μg∕mL are analyzed. The Cd2+ concentrations measured by our sensor are in close agreement with those obtained using AAS. A future research effort should explore genetic engineering and synthetic biology techniques to enhance the performance of sensors for detecting multiple heavy metals at the same time with lower detection limits.
Microwave-based sensor for cadmium detection utilizing bacterial inhibition: A step toward non-contact heavy metal detection
