Real‐time monitoring of Escherichia coli concentration with planar microwave resonator sensor

This work presents a microfluidic chip integrated with a microwave resonator sensor for real‐time and contactless detection of Escherichia coli bacteria concentration. The design is fabricated on a Rogers RT/duroid 5880 high‐frequency substrate and operates at 2.5 ∼ 2.6 GHz, in the ISM band, with an initial quality factor of 112. The presented sensor demonstrates resonant amplitude sensitivity of −0.01231 dB/log(OD600) and resonant frequency sensitivity of −56 kHz/log(OD600) for E. coli concentration in a constant pH of 7.5. To facilitate the analysis of the proposed structure, a lumped equivalent circuit is presented and simulated in ADS and proven accurate by both HFSS microwave simulations and experimental results.