Microwave

Bacteria

Biology

Materials science

Chromatography

Telecommunications

Computer science

Biosensor

Genetics

Physics

Agar

Nanotechnology

Resonator

Bacterial growth

Analytical Chemistry (journal)

Chemistry

Agar plate

Optoelectronics

IEEE Transactions on Biomedical Circuits and Systems

Microwave resonator sensors are attractive for their contactless and label-free capability of monitoring bacterial growth in liquid media. This paper outlines a new label-free microwave biosensor based on a pair of planar split ring resonators for non-invasive monitoring of bacterial growth on a solid agar media. The sensor is comprised of two split ring resonators with slightly different resonant frequencies for differential operation. The transmission coefficient (S 21 ) of the sensor is considered as the sensor's response with a designed and measured quality factor above 200 to ensure a high-resolution operation of the biosensor. Two resonant frequencies of 1.95 and 2.11 GHz represent the sensing signal and the reference signal, respectively. The developed sensor demonstrates high performance in monitoring the growth dynamics of Escherichia coli (E. coli) on Luria-Bertani (LB) agar with 4 mm thickness. The sensor's resonant amplitude response demonstrated 0.5 dB variation corresponding to the bacterial growth over 48 hours when bacteria were spread on LB agar starting with initial OD 600 = 1.5. Moreover, 0.6 dB change in the sensor's response was observed over 96 hours of bacterial growth starting with an initial OD 600 = 1.17 spotted on LB agar. The measured results fit well to the curves created using Richards' bacterial growth model, showing the strength of the sensor as a potential candidate for use in predictive food microbiology systems.

A Label-Free, Non-Intrusive, and Rapid Monitoring of Bacterial Growth on Solid Medium Using Microwave Biosensor