Microstrip Feed Loop Enclosed Resonant Biosensor

In this article, a novel resonator design of a planner microwave sensor for biosensing applications is proposed. The sensor consists of double asymmetric split ring resonators (SRRs) enclosed by a feeding loop. This design leads to high electric field confinement at the sensing area, yet low loss that leads to a high level of sensitivity. The sensor was designed to address various tradeoffs, such as physical dimensions versus a suitable frequency for acceptable penetration depth. The numerical and experimental results are in very good agreement with each other. The resonance frequency shift that appears in the transmission amplitude coefficient as a result of coating a dielectric material on the sensor was the main metric to evaluate the sensitivity. This shift was found to be well-correlated to the change of the dielectric constant of the coated material. The results demonstrate the applicability of the sensor to detect small changes in the dielectric constant. The sensitivity of the biosensor is presented as the coated material thickness varies. Most importantly, this sensor can be utilized to detect a very small amount of analyte with a thickness of one-thousandths of the operation wavelength. The response shows that the frequency shift follows an exponential model as the thickness increases. The design possesses a very high sensitivity of 4.3×105 nm/RIU/mm3. Therefore, the proposed design of the biosensor would ultimately be a great choice to be incorporated with such detection systems for biological substances.