Microwave reflective biosensor for glucose level detection in aqueous solutions

This article presents the design and analysis of a real-time non-invasive microwave microfluidic sensor for measuring glucose concentration in aqueous solutions. The sensor is made of an open-ended microstrip transmission line loaded with a complementary split-ring resonator (CSRR). The CSRR shows a very intense electric field concentration at resonance, which is highly sensitive to the dielectric sample loading. A microfluidic channel is designed to deliver the glucose solutions to the sensitive area of the device. By applying liquid samples to the channel, a resonance frequency shift is detectable in the reflection coefficient (S11) of the device. This in turn leads to a change in the |S11|. Both of the frequency shift and Δ|S11| can be used to measure the glucose level in the solution. Mathematical models are developed based on the measurement results of the glucose-water solutions using the resonance frequency shift and Δ|S11|. The developed sensing models are then used for detecting the glucose levels down to physiological values using the designed biosensor. The results prove the potential compatibility of the proposed biosensor for human glycaemia monitoring.