Plasmonic Metamaterial-Based High-Sensitivity Microwave Sensor for Contactless Glucose Monitoring

This paper presents a highly sensitive mi-crowave sensor for the contactless and real-time moni-toring of glucose solutions, which is based on the cou-pling between a spoof surface plasmon polariton (SSPP) transmission line and a spoof localized surface plasmon (SLSP) resonator. The sensor achieves deep-subwavelength field confinement of the electro-magnetic field and supports slow-wave propagation, thereby enhancing light-matter interaction via slow-wave dispersion engineering between the electromagnetic waves and the sample under test. This effectively miti-gates the strong absorption of microwave energy by water molecules in aqueous samples, leading to en-hanced sensing sensitivity. By analyzing the resonance frequency shifts and the variations in transmission co-efficient magnitude within a specific frequency band, the sensor enables high-precision discrimination among glucose solutions of different concentrations. Experimental results demonstrate that the sensor exhibits an excellent linear response within the concentration range of 0–200 mg/mL. The maximum resonance sensing sensitivity is 91.31×10-2MHz/mgmL-1, and the maximum transmission-based sensing sensitivity is 1.32×10-2dB/mgmL-1, which shows a fair improvement in the sensitivity as compared to the state-of-the-art work. This work thus provides a low-cost, high-precision, real-time, and continuous monitoring solution for aqueous biological applications and industrial bio-processing, such as food production and liquid analysis.