A compact SIR-IDC microwave sensor for high-concentration aqueous glucose solution detection

Purpose The purpose of this study is to develop a compact planar microwave resonant sensor for glucose-solution detection and to evaluate its sensitivity and temperature-compensation capability in high-concentration aqueous environments. Design/methodology/approach A stepped-impedance resonator (SIR) loaded with an interdigital capacitor (IDC) was designed, fabricated on Rogers RO5880 substrate, and integrated with a microfluidic channel. Glucose aqueous solutions from 1000–8000 mg/dL were measured at 5°C, 15°C, 25°C and 35°C using a vector network analyzer. Resonant frequency and resonant-point amplitude were analyzed, and polynomial temperature-compensation models were established. Findings The proposed sensor showed monotonic frequency and amplitude responses to glucose concentration. The frequency sensitivity reached approximately 1.04 × 10−5 /(mg/dL), while the amplitude sensitivity reached approximately 1.14 × 10−3 dB/(mg/dL). The temperature-compensation model reduced thermal interference and improved concentration estimation consistency across the tested temperature range. Originality/value The originality of this work lies in the compact integration of SIR and IDC within a 9 × 9 mm² sensing unit, which enhances electric-field confinement and strengthens interaction with liquid samples. The work also provides a dual-parameter characterization framework combining frequency/amplitude response with temperature compensation for high-concentration glucose-solution sensing.