Abstract
In this study, we propose a high-performance resonator-based biosensor for mediator-free glucose identification. The biosensor is characterized by an air-bridge capacitor and fabricated via integrated passive device technology on gallium arsenide (GaAs) substrate. The exterior design of the structure is a spiral inductor with the air-bridge providing a sensitive surface, whereas the internal capacitor improves indicator performance. The sensing relies on repolarization and rearrangement of surface molecules, which are excited by the dropped sample at the microcosmic level, and the resonance performance variation corresponds to the difference in glucose concentration at the macroscopic level. The air-bridge capacitor in the modeled RLC circuit serves as a bio-recognition element to glucose concentration (), generating resonant frequency shifts at 0.874 GHz and 1.244 GHz for concentrations of 25 mg/dL and 300 mg/dL compared to DI water, respectively. The proposed biosensor exhibits excellent sensitivity at 1.38 MHz per mg/dL with a wide detection range for glucose concentrations of 25–300 mg/dL and a low detection limit of 24.59 mg/dL. Additionally, the frequency shift and concentration are highly linear with a coefficient of determination of 0.98823. The response time is less than 3 s. We performed multiple experiments to verify that the surface morphology reveals no deterioration and chemical binding, thus validating the reusability and reliability of the proposed biosensor.
Highlights
On the sensing section, the microcosmic variations in surface molecules and macroscopic responses are analyzed. The former analysis depends on two kinds of effect: the introduction of glucose and water molecules affects the electromagnetic field distribution, and the existing electromagnetic wave contributes to the polarization of the molecules
The proposed glucose microwave biosensor was developed on the basis of a resonator, wherein the resonant frequency was determined by the total inductance (Ltotal ) and capacitance (Ctotal ), as indicated in Equation (1) [22]
Before performing glucose identification experiments, we investigated the reliability of the biosensor based on the consistency of performance derived from multiple experiments with the 150 mg/dL glucose solution at the macroscopic level (Figure 4a)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. After dropping the SUT on the sensing section, the microcosmic variations in surface molecules and macroscopic responses are analyzed The former analysis depends on two kinds of effect: the introduction of glucose and water molecules affects the electromagnetic field distribution, and the existing electromagnetic wave contributes to the polarization of the molecules. The overall transmission characterization is changed by the combined effect, reflected in S-parameter changes The latter analysis utilized the air-bridge capacitor as the bio-recognition element to SUT permittivity, responding proportionally to ε glucose C0 and resulting in a substantially higher sensitivity of 1.38 MHz per mg/dL than described in existing reports. We investigated the reusability and repeatability through multiple experiments of surface morphology to validate the high performance of the biosensor
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