Microwave Glucose Sensing Using Double Circular Split Ring Resonators for Improved Sensitivity: The Role of Artificial Blood Plasma and Deionized Water
Diabetes affects more than 537 million people globally, and this number continues to rise. Accurate glucose monitoring is essential for managing the disease and preventing serious complications. However, current methods—such as finger-prick tests and continuous glucose monitors—can be costly, uncomfortable, or difficult to use consistently. Researchers worldwide are exploring innovative sensor technologies to make glucose monitoring more accurate, affordable, and user-friendly. Microwave-based sensing is a promising technology due to its non-ionizing properties, potential for continuous monitoring, and low cost.
In this work, researchers propose a microwave-based glucose sensor designed to improve sensitivity and reduce the cost and complexity of glucose monitoring systems. This sensor is still used in laboratories and requires a liquid sample. However, to make it non-invasive at this stage requires significant innovations that could influence future wearable or portable diagnostic devices.
The sensor utilizes a custom Double Concentric Circular Split Ring Resonator (DCCSRR) antenna, a variant of a standard ring antenna. These DCCSRRs are engineered for a narrow bandpass response within the 2.4–2.48 GHz ISM (industrial, scientific, and medical) band, widely used by wireless devices. The optimized DCCSRR was fabricated electronically, and silver nitrate was applied to its copper traces to prevent oxidation. This structure is highly responsive to small changes in the electromagnetic properties of the sample under test, allowing it to detect variations in glucose concentration with high sensitivity.
The sensor was tested over a wide glucose concentration range, from 0 to 400 mg/dL. It exceeded the range typically found in diabetic patients. The device detected concentration changes as small as 25 mg/dL, making it one of the most sensitive microwave sensors for glucose reported.
Many earlier studies have used DeIonized (DI) water as a reference solution to mimic blood plasma during testing. However, DI water lacks ions and other components found in real blood, thus significantly affecting the interaction with microwave signals. This can lead to inaccurate predictions when moving from the lab to real-world conditions.
The researchers have developed and characterized an Artificial Blood Plasma Solution (ABPS) that more closely replicates the dielectric properties of human plasma to tackle the shortcomings of DI water. When analyzed over the 500 MHz to 10 GHz frequency range, ABPS showed very different behavior from DI water—especially regarding signal losses, which are critical for accurate glucose detection. This makes ABPS a more suitable testing medium for developing microwave-based biomedical sensors.
Finally, since the sensor works in an unlicensed frequency band and is totally passive, it offers clear advantages in terms of cost, flexibility, and potential integration into future health monitoring systems. Although still in the experimental and development stage, this research lays the groundwork for next-generation glucose-sensing platforms that could become more comfortable, accurate, and accessible.
By advancing both sensor design and testing methodology, this study contributes significantly to the field of microwave biosensing and opens new pathways for improving diabetes management technologies.