Application of Broadband Microwave Near-Field Sensors for Glucose Monitoring in Biological Media

Abstract

The paper presents results of numerical simulation and experimental testing of a microwave sensor for non-invasive glucose monitoring. The sensor represents a conical horn with a conical conductor inside expanding toward the horn aperture. Such a sensor has a significantly wider passband in comparison with sensors of other designs. It is essential that the sensor geometry provides formation of an extended near-field zone with high electric field strength near the sensor aperture. A clear relationship between the dielectric permittivity of the phantom biological tissue and the frequency dependence of the parameter S11 of the sensor is observed at frequencies in the range from 1.4 to 1.7 GHz. This circumstance can be used to develop a procedure for measuring the glucose level in blood that correlates with the parameter S11 of the sensor. From the viewpoint of monitoring of the glucose content in blood, the most convenient body sensor location is on the hands or feet, in particular, wrists.

Commercial and Scientific Solutions for Blood Glucose Monitoring—A Review

“…This significantly depends on the chosen operating frequency, which defines the penetration depth. The working frequencies are mostly in the range of 0-6 GHz [32,92,[95][96][97]99,104,105,[138][139][140], and the others are in the range of 10-20 GHz [93,98]. In general, the higher the frequency, the lower the penetration depth.…”

“…In the literature, there are three methods discussed for detecting the change of the permittivity and the corresponding BGL: shift of resonance frequency [99][100][101][102][103], reflection (S 11 ) [32,96,98,104,105,111] or transmission (S 21 ) [32,110,112] of the amplitude or phase of the S-Parameters. S. Zeising et al [98] stated that the phase variation of S 11 is more sensitive than of S 21 .…”

“…Based on the different levels of development of the proposed sensor systems in the literature, the archived accuracy varies significantly. Several researchers demonstrated only a proof of concept of their approach, by simulating [98] and measuring [92,93,95,104,105] physical parameters such as S 11 or S 21 . All of them showed that the amplitude and phase as well as the resonance frequency depend on the glucose concentration; however, a specific determination on their measured BGL was missing.…”

First Microwave Tomography Approach Towards a Truly Noninvasive, Pain-Free and Wearable Blood Glucose Monitoring Device

“…The sensor showed frequency shifts of approximately 0.94 MHz/(mg/dl) in response to glucose level variation in blood samples. Another microwave sensor based on a conical horn with a conical conductor for noninvasive glucose monitoring is presented in [15]. The resulting relationship between the dielectric permittivity of the biological tissue phantom and the frequency dependence of the sensor parameter S 11 is obtained at frequencies between 1.4 and 1.7 GHz.…”

Microwave Spoof Surface Plasmon Polariton-Based Sensor for Ultrasensitive Detection of Liquid Analyte Dielectric Constant

“…Due to their possibility for real-time, non-contact and non-invasive measurements, microwave sensors present an excellent solution for a wide range of applications, including dielectric constant sensing [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ], food quality control [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ], gas sensing [ 20 , 21 , 22 ], detection of biomolecules [ 23 , 24 ], glucose monitoring [ 25 , 26 ], measurements of concentration for liquid solutions [ 27 , 28 ], microwave imaging [ 29 , 30 ], and mechanical motion sensing [ 31 , 32 ]. They can also be combined with other technologies, including microfluidics, which provide compact and cost-effective platforms for rapid detection in small amounts of liquid samples [ 33 , 34 , 35 , 36 ].…”