In-Vivo and Ex-Vivo Measurements of Blood Glucose Using Whispering Gallery Modes

Abstract

The permittivity of blood glucose is not a strong function of its concentration in microwave or millimeter-wave frequencies. Measuring glucose concentrations remains a challenge, particularly in the presence of interference caused by the ambient leaky waves. In this paper, however, we demonstrate that a near-linear correlation between the glucose concentration and the blood permittivity was noticeably observed at a whispering gallery mode resonance. Method: the proposed sensor was a vacuum suction aspirator partially wounded with a turn of the Goubau line. This arrangement enabled a fixed cylindrical volume of a skin tissue bump or glucose/water solution to be formed and used as a whispering gallery resonator for in-vivo and ex-vivo measurements. Results: in the in-vivo study, a near-linear correlation between the glucose levels and the S21 parameters was noticeably observed at the fundamental whispering gallery resonance (i.e., at 2.18 GHz). In the ex-vivo study, a similar correlation was observed between the concentration of a glucose/water solution and the S21 parameters 56.6 GHz. Conclusion: the results of both investigations were consistent not only with the invasive measurements using the Accu-checkTM, but also with the conclusion drawn by some other research groups who have successfully measured blood glucose concentrations at millimeter-wave frequencies.

Dielectric coated conductive rod resonantly coupled with a cut transmission line as a tunable microwave bandstop filter and sensor

“…Nevertheless, the spoof-plasmon-based transmission lines usually exhibit higher attenuation than Goubau lines [ 14 ] and the latter is currently in the further development stage. A number of electronic devices have been proposed based on the concept of the Goubau line, to name a few, wideband transmission lines [ 4 , 15 ] and passive components [ 16 ], leaky-wave antennas [ 14 , 17 , 18 ], frequency-selective configurations [ 11 , 12 , 19 ], sensors [ [20] , [21] , [22] ], etc. In particular, Parker-Jervis et al designed a tunable bandstop filter in the THz spectrum using two coupled split-ring resonators integrated with a planar Goubau line and achieved a relatively high Q-factor around 60 at about 270 THz [ 19 ].…”

Noninvasive Glucose Sensing in Dielectrically Equivalent Multilayer Skin Phantoms

“…Minimally invasive measurements can be made with microneedle patches − or implantable sensors , consisting of glucose-responsive materials such as glucose oxidase ,, or phenylboronic acid gel. − Although securing enough glucose selectivity is a challenging issue, noninvasive measurements using electromagnetic waves, − ultrasonic waves, and magnetic resonance have great potential to liberate patients of the above-mentioned burden. In particular, gigahertz-band electromagnetic waves (microwaves) that penetrate the skin can be used to measure glucose in aqueous solutions, − saline solutions, − and hydrogels, − as well as in animals and humans. , In addition, there are various means of radiating radio waves, for example, open-ended coaxial probes, split-ring resonators, , microstripe antennas, patch antennas, cavity sensors, coplanar sensors, and multimodality analysis . Biomimetic homogeneous hydrogel phantoms − made of, for instance, gelatin, agarose, poly­(methyl methacrylate), and flour can be used in combination with computer simulations , for validation before the experiments are conducted on actual organisms.…”

“…In particular, gigahertz-band electromagnetic waves (microwaves) that penetrate the skin can be used to measure glucose in aqueous solutions, 23−26 saline solutions, 27−29 and hydrogels, 30−32 as well as in animals 11 and humans. 33,34 In addition, there are various means of radiating radio waves, for example, openended coaxial probes, 35 split-ring resonators, 36,37 microstripe antennas, 38 patch antennas, 39 cavity sensors, 40 coplanar sensors, 41 and multimodality analysis. 42 Biomimetic homogeneous hydrogel phantoms 43−46 made of, for instance, gelatin, 43 agarose, 44 poly(methyl methacrylate), 45 and flour 46 can be used in combination with computer simulations 47,48 for validation before the experiments are conducted on actual organisms.…”

High-Sensitivity, Quantified, Linear and Mediator-Free Resonator-Based Microwave Biosensor for Glucose Detection

“…Recently, researchers are using microwave sensing technology for blood glucose detection at the clinical level. Liu et al [ 25 ] proposed a microwave resonator-based glucose sensor based on the whispering gallery mode resonance technique for in vivo detection. The authors observed that the in vivo measurement was correlated with the ex vivo measurement (glucose/water solution).…”