Highly Sensitive Closed Loop Enclosed Split Ring Biosensor With High Field Confinement for Aqueous and Blood-Glucose Measurements

Abstract

This paper presents a highly sensitive closed loop enclosed split ring biosensor operating in microwave frequencies for measuring blood glucose levels in the human body. The proposed microwave glucose biosensor, working on the principle of high field confinement and concentrated energy, has been tested using both in-vitro and in-vivo methods. This principle allows the sensor to concentrate energy at the surface which results in improved accuracy of measurements. For in-vitro measurements, the biosensor has been tested using de-ionized water glucose solutions of different concentrations. The miniaturized micrometer scale biosensor is fabricated over a thin Si-substrate using photolithographic technique. The biosensor has been designed in a way to operate at desired microwave frequencies. Highly confined fields and concentrated energy inside the closed loop line containing the split ring resonators are responsible for the sensitivity enhancement. This new biosensor has obtained a high sensitivity of 82 MHz/mgmL −1 within the clinical diabetic range during in-vivo testing over the human body. In addition, the subjects (undergoing experiments) steady state has been continuously monitored throughout the experiment which helps in improving the accuracy of the results. The proposed biosensor has further obtained a low detection limit of <0.05 wt.% and can be useful for continuous non-invasive blood glucose monitoring.

Review of Recent Microwave Planar Resonator-Based Sensors: Techniques of Complex Permittivity Extraction, Applications, Open Challenges and Future Research Directions

“…However, there are certain drawbacks associated with the use of these techniques such as low electric field confinement, Q-factor, and sensitivity, which restrict their use in many applications and limit the range of permittivity detection. To enhance the sensitivity, the electric field must be highly confined on and around the sensor so that most of the energy will be concentrated on desired area [ 117 ]. Table 7 demonstrates the recent designs of microwave resonators aligned with the electric field profile.…”

Millimetre-Wave Metamaterial-Based Sensor for Characterisation of Cooking Oils

“…In this regard, metamaterial resonators offer higher sensitivity than other microwave sensors and they have been reportedly found to sense small variation in EM (electromagnetic) properties of the sample [12]. As a result, metamaterial-based sensors have been presented for dielectric characterisation of ethanol and methanol [13], assessment of dielectric substrates [14], blood glucose monitoring [15][16][17], measurement of material thickness [18], biomedical applications [19], detection of cancerous cells [20], and the evaluation of oils [21]. Metamaterials (MMs) are artificially engineered structures that exhibit negative permeability and permittivity simultaneously [22].…”

“…A substrate-integrated waveguide sensor for characterising chemicals at millimetrewave (mm-W) frequency range was presented in [26]. e researchers have proposed various techniques to increase the sensitivity of these sensors by creating a gap between complementary split-ring resonator (CSRR) [27], employing planar microwave resonators [10], and designing closedloop inside split-ring resonator [17].…”

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

“…The authors concluded that the obtained results were consistent with the readings of a standard glucometer for blood glucose detection. The design of microwave-based glucose sensors is focused on developing a device with high reliability, small size, low limit of detection (LOD), and fast response [ 27 , 28 , 29 ]. High reliability helps to obtain precise results, and a lower LOD is essential for label-free glucose detection [ 30 ].…”