In this article, which is a fundamental step in an underway research, a microwave resonant sensor at two resonance frequencies of 5.5 and 8.5 GHz (in order to increase the accuracy of the application) with a quality factor of 180 and 106, for blood glucose level monitoring is designed, fabricated, and tested by users’ fingertips. In this study, 11 volunteers were tested invasively (using a glucometer) and noninvasively (using the proposed glucose resonant sensor) with range of glucose-level changes from 89 to 262 mg/dL. For this range of glucose-level changes, the frequency detection resolution is 3.53 and 3.58 MHz/ (mg/dL), respectively. The results of the experiments are relatively well matched; so that compared to the glucometer device, the proposed sensor shows a maximum measurement error of about 3% to detect glucose levels.

Dual-Frequency Microwave Resonant Sensor to Detect Noninvasive Glucose-Level Changes Through the Fingertip

An ultra-high sensitive plasmonic refractive index sensor using an elliptical resonator and MIM waveguide

One of the most interesting topics in bio-optics is measuring the refractive index of tissues. Accordingly, two novel optical biosensor configurations for cancer cell detections have been proposed in this paper. These structures are composed of one-dimensional photonic crystal (PC) lattices coupled to two metal-insulator-metal (MIM) plasmonic waveguides. Also, the tapering method is used to improve the matching between the MIM plasmonic waveguides and PC structure in the second proposed topology. The PC lattices at the central part of the structures generate photonic bandgaps (PBGs) with sharp edges in the transmission spectra of the biosensors. These sharp edges are suitable candidates for sensing applications. On the other hand, the long distance between two PBG edges causes that when the low PBG edge is used for sensing mechanism, it does not have an overlapping with the high PBG edge by changing the refractive index of the analyte. Therefore, the proposed biosensors can be used for a wide wavelength range. The maximum obtained sensitivities and FOM values of the designed biosensors are equal to 718.6, 714.3 nm/RIU, and 156.217, 60.1 RIU-1, respectively. The metal and insulator materials which are used in the designed structures are silver, air, and GaAs, respectively. The finite-difference time-domain (FDTD) method is used for the numerical investigation of the proposed structures. Furthermore, the initial structure of the proposed biosensors is analyzed using the transmission line method to verify the FDTD simulations. The attractive and simple topologies of the proposed biosensors and their high sensitivities make them suitable candidates for biosensing applications. 

/pdf/optical-biosensors-using-plasmonic-and-photonic-crystal-band-9ic9ce9f.pdf

Optical biosensors using plasmonic and photonic crystal band-gap structures for the detection of basal cell cancer

Designing broadband absorbers with only one metamaterial layer operating in the terahertz band is a relatively difficult challenge. In this paper, we proposed and investigate a broadband metamaterial perfect absorber (MPA) based on the graphene disk and square ribbon. The conductive substrate of this structure is made of gold and the middle dielectric layer of this structure is made of Rogers RT5880LZ, which acts as a spacer layer between the gold and graphene layers. This structure, while having only one metamaterial layer, also has the advantage of easy implementation because the graphene embedded on the dielectric surface does not have a complex design. The simulation results show that the proposed absorber can provide absorption above 90% with a bandwidth of 2.173 ​THz (1.482–3.655 ​THz). The fractional bandwidth ratio of the proposed structure is 85% for absorption greater than 90%. The absorption mechanism of this structure based on electric fields has been investigated. Since the design of the proposed broadband MPA is symmetrical, this structure is not sensitive to polarization and has a good bearing angle in the range of 0–30°. The proposed structure is tunable because we can shift the absorption frequency by changing the Fermi level of graphene (μ c ). The proposed absorber with these properties is suitable and flexible for applications such as sensing, imaging, and spectroscopy. • The structure has the advantage of easy execution due to its single-layer metamaterial and simple design. • The bandwidth of the structure for absorption above 90% is equal to 2.173 ​THz (1.482–3.655 ​THz). • The structure is tunable without the need for structural changes. • The structure has behaviors such as insensitivity to polarization and high tolerance to the incident angle. • The structure is suitable for applications such as sensing, imaging and spectroscopy. 

Broadband polarization insensitive and tunable terahertz metamaterial perfect absorber based on the graphene disk and square ribbon

Diabetes is a chronic and, according to the state of the art, an incurable disease. Therefore, to treat diabetes, regular blood glucose monitoring is crucial since it is mandatory to mitigate the risk and incidence of hyperglycemia and hypoglycemia. Nowadays, it is common to use blood glucose meters or continuous glucose monitoring via stinging the skin, which is classified as invasive monitoring. In recent decades, non-invasive monitoring has been regarded as a dominant research field. In this paper, electrochemical and electromagnetic non-invasive blood glucose monitoring approaches will be discussed. Thereby, scientific sensor systems are compared to commercial devices by validating the sensor principle and investigating their performance utilizing the Clarke error grid. Additionally, the opportunities to enhance the overall accuracy and stability of non-invasive glucose sensing and even predict blood glucose development to avoid hyperglycemia and hypoglycemia using post-processing and sensor fusion are presented. Overall, the scientific approaches show a comparable accuracy in the Clarke error grid to that of the commercial ones. However, they are in different stages of development and, therefore, need improvement regarding parameter optimization, temperature dependency, or testing with blood under real conditions. Moreover, the size of scientific sensing solutions must be further reduced for a wearable monitoring system.

/pdf/commercial-and-scientific-solutions-for-blood-glucose-2l33ztg2.pdf

Commercial and Scientific Solutions for Blood Glucose Monitoring—A Review

In this paper, a Mercedes-Benz logo antenna with a metal plate located at an optimized distance from the proposed antenna is introduced as a wearable antenna to operate in the industrial, scientific, and medical band with center frequency of 2.45 GHz. The metal plate is integrated with the antenna as an isolator and a reflector to improve the radiation performance of the proposed design, reduce the back radiation and reduce the specific absorption rate, when loaded on the human body. The front-to-back ratio improves by 18.2 dB, by adding a metal plate to the structure. The proposed antenna with coplanar waveguide-fed with dimensions of 35 mm × 35 mm × 0.508 mm is printed on a Rogers 4003C substrate, and has an impedance bandwidth from 2.20 to 2.56 GHz, the gain of 7.3 dBi at 2.45 GHz, and SAR levels is less than the criteria set by the FCC and ICNIRP. Nowadays, attention to health as product quality assurance factor along with other technical specifications is the requirements of industrial productions, especially in competition with superior brands. Based on comparisons made with similar works, the proposed wearable antenna structure can be used for wireless body area network.

A CPW-fed wearable antenna at ISM band for biomedical and WBAN applications

Microwave sensors based on electrically small planar resonant elements are investigated in this season. Due to the high sensitivity of these resonators to the properties of their environment, especially the dielectric constant and the loss coefficient, these sensors are of particular importance for the dielectric characterization of solids and liquids and for measuring the composition of materials. This chapter also deals the main advantages and limitations of planar microwave resonant sensors, and several prototypes are reported, mainly including sensors for measuring the dielectric properties of solids, and sensors based on microfluidics (useful for liquid characterization and liquid composition). The proposed sensors have great potential for use in real scenarios (including industrial processes and characterization of bio-samples).

An Overview of Interdigitated Microwave Resonance Sensors for Liquid Samples Permittivity Detection

In this paper, a leaky-wave antenna based on substrate integrated waveguide is introduced with continuous beam scanning from backward-to-forward through broadside. A new two-part unit cell has been used to achieve the continuous beam without drop of gain in the broadside. This suppresses the open stop-band, the broadside radiation gain would be without a drop, and the side lobe level is kept low. The wide operating bandwidth is obtained, which covers from 11.7 to 19.6 GHz. It is observed that S11 is below − 10 dB from 11.5 to 20 GHz, and the average S21 is − 8.5 dB from 11.5 to 20 GHz. Scanning of this antenna is continuous and covers all angles between − 61° to + 34°. The gain in the direction of the broadside beam is equal to 14.2 dB and without a drop. The gain changes are low in the operating frequency and the average gain is 14.1 dB in this antenna, also the average side lobe level is − 12 dB. The average radiation efficiency of this proposed antenna is 73%.

A symmetrical SIW-based leaky-wave antenna with continuous beam scanning from backward-to-forward through broadside

In this paper, a novel compact planar coronavirus antenna is proposed for wide band applications. In the design of this antenna, the idea of the radiating part has been taken from the 3-D model of the coronavirus, which is fed by a 50 Ω coplanar waveguide. The patch structure and the feed line of the proposed antenna, which have been made of gold, are located on a polyamide substrate with a thickness and dielectric constant of 45 µm and 3.5, respectively, and the antenna has compact physical dimensions of 300 × 300 µm2. The simulation results of the antenna have been analyzed in terms of S11, VSWR, radiation pattern, gain and surface current distribution. The designed antenna covers the frequency band from 0.3627 to 0.5918 THz for S11 ≤ − 0 dB with a fractional bandwidth of > 47.98% and with a bandwidth ratio of 1.63:1. This extended bandwidth coverage allows the antenna to be suitable for a wide range of applications including wireless communications, internet of things, wearable devices, on-chip antennas and multiple-input multiple-output systems. Also, the results of the far-field show an omnidirectional radiation pattern with an average gain and efficiency of 4 dBi and 93% throughout the frequency band, respectively. 

/pdf/on-chip-coronavirus-shape-antenna-for-wide-band-applications-2qf53xrg.pdf

Mina Fakhr

Papers

Dual-Frequency Microwave Resonant Sensor to Detect Noninvasive Glucose-Level Changes Through the Fingertip

A CPW-fed wearable antenna at ISM band for biomedical and WBAN applications

An Overview of Interdigitated Microwave Resonance Sensors for Liquid Samples Permittivity Detection

A symmetrical SIW-based leaky-wave antenna with continuous beam scanning from backward-to-forward through broadside

On-chip coronavirus shape antenna for wide band applications in terahertz band