Current glucose monitoring methods for the ever-increasing number of diabetic people around the world are invasive, painful, time-consuming, and a constant burden for the household budget. The non-invasive glucose monitoring technology overcomes these limitations, for which this topic is significantly being researched and represents an exciting and highly sought after market for many companies. This review aims to offer an up-to-date report on the leading technologies for non-invasive (NI) and minimally-invasive (MI) glucose monitoring sensors, devices currently available in the market, regulatory framework for accuracy assessment, new approaches currently under study by representative groups and developers, and algorithm types for signal enhancement and value prediction. The review also discusses the future trend of glucose detection by analyzing the usage of the different bands in the electromagnetic spectrum. The review concludes that the adoption and use of new technologies for glucose detection is unavoidable and closer to become a reality.

A portable microwave system to detect traumatic brain injuries is described. The wideband system utilizes a unidirectional antenna, microwave transceiver, and processing and image reconstruction algorithms. The utilized antenna is designed to have a compact three-dimensional (3-D) structure using a slotted dipole element and a folded parasitic structure. It attains directional radiation patterns with an average 9-dB front-to-back ratio and 102.2% fractional bandwidth covering the band 1.1–3.4 $~$ GHz, which is suitable for head imaging. To test the system, a realistic head phantom, which attains accurate internal and external anatomical structure and electrical properties, is fabricated by a 3-D printer using a detailed numerical model. Targets imitating the properties of bleeding are inserted at different positions in the fabricated head phantom to emulate brain injury scenarios. The integrated system is used in a virtual arrayed monostatic radar approach to detect the injuries. Using data sets recorded at 32 antenna positions around the head, a back projection algorithm is used to generate images of the scanned head. The achieved results demonstrate the feasibility of such a system as a portable module for brain injuries detection.

Given the increased interest in a fast, portable, and on-spot medical diagnostic tool that enables early diagnosis for patients with brain stroke, a new approach of wearable electromagnetic (EM) head imaging system based on polymer material is proposed. A flexible low profile, wideband, and unidirectional antenna array with electromagnetic band gap (EBG) and metamaterial unit cells reflector is utilized. The designed antenna consists of a 4×4 radiating patch loaded with symmetrical extended open-ended U-slots and fed by combination of series and corporate transmission lines. A mushroom-like 10-EBG unit cell arrays are arranged around the feeding network to reduce surface waves, whereas 4×4 metamaterial (MTM) unit cells are placed on the back-side of the antenna to enable unidirectional radiation. The antenna is designed and embedded on a multi-layer low cost, low loss, transparent and robust polymer poly-di-methyl-siloxane (PDMS) substrate and optimized to operate in contact with the human head. The simulated and measured results show that the antenna has a fractional bandwidth of 53.8% (1.16 GHz - 1.94 GHz), more than 80% of radiation efficiency, and satisfactory field penetration in the head tissues with a safe specific absorption rate (SAR). An eight-element array is then configured on 300 × 360 × 4.1 mm3 PDMS material covering an average human head size and used as a worn part of the imaging system. A realistic-shaped 3D SAM head phantom is used to verify the performance of the designed array. The imaging results indicate the possibility of using the designed conformal array to detect a bleeding inside the brain using a confocal image algorithm.

A quantitative and explicit validation of the performance and safety of microwave systems and devices that have electromagnetic interaction with the human body is critical in the technological development process. Although a numerical model of the system environment can be ideally simulated, it cannot reflect the realistic environment that is vulnerable to various electrical, mechanical, and environmental interferences. Hence, the presence of the human body is the best measurement environment for these systems. However, newly designed devices/ systems that rely on the human body electromagnetic field interactions require multiple tests/measurements under a controlled environment. This environment is needed to validate the performance in all the possible scenarios of operation and make sure of the safety of those devices and systems. For example, a breast imaging system needs to be evaluated by detecting tumors in multiple locations, and it is unthinkable to do that on a real patient; hence, breast phantoms are needed to obtain an optimum system design and algorithms before moving to human clinical trials. Moreover, some experiments, such as the specific absorption rate (SAR) and hyperthermia, cannot be done on human beings due to the need to monitor the variation of the power intensity and temperature inside tissues. Employing live human participants for testing devices exposes the entire test procedure to several inherent uncertainties, such as respiratory movement, cardiovascular vibration, and variable skin humidity in addition, of course, to the safety concern of the new devices. Also, the application of the devices and systems on human subjects or human-related materials is a serious ethical issue where the researchers must receive an ethical clearance from the proper authorities, and it can be difficult to reasonably estimate and investigate the level of risks from various scientific, physical, and psychological aspects beforehand. Thus, the utilization of artificial tissue-emulating (ATE) phantoms is highly beneficial for testing a device or system.

An anatomically realistic human head phantom as a potential mean of experimentally validating microwave-based head imaging systems and other prominent applications is reported. Using an MRI-derived model, the phantom is 3-D-printed using a laser sintering material to represent the external tissue layers starting from the skull. The skull cavity is filled with the help of 3-D-printed molds with tissue-mimicking mixtures that are formed using low-cost ingredients. The included tissues are gray matter, white matter, Dura, CSF, eye, cerebellum, spinal cord, and blood. Our measurements indicate that the properties of the fabricated tissues are stable with time and agree with the real properties with less than 5% variation across the band 0.5-4 GHz, which is widely utilized in various imaging and mobile applications.