We report on the numerical simulations and experimental validation of a microwave planar sensor based on two coupled rings operating in the 4–6 GHz range. The fabricated sensor is used to characterize the dielectric permittivity of vegetable oils. We optimized the geometrical parameters in order to improve the overlap between the oil samples under study and the electric field. The experimental results showed an excellent match with the simulation results. The fabricated sensor allowed to retrieve the oil permittivity with a sensitivity of about 35 MHz per permittivity unit in the frequency range of interest. This paves the way to the realization of compact and sensitive sensors for a wide plethora of fields ranging from industry and food to chemistry and biology.

Graphene is a material with exceptional optical, electrical and physicochemical properties that can be combined with dielectric waveguides. To date, several optical devices based on graphene have been modeled and fabricated operating in the near-infrared range and showing excellent performance and broad application prospects. This paper covers the main aspects of the optical behaviour of graphene and its exploitation as electrodes in several device configurations. The work compares the reported optical devices focusing on the wavelength tuning, showing how it can vary from a few hundred up to a few thousand picometers in the wavelength range of interest. This work could help and lead the design of tunable optical devices with integrated graphene layers that operate in the NIR.

Advances in wearable device technology pave the way for wireless health monitoring for medical and non-medical applications. In this work, we present a wearable heart rate monitoring platform communicating in the sub-6GHz 5G ISM band. The proposed device is composed of an Aluminium Nitride (AlN) piezoelectric sensor, a patch antenna, and a custom printed circuit board (PCB) for data acquisition and transmission. The experimental results show that the presented system can acquire heart rate together with diastolic and systolic duration, which are related to heart relaxation and contraction, respectively, from the posterior tibial artery. The overall system dimension is 20 mm by 40 mm, and the total weight is 20 g, making this device suitable for daily utilization. Furthermore, the system allows the simultaneous monitoring of multiple subjects, or a single patient from multiple body locations by using only one reader. The promising results demonstrate that the proposed system is applicable to the Internet of Healthcare Things (IoHT), and particularly Integrated Clinical Environment (ICE) applications.

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Through the years, inspiration from nature has taken the lead for technological development and improvement. This concept firmly applies to the design of the antennas, whose performances receive a relevant boost due to the implementation of bio-inspired geometries. In particular, this idea holds in the present scenario, where antennas working in the higher frequency range (5G and mm-wave), require wide bandwidth and high gain; nonetheless, ease of fabrication and rapid production still have their importance. To this aim, polymer-based 3D antennas, such as Dielectric Resonator Antennas (DRAs) have been considered as suitable for fulfilling antenna performance and fabrication requirements. Differently from numerous works related to planar-metal-based antenna development, bio-inspired DRAs for 5G and mm-wave applications are at their beginning. In this scenario, the present paper proposes the analysis and optimization of a bio-inspired Spiral shell DRA (SsDRA) implemented by means of Gielis’ superformula, with the goal of boosting the antenna bandwidth. The optimized SsDRA geometrical parameters were also determined and discussed based on its fabrication feasibility exploiting Additive Manufacturing technologies. The results proved that the SsDRA provides relevant bandwidth, about 2 GHz wide, and satisfactory gain (3.7 dBi and 5 dBi, respectively) at two different frequencies, 3.5 GHz and 5.5 GHz.

In this study, we present a two-dimensional dielectric grating which allows achieving high absorption in a monolayer graphene at visible and near-infrared frequencies. Dielectric gratings create guided-mode resonances that are exploited to effectively couple light with the graphene layer. The proposed structure was numerically analyzed through a rigorous coupled-wave analysis method. Effects of geometrical parameters and response to the oblique incidence of the plane wave were studied. Numerical results reveal that light absorption in the proposed structure is almost insensitive to the angle of the impinging source over a considerable wide angular range of 20°. This may lead to the development of easy to fabricate and experimentally viable graphene-based absorbers in the future.