A glucose concentration sensor for microliter-volume water-glucose solutions is presented. The proposed sensor is composed of an open-loop microstrip resonator with a dielectric liquid holder (5-25-μL volume) glued onto the gap between the line ends. The resonator is coupled to two microstrip lines forming a two-port network whose S-parameter response provide information about the dielectric properties of the liquid under study. Three versions of the sensor at resonant frequencies between 2 and 7 GHz are presented. The sensors are assessed by measuring the complex permittivity of standard liquids reported in the scientific literature. Models of the sensors are presented, which properly match the experimental results. This paper presents an experimental study of the sensors as glucose concentration retrievers. The main novelty is the use of Q factor and the maximum S21 of the resonance as sensing magnitudes. The dependence of these parameters on the glucose concentration of the solutions obeys almost linear relationships. Good sensitivities have been obtained for the proposed sensors, which are coherent with previous works by other authors.

An extension of the finite difference time domain is applied to solve the Schrödinger equation. A systematic analysis of stability and convergence of this technique is carried out in this article. The numerical scheme used to solve the Schrödinger equation differs from the scheme found in electromagnetics. Also, the unit cell employed to model quantum devices is different from the Yee cell used by the electrical engineering community. A bound for the time step is derived to ensure stability. Several numerical experiments in quantum structures demonstrate the accuracy of a second order, comparable to the analysis of electromagnetic devices with the Yee cell.

A low-cost, additively manufactured, biocompatible glucose sensor based on the changes in the unloaded quality factor ( $Q_{\mathbf {u}}$ ) with a single split-ring resonator is presented. An exposition of the fundamentals for the use of the $Q_{\mathbf {u}}$ as sensing parameter with microwave planar resonant sensors is shown. The convenience of this sensing parameter is analyzed from the theoretical point of view, and practical design and optimization guidelines are inferred with a special focus on the optimization of $Q_{\mathbf {u}}$ sensitivity to glucose concentration. For practical demonstration and experimental assessment, a novel inverted microstrip configuration is considered, built upon a customized structure made with a certified biocompatible material thanks to 3-D printing techniques, which is aimed to provide for a stronger interaction between the electromagnetic fields and the sample. Two metallization solutions are investigated, yielding devices operating at 4.50 and 4.62 GHz, with operating $Q_{\mathbf {u}}$ of 16.36 and 22.00, relative $Q_{\mathbf {u}}$ sensitivities of 1.377 and 2.727, $Q_{\mathbf {u}}$ sensitivities to glucose content within the physiological range of $0.3\times 10^{-3}$ per mg/dL and $0.6\times 10^{-3}$ per mg/dL, sensing areas of approximately $11.7\times8.8$ mm ² and total structure sizes of 950.0 $\times 35.0\times3.5$ mm ³ . The devices show good performance with water–glucose solutions covering a wide range of concentrations, involving physiological as well as industry-related ones.

The perfectly matched layer (PML) superabsorbing boundary condition is adapted and applied to the non-orthogonal finite difference time domain method. The PML consists of a non-physically realisable material with properties that are highly effective in absorbing electromagnetic waves. The PML gives excellent results when used with a curvilinear mesh.

With the expansion in number and requirements of modern wireless communications, the technology related to their associated antennas has been continuously improved. Among other options, printed antennas offer excellent features, such as low weight, profile, and cost, while maintaining good performance characteristics. In addition, their straightforward integration with electronics has opened new fields of application such as smart sensing systems. Printed antennas can be used in different parts of a wireless smart sensor as a radio link, sensing element, or even as energy harvester. In this paper, we present a thorough review of recent advances of printed antennas as regards their use in smart sensing applications.