This paper describes an innovative design of a wireless, passive LC sensor and its application for monitoring of water content in building materials. The sensor was embedded in test material samples so that the internal water content of the samples could be measured with an antenna by tracking the changes in the sensor’s resonant frequency. Since the dielectric constant of water was much higher compared with that of the test samples, the presence of water in the samples increased the capacitance of the LC circuit, thus decreasing the sensor’s resonant frequency. The sensor is made up of a printed circuit board in one metal layer and water content has been determined for clay brick and autoclaved aerated concrete block, both widely used construction materials. Measurements were conducted at room temperature using a HP-4194A Impedance/Gain-Phase Analyzer instrument.

In this paper we present economical interdigitated flexible sensor on the paper substrate for bacteria detection. The impedance measurement was performed in the frequency range of 12.6 kHz–100 kHz for the suspensions with cell density of 1.5∙108 CFU/mL, 1.5∙105 CFU/mL and 1.5∙102 CFU/mL of Pseudomonas aeruginosa and Staphylococcus aureus bacteria, as well as for a sterile saline. Using the measured impedance data, we observed that sensor impedance magnitude increases when bacteria concentration increases. Moreover, impedance spectroscopic analysis was carried out to identify an equivalent electrical circuit for the sensor modelling. Through statistical analysis it was found that all model parameters changes according to the bacteria type and concentration. Additionally, obtained results showed that all fittings results in root mean square errors lower than 0.072 Ω for impedance magnitude, and 0.157° for impedance phase angle.

This work presents a new multilayered microfluidic platform, manufactured using a rapid and cost-effective xurography technique, for the detection of drug concentrations in sweat. Textile fabrics made of cotton and polyester were used as a component of the platform, and they were positioned in the middle of the microfluidic device. In order to obtain a highly conductive textile, the fabrics were in situ coated with different amounts of polyaniline and titanium dioxide nanocomposite. This portable microfluidic platform comprises at least three layers of optically transparent and flexible PVC foils which were stacked one on top of the other. Electrical contacts were provided from the edge of the textile material when a microfluidic variable resistor was actually created. The platform was tested in plain artificial sweat and in artificial sweat with a dissolved cytostatic test drug, cyclophosphamide, of different concentrations. The proposed microfluidic device decreased in resistance when the sweat was applied. In addition, it could successfully detect different concentrations of cytostatic medication in the sweat, which could make it a very useful tool for simple, reliable, and fast diagnostics.

This paper presents a passive LC wireless sensor for measuring temperature. The sensor is designed as a parallel connection of a spiral inductor and an interdigitated capacitor and it was fabricated in a conductive layer using LTCC (Low Temperature Co-fired Ceramic) technology. The inderdigitated capacitor electrodes were coated with a thin film of bismuth doped barium titanate (Ba_0.9Bi_0.066TiO₃), whose permittivity changes with temperature, which directly induces changes in the capacitance of the interdigitated capacitor and consequently changes the resonant frequency of the sensor. The measurements of S-parameter of the sensor were performed using a Vector Network Analyzer (E5071B, Agilent Technologies, Santa Clara, CA, USA), whose port was connected to the antenna coil that was placed around the sensor in order to be able to wirelessly detect temperature, in the temperature range from 25 °C to 165 °C.

The microfluidics domain has been progressing rapidly recently, particularly considering its useful applications in the field of biomedicine. This paper presents a novel, microfluidics-based design for four fundamental circuit elements in electronics, namely resistor, inductor, capacitor, and memristor. These widely used passive components were fabricated using a precise and cost-effective xurography technique, which enables the construction of multi-layered structures on foil, with gold used as a conductive material. To complete their assembly, an appropriate fluid was injected into the microfluidic channel of each component: the resistor, inductor, capacitor, and memristor were charged with transformer oil, ferrofluid, NaCl solution, and TiO₂ solution, respectively. The electrical performance of these components was determined using an Impedance Analyzer and Keithley 2410 High-Voltage Source Meter instrument and the observed characteristics are promising for a wide range of applications in the field of microfluidic electronics.