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.

In recent years, food packaging has become essential, both for producers and consumers. The increasing use of food packaging has a major impact on food quality, but also on the environment. Ripening, freshness and quality of fruit and vegetable from field to the table became increasingly demanding in the food industry. The classical approach to maintain the freshness of fruits and vegetables after cutting is based on use of plastic foils, which is not eco-friendly and increases plastic waste. The purpose of this study is to explore the possibility of maintaining the freshness of chopped and cut fruits and vegetables using materials based on biopolymers such as protein-based films. Comparing to the most used films and coatings for food packaging, plant protein-based films are edible, biodegradable, vegetarian- and eco-friendly. Non-destructive method used for characterization of freshness during time was electrical impedance spectroscopy connected to the transmission line-based platform. The aim of this work was to correlate the bioelectrical impedance variation with ripening and dehydration of fruit and vegetables (pear and zucchini) without and with a wrapped protein-based films. The impedance of the samples on the microchips was measured at frequency sweeps ranging from 2 kHz to 200 kHz for 39 points. The results demonstrated that the bioimpedance increased with the progresses in fruits and vegetable ripening. For a better understanding of the underlying processes, we provided an equivalent electrical circuit with physical interpretation of circuit elements. Changes of model parameters with time showed excellent correlation with fruits and vegetable ripening.

Following the circular economy concept, all areas of science, including electronics, require individual approach. The green electronics approach implies processing natural based materials for development of electronic components even for single use, so that waste does not exist. This paper describes the production of thermistors from 3 different types of edible materials, their testing in laboratory conditions, as well as the application for measuring the temperature in the human oral cavity. To make the thermistor, three types of natural materials were used (carrageenan, polyvinyl alcohol and apple pomace-based). After fabrication, materials were poured into molds. Aluminium foil contacts were placed so that the electrical characterization of the materials could be performed. Several parameters were measured: resistance (R), impedance (Z) and the phase angle (θ) as a function of frequency. In order to determine whether the thermistors have a positive or negative temperature coefficient and to determine their sensitivity, measurements were conducted at three different temperatures: 25 ℃ (room temperature), 37 ℃ (human body temperature), and 50 ℃. The thermistors demonstrated negative temperature coefficient behaviour. Additionally, it was demonstrated that the apple pomace-based thermistor can successfully measure healthy volunteer's temperature. Graphical Abstract

Essential oils (EOs) have a long tradition of use in the medical and cosmetic fields based on their versatile properties, including fungicidal, antiparasitic, and bactericidal effects. Nowadays, with the development of industry and electronics, EOs are increasingly being used in the agricultural and food industries; health industries, including pharmacy and dental medicine; and as cosmetic enhancements. The purpose of this study is to develop a compact and portable platform for the detection of EO type and the concentration levels using knitted silver threads. The method is based on measuring the variation in values of the electrical parameters of the silver threads using electrochemical impedance spectroscopy (EIS). The impedance of the solutions applied on the testing platform was measured in the frequency range from 1 Hz to 200 kHz. The platform was tested using three types of essential oils: tea tree; clary sage; and cinnamon bark oil. Increasing the concentration of essential oils resulted in increasing the electrical resistance of the platform, decreasing the capacitance, and consequently increasing the impedance. The proposed cost-effective platform can be used for the fast determination of the type and quality of essential oils.