ABSTRACT
Packaging solutions have recently evolved to become smart and intelligent thanks to technologies such as RFID tracking and communication systems, but the integration of sensing functionality in these systems is still under active development. In this paper, chipless RFID humidity sensors suitable for smart packaging are proposed together with a novel strategy to tune their performances and their operating range. The sensors are flexible, fast, low-cost and easy to fabricate and can be read wirelessly. The sensitivity and the humidity range where they can be used are adjustable by changing one of the sensor's structural parameters. Moreover, these sensors are proposed as double parameter sensors, using both the frequency shift and the intensity variation of the resonance peak for the measure of the relative humidity. The results show that the sensitivity can vary remarkably among the sensors proposed, together with the operative range. The sensor suitability in two specific smart packaging applications is discussed. In the first case, a threshold sensor in the low-humidity range for package integrity verification is analyzed, and in the second case, a more complex measurement of humidity in non-hermetic packages is investigated. The discussion shows that the sensor configuration can easily be adapted to the different application needs.
ABSTRACT
Chipless radio-frequency identification (RFID) sensors are not yet widespread in practical applications because of their limited sensitivity and selectivity when compared to more mature sensing technologies. The search for a suitable material to perform the sensing function has often been focused on the most common materials used in electrochemical sensing approaches, but little work has been done to directly relate the performances of chipless or microwave sensors to the characteristics of the materials used to fabricate them. In this work we are simulating the impact of the substrate material on the performances of a chipless RFID sensor for humidity detection. The dielectric parameters of the substrate material turn out to be very important to maximize the sensor performances, in relation to the operative range of the sensor (based on the desired application) and to the effective dielectric properties of the sensitive material used, we verify the simulated results with measurements of real chipless humidity cells with Nafion 117 sensitive material. We show which types of substrate are preferable for low-humidity detection and which substrates' features are instead fundamental to operate in a wider humidity range.
ABSTRACT
Radio-frequency identification (RFID) sensors are one of the fundamental components of the internet of things that aims at connecting every physical object to the cloud for the exchange of information. In this framework, chipless RFIDs are a breakthrough technology because they remove the cost associated with the chip, being at the same time printable, passive, low-power and suitable for harsh environments. After the important results achieved with multibit chipless tags, there is a clear motivation and interest to extend the chipless sensing functionality to physical, chemical, structural and environmental parameters. These potentialities triggered a strong interest in the scientific and industrial community towards this type of application. Temperature and humidity sensors, as well as localization, proximity, and structural health prototypes, have already been demonstrated, and many other sensing applications are foreseen soon. In this review, both the different architectural approaches available for this technology and the requirements related to the materials employed for sensing are summarized. Then, the state-of-the-art of categories of sensors and their applications are reported and discussed. Finally, an analysis of the current limitations and possible solution strategies for this technology are given, together with an overview of expected future developments.
ABSTRACT
The accurate determination of biological parameters by means of rapid, on-line measurements at low-concentrations is an important task within the fields of pharmaceutical screening and medical diagnostic. Nevertheless, in biological samples, the analytes of interest are present as minor components in complex mixtures and with interfering species. Biosensors are the best candidates for these applications providing a direct solution to this need of accuracy, but their intrinsic selectivity often excludes all the other components in the sample. A separation step introduced prior to the sensing component could allow both the increase of selectivity with respect the interfering species and the identification of a large spectrum of molecular components in the sample. This work reports the development of a silicon-based integrated separation microsystem for gas chromatography aimed to biomedical applications, with particular emphasis to monitor the homovanillic acid (HVA) and vanillylmandelic acid (VMA) ratios in mass population screening for neuroblastoma diagnosis and prognosis. The miniaturised system consists of two main modules: (i) a metal oxide semiconductor detector and (ii) a micromachined separation capillary column. As first step, the metal oxide semiconductor capability to detect HVA and VMA has been demonstrated. Then, a technology for a silicon separation capillary microcolumn including the on-chip gas sensor housing has been proposed and a first prototype has been developed. The proposed microsystem is an analytical device with biosensing capabilities for diagnostic and biomedical applications, which yield an electronic signal proportional to the concentration of a specific analyte or group of analytes.
