In the agri-food industry, carbon dioxide sensors can be used for process control, monitoring quality, and assessing safety. A carbon dioxide sensor was developed using poly aniline boronic acid (PABA) conducting polymer as the electrically conductive region of the sensor for use in the agri-food industry and was demonstrated for use in detecting incipient or ongoing spoilage in stored grain. The developed sensor dynamically detected up to 2455 ppm CO2 concentration levels. The performance of the sensor in measurements of low concentrations of dissolved CO2 was characterized using standard solutions of NAHCO3. The dynamic range for the detection of H2CO3 was 4.91X10-4 to 9.81X10-3 mol L-1. The dc resistance values decreased with increasing CO2 concentration indicating an increase of conductivity due to increase in the amount of protonation. The developed CO2 sensor was evaluated for the influence of temperature (by storing it at – 20°C and 0°C as well as at operating temperatures of +10°C to 55°C) and relative humidity (from 20 to 70%). Temperature dependence of sensor's resistance values were observed possibly due to the change in conduction mechanism at different temperatures. The variation in the resistance with humidity was curvi-linear and repeatable, indicating that humidity has a less pronounced effect on the sensor’s performance. The sensor’s response to changes in CO2 concentrations at various humidity and temperature levels was stable indicating that the sensor can detect CO2 levels under fluctuating environmental conditions. The response of the PABA film to CO2 concentration was not affected by the presence of alcohols and ketones, proving that the developed CO2 sensor is not cross-sensitive to these compounds which may be present in spoiling grain. The sensor packaging components were selected and built in such a way to avoid contamination of the sensing material and the substrate by undesirable components including grain dust and chaff. The developed conducting polymer CO2 sensor exhibited dynamic performance in its response, recovery times, sensitivity, selectivity, stability and response slope when exposed to various CO2 levels inside simulated grain bulk conditions.

In the agri-food industry, carbon dioxide sensors can be used for process control, monitoring quality, and assessing safety. A carbon dioxide sensor was developed using poly aniline boronic acid (PABA) conducting polymer as the electrically conductive region of the sensor for use in the agri-food industry and was demonstrated for use in detecting incipient or ongoing spoilage in stored grain. The developed sensor dynamically detected up to 2455 ppm CO2 concentration levels. The performance of the sensor in measurements of low concentrations of dissolved CO2 was characterized using standard solutions of NAHCO3. The dynamic range for the detection of H2CO3 was 4.91X10-4 to 9.81X10-3 mol L-1. The dc resistance values decreased with increasing CO2 concentration indicating an increase of conductivity due to increase in the amount of protonation. The developed CO2 sensor was evaluated for the influence of temperature (by storing it at – 20°C and 0°C as well as at operating temperatures of +10°C to 55°C) and relative humidity (from 20 to 70%). Temperature dependence of sensor's resistance values were observed possibly due to the change in conduction mechanism at different temperatures. The variation in the resistance with humidity was curvi-linear and repeatable, indicating that humidity has a less pronounced effect on the sensor’s performance. The sensor’s response to changes in CO2 concentrations at various humidity and temperature levels was stable indicating that the sensor can detect CO2 levels under fluctuating environmental conditions. The response of the PABA film to CO2 concentration was not affected by the presence of alcohols and ketones, proving that the developed CO2 sensor is not cross-sensitive to these compounds which may be present in spoiling grain. The sensor packaging components were selected and built in such a way to avoid contamination of the sensing material and the substrate by undesirable components including grain dust and chaff. The developed conducting polymer CO2 sensor exhibited dynamic performance in its response, recovery times, sensitivity, selectivity, stability and response slope when exposed to various CO2 levels inside simulated grain bulk conditions.

La technologie d’identification radiofréquence (RFID) se décline aujourd’hui dans des milliers d’applications. Parmi elles nous pouvons citer les applications de gestion logistique des palettes/cartons dans les entrepôts industriels (RFID UHF) ainsi que l’identification des abonnés dans les réseaux de transports urbains (RFID HF). Depuis quelques années, des contributions scientifiques autour des technologies d’identification radiofréquence (RFID) avec un couplage capteur sont de plus en plus visibles. L’intérêt grandissant pour ce type de technologie s’appuie sur la possibilité d’une utilisation en masse de capteurs bon marchés pouvant être intégrés sur chaque objet. On parle alors d’objet connecté ou d’internet des objets (IoT). Dans cette thèse, nous nous focalisons sur l’étude et le développement d’un capteur RFID passif fonctionnant en bande UHF. Cette orientation technologique est dictée par l’application visée, l’agro-alimentaire, qui requiert des coûts de fabrication les plus faibles possibles et une distance de lecture supérieure au mètre. Pour l’élément sensible, nous utilisons un bio-polymère, plus précisément le gluten de blé dont les propriétés diélectriques en fonction de l’humidité relative ont été étudiées précédemment. Nous nous attachons à traiter toutes les problématiques liées à la communication entre un lecteur et un capteur RFID passif, l’objectif ultime de cette thèse étant de récupérer une information capteur à l’aide d’un lecteur RFID conventionnel respectant les standards du domaine et les directives radio en vigueur dans les différentes régions du monde. Pour valider cette étude, nous mettons en œuvre des capteurs-RFID pour réaliser un démonstrateur d’emballage « intelligent » permettant le suivi de la qualité des aliments. / Radio frequency identification (RFID) technology is available today in thousands of applications. Among them we can mention the logistics management applications pallets / cardboard in industrial warehouses (RFID UHF) and the identification of subscribers in urban transport networks (RFID HF). In recent years, scientific contributions around the radio frequency identification (RFID) technologies with a sensor coupling are increasingly visible. The growing interest in this type of development rely heavily on a mass use of inexpensive sensors that can be integrated on each object.It is calledconnected objects or Internet of Things (IoT). In this thesis, we focus on the study and development of a passive RFID sensor operating in UHF band. This technological orientation is dictated by the targeted application, the food industry, which requires the lowest possible manufacturing costs and a reading distance greater than one meter. For the sensitive element, we use a biopolymer, specifically wheat gluten whose dielectric properties as a function of relative humidity have been studied previously. We are committed to dealing with all the issues related to the communication between a reader and a passive RFID sensor, the ultimate objective of this thesis being to get a sensor information using a conventional RFID reader complying with the standards and the radio directives imposed in different regions of the world. To validate this study, we are implementing RFID sensors to create a smart packaging demonstrator for monitoring the quality of food.