Optical fiber sensors based on microstructured optical fibers to detect gases and volatile organic compounds-A review

Since the first publications related to microstructured optical fibers (MOFs), the development of optical fiber sensors (OFS) based on them has attracted the interest of many research groups because of the market niches that can take advantage of their specific features. Due to their unique structure based on a certain distribution of air holes, MOFs are especially useful for sensing applications: on one hand, the increased coupling of guided modes into the cladding or the holes enhances significantly the interaction with sensing films deposited there; on the other hand, MOF air holes enhance the direct interaction between the light and the analytes that get into in these cavities. Consequently, the sensitivity when detecting liquids, gasses or volatile organic compounds (VOCs) is significantly improved. This paper is focused on the reported sensors that have been developed with MOFs which are applied to detection of gases and VOCs, highlighting the advantages that this type of fiber offers.This work was carried out with the financial support of MINECO (Spain) through TEC2016-79367-C2-2-R (AEI/FEDER, UE) as well as Public University of Navarre PhD grants program.This work was carried out with the financial support of MINECO (Spain) through TEC2016-79367-C2-2-R (AEI/FEDER, UE)

Une plate-forme sans fil pour electrochimique spectroscopie d'impédance

Avec l’émergence soutenue de capteurs et de dispositifs électrochimiques innovants, la spectroscopie d'impédance électrochimique est devenue l'un des outils les plus importants pour la caractérisation et la modélisation de la matière ionique et de l'interfaçage des capteurs. La capacité de détecter automatiquement, à l’aide de dispositifs électrochimiques peu couteux, les caractéristiques physiques et chimiques de la matière ionique ouvre une gamme d’application très variée pour la compréhension et l’optimisation des procédés ou interviennent les processus électrochimiques. Cette thèse décrit le développement d’une plate-forme microélectronique miniaturisée, connectée, multiplexée, et à faible coût pour la spectroscopie d'impédance diélectrique (SID) conçue pour les mesures électrochimiques in-situ et adaptée aux architectures de réseau sans fil. La plate-forme développée durant ce travail de maitrise a été testée et validée au sein d’une maille ZigBee et a été en mesure d'interfacer jusqu'à trois capteurs SID en même temps et de relayer l'information à travers le net Zigbee pour l'analyse de données et le stockage. Le système a été construit à partir de composants microélectroniques disponibles commercialement et bénéficie des avantages d'une calibration système on-the-fly qui effectue la calibration du capteur de manière aisée. Dans ce mémoire de maitrise, nous rapportons la modélisation et la caractérisation de senseurs électrochimiques de nitrate; notamment nous décrivons la conception microélectronique, la réponse d'impédance de Nyquist, la sensibilité et la précision de la mesure électrochimique, et les résultats de tests de la plate-forme pour les applications de spectroscopie d'impédance relatives à la détection du nitrate, de la détection de la qualité de l'eau, et des senseurs tactiles.The emergence of the various applications of electrochemical sensors and devices, electrochemical impedance spectroscopy became one of the most important tools for characterizing and modeling of the material and interfacing the sensors. The ability to sense in an automatic manner enables a wide variety of processes to be better understood and optimized cost-effectively. This thesis describes the development of a low-cost, miniaturized, multiplexed, and connected platform for dielectric impedance spectroscopy (DIS) designed for in-situ measurements and adapted to wireless network architectures. The platform has been tested and used as a DIS sensor node on a ZigBee mesh and was able to interface up to three DIS sensors at the same time and relay the information through the Zigbee net for data analysis and storage. The system was built from commercial microelectronics components and benefits from an on-the-fly calibration system that makes sensor calibration easy. The thesis reports characterizing and modeling of two electro-chemical devices (i.e. nitrate sensor and optically-transparent electrically-conductive glasses) and also describes the microelectronics design, the Nyquist impedance response, the measurement sensitivity and accuracy, and the testing of the platform for in-situ dielectric impedance spectroscopy applications pertaining to fertilizer sensing, water quality sensing, and touch sensing

Poly(ethylenedioxythiophene) based electronic devices for sensor applications

Organic electronic devices, based on Poly (3,4-ethylenedioxythiophene)-Poly (styrene sulfonic acid) (PEDOT-PSS) as the active layer for sensor applications, have been studied. Two sets of sensors have been developed. In one case, sensors consisting of PEDOT-PSS resistors have been realized and demonstrated for soil moisture monitoring. The resistor model for the soil moisture sensor enables the sensor device to be fabricated at low cost and easily tested with a simple structure. Unlike the large dimension device used in Time Domain Reflectometry (TDR), the sensors are small and are capable of capturing microscale behavior of moisture in soil which is useful for geological and geotechnical engineering applications. The Field Effect Transistors (FETs) based on PEDOT-PSS and GOx have been developed for a glucose sensing application. The sensitivity of the developed FET-based sensors is enhanced by selecting the channel as the active sensing region as compared with the previously reported devices which use the gate as the active sensing region. This also allows the devices to be designed by a simple and cost-effective means, unlike other complex platform designs for polymer-based sensor devices. PEDOT-PSS based sensors showed higher sensitivity and reversible electrical properties when compared to early versions of sensors fabricated using polymer electrolytes which showed irreversible change in the electrical properties when exposed to high moisture content. The output characteristics, which is the change in electrical sheet resistance of the PEDOT-PSS film versus the percentage change in relative humidity (%RH), show that the conductivity of the film decreases when it is exposed to increasing levels of moisture content. The change in the output resistance of the developed PEDOT-PSS based sensor device was observed to be from 2.5 MΩ to 4.0 MΩ when exposed to soil samples (e.g. Buckshot Clay, CH) with 15–35 % change in gravimetric water content. The FET-based glucose sensor using PEDOT-PSS and GOx as the channel materials, is designed and developed with the capability of precise, fast, and wide sensing range of measurement compared to that of traditional glucose sensors, which are costly and operate on a complex electrochemical based principle. The fabrication and characteristics testing steps of the present glucose sensor are also simpler in comparison to other glucose sensors, which use electrochemical cells for measurements. In the present device, GOx was immobilized on PEDOT-PSS conducting polymer film using a simple cost effective spin-coating technique. A linear increase in the FET drain current was observed, which was resulted from the increase in glucose concentration. The sensitivity of the glucose sensor was determined to be 0.3 Ampere per 1 mg/ml of glucose concentration. A linear range of response was found from 0.2 to 3 mg/ml of glucose, with a response time of 10–20 s. The results indicated that the reported FET-based glucose sensor retains the enzyme bioactivity and can be applied as a glucose biosensor. Moreover, the glucose sensor presented in this dissertation has displayed a reasonable level of sensitivity, repeatability, and stability. The evaluated range of glucose detection shows that the developed biosensor can be used to detect glucose concentration for normal and diabetic patients. This finding also opens a potential pathway for further development of novel biosensor devices

Carbon-based materials for humidity sensing: a short review

Humidity sensors are widespread in many industrial applications, ranging from environmental and meteorological monitoring, soil water content determination in agriculture, air conditioning systems, food quality monitoring, and medical equipment to many other fields. Thus, an accurate and reliable measurement of water content in dierent environments and materials is of paramount importance. Due to their rich surface chemistry and structure designability, carbon materials have become interesting in humidity sensing. In addition, they can be easily miniaturized and applied in flexible electronics. Therefore, this short review aims at providing a survey of recent research dealing with carbonaceous materials used as capacitive and resistive humidity sensors. This work collects some successful examples of devices based on carbon nanotubes, graphene, carbon black, carbon fibers, carbon soot, and more recently, biochar produced from agricultural wastes. The pros and cons of the dierent sensors are also discussed in the present review

Smart Textiles Production

The research field of smart textiles is currently witnessing a rapidly growing number of applications integrating intelligent functions in textile substrates. With an increasing amount of new developed product prototypes, the number of materials used and that of specially designed production technologies are also growing. This book is intended to provide an overview of materials, production technologies, and product concepts to different groups concerned with smart textiles. It will help designers to understand the possibilities of smart textile production, so that they are enabled to design this type of products. It will also help textile and electronics manufacturers to understand which production technologies are suitable to meet certain product requirements

Development of sensors and non-destructive techniques to determine the performance of coatings in construction

The primary objective of this work was to examine and develop techniques for monitoring the degradation of Organically Coated Steel (OCS) in-situ. This included the detection of changes associated with the weathering to both the organic coating and metallic substrate. Initially, a review of current promising techniques was carried out however many were found to be unsuitable for this application and the adaptation of current techniques and the development of new techniques was considered. A brief concept investigation, based on initial testing and considerations, was used to determine a number of sensing techniques to examine. These included embedded, Resonant Frequency Identification (RFID), Magnetic Flux Leakage (MFL) and dielectric sensing. Each of these techniques were assessed for the application, prototyped, and tested against a range of samples to determine the accuracy and sensitivity of degradation detection provided. A range of poorly and highly durable coated samples were used in conjunction with accelerated weathering testing for this aim. Track based electronic printed sensors were presented as both a cut edge corrosion tracking and coating capacitance measurement method. While suffering somewhat from electrical paint compatibility issues both concepts showed merit in initial trials however the capacitive sensor ultimately proved insufficiently responsive to coating changes. The embedded, progressive failure-based, cut edge corrosion sensor was produced and tested in modern coating systems with moderate success. Novel applications of RFID and MLF techniques were considered and proved capable of detecting large changes in substrate condition due to significant corrosion. However, there was a lack of sufficient sensitivity when considering early-stage corrosion of durable modern OCS products. Finally, it was shown that a chipless antenna could be designed and optimised for novelly monitoring the changes to the dielectric properties of a paint layer due to degradation. However, ultimately this test, due to equipment requirements, lent itself more to lab testing than in-situ. Due to some of these limitations a different approach was considered in which the environmental factors influencing degradation were examined with the aim of relating these to performance across a building. It was observed that a combination of high humidity and the build-up of aggressive natural deposits contributed to high degradation rates in sheltered regions, such as building eaves, where microclimates were created. The build-up of deposits and their effect was presented as a key degradation accelerant during in-use service. A unique numerical simulation approach was developed to predict the natural washing, via rain impact and characteristics of the building analysed. This approach showed promise for determining areas unlikely to be naturally washed, and therefore subjected to a degradation accelerating, build-up of deposits. Given these understandings coated wetness sensors were considered as a realistic live-monitoring device capable of determining deposit build up and ultimately OCS lifetime

Impedance Spectroscopy

This book covers new advances in the field of impedance spectroscopy including fundamentals, methods and applications. It releases selected extended and peer reviewed scientific contributions from the International Workshop on Impedance Spectroscopy (IWIS 2017) focussing on detailed information about recent scientific research results in electrochemistry and battery research, bioimpedance measurement, sensors, system design, signal processing

Smart and Safe packaging

In line with the latest innovations in the packaging field, this joint project aims at implementing new and innovative micro- and nanoparticles for the development of active and intelligent packaging solutions dedicated to food and medical packaging applications. More specifically, the project combines two major developments which both falls within the scope of active and intelligent packaging. In this work, a specific focus was given to the development of an antibacterial packaging solution and to the development of smart gas sensors. The antibacterial strategy developed was based on the combination of two active materials - silver nanowires and cellulose nanofibrils - to prepare antibacterial surfaces. The formulation as an ink and the deposition processing has been deeply studied for different surface deposition processes that include coatings or screen-printing. Results showed surfaces that display strong antibacterial activity both against Gram-positive and Gram-negative bacteria, but also interesting properties for active packaging applications such as a highly retained transparency or enhanced barrier properties. Regarding the second strategy, gas sensors have been prepared using a combination of Copper benzene-1,3,5-tricarboxylate Metal Organic Framework and carbon-graphene materials, deposited on flexible screen-printed electrodes. The easy-to-produce and optimized sensors exhibit good performances toward ammonia and toward humidity sensing, proving the versatility and the great potential of such solution to be adapted for different target applications. The results of this project lead to innovative solutions that can meet the challenges raised by the packaging industry

Modifying Commercial RFID Tags using Polydimethylsiloxane based Polymers for Sensing Purposes.

In the last decade, RFID sensing has grown rapidly. Passive RFID tags are attractive due to their low cost, theoretically infinite lifespans, small form factor and the ability to be read without a line of sight required. This has resulted in an enormous increase in research and commercial interest, with RFID sensing growing at an ever expanding rate. Previous RFID sensing has relied upon exploiting the reader side of RFID systems, or incorporating bespoke sensors into RFID systems. Newer classes of sensing tags now allow for useable sensing information to be provided by the tag antenna in the form of a sensor code that relates to a stimuli affecting the tag. A popular research avenue for RFID has been utilising stimuli responsive materials. Using stimuli responsive polymers and other materials has previously relied upon exploiting the analogue changes that result when the stimuli responsive material is affected by an analyte of interest. The primary advantage of using stimuli responsive materials over bespoke sensing components is that the simpler components can be utilised. Nowadays, commercial sensing tags can be purchased for as little as £2.75, that can provide digital information about environmental conditions. Whilst dedicated sensors for other analytes would be expected to have a higher cost, incorporating polymeric materials into lower cost sensors and repurposing them to sense a range of analytes presents an attractive alternative. A commercially available RFMicron RFM-2100 AER moisture sensing tag was modified with polydimethylsiloxane (PDMS) to allow for sensing of aqueous electrolytes of variable concentration. Coating the tag with the hydrophobic layer also allowed for the system to return to be reusable. The system also demonstrated the ability measure the relative amount of water (or alcohol) in water/alcohol mixes. A two part reactive silicone cross-linked polymer was also investigated for the purpose of repurposing the tag to be used as a pH sensor, but was found not to produce enough (if any) changes in response with variable pH. Following this work, a preliminary investigation showed the potential for a PDMS/PANI (polyaniline) composite was tested as a pH responsive coating for the RFMicron RFM2100 AER. The system was capable of measuring 5 distinct ranges of pH, but only on the first use of the system, as after this the system became incapable of measuring pH changes aside from those associated with the large change in dielectric properties of extremely low pH solutions