Development of an artificial olfactory system for lubricant degradation monitoring

Off-line strategies are commonly used to evaluate lubricant aging. These methods are expensive, time consuming and often require skilled personnel. Online detection of lubricant degradation would eliminate some of these issues. Lubricant degradation is principally due to oxidation, additive depletion and contamination by water, acid, fuel, sulphur, and insoluble content which happens gradually through different phases of the lubricant lifetime. The by-products and final products of this chemical process characterise the different evolutive phases of oil aging and are reflected in the volatile compounds emitted by the lubricant while degrading. Hence, the lubricant headspace contains a significant amount of information about oil degradation. This paper reports the development of an artificial olfactory system for real-time oil condition evaluation by headspace analysis. The instrument has been optimised to exhibit high discriminatory power and high sensitivity towards the vapours characterising the oil aging process, while the device costs have been kept low. Preliminary measurements have been carried out on water samples, new engine oil and aged engine oil to evaluate the ability of the system to generate sensor patterns distinctive of the samples under test and to discriminate between new engine oil and relatively aged engine oil. The results of these measurements are presented and discussed in the paper

Description and Characterisation of a Large Array of Sensors Mimicking an Artifical Olfactory Epithelium

Biological olfactory systems show high sensitivity and exquisite discriminatory capacity to odorants. These characteristics are due to hierarchical signal processing of the large numbers of sensory inputs that occurs within the olfactory system. In testing realistic computational models of the olfactory system, large numbers of chemical sensor inputs are required. So far, sensory devices that may serve as model inputs to an artificial olfactory system do not exist. The development of a large scale array of chemical sensors able to mimic the olfactory receptor neurons is described, and these have been characterised in terms of their variability and degree of redundancy. Using this device it is possible to start testing computational hypotheses appropriate to biological chemosensory systems and adapt them to the artificial olfaction

Electronic nose << naris >> optimization for novel applications: simulations and experimental results

Il presente lavoro rappresenta un compendio delle attività svolte nel quadro delle attività di ricerca del gruppo “Sensori e Microsistemi” del Dipartimento di Ingegneria Elettronica dell’università di Tor Vergata di Roma. Tutta la parte relativa alla sperimentazione e alle simulazioni è stata inoltre sviluppata presso l’Istituto di Microelettronica e Microsistemi del CNR di Roma. La finalità della tesi concerne l’ottimizzazione di un “Naso Elettronico” per applicazioni spaziali, da un lato, e lo sviluppo di nuove idee orientate all’ampliamento delle potenzialità del dispositivo. La parte cruciale del design di un Naso Elettronico consiste nella progettazione della camera di misura (la “narice”), dove risiedono i sensori, le cui caratteristiche fluidodinamiche, se non valutate attentamente possono risultare in un complessivo scarso rendimento del sistema. Il lavoro svolto si riassume nelle seguenti tre parti: Ottimizzazione di un naso elettronico basato su microbilance di quarzo per applicazioni spaziali Un lungo periodo di tempo è stato dedicato alle simulazioni fluidodinamiche di differenti camere di misura con lo scopo di evidenziare tutte le anomalie dovute a fenomeni di turbolenza. Questi sono responsabili della non omogeneità nella risposta dei sensori e perciò devono essere controllati e confinati entro certi limiti di tollerabilità. Sono state identificate le condizioni di flusso laminare e le posizioni dei sensori sono state ottimizzate. I risultati delle simulazioni sono stati confermati da riscontri sperimentali. Design di un riscaldatore su QCM Una varietà di riscaldatori integrati su microbilancia di quarzo è stata progettata e le varie caratteristiche di uniformità di distribuzione di temperatura sono state analizzate tramite simulazioni ad elementi finiti. Questa parte della tesi ha avuto l’obiettivo di valutare processi di desorbimento rapidi attivati da un incremento di temperatura. Gli esperimenti che sono seguiti alla progettazione hanno evidenziato la possibilità di ridurre e controllare i tempi di desorbimento necessari per ripristinare il sensore alle condizioni iniziali. Realizzazione di una microbilancia di quarzo multicanale L’ultima parte del lavoro ha riguardato la progettazione e la realizzazione di una microbilancia multicanale. Quattro coppie di elettrodi sono state depositate su un singolo substrato di quarzo al fine di ottenere l’integrazione di quattro risonatori indipendenti su un’unica lamina di cristallo. I risultati ottenuti analizzando le quattro differenti frequenze di oscillazione hanno mostrato la validità dell’idea implementata. Il principale risultato consiste nella bassissima interferenza rilevata tra i quattro canali realizzati, risultato che rende questa soluzione particolarmente adatta ad applicazioni spaziali.This work represents a compendium of the activities developed in the frame of the main research line of the Sensors and Microsystem Group of the Electronic Engineering Department of the University of Roma Tor Vergata. Also it is worth to point out that all the experimental and simulation part was developed at the IMM-Roma CNR. The rationale at the bottom of this thesis was the optimization of an Electronic Nose (EN) for space applications on one hand and on the other hand the development of new ideas oriented to the room and energy saving paradigm. The crucial segment of the overall EN design is certainly the test chamber (naris) where sensors are located and where fluid dynamic problems if not solved, may represent one of the most relevant drawback of the entire system. This PhD thesis has been concentrated on the following three parts: Test chamber optimization of a QCM EN for space applications In this context a long period of time (about two years, was dedicated to the flow simulation in a varieties of chambers including sensors with the aim of revealing all the anomalies due to turbulence phenomena. These are the main responsible of the non homogeneous responses of the sensors and for this reason they should be controlled in order to left them confined in non sensitive spaces. Laminar flow conditions were identified with accuracy and the final position of the sensors well optimized as confirmed by experimental achievements. Heater design on a QCM Also this part was faced in the frame of an optimized simulation with the aim of designing a heater for uniform heat distribution on the QCM surface and volume. This part the thesis was aimed at defining the heating conditions for faster desorption processes temperature activated. In practice the result were fully satisfactory. In fact shorter and controlled desorption times were measured in the context of a campaign aiming at defining the degree of precision which is necessary in real operative conditions. Design of a new multichannel quartz based EN As a further effort a worth of attention and time was paid towards the design and optimization of a new very compact part of the EN In this context a new idea was successfully tested. Four electrode couples were allocated symmetrically in the quartz surfaces in order to have in a single substrate four possible smaller QCM Results obtained analyzing the four different oscillating frequencies demonstrated the success obtained in implementing this idea. The main result was the measurement of a little interference among the different resonators which makes this solution very much suitable for space application in virtue of its robust design and efficiency. All the work done was experimentally evaluated with a high degree of satisfaction from the simulation and practical behaviour achieved in long term experiments

Electronic nose << naris >> optimization for novel applications: simulations and experimental results

Il presente lavoro rappresenta un compendio delle attività svolte nel quadro delle attività di ricerca del gruppo “Sensori e Microsistemi” del Dipartimento di Ingegneria Elettronica dell’università di Tor Vergata di Roma. Tutta la parte relativa alla sperimentazione e alle simulazioni è stata inoltre sviluppata presso l’Istituto di Microelettronica e Microsistemi del CNR di Roma. La finalità della tesi concerne l’ottimizzazione di un “Naso Elettronico” per applicazioni spaziali, da un lato, e lo sviluppo di nuove idee orientate all’ampliamento delle potenzialità del dispositivo. La parte cruciale del design di un Naso Elettronico consiste nella progettazione della camera di misura (la “narice”), dove risiedono i sensori, le cui caratteristiche fluidodinamiche, se non valutate attentamente possono risultare in un complessivo scarso rendimento del sistema. Il lavoro svolto si riassume nelle seguenti tre parti: Ottimizzazione di un naso elettronico basato su microbilance di quarzo per applicazioni spaziali Un lungo periodo di tempo è stato dedicato alle simulazioni fluidodinamiche di differenti camere di misura con lo scopo di evidenziare tutte le anomalie dovute a fenomeni di turbolenza. Questi sono responsabili della non omogeneità nella risposta dei sensori e perciò devono essere controllati e confinati entro certi limiti di tollerabilità. Sono state identificate le condizioni di flusso laminare e le posizioni dei sensori sono state ottimizzate. I risultati delle simulazioni sono stati confermati da riscontri sperimentali. Design di un riscaldatore su QCM Una varietà di riscaldatori integrati su microbilancia di quarzo è stata progettata e le varie caratteristiche di uniformità di distribuzione di temperatura sono state analizzate tramite simulazioni ad elementi finiti. Questa parte della tesi ha avuto l’obiettivo di valutare processi di desorbimento rapidi attivati da un incremento di temperatura. Gli esperimenti che sono seguiti alla progettazione hanno evidenziato la possibilità di ridurre e controllare i tempi di desorbimento necessari per ripristinare il sensore alle condizioni iniziali. Realizzazione di una microbilancia di quarzo multicanale L’ultima parte del lavoro ha riguardato la progettazione e la realizzazione di una microbilancia multicanale. Quattro coppie di elettrodi sono state depositate su un singolo substrato di quarzo al fine di ottenere l’integrazione di quattro risonatori indipendenti su un’unica lamina di cristallo. I risultati ottenuti analizzando le quattro differenti frequenze di oscillazione hanno mostrato la validità dell’idea implementata. Il principale risultato consiste nella bassissima interferenza rilevata tra i quattro canali realizzati, risultato che rende questa soluzione particolarmente adatta ad applicazioni spaziali.This work represents a compendium of the activities developed in the frame of the main research line of the Sensors and Microsystem Group of the Electronic Engineering Department of the University of Roma Tor Vergata. Also it is worth to point out that all the experimental and simulation part was developed at the IMM-Roma CNR. The rationale at the bottom of this thesis was the optimization of an Electronic Nose (EN) for space applications on one hand and on the other hand the development of new ideas oriented to the room and energy saving paradigm. The crucial segment of the overall EN design is certainly the test chamber (naris) where sensors are located and where fluid dynamic problems if not solved, may represent one of the most relevant drawback of the entire system. This PhD thesis has been concentrated on the following three parts: Test chamber optimization of a QCM EN for space applications In this context a long period of time (about two years, was dedicated to the flow simulation in a varieties of chambers including sensors with the aim of revealing all the anomalies due to turbulence phenomena. These are the main responsible of the non homogeneous responses of the sensors and for this reason they should be controlled in order to left them confined in non sensitive spaces. Laminar flow conditions were identified with accuracy and the final position of the sensors well optimized as confirmed by experimental achievements. Heater design on a QCM Also this part was faced in the frame of an optimized simulation with the aim of designing a heater for uniform heat distribution on the QCM surface and volume. This part the thesis was aimed at defining the heating conditions for faster desorption processes temperature activated. In practice the result were fully satisfactory. In fact shorter and controlled desorption times were measured in the context of a campaign aiming at defining the degree of precision which is necessary in real operative conditions. Design of a new multichannel quartz based EN As a further effort a worth of attention and time was paid towards the design and optimization of a new very compact part of the EN In this context a new idea was successfully tested. Four electrode couples were allocated symmetrically in the quartz surfaces in order to have in a single substrate four possible smaller QCM Results obtained analyzing the four different oscillating frequencies demonstrated the success obtained in implementing this idea. The main result was the measurement of a little interference among the different resonators which makes this solution very much suitable for space application in virtue of its robust design and efficiency. All the work done was experimentally evaluated with a high degree of satisfaction from the simulation and practical behaviour achieved in long term experiments

Enhanced Sensory Properties of a Multichannel Quartz Crystal Microbalance Coated with Polymeric Nanobeads

In this study the sensorial performances of a four-channel quartz crystalmicrobalance implemented on a single quartz plate are reported and compared with those offour independent quartz crystal microbalances. Particular attention has been devoted to bothcross talk in responses and sensor sensitivity. A recently synthesized nanostructuredpolymer, poly[phenylacetylene-(co-2-hydroxyethyl methacrylate)], has been used aschemical interactive material. The interactions of our sensor system with relative humidityare also reported. The multichannel device shows a better homogeneity of the masssensitivity with a spread of the values less then 4% compared to a 50% spread observed inthe set of four microbalances

Large-scale chemical sensor array testing biological olfaction concepts

Biological olfactory systems are characterized by a large number of sensors with broad overlapping specificities. The sensitivity and selectivity of the system may be enhanced by the huge redundancy of the olfactory receptor neurons (ORNs). A European project, NEUROCHEM, was devoted to test computational models of the olfactory system of vertebrates and insects. To test these models, a realistic artifact of the olfactory epithelium was developed as a large sensor array mimicking some features of biological ORNs, in particular, the broad and overlapping selectivity to many odors, the combinatorial response, the high level of redundancy, and the different dynamic ranges exhibited by same types of ORNs. The sensor array is composed of 16 384 elements arranged in four smaller arrays of 64×64 interdigitated electrodes deposited on a borosilicate substrate. To mimic the redundancy of the biological ORNs, tens of organic conductive polymers were chosen as active sensing materials because of their broad and diverse, but overlapping, specificity to different classes of volatile organic compounds. These sensors were characterized by their responses to varying concentrations of test analytes. The collected sensor data were processed with standard multivariate techniques and the results are reported in this paper

Very large chemical sensor array for mimicking biological olfaction

Olfactory receptor neurons (ORN) in the mammalian olfactory system, transduce molecular properties of the odorants into electrical signals and project these into the olfactory bulb (OB). In the biological system several millions of receptor neurons of a few hundred types create redundancy and the massive convergence of the ORNs to the OB, is thought to enhance the sensitivity and selectivity of the system. To explore this concept, the NEUROCHEM project will build a polymeric chemical sensor array consisting of 216 (65536) sensors with tens of different types. To interface such a large sensor array, a topological array configuration with n rows and m columns, has been adopted, to reduce the total wiring connections to n+m. A method of addressing a single element in the array in isolation of the rest of the network has been developed. Over the array ten different conductive polymers with different sensing characteristics will be deposited by means of lectrodeposition and inkjet printing. A smaller prototype of 64 elements has been investigated and the results are here reported and discussed