Tesi sul tema "Characterization of sensors"

The population of the world is aging. In Sweden alone, almost 20% of the population is 65 years or older. As people get older, problems with sleep disturbances and sleep quality tends to increase, as do the risks of falling injuries. In this thesis, methods for calculating sleep quality and if a person is about to leave a bed were devised. A bed sensor, measuring ballistocardiographical signals, was used to measure activity in bed and vital signs of the occupant. The Cole-Kripke algorithm, used to calculate sleep quality based on activity from a wrist worn sensor, was adapted to the bed sensor system and compared to results from the ActiGraph wGT3X-BT activity monitor, which is frequently used in research. The bed sensor systems sleep quality estimations showed strong correlation with the ActiGraph, with a Pearson correlation coefficient of 0.946. Two approaches were made to estimate if a subject was about to leave the bed, one by training a neural network on labeled night data, and one using a linear equation with each term consisting of activity data, optimized by linear regression. The neural network approach suffered from limited data, but the linear method showed more promise, with accuracy, specificity and sensitivity all over 70%.

En aquesta tesi, he estudiat i desenvolupat un mètode de deposició química en fase vapor assistit per aerosol (AACVD), per al creixement directe de nanoagulles d'òxid de tungstè funcionalitzades o intrínseques. Els dipòsits s'han realitzat sobre diferents substrats trasndcutors per a la seva aplicació a la detecció de gasos. Aquesta tècnica ofereix la possibilitat de co-dipositar els metalls amb els òxids metàl•lics emprant una sola etapa de deposició. La síntesi del material nanoestructurat, la fabricació del dispositiu, la caracterització dels materials i la detecció de gasos han estat investigades. El mètode AACVD es va emprar per al creixement i la integració directa de la pel•lícula sensible sobre substrats ceràmics (alúmina), MEMS (micro hotplates) i polimèrics flexibles, el que demostra la seva compatibilitat i idoneïtat per al creixement de nanoestructures d'òxid metàl•lics sobre una àmplia gamma de substrats transductors. A més, el mètode AACVD s'ha implementat també en un reactor de paret freda per créixer les nanoestructures de WO3, emprant l'escalfament localitzat que permeten aconseguir les microresistencias calefactores integrades en alguns dels transdcutors emprats. Totes les pel•lícules sintetitzades en aquesta tesi doctoral es componien de nanoagulles de WO3 pur o de WO3 funcionalitzat amb nanopartícules d'or (Au), platí (Pt), òxid de coure (Cu2O) o pal•ladi (Pd). Es van utilitzar diverses tecnologies d'anàlisi per caracteritzar la morfologia, l'estructura i la composició de les pel•lícules produïdes. Els resultats van mostrar que el nostre mètode és eficaç per al creixement de nanoagulles cristal•lines de WO3 decorades amb nanopartícules de metalls / òxids metàl•lics, a temperatures moderades (és a dir, 380 ° C), amb eficàcia en els seus costos i amb temps de fabricació curts, directament sobre l'element transdcutor amb vista a obtenir sensors de gasos. Els estudis de detecció de gasos han mostrat que aquest nanomaterial híbrid té una excel•lent sensibilitat i selectivitat en comparació amb mostres de WO3 pur. A més, els nanocompostos Cu2O / WO3 i Pd / WO3 han demostrat posseir una excel•lent sensibilitat i selectivitat cap als gasos H2S i H2, respectivament.
En esta tesis, he estudiado y desarrollado un método de deposición química en fase vapor asistido por aerosol (AACVD), para el crecimiento directo de nanoagujas de óxido de tungsteno funcionalizadas o intrínsecas. Los depósitos se han realizado sobre distintos sustratos transdcutores para su aplicación a la detección de gases. Esta técnica ofrece la posibilidad de co-depositar los metales con los óxidos metálicos empleando una sola etapa de deposición. La síntesis del material nanoestructurado, la fabricación del dispositivo, la caracterización de los materiales y la detección de gases han sido investigadas. El método AACVD se empleó para el crecimiento y la integración directa de la película de sensible sobre sustratos cerámicos (alúmina), MEMS (micro hotplates) y poliméricos flexibles, lo que demuestra su compatibilidad e idoneidad para el crecimiento de nanoestructuras de óxido metálicos sobre una amplia gama de sustratos transductores. Además, el método AACVD se ha implementado también en un reactor de pared fría para crecer las nanoestructuras de WO3, empleando el calentamiento localizado que permiten conseguir las microresistencias calefactoras integradas en algunos de los transductores empleados. Todas las películas sintetizadas en esta tesis doctoral se componían de nanoagujas de WO3 puro o de WO3 funcionalizado con nanopartículas de oro (Au), platino (Pt), óxido de cobre (Cu2O) o paladio (Pd). Se utilizaron diversas tecnologías de análisis para caracterizar la morfología, la estructura y la composición de las películas producidas. Los resultados mostraron que nuestro método es eficaz para el crecimiento de nanoagujas cristalinas de WO3 decoradas con nanopartículas de metales / óxidos metálicos, a temperaturas moderadas (es decir, 380 ° C), con eficacia en sus costes y con tiempos de fabricación cortos, directamente sobre el elemento trasndcutor con vistas a obtener sensores de gases. Los estudios de detección de gases han mostrado que este nanomaterial híbrido tiene una excelente sensibilidad y selectividad en comparación con muestras de WO3 puro. Además, los nanocompuestos Cu2O / WO3 y Pd / WO3 han demostrado poseer una excelente sensibilidad y selectividad hacia los gases H2S y H2, respectivamente.
In this thesis, I have studied and developed aerosol assisted chemical vapour deposition (AACVD) methods for the direct growth of non-functionalized and functionalized tungsten oxide nanoneedles, onto different transducer substrates, for gas sensing applications. This technique gives the possibility to co-deposit metals with metal oxides nanostructures within a single step deposition. The nanostructured material synthesis, device fabrication, material characterization and gas sensing performance have been investigated. AACVD method was employed for the direct growth and integration of the sensing film onto ceramic (alumina), MEMS (silicon micro hotplates) and flexible polymeric substrates, demonstrating its compatibility and suitability for growing metal oxide nanostructures onto a wide spectrum of sensor substrates. Furthermore, AACVD based on the localized heating of substrates employing their embedded resistive microheaters has been also performed and developed for the growth of WO3 nanostructures, using a cold wall reactor. All the synthesized films used in this doctoral thesis were composed of pure WO3 nanoneedles or WO3 nanoneedles functionalized with either gold (Au), platinum (Pt), cuprous oxide (Cu2O) or palladium (Pd) nanoparticles. Various analytical techniques were used to characterize the morphology, the structure and the composition of the produced films. The results showed that our method is effective for growing single crystalline WO3 nanoneedles decorated with metals/metal oxides nanoparticles at moderate temperatures (i.e., 380 °C), with cost effectiveness and short fabrication times, directly onto transducers in view of obtaining gas sensors. The gas sensing studies performed showed that these hybrid nanomaterials have excellent sensitivity and selectivity compared to pristine WO3 samples. Cu2O/WO3 and Pd/WO3 nanocomposites have shown excellent sensitivity and selectivity toward H2S and H2 gases respectively.

Ionomeric polymer transducers (IPTs) are an exciting new class of smart materials that can serve a dual purpose in engineering or biomedical applications as sensors or actuators. Most commonly they are used for mechanical actuation, as they have the ability to generate large bending strains and moderate stress under low applied voltages. Although the actuation capabilities of IPTs have been extensively studied, the sensing capabilities of these transducers have yet to be fully explored. The work presented herein aims to investigate the fundamental sensing characteristics of these transducers and apply the acquired knowledge toward the development of an electronic stethoscope for digital auscultation. The sensors were characterized both geometrically and electrically to determine their effectiveness in resolving a signal from sub 1 Hz to 2 kHz. Impedance spectroscopy was used to interrogate the sensing mechanism. Following the characterization of the transducer, a bioâ acoustic sensor was designed and fabricated. The bioâ acoustic sensor was placed over the carotid artery to resolve the arterial pressure waveform in situ and on the thorax to measure the S1 and S2 sounds generated by the heart. The temporal response and spectral content was compared with previously known data and a commercially available electronic stethoscope to prove the acquisition of cardiovascular sounds.
Master of Science

DE LA TESIS DOCTORAL
Título: Diseño, fabricación y caracterización de sensores de capa gruesa
Doctorando: Peter Tsolov Ivanov
Director: Xavier Correig Blanchar
Los sensores de gases de estado sólido han demostrado ser muy prometedores para
supervisar la emisión de los agentes contaminadores en el aire, porque son una opción
de bajo coste para la construcción de analizadores de gases. Algunos problemas se
relacionados con este tipo de dispositivos, especialmente su baja selectividad y el alto
consumo de energía, siguen sin resolver. El objetivo de esta tesis doctoral es el
desarrollo de nuevos sensores y matrices de sensores con mejorada selectividad y
reducido consumo de energía.
La metodología usada en esta tesis consiste en fabricar matrices de sensores hechas de
sensores con distintas selectividades. Como la respuesta del sensor es diferente en
distintas temperaturas de trabajo y como los distintos dopantes o los filtros catalíticos
aceleran o reducen la respuesta del sensor, los diferentes sensores dan diferentes
reacciones. Combinando estas reacciones y con la ayuda de técnicas del reconocimiento
de patrones, se pueden crear grupos de sensores capaces de distinguir entre distintos
agentes contaminantes.
La tesis comienza repasando los métodos usados para la fabricación de los sensores de
gases y discutiendo los problemas relacionados con la baja selectividad de los óxidos
metálicos. Se especifican también los diferentes métodos para aumentar la selectividad.
Se introduce y se describe detalladamente la técnica de screen-printing. Los
experimentos se realizaron con cuatro tipos de substratos de sensores (cerámica, silicio,
microhotplate y silicon-on-insulator) y con más de 15 capas activas basadas en dióxido
de estaño y trióxido de tungsteno (puras y dopadas con oro, platino, plata, titanio y
paladio). Una amplia variedad de compuestos volátiles (amoníaco, etanol, acetona y
benceno), de gases (monóxido de carbono, dióxido de nitrógeno, metano y sulfuro de
PhD thesis of Peter Tsolov Ivanov Resumen de la tesis doctoral
hidrógeno) y de algunas mezclas binarias ha sido medida. Los resultados obtenidos por
los análisis cuantitativos y cualitativos de los gases estudiados con una matriz de
sensores basada en cuatro sensores simples nos han llevado a descubrir el óptimo
sensor/matriz para los distintos gases/mezclas binarias.
Los resultados demostraron que, con la ayuda de redes neuronales Fuzzy ARTMAP, es
posible identificar y cuantificar simultáneamente los gases analizados usando solamente
una matriz de microhotplates (cuatro sensores) con la misma capa activa. Los sensores
de SnO2 y de WO3 dopados demostraron diversa respuesta a los agentes contaminantes
probados. Componiendo cuidadosamente la matriz de sensores y definiendo bien la
temperatura de trabajo podemos discriminar, con un alto grado de éxito, los diversos
gases probados sin la necesidad de técnicas de reconocimiento de patrones.
La conclusión principal que se puede sacar de esta tesis es que las matrices de sensores,
junto con las técnicas de reconocimiento de patrones, se pueden utilizar para aumentar
perceptiblemente la selectividad de los sensores de óxidos metálicos. La simplicidad de
los métodos propuestos permite su uso en el desarrollo de analizadores de gases más
baratos y narices electrónicas portátiles.
A partir de la investigación realizada durante esta tesis doctoral se han elaborado 15
artículos publicados en revistas internacionales, 10 comunicaciones en las conferencias
internacionales y 3 comunicaciones en conferencias españolas.



PhD thesis of Peter Tsolov Ivanov Resume of the doctoral thesis
OF THE DOCTORAL THESIS
Title: Design, Fabrication and Characterization of Thick-Film Gas Sensors
Doctorate: Peter Tsolov Ivanov
Director: Xavier Correig Blanchar
Solid-state gas sensors have proved to be very promising for monitoring the emission of
air pollutants because they are a low cost option for constructing gas analysers. Some
problems associated to this approach, especially their deficient selectivity and high
power consumption, remain unsolved. The aim of this doctoral thesis is to develop new
sensors and sensor matrices that can improve the selectivity of metal oxide gas sensors
and decrease their power consumption.
The methodology used here consists of creating sensor matrices made from sensors with
different selectivities. As the sensor response is different at different working
temperatures and as the different dopants or catalytic filters accelerate or reduce the
sensor response, the different sensors give different reactions. If these reactions are
combined, sensor groups capable of discriminating between different pollutants can be
obtained with the help of pattern recognition techniques.
The thesis begins by reviewing the methods used for fabricating gas sensors and
discussing the problems caused by the poor selectivity of metal oxide gas sensors and
the methods for increasing their selectivity. Then, the screen-printing technique is
introduced and described. The experiments were performed with four different types of
gas sensor substrates (ceramic, silicon, microhotplate and silicon-on-insulator) and more
than 15 active layers (undoped and doped with gold, platinum, silver, titanium and
paladium tin dioxide and tungsten trioxide sensitive layers). A wide variety of volatile
compounds (ammonia, ethanol, acetone and benzene), gases (carbon monoxide,
nitrogen dioxide, methane and hydrogen sulphide) and some binary mixtures were
measured. The results obtained from quantitative and qualitative gas analysis using the
PhD thesis of Peter Tsolov Ivanov Resume of the doctoral thesis
sensor response from a simple 4 sensor based matrix led to the optimal sensor/sensor
matrix for gas/binary mixtures.
The results showed that, with the help of fuzzy ARTMAP neural networks, it is possible
to identify and simultaneously quantify the gases analysed by using only one MHP-chip
(four sensors) with the same active layer. The doped SnO2 and WO3 sensors showed
different response to the tested pollutants. Composing carefully the sensor matrix and
defining well the working temperature we were able to discriminate, with a high success
rate, between the different test gases with no need for pattern recognition techniques.
The main conclusion that can be drawn from this thesis is that sensor matrices can be
used, coupled to dynamic pattern recognition techniques, to significantly increase the
selectivity of metal oxide sensors. The simplicity of the methods implemented makes
them suitable for developing low-cost gas analysers and hand-held e-noses.
The research carried out during this doctoral thesis resulted in 15 articles being
published in international journals, 10 communications at international conferences and
3 communications at a Spanish national conference.
PhD thesis of Peter Tsolov Ivanov Resumen de la tesis doctoral

Currently there are very significant interests in printed electronics in the world. The possibility to produce electronics in a roll to roll printing process will considerably reduce the cost of the electronic devices. However, these new devices will most probably not replace the traditional silicon based electronics, but will be a complement in low cost applications such as in intelligent packages and other printable media. One interesting area is printable low cost sensors that add value to packages. In this thesis a study of the performance of low cost sensors is presented. The sensors were fabricated using commercial printing processes used in the graphical printing business. The sensors were characterized and evaluated for the intended application. The evaluated sensors were moisture sensing sensor solutions and touch sensitive sensor solutions.

A printable touch sensitive sensor solution is presented where the sensor is incorporated into a high quality image such as in point of sales displays. The sensor solution showed good touch sensitivity at a variety of humidity levels. Four printed moisture sensor concepts are presented and characterized. Firstly, a moisture sensor that shows good correlation to the moisture content of cellulose based substrates. Secondly, a sensor that measures the relative humidity in the air, the sensor has a measuring accuracy of 0.22% at high relative humidity levels. Thirdly, a moisture sensor that utilizes unsintered silver nano-particles to measure the relative humidity in the air, the sensor has a linear response at very low relative humidity levels. And fourth, an action activated energy cell that provides power when activated by moisture. A concept of remote moisture sensing that utilizes ordinary low cost RFID tags has also been presented and characterized. The remote sensor solution works both with passive and semi-passive RFID systems. The study shows that it is possible to manufacture low cost sensors in commercial printing processes.

Det är för närvarande ett stort intresse för tryckt elektronik. Att kunna tillverka elektroniska komponenter i en rulle till rulle process möjliggör en reducering av tillverkningskostnaden. Dessa nya komponenter kommer sannolikt inte konkurrera ut den traditionella kiselbaserade elektroniken utan kommer att kunna komplimentera kiselelektronik i segment där kostnaden är väldigt viktig som i intelligenta förpackningar och andra tryckta medier. Ett intressant område är tryckta sensorer som kan addera värde till förpackningar. I denna avhandling presenteras en studie kring tryckta sensorer som kan tillverkas till låg kostnad. Sensorerna är tillverkade i kommersiella grafiska tryckpressar. Sensorerna karakteriseras och utvärderas för de applikationer som de är tänkta för. I denna avhandling har fuktsensorer och beröringskänsliga sensorer undersökts.

Det presenteras en tryckt beröringskänslig sensor som integreras i ett högkvalitativt grafiskt tryck. Denna sensor är tänkt att användas i reklamskyltar för att skapa interaktivitet. Sensorn har en bra känslighet vid varierande fukthalter. Även fyra fuktsensorer presenteras och utvärderas. Den första sensorn mäter fukthalten i cellulosabaserade substrat och visar en bra korrelation till fukthalten i substratet. Den andra sensorn mäter den relativa fukten i luften, denna sensor har en mätnoggrannhet på 0.22% för höga fukthalter. Den tredje sensorn använder partiklar i nanostorlek för att mäta fukthalten i luften. Denna sensor fungerar väldigt bra vid låga fukthalter. Den fjärde sensorn är en energicell som producerar el när den blir fuktig. Även en fuktsensor som kan läsas av på håll utvärderas. Detta sensorkoncept är baserad på vanliga RFID taggar och kan användas med både passiva och semi-passiva taggar. Denna avhandling visar att det är möjligt att tillverka sensorer till en låg kostnad in en traditionell grafisk tryckpress.

Fiber tapers have attracted much attention and have been successfully employed in various applications, ranging from resonators, filters, interferometers to sensors. This thesis studies the properties of fiber tapers for the purpose of making tapered-based devices and sensors in aerospace related application where small size and light weight are critical. This thesis includes theoretical derivation and experimental verifications of distributed mode coupling in tapered single-mode fibers (SMFs) with high-resolution optical frequency-domain reflectometry (OFDR) technique. The studies are realized with OFDR through phase detection of a Mach-Zehnder interferometer (MZI), which measures local refractive index change relative to the reference arm. The wavelength shifts converted by the phase change give the group index differences between the fundamental mode and higher-order modes of fiber tapers. The energy re-distribution is observed in Rayleigh backscatter amplitude as a function of fiber length with a ~13µm resolution over the entire fiber taper, and group index difference between core and cladding modes is measured with a spatial resolution of ~2cm by using autocorrelation data processing. The thermal and mechanical properties of fiber tapers have also been characterized with OFDR. The cross-correlation wavelength shift is related to the refractive index change of the modes. It is shown that residual stress induced by the tapering process results in the inhomogeneous thermal property, which can be significantly reduced by an annealing treatment. A fiber taper with a waist diameter of ~6µm has a force sensitivity of ~620.83nm/N, ~500 times higher than that of SMF. Furthermore, polarization-preserving character of tapered polarization-maintaining fibers (PMFs) is evaluated by OFDR-based distributed birefringence along tapered PMFs. Three tapered-based micro-fiber devices have been used as effective mode selecting components to build narrow-linewidth tunable Erbium-doped fiber ring lasers. The fabrication is easy and at a low cost. 1) a tapered fiber tip forms multimode interference mechanism; 2) a two-taper MZI has been demonstrated by splitting/combining the fundamental mode and higher-order modes through fiber tapers and is tuned by bending one taper waist; 3) a novel tunable fiber Fabry-Perot filter, consisting of a hollow-core photonic bandgap fiber and a micro-fiber, is employed in the reflection mode.

Une architecture de capteurs à pixels CMOS permettant la désertion du volume sensible par polarisation via la face avant du circuit est étudiée à travers la caractérisation en laboratoire d’un capteur prototype. Les performances de collection de charge confirment la désertion d‘une grande partie de l’épaisseur sensible. De plus, le bruit de lecture restant modeste, le capteur présente une excellente résolution en énergie pour les photons en dessous de 20 keV à des températures positives. Ces résultats soulignent l’intérêt de cette architecture pour la spectroscopie des rayons X mous et pour la trajectométrie des particules chargées en milieu très radiatif. La profondeur sur laquelle le capteur est déserté est prédite par un modèle analytique simplifié et par des calculs par éléments finis. Une méthode d’évaluation de cette profondeur par mesure indirecte est proposée. Les mesures corroborent les prédictions concernant un substrat fin, très résistif, qui est intégralement déserté et un substrat moins résistif et mesurant 40 micromètres, qui est partiellement déserté sur 18 micromètres mais détecte correctement sur la totalité de l’épaisseur. Deux développements de capteurs destinés à l’imagerie X et à la neuro-imagerie intracérébrale sur des rats éveillés et libres de leurs mouvements sont présentés
An architecture of CMOS pixel sensor allowing the depletion of the sensitive volume through frontside biasing is studied through the characterization in laboratory of a prototype. The charge collection performances confirm the depletion of a large part of the sensitive thickness. In addition, with a modest noise level, the sensor features an excellent energy resolution for photons below 20 keV at positive temperatures. These results demonstrate that such sensors are suited for soft X-ray spectroscopy and for charged particle tracking in highly radiative environment. A simplified analytical model and finite elements calculus are used to predict the depletion depth reached. An indirect measurement method to evaluate this depth is proposed. Measurements confirm predictions for a thin highly resistive epitaxial layer, which is fully depleted, and a 40micrometers thick bulk less resistive substrate, for which depletion reached 18 micrometers but which still offers correct detection over its full depth. Two sensor designs dedicated to X-ray imaging and in-brain neuroimaging on awake and freely moving rats are presented

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2011.
"June 2011." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 42-43).
The potential of using carbon nanotube coated flexible cloth as strain gauges was studied. Samples were prepared by sonicating strips of cloth inside a 1mg/ml carbon nanotube in propylene carbonate solution. A dynamic mechanical analyzer was built that applied uniaxial cyclical strains to the samples and recorded the force and strain applied. The DMA also provided a constant voltage to the samples while recording the resistance response of the strain gauges. The samples were tested using the dynamic mechanical analyzer for their response to variables such as strain and time. The samples were successfully tested at strains ranging from 1% to 50%. The conductivity of the samples was measured. We studied the effects that a carboxylate and the sulfonate functional groups of the carbon nanotubes have on the strain sensors, the effect of the sonication time, and the effect that leaving the strain sensors inside the solution for different amount of times has on the strain sensors. It was discovered that the samples dried overtime, thus decreasing the conductivity of the samples and damaging the strain sensors. An encapsulation method was developed and studied to counter the drying effect. The results showed that the encapsulation method did delay the decaying of the samples. Moreover, it was concluded that the sulfonate group had higher changes in resistance than the carboxylate group. While increased sonication time did not seem to have a measurable effect on the resistance of the sulfonate CNT samples, this was not true for the carboxylate group CNTs. The carboxylate group CNTs seemed to have a higher initial resistance with longer sonication time and a lower resistance with increasing time sitting in the solution. Overall, it was concluded that carbon nanotubes have a promising potential as macro level strain sensors for high-elongation applications but more development is yet to be done.
by Juan D. Diaz.
S.B.

Multifunctional "self-sensing" materials at the frontiers of current research are generally designed to gather only a single type of information (such as quasi-static strain data). This project introduces a new sensor that is both multifunctional and dual-response, indicating its ability to not only perform in mechanical and sensing functions but also in its ability to sense multiple types of response. The proposed new class of sensing materials, comprised of nanocomposite polymer foams, exhibits measurable piezoresistive and quasi-piezoelectric phenomena in the form of change in resistance and voltage generation in response to deformation, respectively. An initial sampling of the envelope of dual-response nanocomposite foam sensors is mapped. The sensing materials can also be tailored to provide desired mechanical compliance and damping. Nanocomposite foam sensors decrease in resistance with increased strain in both static and cyclic compression environments. The quasi-piezoelectric voltage response of nanocomposite foam sensors increases linearly with compression frequency. A circuit and signal demodulation system was developed enabling simultaneous capture of a dual-response foam sensor's change in resistance and voltage generation. Measuring the two responses provides both long-term and immediate performance and health status of mechanical systems, enabling improved monitoring and decreased risk of failure.

Cancer is a major health issue that has been associated with over 80 million deaths worldwide in the last decade. Recently, significant improvements have been made in terms of treatment and diagnosis. However, despite these advancements there is still a demand for low-cost, high-accuracy, and easy-to-use technologies capable of classifying cells. Analysis of cell behavior in microfluidic deformability assays provides a label-free method of observing cell response to physical and chemical stimuli. This body of work shows advancements made toward reaching our goal of a robust and cost-effective biosensing device that allows for the identification of normal and cancer cells. These devices can also monitor cell responses to physical and chemical stimuli in the form of mechanical deformation and chemotherapeutic drugs, respectively. Our initial design was a microfluidic device that consisted of three channels with varying deformation and relaxation regions. Cell velocities from the deformations regions allowed us to distinguish between normal and cancer cells at the single-cell level. The next design used a singular deformation channel that was embedded with an array of electrodes in order to measure entry time, transit time and velocities as a single cell passes through the channel. These factors were found to reveal information about the biomechanical properties of single cells. Embedded electrodes were implemented in order to reduce post processing times of the data analysis and provide more insight into the bioelectrical information of cells. Finally, we report a microfluidic device with parallel deformation channels and a single electrode pair to improve throughput and automate data collection of deformability assays. This thesis demonstrates how microfluidic deformability assays, with and without embedded electrodes, show promising capabilities to classify different cells based on their biophysical traits which can be utilized as a valuable tool for testing responses to physical and chemical stimuli.
MS

A novel line of integrated-optic-based chemical sensors was developed. The sensors are based on modification of the optical cavity of a single-mode semiconductor distributed Bragg reflector (DBR) laser. A sensitive layer changes its refractive index in presence of a specific chemical, thus changing the effective refractive index of the section and the optical length of the cavity. This results in laser frequency shift measured either directly or by heterodyne detection using a reference laser as the second source. It is shown that DBR-laser-based sensors can achieve in principle a much higher sensitivity than passive sensors, such as Mach-Zehnder interferometers, due to the narrow linewidth of DBR lasers. The theory of DBR-laser-based sensors is described. It allows optimizing the sensitive section length and field confinement in the sensitive layer for the lowest detection limit. The optimum parameters depend on cavity losses and absorption of the sensitive material. Numerical modeling shows a wide acceptable range of sensitive section parameters for low-loss materials, while for higher-loss materials this range becomes much narrower. Narrow-linewidth DBR lasers are required for high sensitivity. In this respect, sol-gel waveguides with and without Bragg grating were incorporated in the DBR laser scheme. Single-mode operation of DBR lasers with sol-gel waveguide gratings was demonstrated for the first time, with 34-dB side mode suppression and a short-term linewidth of 150 to 500 kHz. A 3-section configuration with sol-gel waveguides and fiber grating showed 28-dB side mode suppression and a short-term linewidth of 600 kHz. Chemical sensing was performed with fiber grating, sol-gel waveguide grating, and 3-section DBR lasers. The first two types showed frequency shift of over 130 MHz in the presence of acetone vapors, and reversibility within experimental errors. The 3-section scheme showed significant dispersion of response and lack of reversibility due to parasitic reflections and instability of the setup. The effect of reflections from facets on performance of this design was examined and found to reduce the maximum sensitivity.

I characterize the behavior of microcantilever arrays which utilize the in-plane photonic transduction that I've previously developed and evaluate the performance of the microcantilever arrays in simple sensing scenarios with integrated microfluidics. First the thermal responses of microcantilevers with a variety of patterns of deposited gold films are compared. Using a scanning electron microscope, I observe the deflection thermal sensitivities of 300 µm long microcantilevers to be -170.82 nm/K for a full gold coating and -1.93 nm/K for no gold coating. Using the photonic transduction method I measure a thermal sensitivity of -1.46 nm/K for a microcantilever array with no gold. A microcantilever array integrated with microfluidics is exposed to a solution of bovine serum albumin (BSA) followed by solutions of various pH's. In all cases I observe a previously unreported transient deflection response. We find that the transient response is due to temporary nonuniform concentration distributions. In response to nonspecific binding of BSA, I observe a transient surface stress of -0.23 mN/m that agrees well with the -0.225 mN/m predicted by simulations. We hypothesize that the deflection response to pH changes is due to stress generated by conformational changes of bound BSA.The deflection response of an integrated microcantilever array to different types of flow and different flow rates is observed. Simulations of the deflection response match well with experimental results but disagree at higher flow rates. For flow rates greater than 200 µL/min, the limitation of the differential signal's dynamic range becomes apparent. We then investigate flow driven by an on-chip reciprocating reservoir pump. We demonstrate that it is possible to use the reciprocating pump to achieve high flow rates while making deflection measurements in-between reservoir actuations. Investigations of the microcantilever array noise show that flicker noise dominates below 10 Hz, while above 10 Hz, readout noise dominates. A minimum deflection noise density of 15 pW/√Hz is achieved. To improve the signal-to-noise ratio I develop algorithms for a digital lock-in amplifier with a digital phase-lock loop. In simulation the lock-in amplifier is able to improve the SNR by up to a factor of 6000, and self-lock to a noisy carrier signal without an external reference signal.

The aim of this Ph.D. project has been the design and characterization of new and more efficient luminescent tools, in particular sensors and labels, for analytical chemistry, medical diagnostics and imaging. Actually both the increasing temporal and spatial resolutions that are demanded by those branches, coupled to a sensitivity that is required to reach the single molecule resolution, can be provided by the wide range of techniques based on luminescence spectroscopy. As far as the development of new chemical sensors is concerned, as chemists we were interested in the preparation of new, efficient, sensing materials. In this context, we kept developing new molecular chemosensors, by exploiting the supramolecular approach, for different classes of analytes. In particular we studied a family of luminescent tetrapodal-hosts based on aminopyridinium units with pyrenyl groups for the detection of anions. These systems exhibited noticeable changes in the photophysical properties, depending on the nature of the anion; in particular, addition of chloride resulted in a conformational change, giving an initial increase in excimeric emission. A good selectivity for dicarboxylic acid was also found. In the search for higher sensitivities, we moved our attention also to systems able to perform amplification effects. In this context we described the metal ion binding properties of three photoactive poly-(arylene ethynylene) co-polymers with different complexing units and we highlighted, for one of them, a ten-fold amplification of the response in case of addition of Zn2+, Cu2+ and Hg2+ ions. In addition, we were able to demonstrate the formation of complexes with Yb3+ an Er3+ and an efficient sensitization of their typical metal centered NIR emission upon excitation of the polymer structure, this feature being of particular interest for their possible applications in optical imaging and in optical amplification for telecommunication purposes. An amplification effect was also observed during this research in silica nanoparticles derivatized with a suitable zinc probe. In this case we were able to prove, for the first time, that nanoparticles can work as “off-on” chemosensors with signal amplification. Fluorescent silica nanoparticles can be thus seen as innovative multicomponent systems in which the organization of photophysically active units gives rise to fruitful collective effects. These precious effects can be exploited for biological imaging, medical diagnostic and therapeutics, as evidenced also by some results reported in this thesis. In particular, the observed amplification effect has been obtained thanks to a suitable organization of molecular probe units onto the surface of the nanoparticles. In the effort of reaching a deeper inside in the mechanisms which lead to the final amplification effects, we also attempted to find a correlation between the synthetic route and the final organization of the active molecules in the silica network, and thus with those mutual interactions between one another which result in the emerging, collective behavior, responsible for the desired signal amplification. In this context, we firstly investigated the process of formation of silica nanoparticles doped with pyrene derivative and we showed that the dyes are not uniformly dispersed inside the silica matrix; thus, core-shell structures can be formed spontaneously in a one step synthesis. Moreover, as far as the design of new labels is concerned, we reported a new synthetic approach to obtain a class of robust, biocompatible silica core-shell nanoparticles able to show a long-term stability. Taking advantage of this new approach we also showed the synthesis and photophysical properties of core-shell NIR absorbing and emitting materials that proved to be very valuable for in-vivo imaging. In general, the dye doped silica nanoparticles prepared in the framework of this project can conjugate unique properties, such as a very high brightness, due to the possibility to include many fluorophores per nanoparticle, high stability, because of the shielding effect of the silica matrix, and, to date, no toxicity, with a simple and low-cost preparation. All these features make these nanostructures suitable to reach the low detection limits that are nowadays required for effective clinical and environmental applications, fulfilling in this way the initial expectations of this research project.

The aim of this Ph.D. project has been the design and characterization of new and more efficient luminescent tools, in particular sensors and labels, for analytical chemistry, medical diagnostics and imaging. Actually both the increasing temporal and spatial resolutions that are demanded by those branches, coupled to a sensitivity that is required to reach the single molecule resolution, can be provided by the wide range of techniques based on luminescence spectroscopy. As far as the development of new chemical sensors is concerned, as chemists we were interested in the preparation of new, efficient, sensing materials. In this context, we kept developing new molecular chemosensors, by exploiting the supramolecular approach, for different classes of analytes. In particular we studied a family of luminescent tetrapodal-hosts based on aminopyridinium units with pyrenyl groups for the detection of anions. These systems exhibited noticeable changes in the photophysical properties, depending on the nature of the anion; in particular, addition of chloride resulted in a conformational change, giving an initial increase in excimeric emission. A good selectivity for dicarboxylic acid was also found. In the search for higher sensitivities, we moved our attention also to systems able to perform amplification effects. In this context we described the metal ion binding properties of three photoactive poly-(arylene ethynylene) co-polymers with different complexing units and we highlighted, for one of them, a ten-fold amplification of the response in case of addition of Zn2+, Cu2+ and Hg2+ ions. In addition, we were able to demonstrate the formation of complexes with Yb3+ an Er3+ and an efficient sensitization of their typical metal centered NIR emission upon excitation of the polymer structure, this feature being of particular interest for their possible applications in optical imaging and in optical amplification for telecommunication purposes. An amplification effect was also observed during this research in silica nanoparticles derivatized with a suitable zinc probe. In this case we were able to prove, for the first time, that nanoparticles can work as “off-on” chemosensors with signal amplification. Fluorescent silica nanoparticles can be thus seen as innovative multicomponent systems in which the organization of photophysically active units gives rise to fruitful collective effects. These precious effects can be exploited for biological imaging, medical diagnostic and therapeutics, as evidenced also by some results reported in this thesis. In particular, the observed amplification effect has been obtained thanks to a suitable organization of molecular probe units onto the surface of the nanoparticles. In the effort of reaching a deeper inside in the mechanisms which lead to the final amplification effects, we also attempted to find a correlation between the synthetic route and the final organization of the active molecules in the silica network, and thus with those mutual interactions between one another which result in the emerging, collective behavior, responsible for the desired signal amplification. In this context, we firstly investigated the process of formation of silica nanoparticles doped with pyrene derivative and we showed that the dyes are not uniformly dispersed inside the silica matrix; thus, core-shell structures can be formed spontaneously in a one step synthesis. Moreover, as far as the design of new labels is concerned, we reported a new synthetic approach to obtain a class of robust, biocompatible silica core-shell nanoparticles able to show a long-term stability. Taking advantage of this new approach we also showed the synthesis and photophysical properties of core-shell NIR absorbing and emitting materials that proved to be very valuable for in-vivo imaging. In general, the dye doped silica nanoparticles prepared in the framework of this project can conjugate unique properties, such as a very high brightness, due to the possibility to include many fluorophores per nanoparticle, high stability, because of the shielding effect of the silica matrix, and, to date, no toxicity, with a simple and low-cost preparation. All these features make these nanostructures suitable to reach the low detection limits that are nowadays required for effective clinical and environmental applications, fulfilling in this way the initial expectations of this research project.

This Ph.D. Thesis concerns the design and characterisation of functional electrochemical interfaces in organic electronic devices for bioelectronic applications. The Thesis is structured as follows: Chapter I – Technological context that has inspired the research, introduction to Organic Bioelectronics and literature review concerning Organic Electrochemical Transistors (OECTs) for sensing applications. Chapter II – Working principle of an all-polymeric OECT and operando microscopic characterization using scanning electrochemical techniques. Chapter III – Dopamine detection with all-polymeric OECT sensors. Development of a potentiodynamic approach to address selectivity issues in the presence of interfering species and design of a needle-type, sub-micrometric OECT sensor for spatially resolved detection of biological Dopamine concentrations. Chapter IV – Development of an OECT pH sensor. Characterization of the electrochemical transducer and functionalization of the OECT gate electrode with the sensing material. Potentiodynamic and potentiostatic operation modalities are explored and the sensing performances are assessed in both cases. The final device is realized on a flexible substrate and tested in Artificial Sweat. Chapter V – Study of two-terminal, electrochemically gated sensors inspired by the OECT configuration. Design and characterization of novel functional materials showing a potentiometric transduction of the chemical signal that can be exploited in the realization of electrochemical sensors with simplified geometry for wearable applications. Chapter VI – Conclusion.

The water content in surrounding air is an important factor for the well-being of humans and animals, as the level of comfort is determined by a combination of two factors: relative humidity and ambient temperature. Humidity is also an important factor for operating certain equipment such as high-impedance electronic circuits, electrostatic-sensitive components, high-voltage devices, fine mechanisms, etc. Nonetheless, moisture is the ingredient common to most manufactured goods and processed materials. Thus, humidity sensors have been receiving wide attentions since decades. Yet, despite the high request, major advances in these sensors in terms of simple structure, lower cost, better selectivity, durability and reliability are always needed. Throughout the years, a large number of materials based on polymers, composite and ceramics have been tested, due to their own features and specific operating conditions. However, great attention has been paid to ceramic materials due to their chemical inertness which allow them to operate in harsh conditions. Amongst the different studied humidity sensors, impedance-based ones are used most commonly. The operation principle of the impedance sensors is based on the dependence of the impedance (or either capacitance or resistance) of the sensor element recognizing the nature and amount of water molecules on the surface or in the bulk. The resistance or impedance of the resistive-type sensor decreases as the relative humidity (RH)increases. Ions or electrons, or both of them, are the conduction carriers for resistive-type humidity sensors. The common construction of the resistive-type ceramic humidity sensors consists of a ceramic substrate with noble metal interdigitated electrodes coated with humidity sensing ceramic materials, both deposited by screen-print technique [1]. Metal oxides and metal oxide based composites are the most popular materials to be used as resistive sensing elements: TiO2, TiO2–SnO2, TiO2–WO3, TiO2–Cu2O–Na2O, KTaO3//TiO2(bilayered), TiO2/KTaO3 (bilayered), TiO2–K2O–LiZnVO4, Al2O3, AlO(OH), SiO2, WO3, Cr2O3–WO3, SnO2, a noble metal doped SnO2, SnO2: ZrO2 (bilayered), single Sb doped SnO2, K+-dopedSnO2–LiZnVO4, MnO2 –Mn3O4, Li+-doped Fe2O3, Au3+ and Li+ co-doped Fe2O3, Li+, Zn2+ and Au3+ co-doped Fe2O3, NiMoO4–MoO3, Li+-doped NiMoO4–MoO3, CuMoO4–MoO3 and PbMoO4–MoO3 [1]. Spinel-type oxides and composites based on spinel-type oxides are also used for humidity resistive sensing elements: MgAl2O4, Sr2+-doped CoAl2O4, Sr2+-doped BaAl2O4, Sr2+-doped ZnAl2O4, MgFe2O4, MgAl2O4–MgFe2O4, Mg0.8Li0.2Fe2O4, Mg0.9Sn0.1Fe2O4, MgFe2O4–CeO2, MgCr2O4–TiO2, Zn2SnO4–LiZnVO4 and ZnCr2O4–K2CrO4 [1]. Finally, Perovskite-type oxides and composites based on perovskites have been used for humidity sensing elements too: NaH2PO4 doped BaTiO3, MnTiO3, Li+ doped Ca0.35Pb0.65TiO3, BaNbO3, LaFeO3, K+-doped nanocrystalline LaCo0.3Fe0.7O3 (La0.93K0.07Co0.3Fe0.7O3) and Sr-doped SmCrO3 (Sm0.90Sr0.10CrO3) [1]. Preparation techniques can considerably affect the physical, chemical and gas sensing properties of the metal oxide sensors. Developments of new preparative routes, as well as compositional variations, are two perspective approaches for the design of highly sensitive and selective gas sensor materials.Reference: [1] T.A. Blanka, L.P. Eksperiandova, K.N. Belikov, Recent trends of ceramic humidity sensors development: A review. Sensors and Actuators B, 228 (2016) 416–442.

The ATLAS pixel detector will be upgraded with a new Insertable B-layer (IBL). The IBL will be inserted between the existing pixel detector and the reduced diameter vacuum pipe of the Large Hadron Collider. The extreme operating conditions at this location have required the development of new radiation hard pixel sensor technologies and a new front end chip.3D-silicon sensors will populate 25% of the IBL sensing area. They are a newgeneration of micro-machined sensors with electrodes etched inside the silicon bulk rather than on the wafer surface. 3D-silicon sensors were studied by performing simulations, laboratory measurements and beam tests on irradiated and not irradiated samples.This thesis describes the development of a fast algorithm of the signal response in 3D-silicon sensors using Geant4 simulations. The simulation of the signal response is compared to actual data from test-beam and radioactive source measurements. The setup for each of these measurements is also simulated in Geant4 using experience gained after working with the real setup.

O presente trabalho consiste no desenvolvimento de uma nova técnica de identificação de materiais poliméricos por meio do uso de um nariz eletrônico. Narizes eletrônicos têm sido desenvolvidos para detecção automática e classificação de odores e gases. São instrumentos capazes de medir a concentração ou intensidade odorante de modo similar a um olfatômetro, mas sem as limitações inerentes ao uso de painel humano, o que é altamente desejável. O nariz eletrônico é composto por um sistema de sensores, no nosso caso, utilizamos um arranjo de quatro sensores, que foram confeccionados pela deposição de finos filmes de polímeros condutores dopados sobre a superfície de eletrodos interdigitados. Estes sensores foram conectados a condutivímetros acoplados a um computador de uso pessoal (PC) através de um conversor AD. O PC era dotado de softwares de aquisição e tratamento de dados. Amostras dos materiais a serem analisados foram aquecidas a 257°C e o arranjo de sensores foi exposto aos compostos voláteis produzidos durante esse aquecimento. Realizaram-se 30 ensaios formados por períodos de exposição (5 segundos; compostos voláteis) intercalados por períodos de recuperação (45 segundos; ar puro). Os dados obtidos foram tratados estatisticamente por Análises de Componentes Principais (PCA). Esse arranjo de sensores mostrou-se eficiente, sendo capaz de diferenciar nove tipos de materiais poliméricos testados. Apresentou 100% de acerto em 30 ensaios de classificação realizados.
This research consists in the development of a new technique capable of the identification of polymeric materials using an electronic nose. Electronic noses have been developed for automatic detection and classification of odors, vapors and gases. They are instruments capable of measuring the concentration or intensity of an odorant similarly to an olfactometer, but without the inherent limitations of the human panel, which is highly desired. The electronic nose is composed by a system of chemoresistive sensors, in this case, an array of four sensors was used, which were made through a deposition of thin films of doped conductive polymers, on the surface of interdigitated electrodes. These sensors were connected to conductivity meters coupled to a personal computer (PC) through AD converters. The PC had acquisition and data processing softwares installed on it. Thirty readings were made or each analyzed polymer consisting of alternated 5 seconds exposure periods and 45 seconds recovery periods. The collected data were statistically processed by Principal Component Analysis (PCA). This electronic nose was efficient, being able to identify nine types of polymeric materials through the analysis of the different volatile compounds released when these materials were heated to the heat of 257ºC. A 100% correct classification score was obtained in the 30 sets of analysis.

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xi, 98 p.; also includes graphics. Includes bibliographical references (p. 93-98). Available online via OhioLINK's ETD Center

Brillouin scattering based fibre optic sensors have been actively researched over the past decade due to their enhanced sensitivity to environmental parameters such as temperature and strain. Applications range from dynamic health monitoring of civil structures such as bridges, pipelines, and nuclear reactors to real-time threshold applications such as fire detection. As temperature and strain changes often represent the first symptoms of structural degradation, the development of Brillouin scattering based technology will bear considerable scientific as well as economic benefit. Brillouin sensors employing the probe-pump amplification technique obtain distributed spatial information along a fibre using narrow pulses. In this study, the impact of pulse width and extinction ratio on the overall Brillouin spectrum shape is investigated. From independent theoretical and experimental investigations, a comprehensive curve fitting method is proposed to reveal the physical nature of Brillouin scattering in the transient regime.

A preliminary gas detection study was conducted on as-grown multi-walled carbon nanotubes and anodized aluminum oxide (MWNTs/AAO) template. The material demonstrated room temperature gas sensitivity and p-type semiconductor characteristics. Plasma-etched MWNTs/AAO templates were employed to construct capacitive gas sensors. The capacitances of the sensors were sensitive to both reducing and oxidizing gases at room temperature. Single-walled carbon nanotubes (SWNTs) dispersed in binder andamp;aacute;-terpineol were applied on sensor platforms to form resistive gas sensors. The sensors demonstrated excellent sensitivity to low concentrations of reducing and oxidizing gases at room temperature, which suggests the p-type semiconducting behavior of SWNTs. The sensor recovery was found to be incomplete at room temperature in flow of nitrogen and air, thus possible solutions were investigated to enhance sensor performance. The sensor operating principles and suggestions for possible future work are discussed. The room temperature and air background functionality of the sensor suggest that SWNT is a promising gas sensing material for application in ambient conditions.

Approved for public release; distribution is unlimited
THz radiation covers the region of the electro-magnetic (EM) spectrum between the microwaves and infra-red (IR), corresponding to frequencies from approximately 100 GHz to 10 THz. Recently, new imaging techniques, which take advantage of the special properties of THz waves, have been developed. Despite the great interest in these new techniques, limitations such as the lack of appropriate detectors and powerful sources are placing the technology in the research domain. The objective of this thesis is to characterize and analyze a set of fabricated bi-material detectors integrated with thin metamaterial films. Different experimental measurements were performed to measure the main figures of merit of the detectors and analyze them. Initially, optical microscopy was used to measure the dimensions of the sensors and stress induced curvature. Then, the thermal response of the sensors was tested and analyzed. The responsivity, the speed of operation and the minimum detected incident power were measured using a quantum cascade laser (QCL), operating at 3.8 THz. The measured experimental data agree well with the theoretical calculated values of the performance parameters.

Carbon dioxide is an important gas for life on Earth. But as human activities have been expanding throughout modern history, the CO2 concentration in the atmosphere is increasing. High concentrations of carbon dioxide can lead to various consequences, such as climate change and poor air quality both indoors and outdoors. It is therefore of importance to detect this gas, in order to understand our environment, and to avoid health impacts that it may cause. Non-dispersive infrared sensors are widely used in CO2 sensing and are based on optical absorption technology. This thesis investigates the optical performance of suspended waveguides for non-dispersive infrared sensors, with regard to different material qualities, i.e. monocrystalline and polycrystalline silicon, and geometries of these waveguides. The waveguides that are studied in this thesis consist of splitters, and at the end of each splitter a grating coupler that projects the IR radiation perpendicularly from the plane of the chip. Measurements are conducted to evaluate the IR radiation propagation loss of the waveguides and their feasibility for sensing carbon dioxide. It has been found that longer waveguides suffer from high propagation losses. When comparing the polycrystalline silicon with monocrystalline silicon waveguides, it has been observed in the measurements that the IR radiation propagates better in monocrystalline silicon waveguides than in polycrystalline silicon because of their crystal structures. The measured propagation loss in polycrystalline silicon waveguides is less than the loss obtained for the monocrystalline silicon waveguides, although some intensities from the grating couplers are excluded in the calculations, due to low signal strength. It is also concluded that the studied waveguides are feasible for detecting carbon dioxide with a concentration of 1%. Further investigation regarding the feasibility of gas sensing using lower concentrations of CO2 would be interesting for future work.

Afferent activity, from the statocyst thread hairs of Carcinus maenas (L.), was altered by micro-pressure stimulation. Recordings showed that thread hair responses lag peak pressuring during low (1 kPa) pressure stimulation, but that response gain was maximal during such pressures. Increasing amplitude and decreasing cycle period reduced both lag and response gain. Data suggest a role for the thread hair in determining pressures and rates of pressure change of tidal periodicity. All available data were compatible with a transduction mechanism differentially activating paired bipolar neurones to a pressure increase. During angular acceleration evoked responses, post stimulus time histograms revealed an increased phase lag (re peak acceleration) with increasing pressure. Abrupt increases in directional class of unit responding to oscillation appeared at between 5-15 kPa. Comparative experiments, using the portunid crabs Necora puber (L.) and Liocarcinus depurator (L.) found that responses to rapid rates of pressure change were significant. No such responses were found in Carcinus maenas. Interneurone recordings were composed of abrupt elevations in spike frequencies followed by quiescent periods. In freshly caught animals, burst duration does not differ significantly throughout the tidal period. The quiescent period (interburst interval) was significantly longer at periods of expected low tide. Recordings made during pressure cycling show periodicities similar to that of the imposed pressure cycle. Applying 30 minute period, 30 kPa hydrostatic pressure cycles to loosely tethered crabs reduced burst duration significantly. Interburst interval increases significantly during pressure application. At cycle periods greater than 120 minutes, interburst intervals and burst durations were not significantly affected. At longer cycle periods (between 3-12 hrs) there were spike frequency and distributions of activity cycles comparable to those found in freshly caught, free-walking crabs. Preliminary results from recordings of statocyst afferents in the mysid Praunus flexuosus (Müller) show graded responses to micro-pressure stimulation.

PREPARATION AND CHARACTERIZATION OF SEMICONDUCTOR NANOSTRUCTURES FOR CHEMICAL SENSORS APPLICATIONS
PREPARATION AND CHARACTERIZATION OF SEMICONDUCTOR NANOSTRUCTURES FOR CHEMICAL SENSORS APPLICATIONS

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.
Includes bibliographical references (leaf 31).
A novel dual differential hall-effect based proving ring force sensor has been designed, manufactured, and tested. Strain gauge based force sensors are among the most common methods of measuring static and dynamic forces, yet they suffer from a wide array of negative attributes including: high cost due to signal amplification instrumentation, high temperature sensitivity, and only moderate dynamic range. The goal of the research herein described was to design and test a low cost, high dynamic range force sensor. Hall-Effect sensors have high bandwidth (>100 kHz), a wide dynamic range, are low in cost (<0.5$), and are ideally suited to dynamic and static force measurements. Proving rings - diametrally loaded hoops of metal, have long been used to measure force yet suffer many setbacks due to their historical designs utilizing mechanical and strain gauge methods of strain detection. A novel nested proving ring flexure has been combined with hall-effect sensors to fulfill the design requirements of a low cost and robust force sensor. Initial data demonstrates that the nested proving ring force sensor herein described is capable of resolving forces of in the range of 0 to 30 Newtons with an accuracy of 0.235 Newtons, all at a potential mass-manufactured cost of U.S. $10.00 per unit.
by Christopher W. Rivest.
S.B.

Zinc is an important micronutrient but the biological function of its labile form is poorly understood. Zinc selective fluorescence sensors, recognized as the major tool to gain information about the role of zinc in living systems, have been attracting more and more interest. The most promising solution currently being studied comes in the form of ratiometric sensors. Unlike sensors based on the switch-on mechanism, ratiometric sensors determine the free metal concentration directly from the ratio of the emission intensities at two wavelengths. The major restriction on the design of this type of sensor is from the necessity for a spectral-shift upon binding metal ions. To develop novel ratiometric sensors, we have developed designs based on excited-state intramolecular proton transfer (ESIPT). In the absence of ZnII at neutral pH, the 2-(2 -sulfonamidophenyl)benzimidazole family undergoes ESIPT to yield a highly Stokes-shifted emission from the proton-transfer tautomer. Coordination of ZnII inhibits the ESIPT process and yields a significant hypsochromic shift of the fluorescence emission maximum. By implementing structural modifications, we were able to gauge free ZnII concentrations in the millimolar to picomolar range. To tune the peak excitation towards lower energy, a property that is of particular importance in the light of biological applications, we modified the platform molecule with extended pi-conjugation and by substituent engineering. The position of the modification and the nature of the substituents strongly influenced the photophysical properties of the investigated derivatives. Several fluorophores revealed emission ratiometric properties with a large dynamic range combined with a peak absorption beyond 350 nm, rendering these probes promising candidates for applications. To further understand the origin of the substituent effect, we studied five derivatives for the solvatochromic shift analysis and quantum chemical studies. The results showed that the negative solvatochromic shift behavior was most pronounced in protic solvents presumably due to specific hydrogen-bonding interactions. The extrapolated gas-phase emission energies correlated qualitatively with the trends in Stokes shifts, suggesting that solute-solvent interactions do not play a significant role in explaining the divergent emission energy shifts. Detailed quantum chemical calculations not only confirmed the moderately polarized nature of the ESIPT tautomers but also provided a rationale for the observed emission shifts based on the differential change in the HOMO and LUMO energies. This study revealed the great potential of 2-(2 -arylsulfonamidophenyl)- benzimidazoles, such as tunable peak absorption and emission, a very wide dynamic range regarding to zinc binding, very little solvent polarity dependence, and especially, the emission ratiometric property. All these properties make this system a unique candidate to tackle the problems in the research of zinc biology.

A phenomenon termed the piezoionic effect is described and characterized in various ionic polymers including polymer networks containing aqueous electrolytes (hydrogels) and organic electrolytes. Initial observations suggest that when an ion containing polymer is compressed, a concentration gradient is induced by the pressure differential, leading to an electrical potential difference detectable at electrodes placed at compressed and uncompressed portions of the polymer. The work focuses on the fundamental characterization of the nature of the piezoionic transduction to probe the effects of relative mobilities of the ions present in the system. The effective ion radii due to ion-solvent interactions and electrostatic ion-polymer interactions have been investigated for their contribution in dictating the piezoionic behavior by NMR measurements of the self-diffusion coefficients. The results are qualitatively correlated to the voltage response to mechanical compression of the polymer samples. Following the experiments, a numerical model is developed which incorporates a number of contributing events believed to be taking place in a concerted manner to cause the piezoionic effect. The deformation induced solvent flow is modeled by means of Biot’s constitutive equations on poroelasticity, a combination of thermodynamic equilibrium and Darcy’s law. The Darcy’s flow induced is then used as the input to model transport of dilute species. Here, the convective factor is being continuously modulated by Darcy’s flow, while Fickian diffusion concurrently takes place. The ionic species experience different displacements due to Stokes' drag experienced by the solvation spheres of the ionic species and solvent molecules and the electrostatic interactions between the charged polymer chains and the mobile ions. Furthermore, this non-homogeneous ionic charge distribution yields a voltage distribution via the Poisson’s equation. This voltage distribution is used to account for the migration of ionic species. The following chapter is dedicated to a novel electrochemical method and modelling approach designed to probe various ionic polymers, some electronically conductive and others interpenetrated, to determine the phase-wise contributions to ionic conductivities. Finally, potential applications of the piezoionic polymers as soft sensors in medicine, particularly in unobtrusive and longitudinal monitoring of physical parameters, are discussed and some preliminary prototypes are introduced and ultimate feasibility is assessed.
Applied Science, Faculty of
Graduate

The main purpose of this thesis was to investigate and characterize the use of piezoelectric yarn for use in textile (fingertip) pressure sensors in glove applications. Such applications could include healthcare, security and safety, game applications or intelligent control. Piezoelectric materials generate a voltage when pressed or squeezed. Poly(vinylidene fluoride) (PVDF) is a polymorphic material with piezoelectric properties. PVDF yarns were integrated into block sensors. These blocks consist of thermoplastic material glued to a knitted supporting fabric. The electrical signal given off by the PVDF yarn was measured with the help of an oscilloscope. The block sensor generated a distinguishable signal under a dynamic compression of 0.003 N, indicating that the structure is sensitive enough compared to the average male fingertip sensitivity threshold (0.0054N).
Program: Master programme in Textile Engineering

Small satellites, and CubeSats in particular, have quickly become a hot topic in the aerospace industry. Attitude determination is currently one of the most intense areas of development for these miniaturized systems and future Cal Poly satellite missions will depend heavily on magnetometers. In order to utilize magnetometers as a viable source of attitude knowledge, precise calibration is required to ensure the greatest accuracy achievable. This paper outlines a procedure for calibrating and testing magnetometers on the next generation of Cal Poly CubeSates, utilizing a Helmholtz cage to simulate any desired orbital magnetic field that would be experienced by a spacecraft around Earth, as well as investigation of magnetic interference as a result of on-board electrical activity.

Dins de l’amplia gama de nanocompòsits, la incorporació de materials conductors de carboni nanoestructurats, entre els quals s’hi troben els nanotubs de carboni (NTCs) i el grafè, a dins d’una matriu polimèrica aïllant, és una forma molt atractiva de combinar les propietats mecàniques i elèctriques úniques del material de farciment amb els atributs dels plàstics. Concretament, els materials nanocompòsits basats en carboni han jugat un gran lideratge en el camp de l’electroquímica analítica, sobre tot en el desenvolupament de dispositius (bio)sensors, degut a les seves interessants avantatges respecte a un material conductor pur. Aquestes avantatges els hi proporcionen un alt valor afegit, com versatilitat, durabilitat, una fàcil regeneració de la superfície i integració, simplicitat a l’hora d’incorporar diferents (bio)modificadors o una baixa corrent de fons, entre d’altres. En aquest sentit, aquesta tesi aborda el desenvolupament de sensors nanocompòsits avançats de tipus amperomètrics que, havent sigut optimitzada la seva relació carboni/polímer, poden ser modificats amb un ampli ventall de nanopartícules (NPs) per millorar-ne la seva eficiència electroanalítica. Les propietats elèctriques d’aquests nanocompòsits i, per tant, la seva aplicabilitat analítica, es troben directament influenciades tant per la naturalesa de les partícules conductores com per la quantitat i distribució espacial de les mateixes a través de la matriu polimèrica aïllant. Una de les propietats electroquímiques més importants que envolten a aquests materials, és la similitud del seu comportament electroquímic amb el d’un array de microelèctrodes. Per tant, una optimització de la seva relació carboni/polímer respecte a la naturalesa del material conductor de partida, permetrà assolir una major dispersió de les àrees conductores a través de les zones no conductores, presentant així beneficis similars als d’un array de microelèctrodes. A més, és conegut que alguns paràmetres, tals com la resistivitat del material compost, la transferència electrònica, la robustesa del material i la corrent capacitiva es troben fortament influenciades per la naturalesa física de la mostra de nanotubs de partida, com és la seva relació longitud/diàmetre i la seva puresa, fet que poden influir fortament la resposta electroanalítica final del material transductor. Sota aquest context, la primera etapa de la Tesi va consistir en la implementació d’un conjunt de tècniques instrumentals que, aplicades de manera sistemàtica, han permès la caracterització i la optimització de la composició dels materials nanocompòsits basats en nanotubs de carboni i resina epoxi (Epotek H77) en relació a la naturalesa dels NTCs de partida per a la fabricació de sensors electroquímics més eficients. El protocol de caracterització dut a terme inclou eines elèctriques, electroquímiques, morfològiques, microscòpiques, espectroscòpiques i electro-analítiques. Un cop optimitzada les proporcions de CNT/epoxi, el següent pas va consistir en millorar el rendiment analític d’aquests sensors electroquímics nanocompòsits incorporant-ne diferents NPs per a la introducció d’algun tipus d’efecte electrocatalític. Per arribar a aquesta fita, es va desenvolupar una metodologia simple per a la síntesi d’una amplia gama de NPs. La Síntesi Intermatricial (IMS) va ser utilitzada com a tècnica verda per al disseny de tres rutes diferents que permetin una incorporació personalitzada d’aquestes NPs dintre del material transductor, obtenint així sensors amperomètrics més sensibles a diferents analits. Finalment, els estudis de caracterització i funcionalització implementats en els sensors nanocompòsits basats en NTCs han estat estesos a materials nanocompòsits basats en una altra forma al·lotròpica del carboni: el grafè, el qual és l’últim descobriment en termes de material de carboni nanoestructurat.
Entre la amplia gama de nanocompósitos, la incorporación de materiales conductores nanoestructurados de carbono, entre los que se encuentran los nanotubos de carbono (NTCs) y el grafeno, dentro de una matriz polimérica aislante, es una forma muy atractiva de combinar las propiedades mecánicas y eléctricas únicas del material de relleno con los atributos de los plásticos. Concretamente, los materiales nanocompósitos basados en carbono han jugado un gran liderazgo en el campo de la electroquímica analítica, sobre todo en el desarrollo de dispositivos (bio)sensores, debido a sus interesantes ventajas con respecto a un material conductor puro. Dichas ventajas les proporcionan un alto valor añadido, como versatilidad, durabilidad, fácil regeneración de la superficie e integración, simple incorporación de (bio)modificadores o baja corriente de fondo, entre otras. En este sentido, esta tesis aborda el desarrollo de sensores nanocompósitos avanzados de tipo amperométrico que, habiendo sido optimizada su relación carbono/polímero, pueden ser modificados con un amplio abanico de nanopartículas (NPs) para mejorar su eficiencia electroanalítica. Las propiedades eléctricas de estos nanocompósitos y, por lo tanto, su aplicabilidad analítica, están directamente influenciadas tanto por la naturaleza de las partículas conductoras como por la cantidad y distribución espacial de éstas a través de la matriz polimérica aislante. Una de las propiedades electroquímicas más importantes que envuelven a estos materiales es la similitud de su comportamiento electroquímico con respecto a un array de microelectrodos. Por lo tanto, una optimización de la relación carbono/polímero con respecto a la naturaleza del material conductor de partida permitirá lograr una mayor dispersión de las áreas conductoras a través de las zonas no conductoras, presentando beneficios similares a los de un array de microelectrodos. Además, es conocido que algunos parámetros, tales como la resistividad del material compuesto, la transferencia electrónica, la robustez del material y la corriente capacitiva están fuertemente influenciadas por la naturaleza física de la muestra de nanotubos de partida, como son su relación longitud/diámetro o su pureza, hecho que pueden influir fuertemente en la respuesta electroanalítica final del material transductor. Bajo este contexto, la primera etapa de esta tesis consistió en la implementación de un conjunto de técnicas instrumentales que, aplicadas de manera sistemática, han perimitido, la caracterización y optimización de la composición de materiales nanocompósitos basados en nanotubos de carbono y resina epoxi (Epotek H77) con respecto a la naturaleza de los NTCs de partida para la fabricación de sensores electroquímicos más eficientes. El protocolo de caracterización llevado a cabo incluye herramientas eléctricas, electroquímicas, morfológicas, microscópicas, espectroscópicas y electroanalíticas. Una vez optimizada las proporciones de NTC/epoxi, el siguiente paso consistió en mejorar el rendimiento analítico de estos sensores electroquímicos nanocompósitos incorporándoles diferentes NPs con la finalidad de introducir algún tipo de efecto electrocatalítico. Para alcanzar este objetivo, se desarrolló una metodología simple para la síntesis de una amplia gama de NPs. La Síntesis Intermatricial (IMS) fue utilizada como técnica verde para el diseño de tres rutas diferentes que permitan una incorporación personalizada de estas NPs en el material transductor, obteniendo así sensores amperométricos más sensibles a diferentes analitos. Finalmente, los estudios de caracterización y funcionalización implementados en los sensores nanocompósitos basados en NTCs han sido extendidos para materiales nanocompósitos basados en otra forma alotrópica del carbono: el grafeno, el cual es el último descubrimiento en términos de material de carbono nanoestructurado.
Among the wide range of nanocomposites, the incorporation of conducting nanostructured carbon materials, such as carbon nanotubes (CNTs) and graphene, into an insulating polymeric matrix is a very attractive way to combine the unique mechanical and electrical properties of individual filler with the advantages of plastics. Concretely, carbon–based nanocomposite materials have played a leading role in the analytical electrochemistry field, particularly in (bio)sensor devices, due to their interesting advantages regarding to a pure conductive material, such as versatility, durability, easy surface regeneration and integration, facile incorporation of a variety of (bio)modifiers or low background current, among others. Accordingly, this thesis tackles the development of advanced amperometric nanocomposite sensors that having been optimized regarding to carbon/polymer composition ratios, can be tunable with different types of nanoparticles (NPs) for improving their electroanalytical efficiency. The electrical properties of these nanocomposites and, therefore, their analytical applicability, are directly influenced by the conducting particles nature and the amount and spatial distribution of them through the insulating polymeric matrix. One of the most important electrochemical properties of these materials is the similarity of their electrochemical behavior with a microelectrode array. Thus, an optimization of the carbon/polymer ratio with respect to the nature of the conducting material will allow to achieve a greater dispersion of the conducting areas through the non-conducting areas, presenting similar benefits to the microelectrode array. In addition, it is known that some parameters, such as composite resistivity, heterogeneous electron transfer rate, material robustness and background capacitance current are strongly influenced by the physical nature of the raw CNT sample, such as their diameter/length ratio and purity, fact that may strongly influences the final electroanalytical response of the transducer material. Under this context, the first step of this thesis consisted of implementing a group of instrumental techniques that, systematically applied, have allowed the characterization and optimization of nanocomposite materials composition based on CNTs and epoxy resin (Epotek H77) in relation to the nature of the raw CNT sample for the fabrication of more efficient electrochemical sensors. The developed characterization protocol includes electrical, electrochemical, morphological, microscopic, spectroscopic and electroanalytical tools. Having been optimized the MWCNT/epoxy composition ratios, the next step consisted of enhancing the analytical performance of these electrochemical nanocomposite sensors introducing some electrocatalytical effect by the incorporation of different NPs. For this goal, a simple methodology for synthesizing a wide range of different NPs has been developed. Intermatrix Synthesis (IMS) has been used as a green technique to design three different routes for CNT/epoxy nanocomposite electrodes modification, which offer a customized way for the preparation of sensitive amperometric sensors. Finally, the characterization and functionalization studies applied for CNT–based electrochemical nanocomposite sensors have been extended for nanocomposite materials based on another allotropic form of carbon: the graphene, which is the last discovery in terms of nanostructured carbon material.

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Esse trabalho apresenta a produção e caracterização estrutural e morfológica das perovskitas simples TRFeO3 (TR = Sm, Eu, Gd), e o estudo da possibilidade de utilização desses sistemas como sensores de gás. Todas as amostras de TRFeO3 foram produzidas pela síntese de reação no estado sólido, que é uma síntese ainda pouco explorada na literatura para a obtenção desse sistema. O estudo das propriedades estruturais foram realizados por difração de raios X e adsorção e dessorção de N2, e a análise morfológica foi realizada através da microscopia eletrônica de varredura (MEV). Todas essas análises foram estudadas em função da temperatura e tempo de sinterização, bem como do cátion da terra rara utilizada. Através das análises por difratometria, foi possível a identificação da fase formada e a estimativa do tamanho médio do cristalito. Tais análises revelaram coexistência de fase com o composto TR3Fe5O12 para amostras sinterizadas a 1200°C, independente do tempo de sinterização utilizado, onde houve uma tendência a um equilíbrio na formação das fases. Já as amostras sinterizadas a 1100°C apresentaram-se monofásicas com o composto TRFeO3, com tamanho de cristalito variando conforme o tempo de sinterização. As imagens de MEV mostraram uma morfologia porosa, adequada para sensores de gás, apresentando grãos com formatos arredondados e formação de pescoço, conforme o tempo de sinterização utilizado. Independente da temperatura e tempo de sinterização, o tamanho dos grãos variaram em torno de 1 mm. Para avaliar a sensibilidade aos vapores de gasolina, foi desenvolvido um sistema baseado em medidas de resistividade elétrica, usando o método de 4-fios de Kelvin. Os resultados revelaram que um mecanismo diferente da literatura, onde a resistividade do material diminuiu quando exposto à atmosfera da mistura ar sintético/gasolina, a partir da temperatura ambiente, com boa reprodutibilidade. Através da dinâmica de tempo de resposta, em alta concentração de vapor do combustível utilizado, foi verificado que a capacidade sensorial dos compostos estudados, possivelmente, possui uma limitação com relação aos parâmetros estruturais, já que ambas propriedades estão relacionadas. Essa observação foi comprovada através do estudo realizado pelas medidas de adsorção e dessorção de N2, onde a área superficial das amostras foi em torno de 1,8 m2/g, o que diminui, significantemente, a sensibilidade.
This paper presents the production and structural and morphological characterization of simple perovskites REFeO3 (RE = Sm, Eu, Gd), and the possibility of using such systems as gas sensors. All REFeO3 samples were produced by the synthesis of solid state reaction, which is still little explored in the literature to obtain this system. The study of structural properties were carried out by X-ray diffraction and N2 adsorption and desorption, and the morphological analysis by scanning electron microscopy (SEM). All these tests were studied as a function of temperature and sintering time, and the rare earth cation used. Through this analysis by diffraction was possible to identify the phase formed and the estimated average size of crystallite. Such analysis revealed the coexistence of phase with the compound RE3Fe5O12 for samples sintered at 1200°C, regardless of time of sintering, where there was a tendency to an equilibrium in the formation stage. The samples sintered at 1100°C were presented with the monophasic compound REFeO3, with crystallite size varying according to the sintering time. The SEM images showed a porous morphology, suitable for gas sensors, showing grains with rounded shapes and neck formation, in accordance with the sintering time used. The grain size varied around 1 mm independent of temperature and sintering time. A system based on measurements of electrical resistivity, using the method of 4-wire Kelvin, was developed to detect the sensitivity to the vapors of gasoline. The results revealed that a different mechanism from literature, where the resistivity of the material decreased when exposed to atmospheric mixing synthetic air/gasoline from the ambient temperature, with good reproducibility. Through the dynamic response time, at high concentration of gasoline vapor, it was found that the sensory ability of the compounds studied, possibly, has a limitation with respect to structural parameters, since both properties are related. This observation was confirmed by the study performed by the measures of the adsorption and desorption of N2, where the surface area of the samples was about 1.8 m2/g, which decreases significantly the sensitivity.

Thesis (Ph. D.)--University of New Orleans, 2005.
Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry."--Dissertation t.p. Vita. Includes bibliographical references.

Surface acoustic waves (SAWs) have a large number of applications and the majority of them are in the sensor and actuator fields targeted to satisfy market needs. Recently, researchers have focused on optimizing and improving device functions, sensitivity, power consumption, etc. However, SAW actuators and sensors still cannot replace their conventional counterparts in some mechanical and biomedical areas, such as actuators for liquid pumping under microfluidic channels and sensors for real-time cell culture monitoring. The two objectives of this dissertation are to explore the potential of piezoelectric materials and surface acoustic waves for research on actuators and sensors in the mechanical pump and biosensor areas. Manipulation of liquids in microfluidic channels is important for many mechanical, chemical and biomedical applications. In this dissertation, we first introduced a novel integrated surface acoustic wave based pump for liquid delivery and precise manipulation within a microchannel. The device employed a hydrophobic surface coating (Cytop) in the device design to decrease the friction force and increase the bonding. Contrary to previous surface acoustic wave based pumps which were mostly based on the filling and sucking process, we demonstrated long distance media delivery (up to 8mm) and a high pumping velocity, which increased the device’s application space and mass production potential. Additionally, the device design didn’t need precise layers of water and glass between substrate and channel, which simplified the design significantly. In this study, we conducted extensive parametric studies to quantify the effects of the liquid volume pumped, microchannel size, and input applied power as well as the existence of hydrophobic surface coating on the pumping velocity and pump performance. Our results indicated that the pumping velocity for a constant liquid volume with the same applied input power could be increased by over 130% (2.31 mm/min vs 0.99 mm/min) by employing a hydrophobic surface coating (Cytop) in a thinner microchannel (250 µm vs 500 µm) design. This device could be used in circulation, dosing, metering and drug delivery applications which necessitated small-scale precise liquid control and delivery. This dissertation also introduced a novel SAW-based sensor designed and employed for detecting changes in cell concentration. Before conducting cell concentration experiments, preliminary experiments were conducted on weight concentration differentiation of microfluidic particles based on a polydimethylsiloxane (PDMS) channel and surface acoustic wave resonator design. The results confirmed that our device exerted an ultra-stable status to detect liquid properties by monitoring continuous fluids. An improved design was carried out by depositing a 200 nm ZnO layer on top of the lithium tantalate substrate surface increased the sensitivity and enabled cell concentration detection in a microfluidic system. Comprehensive studies on cell viability were carried out to investigate the effect of shear horizontal (SH) SAWs on both a cancerous (A549 lung adenocarcinoma) and a non-cancerous (RAW264.7 macrophage) cell line. Two pairs of resonators consisting of interdigital transducers (IDTs) and reflecting fingers were used to quantify mass loading by the cells in suspension media as well as within a 3-dimensional cell culture model. In order to predict the characteristics and optimize the design of the SH-SAW biosensor, a 3D COMSOL model was built to simulate the mass loading response of the cell suspensions. These results were compared to experimental data generated by pipetting cell concentrations of 3.125K, 6.25K 12.5K, 25K and 50K cells per 100µL into the PDMS well and measuring to obtain the relative frequency shift from the two oscillatory circuit systems (one of which functioned as a control). Frequency shift measurements were also collected from A549 cells cultured on a 3D nanofiber scaffold produced by electrospinning to evaluate the device’s ability to detect changes in cell density as the cells proliferated in culture over the course of eight days. The device’s ability to detect changes in cell density over time in a 3D model along with its biocompatibility reveal great potential for this device to be incorporated into 3D in vitro cancer research applications.