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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Polymer thick-film sensors and their integration with silicon : a route to hybrid microsystems

Papakostas, Thomas January 2000 (has links)
No description available.
2

The design, manufacture and testing of a silicon multiple axis accelerometer

Hussain, Fahad January 1998 (has links)
No description available.
3

A new strain sensor based on pure CNT films

Miao, Yu 27 August 2010
The use of carbon nanotubes (CNTs) as a material for construction of sensors is a promising effort. This is due to some unique characteristics of CNTs. In recent years, strain sensors built from CNT composite films have been developed. This thesis study first proposed that the piezoresistive sensitivity of CNT composite films can be limited due to the presence of one of the constituent elements in the CNT composite films, that is, surfactant. CNT films free of surfactants were thus hypothesized to have a great promise to improve piezoresistive sensitivity. The motivation of this thesis study was to explore this promise.<p> This thesis presents an experimental study on Single-Wall CNT (SWNT) films free of surfactants. Such SWNT films are called pure SWNT films. The study has concluded: (1) the gauge factor of one layer SWNT film is much higher than that of CNT composite film; (2) the fabrication of multilayered pure CNT films is highly possible; (3) the gauge factor of multilayered pure SWNT films (10 layers and 0.8mg/ml concentration) can reach as high as 2.59 with non-linearity of 0.89% and repeatability of 0.1%, which outperforms the strain sensor built from CNT composite films; (4) the role of surfactants is indeed restrictive to piezoresistive response, and (5) the junction theory is likely applicable to pure SWNT film sensors.<p> The main contributions of this thesis study are: (1) the finding of a new type of strain sensors built from pure CNT films and (2) the development of a fabrication process for multilayered pure SWNT films.
4

A new strain sensor based on pure CNT films

Miao, Yu 27 August 2010 (has links)
The use of carbon nanotubes (CNTs) as a material for construction of sensors is a promising effort. This is due to some unique characteristics of CNTs. In recent years, strain sensors built from CNT composite films have been developed. This thesis study first proposed that the piezoresistive sensitivity of CNT composite films can be limited due to the presence of one of the constituent elements in the CNT composite films, that is, surfactant. CNT films free of surfactants were thus hypothesized to have a great promise to improve piezoresistive sensitivity. The motivation of this thesis study was to explore this promise.<p> This thesis presents an experimental study on Single-Wall CNT (SWNT) films free of surfactants. Such SWNT films are called pure SWNT films. The study has concluded: (1) the gauge factor of one layer SWNT film is much higher than that of CNT composite film; (2) the fabrication of multilayered pure CNT films is highly possible; (3) the gauge factor of multilayered pure SWNT films (10 layers and 0.8mg/ml concentration) can reach as high as 2.59 with non-linearity of 0.89% and repeatability of 0.1%, which outperforms the strain sensor built from CNT composite films; (4) the role of surfactants is indeed restrictive to piezoresistive response, and (5) the junction theory is likely applicable to pure SWNT film sensors.<p> The main contributions of this thesis study are: (1) the finding of a new type of strain sensors built from pure CNT films and (2) the development of a fabrication process for multilayered pure SWNT films.
5

Development of cantilevers for biomolecular measurements

Villanueva Torrijo, Luis Guillermo 14 December 2006 (has links)
Aquesta tesi ha estat realitzada al Centre Nacional de Microelectrònica, Institut de Microelectrònica de Barcelona (CNM-IMB) que és un institut d'investigació que forma part del Consell Superior d'Investigacions Científiques (CSIC). La memòria és un recull de la feina realitzada per en Luis Guillermo Villanueva Torrijo sota la direcció del Professor d'Investigació Joan Bausells Roigé al període comprès entre setembre de 2002 i octubre de 2006. El treball queda dividit en tres apartats, tots tres relacionats amb el disseny i la fabricació de bigues de mida micromètrica (micro-cantilevers en anglès) per a diferents aplicacions. Al segon capítol es descriu la feina realitzada amb bigues piezoresistives. L'objectiu fonamental d'aquesta part del treball consistia en la fabricació d'un element sensor capaç de detectar forces dins del rang de 10 a 100 pN. Per això, en primer lloc, es va realitzar una anàlisi teòrica del comportament d'aquestes estructures mecàniques quan se les hi aplica una força al seu extrem lliure. També es va estudiar el soroll (tant electrònic com mecànic) que presentaven. D'aquesta manera, es van establir uns criteris per a la maximització de la sensibilitat i la resolució del sensor. Els resultats analítics es van comparar amb els resultats de simulacions per elements finits, obtenint divergències molt baixes. Això va ser interpretat com una validació dels resultats analítics. Es van dissenyar i fabricar unes bigues piezoresistives de polisilici amb forma de "U". Les dimensions i la resta de paràmetres es van determinar mitjançant els criteris obtinguts per l'optimització del comportament de les bigues. Aquestes es van fabricar a la Sala Blanca del CNM i també fent servir una tecnologia CMOS comercial (0.8 m de AustriaMicroSystems). Els processos de fabricació dins de la Sala Blanca del CNM es van optimitzar per augmentar el rendiment de les oblies. Així, finalment, es va arribar a un rendiment que estava a prop del 95% (aproximadament 95 de cada 100 dispositius es van obtenir correctament). Es va optimitzar el post procés dels xips CMOS al CNM per obtenir un alt rendiment. En aquest cas no només es va considerar la supervivència de les estructures, sinó també la dels circuits CMOS integrats al costat de les bigues. Aquests circuits, dissenyats al ETH de Zürich, consisteixen en un filtre i un amplificador per a millorar la resolució del sensor. Una vegada fabricats, els dispositius es van caracteritzar. La part principal d'aquesta caracterització recollia dos aspectes: la mesura del soroll del senyal de sortida del circuit i la determinació de la sensibilitat dels dispositius. Considerant tots dos resultats es va calcular la resolució dels sensors. Els millors resultats obtinguts van ser aproximadament 30 nN per a les bigues fabricades al CNM i 30 pN per les bigues fetes amb tecnologia CMOS. Aquesta diferència de tres ordres de magnitud a la resolució és deguda als circuits amplificadors i ens permetria mesurar forces al rang requerit. Per altra banda, amb l'objectiu de realitzar mesures de conducció en un ambient líquid, es van fabricar unes bigues conductores però aïllades. La capa conductora en aquestes bigues (una capa d'or) ha d'estar aïllada del exterior per una capa dielèctrica (nitrur de silici) per disminuir d'aquesta manera les capacitats paràsites. Al extrem lliure, s'ha de situar una punta de polisilici afilada per poder escanejar superfícies. La punta ha d'estar coberta per or i, sobre l'or, tenir nitrur a tot arreu menys al vèrtex. Per obtenir aquests dispositius, es va optimitzar el gravat de puntes de polisilici obtenint finalment puntes amb un diàmetre de vèrtex més petit que 20 nm (fent servir un atac sec en un equip DRIE seguit d'unes oxidacions per esmolar). A més, es va realitzar un estudi dels esforços interns per intentar obtenir bigues planes. A l'última part del treball, es va dur a terme la fabricació de sondes per AFM (bigues amb una punta esmolada al seu extrem lliure). Aquests dispositius es fan servir moltíssim actualment per caracteritzar superfícies i realitzar experiments que requereixen molta precisió i/o resolució. L'objectiu fonamental d'aquesta feina era el possibilitar la fabricació de sondes per AFM al nostre centre de manera que els dissenys poguessin ser triats pels investigadors d'acord amb les necessitats de cadascú d'ells. Per això, es van considerar diferents materials i processos de fabricació de puntes. La millor opció va ser el gravat sec amb un equip DRIE d'unes puntes "tipus coet" amb una part superior afilada, situada al cim d'una columna cilíndrica. Els processos de gravat es van optimitzar per així obtenir una alta uniformitat arreu de l'oblia, així com uns perfils de puntes apropiats per poder fer-les servir en un AFM. A continuació, es van fabricar sondes completes. Per comprovar com de bona era la tecnologia de fabricació que havíem dissenyat, es van fabricar dispositius de dos tipus diferents: per fer-les servir en mode contacte (constant elàstica baixa) i per fer-les servir en mode dinàmic (constant elàstica alta). Aquests dispositius es van utilitzar per escanejar unes mostres d'alumini i es van comparar amb els resultats obtinguts amb sondes comercials, obtenint resultats similars en ambdós casos. Finalment, es van fabricar sondes per a aplicacions específiques: sondes amb puntes amb la part superior plana per l'estudi de la elasticitat de polímers i materials biològics (molt baix mòdul de Young) i sondes amb bigues d'una geometria especial per a que les freqüències de ressonància del mode fonamental i del primer harmònic transversal estiguessin més juntes, per així millorar la detecció del potencial de superfície en la tècnica KPFM. Amb la fabricació d'aquestes puntes, es va demostrar que el disposar d'una tecnologia que permetés la fabricació de sondes pot ser molt útil per al desenvolupament de noves aplicacions de l'AFM. / Este trabajo queda dividido en tres apartados, todos ellos relacionados con el diseño y fabricación de vigas en voladizo de tamaño micrométrico (micro-cantilevers en inglés) para diferentes aplicaciones. En el segundo capítulo se describe el trabajo realizado con vigas piezorresistivas. El objetivo fundamental de esa parte del trabajo consistía en la consecución de un elemento sensor capaz de detectar fuerzas en el rango de 10 a 100 pN. Para ello, en primer lugar, se realizó un detallado análisis teórico del comportamiento de estas estructuras mecánicas cuando se les aplica una fuerza en su extremo libre. Se estudió asimismo el ruido (tanto eléctrico como mecánico) presente en ellas. De esta manera se establecieron unos criterios para la maximización de la sensibilidad y la resolución del sensor. Los resultados analíticos se compararon con los resultados de simulaciones por elementos finitos, obteniendo divergencias muy bajas, lo cual fue interpretado como una validación de los primeros. Se diseñaron y fabricaron unas vigas piezorresistivas de polisilicio con forma de U. Las dimensiones y demás parámetros se fijaron mediante los criterios obtenidos para la optimización del comportamiento de las vigas. Las vigas se fabricaron tanto en la Sala Blanca del CNM como usando una tecnología CMOS comercial (0.8 m de AustriaMicroSystems). Los procesos de fabricación dentro de la Sala Blanca del CNM se optimizaron para aumentar el rendimiento de las obleas. De esta forma, finalmente, se alcanzó un rendimiento cercano al 95% (aproximadamente 95 de cada 100 dispositivos se obtuvieron correctamente). Se optimizó asimismo el post proceso de los chips CMOS en el CNM para obtener un alto rendimiento. En este caso, se consideró la supervivencia de las estructuras mecánicas así como de la circuitería CMOS integrada junto con las vigas. Esta circuitería, diseñada en el ETH de Zürich, consistía en un filtro y un amplificador para mejorar la resolución del sensor. Una vez fabricados, los dispositivos se caracterizaron. La parte central de esta caracterización englobó dos aspectos: la medida del ruido de la señal de salida del circuito y la determinación de la sensibilidad de los dispositivos. Teniendo en cuenta ambos resultados se calculó la resolución de nuestros sensores. Los mejores resultados obtenidos fueron de unos 30 nN para las vigas fabricadas en el CNM y de unos 30 pN para las provenientes de la tecnología CMOS. Esta diferencia de tres órdenes de magnitud en la resolución es debida a la circuitería adjunta a los dispositivos transductores (vigas) y nos permitiría medir fuerzas del orden de magnitud requerido. Por otro lado, con el objetivo de realizar medidas de conducción en medio líquido, se fabricaron unas vigas conductoras pero aisladas. La capa conductora en dichas vigas (capa de oro) ha de estar aislada del exterior por medio de una capa dieléctrica (nitruro de silicio) para así disminuir las capacidades parásitas. En el extremo libre, se ha de situar una punta de polisilicio afilada para poder escanear superficies. Dicha punta ha de estar cubierta por oro y, sobre el oro, tener nitruro en todas partes salvo en el vértice. Para obtener estos dispositivos, se optimizó el grabado de puntas de polisilicio, obteniendo finalmente puntas con un diámetro de vértice menor que 20 nm (usando un ataque en un equipo DRIE seguido por unas oxidaciones para afilar). Además, se realizó un estudio de los esfuerzos internos para intentar obtener vigas lo más planas posible. En la última parte del trabajo, se llevó a cabo la fabricación de sondas para AFM (vigas con una punta afilada en su extremo libre). Estos dispositivos son ampliamente usados en la actualidad para caracterizar muestras y para realizar experimentos en los que se requiere una alta precisión y/o resolución. El objetivo fundamental de este trabajo era el posibilitar la fabricación de sondas para AFM en nuestro centro de manera que los diseños pudieran ser elegidos a voluntad y acordes con las necesidades de cada investigador. Para ello se consideraron diferentes materiales y procesos de fabricación de puntas. La mejor opción fue la definición por medio de un equipo DRIE de puntas "tipo cohete" con una parte superior afilada, situada sobre una columna cilíndrica. Los procesos de grabado se optimizaron para así obtener una alta uniformidad a lo largo y ancho de la oblea así como unos perfiles de puntas apropiados para poder ser usadas después en un AFM. A continuación, se fabricaron sondas completas. Para comprobar cómo de buena era la tecnología de fabricación que habíamos diseñado, se fabricaron puntas de dos tipos diferentes: para ser usadas en modo contacto (constante elástica baja) y para ser usadas en modo dinámico (constante elástica alta). Dichos dispositivos se usaron para escanear algunas muestras y se compararon con algunos disponibles comercialmente, obteniendo resultados similares tanto para modo contacto como para dinámico. Finalmente, se fabricaron sondas para aplicaciones específicas: sondas con puntas con la parte superior plana para el estudio de la elasticidad de polímeros y materiales biológicos (con bajo módulo de Young) y sondas con vigas de una geometría especial para que las frecuencias de resonancia del modo fundamental y del primer harmónico transversal estuvieran más juntas, para así mejorar la detección del potencial de superficie en la técnica KPFM. Con la fabricación de estas puntas, se demostró que el disponer de una tecnología que permita la consecución de puntas puede ser muy útil para el desarrollo de nuevas aplicaciones del AFM. / The main objective of this thesis has been the research in the design and fabrication of micro-cantilevers that are one of the most used mechanical transducers because of their versatility. The use of polysilicon piezoresistive cantilevers has been explored in order to detect binding forces between biomolecules. Force resolution under 100 pN was required. A detailed analytical study has been performed in order to calculate sensitivity and resolution when applying a force at their free end. The results obtained with this analysis have been confirmed by the use of FEM simulations and hence used to determine the optimum design of the piezoresistive sensor. U-shaped polysilicon cantilevers have been fabricated at CNM clean room facilities using a novel and dedicated technology. Designs were made following the criteria imposed by the previously obtained analytical results. The high force resolution required implied the fabrication of some cantilevers among the softest piezoresistive cantilevers reported up to date (elastic constants down to 0.5 mN/m). With the final optimized fabrication process, a yield of 95% has been achieved. Using a commercial CMOS technology (0.8 m from AustriaMicroSystems), polysilicon piezoresistive cantilevers have been designed and fabricated following again the criteria imposed by the theoretical analysis and, in this case, also design rules from the CMOS technology. Cantilevers were integrated with a filtering and amplifying circuitry to reduce noise. The softest piezoresistive CMOS integrated cantilevers have been obtained with a high yield and with an undamaged circuitry. In order to determine the actual sensitivity of such soft sensors and their gauge factor, a characterization method (consisting in AFM actuation) has been developed. Gauge factor for polysilicon deposited at CNM and at AustriaMicroSystems was -12 and -9 respectively. The maximum force sensitivity and force resolution obtained for CNM fabricated sensors have been 11 V/nN and 28 nN respectively. The maximum force sensitivity and force resolution obtained for CMOS fabricated sensors have been 11 V/pN and 27 pN respectively. In both cases, resolution is limited by the noise in the circuit, whose main contributions are Hooge noise (or 1/f) and Johnson noise (or thermoelectric). Conductive, but isolated, nitride cantilevers (with a wrapped gold layer) with a sharp tip (that has an opened contact) have been designed and fabricated to be used in conductive measurements in liquid environments. Polysilicon tips definition has been optimized to improve the whole probes fabrication process, achieving apex radii smaller than 20 nm using a dry etching by means of a DRIE equipment followed by sharpening oxidation. A complete and novel technological process has been developed for the fabrication of AFM cantilevers. Different tip materials and machining processes have been analyzed, obtaining the best results for crystalline silicon tips defined using a DRIE equipment to machine rocket tips. Isotropic processes with low cross-wafer dispersion and anisotropic processes with low cross-wafer dispersion and low scalloping have been achieved. After a sharpening oxidation, apex radii smaller than 5 nm have been achieved. Complete AFM probes have been fabricated. In order to test the developed technology, probes with similar characteristics to commercial ones were fabricated and used to raster scan some samples (in contact and non-contact mode) yielding results similar to those obtained with commercial probes. In addition, some special probes have been fabricated for nanoindentation over polymers and also to improve Kelvin Probe Force Microscopy (KPFM) performance. Thus, the availability of a technology that allows the fabrication of customized cantilevers is very useful for the development of new SPM applications.
6

Design and Frequency Characterization of Dual-Piezoresponsive Foam Sensors

Newton, Cory Nelson 09 December 2016 (has links)
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.
7

ON UNDERSTANDING OF PIEZORESISTIVE RESPONSE IN CARBON NANOTUBE NETWORKS UNDER IN-PLANE STRAINING

2013 November 1900 (has links)
Strain detecting with carbon nanotube (CNT) networks is one of the encouraging findings in sensor technologies. Two types of CNT based films are available for strain detection, namely CNT composite films and CNT films. Configurations of the CNT networks in these films can be made into random and aligned distributions. Understanding of fundamental knowledge regarding piezoresistive response in CNT networks in particular of the CNT film is not quite available, and this is the motivation of the present thesis. In this thesis, piezoresistive response of CNT networks under in-plane straining was studies in details first. Based on the stick percolation model, the relation between the density and conductance in CNT networks (with randomly distributed) was established and then the models which describe the relation between the density and piezoresistive sensitivity and the relation between density and piezoresistive linearity, respectively, were developed. After that, fabrication of CNT networks with aligned distributions was studied. Likewise, the models as developed for CNT network with random distributions were developed for ones with aligned distributions. Finally, modeling of the stress transfer between the nanotubes and polymer matrix was studied. This study has led to the following conclusions: (1) piezoresistive response in CNT networks of the CNT film follows the stick percolation model with the critical exponent coefficient (α) in the model being 1.938; (2) it is feasible to fabricate aligned CNT networks of varying densities with the technique which combines the spray deposition and externally applied magnetic field; (3) the configuration of CNT networks, in addition to their density, was a primary factor governing their piezoresistive response; (4) slipping occurs at the interface between the nanotube and polymer matrix when the films are subject to in-plane straining. The contributions of this study are: (1) the knowledge along with a percolation model for piezoresistive response of CNT networks of the CNT film, (2) a fabrication technique to align CNT networks of the CNT film, and (3) the knowledge along with a model for interaction between the CNT and polymer substrate in the CNT film.
8

Utilization of Semiconductors Piezoresistive Properties in Mechanical Strain Measurements under Varying Temperature Conditions for Structural Health Monitoring Applications

Mohammed, Ahmed Ahmed Shehata Unknown Date
No description available.
9

A piezoresistive microcantilever array for chemical sensing applications

Choudhury, Arnab 14 November 2007 (has links)
Numerous applications in the present day ranging from testing humidity in air to detecting miniscule quantities of potentially hazardous chemical and biological agents in the air or water supplies require the development of chemical sensors capable of analyte detection with high sensitivity and selectively. Further, it has become desirable to create lab-on-chip systems that can detect multiple chemical agents and allow for sampling and testing of environments at locations distant from conventional laboratory facilities. Current challenges in this area include design, development and characterization of low detection limit sensors, development of low-noise readout methods, positive identification of analytes and, identification and reduction of the effect of various noise sources - both intrinsic and extrinsic to the sensor. The current work examines the performance limits of a 10-cantilever piezoresistive microcantilever array (PµCA) sensor. The microcantilevers measure analyte concentration in terms of the surface stress associated with analyte binding to the functionalized cantilever surface. The design, fabrication, characterization and testing of this measurement platform is presented. A novel aspect of the sensors developed is the use of n-type doping which increases the sensitivity of the device by one order of magnitude. In addition, design rules for surface stress-based chemical sensors have been developed. Extensive thermal characterization of the piezoresistive microcantilevers has been performed for DC and AC electrical excitation and values of heat transfer coefficient for the associated microscale phenomena are reported. Further, a method of low-noise measurement of cantilever resistance has been developed based on phase-sensitive detection techniques and this has been integrated with a multiplexing circuit to measure piezoresistance change in multiple cantilevers. Finally, the two novel techniques of chemical sensing- double-sided sensing and thermal array-based sensing have been investigated. These methods are presented as a means of extending the applicability and functionality of piezoresistive microcantilever sensors for chemical sensing.
10

POLYMER FLIP-CHIP BONDING OF PRESSURE SENSORS ON FLEXIBLE KAPATON FILM FOR NEONATAL CATHETERS

LI, CHUNYAN 06 October 2004 (has links)
No description available.

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