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Dissertations / Theses on the topic 'Sensors and sensing'
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Jia, Xiaodan (Xiaodan Stella). "Tactile sensing using elastomeric sensors." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78183.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 99-111).<br>GelSight, namely, elastomeric sensor, is a novel tactile sensor to get the 3D information of contacting surfaces. Using GelSight, some tactile properties, such as softness and roughness, could be gained through image processing techniques. In this thesis, I implemented GelSight principle to reconstruct surface geometry of tested surfaces, based on which, the roughness comparison and lump detection experiment are conducted. Roughness of five different types of sandpapers are successfully compared using GelSight Ra value. In the lump detection experiment, a visual display for tactile information is presented. To get binary feedback of lump presence or not, a simple threshold method is introduced in this thesis. To evaluate the performance of GelSight sensor, human psychological experiments are conducted. In similar tasks, GelSight sensor outperforms humans in lump detection.<br>by Xiaodan (Stella) Jia.<br>S.M.
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Khunou, Ramotseng. "Gas sensing properties of Ceo2 nanostructures." University of the Western Cape, 2020. http://hdl.handle.net/11394/7909.
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>Magister Scientiae - MSc<br>The industrial safety requirements and environmental pollution have created a high demand to develop gas sensors to monitor combustible and toxic gases. As per specifications of World Health Organization (WHO) and Occupational Safety and Health Administration (OSHA), lengthy exposure to these gases lead to death which can be avoided with early detection. Semiconductor metal oxide (SMO) has been utilized as sensor for several decades. In recent years, there have been extensive investigations of nanoscale semiconductor gas sensor.
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Vukusic, Peter. "Sensing thin layers using surface plasmon resonance." Thesis, University of Exeter, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358142.
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Mishu, Pujan Kumar Chowdhury. "DESIGN OF CMOS COMPRESSIVE SENSING IMAGE SENSORS." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2446.
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This work investigates the optimal measurement matrices that can be used in compressive sensing (CS) image sensors. It also optimizes CMOS current-model pixel cell circuits for CS image sensors. Based on the outcomes from these optimization studies, three CS image senor circuits with compression ratios of 4, 6, and 8 are designed with using a 130 nm CMOS technology. The pixel arrays used in the image sensors has a size of 256X256. Circuit simulations with benchmark image Lenna show that the three images sensors can achieve peak signal to noise ratio (PSNR) values of 37.64, 33.29, and 32.44 dB respectively.
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Rasheed, Raymond Kelvin. "New sensing materials for the detection of malodours." Thesis, University of the West of England, Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308791.
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Cánovas, Martínez Rocío. "Tailor-made chemical sensing platforms for decentralized healthcare and wellbeing." Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/462914.
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Aquesta tesis fa referència a la necessitat social de la implementació de sensors electroquímics en la nostra vida quotidiana a diferents nivells. Des d’un enfocament sanitari, l’ús i l’aplicació real de plataformes fàcils d’utilitzar pel propi pacient facilitarien la presa de decisions gràcies a la obtenció d’informació rellevant i monitoratge d’una malaltia. Així mateix, l’ús d’aquestes eines de manera individual, en centres de salut o inclús hospitals, ajudarien a disminuir el cost que la sanitat ha d’afrontar diàriament. Des d’un enfocament diferent, aquest tipus de sensors poden oferir també altres tipus de aplicacions, poden ser usats amb finalitats mediambientals o de seguretat. La fabricació de sensors electroquímics (amperomètrics i potenciomètrics) integrats i impresos en diferents substrats fàcils de manipular, de baix cost i robustos (com tèxtils, globus o paper) ha estat aconseguida durant aquesta tesis. L’estudi del seu rendiment analític sota la influencia de diferents situacions d’estres i en diferents fluids biològics (detectant ions en suor o glucosa en sèrum i sang) també ha estat realitzat amb èxit. Aquestes aportacions tecnològiques van dirigides a superar els reptes que la societat d’avui en dia necessita solucionar: com pot ser la sostenibilitat del sistema sanitari en una població cada vegada mes envellida; el manteniment d’una seguretat i un estat del benestar; i el control mediambiental. Aquesta tesis suposa un avenç en aquest sentit i mostra diferents solucions científiques i eines útils per aquests reptes que la societat necessita afrontar.<br>Esta tesis hace referencia a la necesidad social de la implantación de sensores electroquímicos en nuestra vida diaria a distintos niveles. Desde un enfoque sanitario, el uso y la aplicación real de plataformas fáciles de usar mediante el propio paciente facilitarían la toma de decisiones gracias a la obtención de información relevante y monitoreo de una enfermedad. Así mismo, el uso de estas herramientas de manera individual, en centros de salud o incluso hospitales disminuiría el costo que la sanidad debe afrontar diariamente. Desde un enfoque diferente, este tipo de sensores pueden ofrecer también otro tipo de usos, pudiendo ser aplicados para fines medioambientales o de seguridad. La fabricación de sensores electroquímicos (amperométricos y potenciométricos) integrados e impresos en diferentes sustratos fáciles de manipular, de bajo costo y robustos (como textiles, globos o papel) ha sido lograda durante esta tesis. El estudio de su rendimiento analítico bajo diferentes situaciones de estrés y en diferentes fluidos biológicos (detectando iones en sudor o glucosa en suero y sangre) también ha sido realizado de manera exitosa. Estas aportaciones tecnológicas van dirigidas a superar los retos que la sociedad de hoy en día necesita solucionar: como puede ser la sostenibilidad del sistema sanitario en una población cada vez más envejecida; el mantenimiento de una seguridad y un bienestar general; y el control medioambiental. Esta tesis supone un avance en este sentido y muestra diferentes soluciones científicas y herramientas útiles para estos retos que la sociedad necesita afrontar.<br>This thesis refers to the social need of the implementation of electrochemical sensors in our daily life at different levels. From a sanitary point of view, the use and real application of user-friendly platforms by the patient itself would facilitate the decision-making process thanks to the obtaining of relevant information and monitoring of a disease. Besides, the use of these tools individually, in health centers or even hospitals, would reduce the cost that healthcare must pay on a daily basis. In a different approach, this type of sensors can also offer other types of applications, which can be applied for environmental or safety purposes. The manufacturing of electrochemical sensors (amperometric and potentiometric) integrated and embedded on different substrates easy to manipulate, low cost and robust (such as textiles, balloons or paper) has been achieved during this thesis. The study of their analytical performance under different mechanical stress and using different biological fluids (detecting ions in sweat or glucose in serum and blood) has also been carried out successfully. These technological contributions are aimed at overcoming the challenges that today's society needs to solve: such as the sustainability of the health system in an aging population; the maintenance of security and general wellbeing; and environmental control. This thesis contributes with huge advancements to face these issues and shows different scientific solutions and useful tools for these challenges that society needs to address. This thesis refers to the social need of the implementation of electrochemical sensors in our daily life at different levels. From a sanitary point of view, the use and real application of user-friendly platforms by the patient itself would facilitate the decision-making process thanks to the obtaining of relevant information and monitoring of a disease. Besides, the use of these tools individually, in health centers or even hospitals, would reduce the cost that healthcare must pay on a daily basis. In a different approach, this type of sensors can also offer other types of applications, which can be applied for environmental or safety purposes. The manufacturing of electrochemical sensors (amperometric and potentiometric) integrated and embedded on different substrates easy to manipulate, low cost and robust (such as textiles, balloons or paper) has been achieved during this thesis. The study of their analytical performance under different mechanical stress and using different biological fluids (detecting ions in sweat or glucose in serum and blood) has also been carried out successfully. These technological contributions are aimed at overcoming the challenges that today's society needs to solve: such as the sustainability of the health system in an aging population; the maintenance of security and general wellbeing; and environmental control. This thesis contributes with huge advancements to face these issues and shows different scientific solutions and useful tools for these challenges that society needs to address.
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Wu, Terence. "Antenna integration for wireless and sensing applications." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41098.
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As integrated circuits become smaller in size, antenna design has become the size limiting factor for RF front ends. The size reduction of an antenna is limited due to tradeoffs between its size and its performance. Thus, combining antenna designs with other system components can reutilize parts of the system and significantly reduce its overall size. The biggest challenge is in minimizing the interference between the antenna and other components so that the radiation performance is not compromised. This is especially true for antenna arrays where the radiation pattern is important.
Antenna size reduction is also desired for wireless sensors where the devices need to be unnoticeable to the subjects being monitored. In addition to reducing the interference between components, the environmental effect on the antenna needs to be considered based on sensors' deployment.
This dissertation focuses on solving the two challenges: 1) designing compact multi-frequency arrays that maintain directive radiation across their operating bands and 2) developing integrated antennas for sensors that are protected against hazardous environmental conditions.
The first part of the dissertation addresses various multi-frequency directive antennas arrays that can be used for base stations, aerospace/satellite applications. A cognitive radio base station antenna that maintains a consistent radiation pattern across the operating frequencies is introduced. This is followed by multi-frequency phased array designs that emphasize light-weight and compactness for aerospace applications. The size and weight of the antenna element is reduced by using paper-based electronics and internal cavity structures.
The second part of the dissertation addresses antenna designs for sensor systems such as wireless sensor networks and RFID-based sensors. Solar cell integrated antennas for wireless sensor nodes are introduced to overcome the mechanical weakness posed by conventional monopole designs. This can significantly improve the sturdiness of the sensor from environmental hazards. The dissertation also introduces RFID-based strain sensors as a low-cost solution to massive sensor deployments. With an antenna acting as both the sensing device as well as the communication medium, the cost of an RFID sensor is dramatically reduced. Sensors' strain sensitivities are measured and theoretically derived. Their environmental sensitivities are also investigated to calibrate them for real world applications.
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Kampouris, Dimitrios. "Developing novel sensors for sensing drugs of abuse." Thesis, Manchester Metropolitan University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534245.
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Mayne, Laura J. "Metal ion sensors using Tunable Resistive Pulse Sensing." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/36055.
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There is a drive to develop rapid, portable and simple methods for detecting heavy metal ions. Due to their toxic nature, heavy metal ions are monitored in aqueous solutions such as drinking water. Standard methods for metal detection rely on instrumentation such as atomic absorption/emission and mass spectrometry. These are often costly and do not allow for rapid on-site or real-time measurements. The aim of this PhD was to develop and optimise tunable resistive pulse sensing (TRPS) for sensing metal ions. This combines nanomaterials, dual molecular recognition with an emerging nanopore technology. TRPS is a label-free portable sensor that allows characterisation of particles based on their size, concentration and charge. Monitoring changes upon the particle surface via changes to the particle charge could be a powerful analytical tool for studying metal ion binding and new sensors. Tuning functional groups on the nanoparticle surface will allow for an array of metal ions to be detected. Nanoparticles will be modified with functional groups that bind to metal ions in solution, in turn this will change the charge on the nanoparticle which will be studied using TRPS. Particle velocity through the pore is dependent on particle charge so changes on the nanoparticle surface can be monitored. The literature review in Chapter 1 focuses on the use of different ligands for the detection of metals focusing on aptamers and modified nanoparticles. The application of the theory of resistive pulse sensors (RPS), which is the main sensing platform within the thesis is covered in detail however these sensors to date have little use in metal ion detection. The theory behind RPS follows the literature review. This covers the theory of transport through a conical nanopore, a brief introduction to zeta potential and particle surface charge and ion current rectification. Before developing a metal ion sensor, the translocation of a particle through the pore, focusing on its relative velocity needed to be understood. Chapter 3 demonstrates how changes in the double layer can affect the measured particle velocity. Understanding how the double layer changes with ionic strength and pH is essential in designing a metal ion sensor where the velocity of the particle through the pore is being measured. The work presented in Chapter 3 gave confidence that TRPS could be used to monitor metal ion binding to the surface of nanoparticles. The nanoparticles were modified with a ligand (APTES) and DNA. The subsequent particle velocities differ to those of the unmodified particles, making TRPS a suitable platform for monitoring changes upon a nanoparticle surface. Building on the knowledge gained from Chapter 3, particle translocation velocities were used for the detection of copper (II) on the surface of modified nanoparticles, Chapter 4. Changes in particle velocity through the nanopore allows for detection of copper (II) as low as 1 ppm and at 10 ppm with competing metal ions present. Chapter 4 also presents the first use of studying pulse waveshape for the detection of an analyte. At low ionic strengths, particles passing through the conical pore generated a biphasic pulse containing a conductive pulse and resistive pulse. The biphasic pulse behaviour was used to monitor changes on the nanoparticle surface, and infer the presence of ions within the particles double layer. The method can be easily adapted to different analytes by altering the ligand used. As an alternative to a particle-based assay, a pore-based assay was developed which exploited the current rectification properties of the conical pores used in TRPS. Chapter 5 presents the use of Layer-by-Layer (LbL) assembly of polyelectrolytes onto the surface of the polyurethane pore for the modification of the pore wall, a DNA aptamer was then easily immobilized onto the pore wall. Vascular Endothelial Growth Factor (VEGF) was chosen as the analyte prior to developing a metal ion assay as it was a system studied in more detail in the literature and within the group. An advantage of TRPS is the particle-by-particle analysis. This allows for simple multiplex detection by using particles of two different sizes to detect two different analytes. In Chapter 6 the methodology and techniques from Chapter 4 is applied to the multiplexed detection of lead (II) and mercury (II) using particle translocation velocities to detect the metal ion binding to DNA aptamers. The method is applicable over a large range of ionic strengths with little interference from a high salt content. Finally, to advance the multiplexed concept, the two independent aptamer sequences used in Chapter 6 are merged together. While both aptamer halves retain their initial functionality and bind to the respective metals, the location of the binding and change in DNA structure with respect to the particles surface is the dominating factor in determining the sensitivity of the RPS technology.
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Blanchard, Jeffrey Allen 1974. "Specific gas sensing using zirconia amperometric oxygen sensors." Thesis, The University of Arizona, 1998. http://hdl.handle.net/10150/278662.
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An analytical model for the specific gas detection of oxygen, carbon dioxide, and water vapor using zirconia amperometric oxygen sensors has been developed. Sensors of this type have been designed, fabricated, and tested using planar ceramic technology. Furthermore, an experimental setup has been designed and constructed for sensor characterization. This testbed can accurately control gas partial pressures as well as the total system pressure over a wide range of flow rates. Extensive effort has been put into design and construction of this testbed to ensure accurate scientific measurements. Special attention has been paid to ensuring that the apparatus is leak-tight from air to ensure accurate measurements at low oxygen partial pressures. Results of the experimentation for oxygen detection as well as the detection of carbon dioxide and water vapor are presented. The effects of electronic conduction in the zirconia electrolyte at low oxygen partial pressures are examined. Possible applications of the sensor, as well as suggestions for further research are discussed.
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Seng, Frederick Alexander. "Body Armor Shape Sensing with Fiber Optic Sensors." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6950.
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In this dissertation, the rate of the BFD during body armor impact is characterized with fiber Bragg gratings for the first time ever. The depth rate is characterized using a single fiber optic sensor, while the entire shape rate can be characterized using multiple fiber optic sensors. This is done with a final depth accuracy of less than 10% and a timing accuracy of 15% for BFDs as deep as 50 mm and impact event of less than 1 millisecond. The shape sensing method introduced in this dissertation is different from traditional fiber optic sensor shape reconstruction methods in the fact that strain from the kinetic friction regime is used rather than the static friction regime. In other words, information from the fiber optic sensors slipping is used to reconstruct the shape in this work, whereas strain from the fiber optic sensor remaining fixed to a reference is used for typical fiber optic shape sensing purposes.
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Diamond, D. "Ubiquitous sensing - the development of analytical measurements." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246459.
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Smith, Stephen Roy Walter. "Remote optical fibre temperature and groundwater sensing." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266224.
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Bhatia, Vikram. "Properties and sensing applications of long-period gratings." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11082006-133634/.
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Pol, Arcas Roberto. "Printing technologies for biotechnological and environmental sensing applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/667857.
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Las actividades industriales han dejado contaminación en el suelo, el aire y el agua en todo el mundo. Las emisiones de SOx provenientes de gases de combustión requieren tratamiento antes de su liberación al medio ambiente. Los tratamientos fisicoquímicos convencionales utilizados hasta ahora son costosos y requieren mucho tiempo. Además, esos tratamientos también generan aguas residuales que requieren un procesamiento adicional. Para superar el desafío del tratamiento de SOx, se propone un nuevo enfoque que utiliza un método biológico respetuoso con el medio ambiente. El proceso se basa en una adsorción selectiva de SOx, seguida de un tratamiento biológico de dos etapas. Una vez adsorbidos los SOx, se someten a una primera etapa biocatalítica, en la que los microorganismos reductores de sulfato catalizan su conversión en sulfuro de hidrógeno. Posteriormente, se realiza una segunda etapa biocatalítica por microorganismos oxidantes de sulfuro, obteniendo finalmente azufre elemental.
Un punto crucial que tratar en este proceso biotecnológico es la cuantificación en tiempo real de las especies de azufre antes y después de cada etapa biocatalítica. Los métodos convencionales, tales como la gravimetría, la turbidimetría, la nefelometría, la electroforesis capilar y la cromatografía iónica se han utilizado para la cuantificación de especies de azufre. Aunque esos métodos se han implementado de manera abrumadora hace unas décadas, no son adecuados para mediciones in situ y en tiempo real, requieren personal capacitado, son costosos y consumen mucho tiempo. Por lo tanto, existe la necesidad de proporcionar nuevos sistemas analíticos que puedan reemplazar a los convencionales.
Las plataformas microfluídicas se han estudiado debido a su posibilidad de reemplazar un laboratorio convencional totalmente equipado. Las ventajas bien conocidas de estos sistemas de detección incluyen: compacidad, bajo consumo de muestra, producción de bajo coste, mejor monitoreo y control de procesos, análisis en tiempo real y una respuesta rápida. Estas características abren la posibilidad de realizar medidas in situ y en tiempo real. Además, funcionan de tal manera que el pretratamiento de la muestra y el ensayo químico se pueden realizar en su interior. Su diseño ergonómico y fácil de usar les permite adaptarse fácilmente para realizar el análisis deseado simplemente modificando la geometría de los canales. Estas características hacen que la microfluídica sea de interés en procesos que requieren múltiples análisis al mismo tiempo.
Para la producción de sistemas analíticos miniaturizados se han utilizado varias técnicas de microfabricación (por ejemplo, micromaquinado, estampado en caliente, moldeo por inyección, ablación por láser, micromilling y litografía) y materiales (por ejemplo, silicio, polímeros, metales, cerámica, etc.). No obstante, todos estos métodos requieren personal capacitado, son costosos y requieren mucho tiempo. Además, requieren más pasos de procesamiento (por ejemplo, grabado químico, sellado, etc.) después de la fabricación. Hoy en día, los científicos han estado explorando nuevas metodologías para producir tales sistemas analíticos de una manera más factible y más barata.
En esta tesis, se promueve el uso de tecnologías de impresión (impresión por chorro de tinta, serigrafía e impresión 3D) para producir plataformas analíticas para la cuantificación de compuestos químicos relevantes en reactores biotecnológicos y en el medio ambiente (S2-, SO42- and NO2-). Por lo tanto, el estado del arte de los dispositivos microfluídicos y los sistemas analíticos impresos se han desarrollado ampliamente:<br>Modern industrial activities have left wide-spread hazardous pollution in soil, air and water across the globe. Emissions of SOx coming from flue gases require treatment before their release into the environment. Conventional physic-chemical treatments used hitherto are expensive and time-consuming. Moreover, those treatments also generate wastewater that requires further processing. To overcome the SOx treatment challenge, a new approach using environmentally friendly biological method is proposed. The process is based on a selective adsorption of SOx, followed by a two-stage biological treatment. Once the SOx are adsorbed they undergo a first biocatalytic stage, in which sulfate-reducing microorganisms catalyze their conversion into hydrogen sulfide. Afterwards, a second biocatalytic stage by sulfide-oxidizing microorganisms is done, finally obtaining elemental sulfur.
A crucial point to address in this biotechnological process is the real-time quantification of sulfur species before and after each biocatalytic stage. Conventional methods, such as gravimetry, turbidimetry, nephelometry, capillary electrophoresis and ionic chromatography have been widely used for sulfur species quantification. Although those methods have been overwhelmingly implemented a few decades ago, they are not suitable of in situ real-time measurements, require trained personnel and they are costly and time consuming. Therefore, there is a need to provide new analytical systems that can replace conventional ones.
Microfluidic platforms have been extensively studied due to their possibility of replacing a fully equipped conventional laboratory. Well-known advantages of these microfluidic sensing systems include: compactness, low sample consumption, low-cost production, better overall monitoring and process control, real-time analysis and a fast response. These characteristics open the possibility of performing in situ and real-time measurements. Also, they operate in such a manner that sample pre-treatment as well as chemical assay can be performed therein. Their ergonomic and user-friendly design allows them to be easily adapted to perform a desired analysis just by simply modifying the geometry of the channels. These features make microfluidics of interest in processes that require multiple analyses at the same time.
Several microfabrication techniques (e.g., micromachining, hot embossing, injection molding, laser ablation, micromilling and soft lithography) and materials (e.g., silicon, polymers, metals, ceramics, etc.) have been used for the production of miniaturized analytical systems. Nonetheless, all these methods require trained personnel and are expensive and time consuming. Moreover, they require further processing steps (e.g., etching, sealing, etc.) after the fabrication. Nowadays, scientists have been exploring new methodologies to produce such analytical systems in a more feasible and cheaper manner.
In this thesis, the use of printing technologies (inkjet printing, screen-printing and 3D printing) to produce analytical platforms for quantification of relevant chemical compounds in biotechnological reactors and in the environment (S2-, SO42- and NO2-) are promoted. Hence, the state-of-the-art of microfluidic devices and the printed analytical systems have been widely developed.
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Moghe, Rohit. "Smart sensors for utility assets." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44729.
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This dissertation presents the concept of a small, low-cost, self-powered smart
wireless sensor that can be used for monitoring current, temperature and voltage on a
variety of utility assets. Novel energy harvesting approaches are proposed that enable the
sensor to operate without batteries and to have an expected life of 20-30 years.
The sensor measures current flowing in an asset using an open ferromagnetic core,
unlike a CT which uses a closed core, which makes the proposed sensor small in size, and
low-cost. Further, it allows the sensor to operate in conjunction with different assets
having different geometries, such as bus-bars, cables, disconnect switches, overhead
conductors, transformers, and shunt capacitors, and function even when kept in the
vicinity of an asset. Two novel current sensing algorithms have been developed that help
the sensor to autonomously calibrate and make the sensor immune from far-fields and
cross-talk. The current sensing algorithms have been implemented and tested in the lab at
up to 1000 A.
This research also presents a novel self-calibrating low-cost voltage sensing
technique. The major purpose of voltage sensing is detection of sags, swells and loss-ofpower
on the asset; therefore, the constraint on error in measurement is relaxed. The
technique has been tested through several simulation studies. A voltage sensor prototype
has been developed and tested on a high voltage bus at up to 35 kV.
Finally, a study of sensor operation under faults, such as lightning strikes, and large
short circuit currents has been presented. These studies are conducted using simulations
and actual experiments. Based on the results of the experiments, a robust protection
circuit for the sensor is proposed. Issues related to corona and external electrical noise on
the communication network are also discussed and experimentally tested. Further, optimal
design of the energy harvester and a novel design of package for the sensor that prevents
the circuitry from external electrical noise without attenuation of power signals for the
energy harvester are also proposed.
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McConney, Michael Edward. "Learning and applying material-based sensing lessons from nature." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29749.
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Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2010.<br>Committee Chair: Tsukruk, Vladimir; Committee Member: Shofner, Meisha; Committee Member: Srinivasarao, Mohan; Committee Member: Thio, Yonathan; Committee Member: Weissburg, Marc. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Besnard, Isabelle. "Improvement of conducting polymer gas sensors." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341716.
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Gautam, Madhav. "Development of Graphene Based Gas Sensors." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1365030920.
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Strakosas, Xenofon. "Integration of proteins with organic electrochemical transistors for sensing applications." Thesis, Saint-Etienne, EMSE, 2015. http://www.theses.fr/2015EMSE0774/document.
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Le domaine de la bioélectronique, qui couple l'électronique et la biologie, présente un fort potentiel pour le développement de nouveaux outils biomédicaux. Les dispositifs à base d’électronique organique sont particulièrement prometteurs; l'utilisation de ces matériaux organiques confère une interface idéale entre les mondes biologique et électronique en raison de leur biocompatibilité et de leur possible grande flexibilité. Le transistor électrochimique organique (OECT) représente un dispositif prometteur dans ce domaine. Des OECT ont par exemple été intégrés dans des systèmes permettant de détecter localement l’activité ionique/biomoléculaire, de mesurer l'activité d'une cellule unique, mais aussi d’effectuer la caractérisation de tissus et le suivi du fonctionnement d’organes entiers. L'OECT est un dispositif extrêmement polyvalent qui apparaît comme un outil thérapeutique et de diagnostic de première importance. L'utilisation de matériaux organiques tels que les polymères conducteurs, rend l‘OECT adaptable pour une large gamme d'applications. Un exemple représentatif est le capteur de glucose. L'OECT, en raison de ses propriétés d'amplification, peut augmenter ces courants de plusieurs ordres de grandeurs. Utilisé comme capteur de glucose, il montre une forte sensibilité et des limites de détection des concentrations de l’ordre du nanomolar. Cependant, en dehors d’une meilleure précision de mesure, la stabilité est nécessaire pour les applications à long terme. Par exemple, ces capteurs se doivent d'enregistrer en continu les variations de glycémie chez des personnes pendant plusieurs jours et sans défaillance. Le glucose est la source d'énergie principale du cerveau. Ainsi, l'enregistrement de la modulation des niveaux de glucose avant et/ou pendant la crise d'épilepsie peut donner beaucoup d'informations dans la compréhension de cette maladie. Pour des applications à long termes, une liaison covalente de la biomolécule est préférable.La biofonctionnalisation des polymères conducteurs, qui sont utilisés comme matières actives dans les OECTs, est une étape obligatoire qui mettra en évidence les propriétés de l’OECT telles que la biocompatibilité, la stabilité, et la fonctionnalité. Dans ce travail, des méthodes de biofonctionnalisation du poly (3,4-éthylènedioxythiophène) dopé avec des anions de tosylate (PEDOT: TOS) ou dopé avec du poly (styrène sulfonate) (PEDOT: PSS) ont été développéeset ont conduitsent à des améliorations telles que la biocompatibilité accrue avec les cellules et à une stabilité accrue pour les applications de détection. En outre, nous avons étudié l'utilisation de liquides ioniques en combinaison avec des polymères réticulables comme alternatives aux électrolytes conventionnelles. Ces gels ioniques électrolytes ont amélioré la stabilité des enregistrements électrophysiologiques. Enfin, des mesures in vitro de l'activité métabolique de la cellule ont été effectuées. Le suivi de l'absorption du glucose et de la conversion en lactate fournit des informations sur la santé des cellules et comment ses activités métaboliques sont affectées par la présence de composés toxiques et d’agents pathogènes<br>The rising field of bioelectronics, which couples the realms of electronics and biology, holds huge potential for the development of novel biomedical devices for therapeutics and diagnostics. Organic electronic devices are particularly promising; the use of robust organic electronic materials provides an ideal bio-interface due to their reported biocompatibility, and mechanical matching between the sensor element and the biological environment, are amongst the advantages unique to this class of materials. One promising device emerging from this field is the organic electrochemical transistor (OECT). The OECT combines properties and characteristics that can be tuned for a wide spectrum of biological applications. These applications have allowed the development of OECTs to sense local ionic/biomolecular and single cell activity, as well as characterization of tissue and even monitoring of function of whole organs. The OECT is an extremely versatile device that emerges as an important player for therapeutics and diagnostics.The use of organic materials, such as conducting polymers, makes the OECT tunable for a wide range of applications. For example, OECTs have been used for sensing applications. A representative example is the glucose sensor. The OECT has been used as glucose sensor and has shown high sensitivities and low limit of detection for concentrations at the nanomolar range. However, apart from high sensitivities, stability and reproducibility are common necessities for long term applications. For example, it is of equal importance for these sensors to continuously record variations of glucose for diabetic patients, since multiple measurements per day without failure are necessary. Additionally, stability is necessary for implantable sensors. For brain cells such as neurons, glucose is the main energy source. Thus recording modulations of glucose levels before or during an epileptic crisis will enhance our understanding of this disease. Long-term stabilities for these sensors can be achieved through biofunctionalization, which is a method to attach a biomolecule to a device. For long term applications a covalent binding of the biomolecule is preferred. Biofunctionalization of conducting polymers, which are used as active materials in OECTs, is a mandatory step that can enhance OECT properties such as biocompatibility, stability, and functionality. In this work, different biofunctionalization methods of poly(3,4-ethylenedioxythiophene) doped with tosylate anions (PEDOT:TOS) or doped with poly(styrene sulfonate) (PEDOT:PSS) have been explored. The biofunctionalization methods have led to improvements for different applications such as better interfaces with living cells, and better stability for enzymatic sensors. Additionally, we have employed the use of ionic liquids in combination with cross-linkable polymers as alternative solid state electrolytes. These electrolytes are improving the stability of recordings in electrophysiology. Finally, in vitro measurements of metabolic activities in cells have been explored. The monitoring of glucose uptake and its conversion to lactate is a sensitive indicator of the viability of these cells. Furthermore, in the presence of toxic compounds and pathogens, the nature or kinetics of these metabolic activities is getting affected. Therefore, OECTs used for glucose and lactate sensing can at the same time be used for Immunosensing
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Baptista, Pires Luis Miguel. "From nanoparticles to graphene: architecting novel (bio)sensing platforms and devices." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399332.
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La tesis presentada y titulada “De las nanopartículas al grafeno: arquitectando novedosas plataformas y dispositivos para biosensores” presenta el desarrollo de varios biosensores basados en el uso de nanoparticulas y grafeno. Se presentan dos trabajos que han dado lugar a la publicación de dos artículos científicos en la revista SMALL y Biosensors and Bioelectronics. El primer trabajo está enfocado a la detección de DNA de Leishmania usando nanoparticulas de oro como señal electroquímico y partículas magnéticas como método de separación del medio de la muestra a analizar. Además en este trabajo se demuestra el desarrollo de una técnica de amplificación de DNA en la presencia de nanoparticulas, un logro de gran importancia para biosensores ya que se puede extender a varias otras aplicaciones de interés para el diagnóstico. El sensor desarrollado puede ser usado para pruebas rutinarias para la detección rápida de Leishmania de interés para la clínica veterinaria. El segundo trabajo trata sobre la caracterización óptica y electroquímica del grafeno oxidado y su aplicación para la detección de catecol. En este trabajo, el mejoramiento de un electrodo ya existente y ampliamente utilizado es evidente, mejorando tanto a nivel de absorción de enzima utilizada como receptor como en la sensibilidad del dispositivo obtenido.
En el tercer trabajo (publicado en la revista ACS Nano), el desarrollo de una nueva metodología de impresión de grafeno oxidado trae importantes avances científicos y tecnológicos en el campo de los dispositivos a base de grafeno. Esta técnica es de bajo coste y fácil de utilizar permitiendo incluso su uso fuera del laboratorio. Este trabajo se ha concluido con la impresión del grafeno oxidado en substratos como plásticos, papel o textiles teniendo una gran importancia en futuras aplicaciones de biosensores portátiles además de los del tipo “wearable” (impresos/integrados en el cuerpo humano o textiles) una tecnología emergente para el campo de los (bio)sensores. Como prueba de concepto, se ha desarrollado un sensor de tipo “pantalla de contacto” / (touch-screen) que permite encender y apagar una pequeña lámpara (LED).
Además de estos trabajos experimentales la tesis incluye una revisión bibliográfica sobre el estado del arte de los diferentes materiales de grafeno y su producción, así como de una variedad de aplicaciones que puede tener este material.<br>The thesis presented and entitled "From nanoparticles to graphene: architecting novel (bio)sensing platforms and devices" presents the development of several biosensors based on the use of nanoparticles and graphene. Two works that have led to the publication of two scientific articles in the journal Biosensors and Bioelectronics SMALL and presented. The first work is focused on the detection of Leishmania DNA using gold nanoparticles as an electrochemical signal and magnetic nanoparticles as the separation method through the test sample. Also in this work the development of a DNA amplification technique in the presence of nanoparticles, an achievement of great importance for biosensors as it can be extended to several other applications of interest for the diagnosis demonstrated. The developed sensor can be used for routine for rapid detection of Leishmania of interest for veterinary clinical trials. The second paper deals with the optical and electrochemical characterization of oxidized graphene and its application for the detection of catechol. In this paper, the improvement of an existing and widely used electrode is evident both at improving absorption of enzyme used as receiver and device sensitivity obtained.
In the third study (published in the journal ACS Nano), the development of a new methodology printing oxidized graphene brings important advances in science and technology in the field of devices based on graphene. This technique is inexpensive and easy to use even allowing its use outside the laboratory. This work was completed with the printing of oxidized graphene on substrates such as plastics, paper or textiles having a great importance in future applications of portable biosensors addition to the "wearable" (printed / integrated into the human body or textiles) type technology for the emerging field of (bio) sensors. As proof of concept, it has developed a sensor type "touch screen" that allows on and off a small lamp (LED).
In addition to these experimental work the thesis includes a literature review on the state of art of different graphene materials and production, as well as a variety of applications that can have this material.
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Srinivasan, krishnan. "Nanomaterial sensing layer based surface acoustic wave hydrogen sensors." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001325.
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Cegla, Frederic Bert. "Ultrasonic waveguide sensors for fluid characterisation and remote sensing." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/11973.
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Shreeve, Bryson J. "Magnetic Field Sensing with Slab Coupled Optical Fiber Sensors." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2774.
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This thesis reports an in-fiber magnetic field sensor that is able to detect magnetic fields as low as 2 A/m at a spatial resolution of 1 mm. The small sensor consists of a magneto-optic slab waveguide, bismuth-doped rare earth iron garnet (Bi-RIG) that is coupled to an optical fiber. By coupling light from the fiber to the slab waveguide, it becomes an in-fiber magnetic field sensor. This is due to the Magneto-Optic Kerr effect; a change in refractive index is proportional to the applied magnetic field. When an AC field is applied, an AC component in the output power can be detected by a spectrum analyzer. The novelties of Magneto-Optic Slab Coupled Optical Sensor (MO-SCOS) devices include their small compact nature and a dielectric structure allowing low electromagnetic interference. Due to their compact size they are capable of placement within devices to measure interior electromagnetic fields immeasurable by other sensors that are either too large for internal placement or disruptive of the internal fields due to metallic structure. This work also reports progress on EO SCOS development. The EO sensor has found application in new environments including the electromagnetic rail gun, and a dual-axis sensor.
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Srinivasan, Krishnan. "Nanomaterial Sensing Layer Based Surface Acoustic Wave Hydrogen Sensors." Scholar Commons, 2005. https://scholarcommons.usf.edu/etd/873.
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This thesis addresses the design and use of suitable nanomaterials and surface acoustic wave sensors for hydrogen detection and sensing.
Nanotechnology is aimed at design and synthesis of novel nanoscale materials. These materials could find uses in the design of optical, biomedical and electronic devices. One such example of a nanoscale biological system is a virus. Viruses have been given a lot of attention for assembly of nanoelectronic materials. The tobacco mosaic virus (TMV) used in this research represents an inexpensive and renewable biotemplate that can be easily functionalized for the synthesis of nanomaterials. Strains of this virus have been previously coated with metals, silica or semiconductor materials with potential applications in the assembly of nanostructures and nanoelectronic circuits. Carbon nanotubes are another set of well-characterized nanoscale materials which have been widely investigated to put their physical and chemical properties to use in design of transistors, gas sensors, hydrogen storage cells, etc. Palladium is a well-known material for detection of hydrogen. The processes of absorption and desorption are known to be reversible and are known to produce changes in density, elastic properties and conductivity of the film. Despite these advantages, palladium films are known to suffer from problems of peeling and cracking in hydrogen sensor applications. They are also required to be cycled for a few times with hydrogen before they give reproducible responses.
The work presented in this thesis, takes concepts from previous hydrogen sensing techniques and applies them to two nanoengineered particles (Pd coated TMV and Pd coated SWNTs) as SAW resonator sensing materials. Possible sensing enhancements to be gained by using these nanomaterial sensing layers are investigated. SAW resonators were coated with these two different nano-structured sensing layers (Pd-TMV and Pd-SWNT) which produced differently useful hydrogen sensor responses. The Pd-TMV coated resonator responded to hydrogen with nearly constant increases in frequency as compared to the Pd-SWNT coated device, which responded with concentration-dependent decreases in frequency of greater magnitude upon hydrogen exposure. The former behavior is more associated with acousto-electric phenomena in SAW devices and the later with mass loading. The 99% response times were 30-40 seconds for the Pd-TMV sensing layer and approximately 150 seconds for the Pd-SWNT layer. Both the films showed high robustness and reversibility at room temperature. When the Pd film was exposed to hydrogen it was observed that it produced decreases in frequency to hydrogen challenges, conforming to mass loading effect. It was also observed that the Pd film started degrading with repeated exposure to hydrogen, with shifts after each exposure going smaller and smaller.
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DEMATTEIS, NICCOLÒ. "Integrated ground-based remote sensing sensors for glaciological monitoring." Doctoral thesis, Università degli studi di Pavia, 2020. http://hdl.handle.net/11571/1317327.
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Glaciological processes, such as glacier break-offs, snow/ice avalanches, can threaten the population, urban areas and infrastructures. For their potential hazard, it is necessary to study their activity in order to understand their possible geophysical dynamics evolution and to develop strategies of preventive alert and mitigation actions.
Therefore, the first step of this observation-alert-mitigation framework is the monitoring of such phenomena. One of the most relevant parameters to be investigated is the surface deformation, as it provides a direct measurement of the process activity.
The gravitational slope processes are common in mountain environment and hence they are often placed in harsh and remote areas. Therefore, a practical approach for their monitoring is the adoption of remote-sensing apparatuses, which allow at not accessing into possible perilous investigated areas, with consequent reduction of human resources and risks.
The remote sensing systems can be classified into two main categories: i) systems installed on aerospace platforms and ii) ground-based sensors. The first group provides data at global scale and the recent free availability of satellite constellations such as Sentinel 1 e Sentinel 2 is making their use widely studied. However, such systems suffer limitation of low temporal resolution, with revisiting time of days or weeks. The data availability of specific and localised areas is not always guaranteed and/or it can require high financial costs (e.g., airborne surveys, private satellite constellations). Moreover, complex geometries, typical of gravitational processes located in mountain areas, can affect the data acquisition.
By contrast, ground-based apparatuses are able to acquire data in environments with complex geometry. Furthermore, they can often operate in continuous, therefore providing data with high spatio-temporal resolution.
In general, a single monitoring system is able to measure specific parameters that can partially describe the state and the evolution of the investigated phenomenon. Therefore, a common approach consists in adopt different sensors and to collect separately their measurements to obtain a more comprehensive outline of the process. However, the independent analysis of the data of each sensor might not be sufficient to exploit all the available information. Rather, merging the different data in a coupled model can provide more informative results. Moreover, the data coupling allows at exploiting the qualities and potentialities of each sensor and to minimise their limits.
However, the realisation of an integrated system requires an accurate assessment of the instrument capacities. Therefore, the first step of such realisation involves the characterisation of the monitoring devices. Moreover, the development of specific and innovative processing techniques might be necessary to optimise the coupling process.
The methodologies developed for processing data of single and coupled sensors can be applied to practical case studies where the monitoring of gravitational slope phenomena can yield results about their present geophysical state, their dynamics and their possible evolution.
This text presents a collection of articles published in international scientific journals. The papers represent the work conducted during the PhD whose focus was the development of methodologies for coupling data collected by different sensors to monitor glaciological processes.
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Kilpatrick, Stephen A., and Austin J. Whittington. "NON-TRADITIONAL FLIGHT TEST SENSING SYSTEMS." International Foundation for Telemetering, 2017. http://hdl.handle.net/10150/626983.
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Traditional flight test sensing applications require installation of not only the sensor but also supporting cabling and interfacing infrastructure. The cost of this supporting infrastructure increases when it must cross pressure vessel boundaries, extend long distances, or interfere with operation of the aircraft. The continuing cost and schedule pressures on flight test programs demand approaches that minimize installation complexity and reduce the need to modify the aircraft under test. Some emerging approaches have leveraged wireless techniques for data transmission but this can only be used in certain circumstances and does not address the problem of power distribution. This paper describes ongoing research into alternative sensing approaches that utilize a mix of video processing, distributed processing, and power harvesting to provide additional solutions.
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Cadevall, Riera Miquel. "Bismuth based (nano)materials and platforms for (bio)sensing." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/285769.
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La tesi està basada en la fabricació de nous sensors i biosensors per a la detecció de contaminants. Els micro i nanomateials basats en bismut semblen ser materials molt apropiats per aconseguir aquest objectiu, tanmateix també s’han proposat altres plataformes sensores. En el primer capítol es descriuen detalladament els principals objectius d’aquesta tesi.
La introducció d’aquesta tesi descriu les aplicacions més recents i rellevants basades en la utilització de nanomaterials de bismut, com ara en els camps de la medicina, la fotodegradació de contaminants orgànics, la cosmètica, els pigments o els aliatges. Aquesta part precedeix la descripció dels mètodes de síntesi més innovadors, dels sensors més eficients, bàsicament de metalls pesants, i de les aplicacions en el camp dels biosensors. Aquest recull es pot trobar al capítol 2.
Les nanopartícules de bismut són una bona plataforma per a sensors i biosensors. En aquest sentit s’ha estudiat la modificació d’elèctrodes serigrafiats amb nanopartícules de bismut. En el capítol 3, s’avaluen diferents mètodes de síntesi de nanopartícules de bismut amb l’objectiu d’obtenir les nanopartícules més eficients en la detecció de metalls pesants; en aquest cas centrat en la detecció de cadmi i plom.
Al capítol 4 es presenta una nova estratègia de modificació d’elèctrodes. Aquesta estratègia es basa en la utilització de nanopartícules core-shell. Tenint en compte l’avantatge que dóna el recobriment de bismut, aquestes nanopartícules s’han utilitzat en la detecció de metalls pesants en diferents plataformes sensores. La bona modificació d’aquests elèctrodes es demostra clarament fent cicles de modificat i neteja; el comportament d’aquests elèctrodes modificat es podria considerar com a una resposta digital.
L’última plataforma sensora per a metalls pesants proposada es basa en xips de paper. El capítol 5 descriu la fabricació i optimització d’aquests dispositius. Aprofitant la capacitat de filtrar del substrat de paper de filtre, aquestes simples plataformes són capaces de detectar plom i cadmi en diferents matrius, com ara solució tampó, aigua de mar o fangs.
En aquest últim capítol es mostra la integració de les nanopartícules de bismut en un biosensor de fenol, basat en l’activitat enzimàtica de la tirosinasa. El capítol 6 inclou la caracterització morfològica i electroquímica del sensor. Aquests elèctrodes modificats amb nanopartícules de bismut i tirosinasa tenen una molt bona resposta en la detecció de fenol i catecol i un baix efecte de les interferències.
Finalment al capítol 7 hi ha les conclusions generals i les futures perspectives que obre aquest treball.
En els annexos s’hi pot trobar una descripció dels mètodes de fabricació de les diferents plataformes sensores, les abreviatures utilitzades i la producció científica derivada d’aquest treball.<br>The thesis is focused on the fabrication of new sensing and biosensing platforms for pollutants detection. Although bismuth-based micro and nanomaterials seem to be the appropriated materials to achieve this objective nevertheless new platforms including for example those based on paper are also proposed. In the first chapter the main objectives of this thesis are described in detail.
The introduction part (chapter 2) of this thesis is dedicated to the revision of the recent reports / achievements on bismuth-based nanomaterials in different application fields that include medicine, photodegradation of organic pollutants, cosmetics, pigments and alloys. An important section of this part is focused on the description of the effect of bismuth-based materials in heavy metals and biosensing applications.
Bismuth nanoparticles are found as an innovative material in heavy metals sensing and biosensing applications. A study on the effect of the modification of screen-printed electrodes with bismuth nanoparticles and its use for the heavy metal detection is shown (chapter 3). Different modifications of polyol based bismuth nanoparticles synthesis have been evaluated in aim to obtain the more efficient nanoparticles with interest in heavy metal sensing. In addition the results obtained for the detection of lead and cadmium is also shown in the same chapter.
In the chapter 4 a new electrode modification strategy is presented. This new strategy is based on the use of magnetic core/shell bismuth nanoparticles. Taking advantages of the bismuth oxide presence onto the shell of these nanoparticles, heavy metal detection in different On-Off sensing platforms is shown. The modification of electrodes is clearly demonstrated by doing cycles with both modification and cleaning of the electrodes obtaining a kind of digital (On-Off) response of heavy metals.
To solve sampling and sample pretreatment issues a heavy metal sensing platform that uses a paper-based lateral flow chip is also developed and described at chapter 5. Fabrication and the optimization of this new heavy metal sensor are shown; it takes advantage of the use of a filter paper substrate. This new platform is capable to detect lead and cadmium in different matrixes including mud.
In the last chapter (chapter 6), the integration of bismuth nanoparticles into a phenol biosensing system is shown. It takes advantages of the use of tyrosinase enzyme which brings certain selectivity in phenolic compounds detection. Morphological and electrochemical characterizations of the developed biosensor also are shown in this chapter. The developed biosensor shows good performance in catechol detection.
Finally in the chapter 7 the general conclusions and some future perspectives are given.
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Li, Guofeng. "Electrochemical functionalization of conducting polymers towards chemical sensing applications." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/30313.
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Slyper, Ronit. "Sensing Through Structure." Research Showcase @ CMU, 2012. http://repository.cmu.edu/dissertations/158.
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We present an approach to designing input devices that focuses on the structure of materials. We explore and visualize how a material reacts under manipulation, and harness the material’s properties to design new movement sensors. Two benefits spring out of this approach. One, simpler sensing emerges from making use of existing structure in the material. Two, by working with the natural structure of the material, we create input devices with readily recognizable affordances. We present six projects using this approach. We use the natural structure (coordination) of the human body to enable a mapping from five clothing-mounted accelerometers to high-quality motion capture data, creating a low-cost performance animation system. We design silicone input devices with embedded texture allowing single-camera tracking. We study squishable, conformable materials such as foam and silicone, and create a vocabulary of unit structures (shaped cuts in the material) for harnessing patterns of compression/tension to capture particular manipulations. We use this vocabulary to build soft sensing skeletons for stuffed animals, making foam cores with e-textile versions of our unit structures. We also use this vocabulary to design a tongue input device for a collaboration with Disney Imagineering. Finally, we rethink this vocabulary and apply it to capturing, using air pressure sensors, manipulations of hollow 3D-printed rubber shapes, and 3D-print several interactive robots incorporating the new vocabulary.
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Alrowaijeh, Jamal Salem. "Fluidic Energy Harvesting and Sensing Systems." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/96241.
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Smart sensors have become and will continue to constitute an enabling technology to wirelessly connect platforms and systems and enable improved and autonomous performance. Automobiles
have about two hundred sensors. Airplanes have about eight thousand sensors. With technology advancements in autonomous vehicles or fly-by-wireless, the numbers of these sensors is expected to increase significantly. The need to conserve water and energy has led to the development of advanced metering infrastructure (AMI) as a concept to support smart energy and water grid systems that would respond to emergency shut-offs or electric blackouts. Through the Internet of things (IoT) smart sensors and other network devices will be connected to enable exchange and control procedure toward reducing the operational cost and improving the efficiency of residential and commercial buildings in terms of their function or energy and water use.
Powering these smart sensors with batteries or wires poses great challenges in terms of replacing the batteries and connecting the wires especially in remote and difficult-to-reach locations. Harvesting free ambient energy provides a solution to develop self-powered smart sensors that can support different platforms and systems and integrate their functionality. In this dissertation, we develop and experimentally assess the performance of harvesters that draw their energy from air or water flows. These harvesters include centimeter-scale micro wind turbines, piezo aeroelastic harvesters, and micro hydro generators. The performance of these different harvesters is determined by their capability to support wireless sensing and transmission, the level of generated power, and power density. We also develop and demonstrate the capability of multifunctional systems that can harvest energy to replenish a battery and use the harvested energy to sense speed, flow rate or temperature, and to transmit the data wirelessly to a remote location.<br>PHD
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Salehi-Abari, Omid. "Building compressed sensing systems : sensors and analog-to-information converters." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78472.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 93-96).<br>Compressed sensing (CS) is a promising method for recovering sparse signals from fewer measurements than ordinarily used in the Shannon's sampling theorem [14]. Introducing the CS theory has sparked interest in designing new hardware architectures which can be potential substitutions for traditional architectures in communication systems. CS-based wireless sensors and analog-to-information converters (AIC) are two examples of CS-based systems. It has been claimed that such systems can potentially provide higher performance and lower power consumption compared to traditional systems. However, since there is no end-to-end hardware implementation of these systems, it is difficult to make a fair hardware-to-hardware comparison with other implemented systems. This project aims to fill this gap by examining the energy-performance design space for CS in the context of both practical wireless sensors and AICs. One of the limitations of CS-based systems is that they employ iterative algorithms to recover the signal. Since these algorithms are slow, the hardware solution has become crucial for higher performance and speed. In this work, we also implement a suitable CS reconstruction algorithm in hardware.<br>by Omid Salehi-Abari.<br>S.M.
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Jackson, Cornelius Christiaan. "Tactile force-sensing for dynamic gripping using piezoelectric force- sensors." Thesis, Bloemfontein : Central University of Technology, Free State, 2009. http://hdl.handle.net/11462/34.
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Davies, Edward. "Optical fibre sensors with applications in gas and biological sensing." Thesis, Aston University, 2011. http://publications.aston.ac.uk/15800/.
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This thesis describes the study of various grating based optical fibre sensors for applications in refractive index sensing. The sensitivity of these sensors has been studied and in some cases enhanced using novel techniques. The major areas of development are as follows. The sensitivity of long period gratings (LPGs) to surrounding medium refractive index (SRI) for various periods was investigated. The most sensitive period of LPG was found to be around 160 µm and this was due to the core mode coupling to a single cladding mode but phase matching at two wavelength locations, creating two attenuation peaks, close to the waveguide dispersion turning point. Large angle tilted fibre gratings (TFGs) have similar behaviour to LPGs, in that they couple to the co-propagating cladding modes. The tilted structure of the index modulation within the core of the fibre gives rise to a polarisation dependency, differing the large angle TFG from a LPG. Since the large angle TFG couple to the cladding mode they are SRI sensitive, the sensitivity to SRI can be further increased through cladding etching using HF acid. The thinning of the cladding layer caused a reordering of the cladding modes and shifted to more SRI sensitive cladding modes as the investigation discovered. In a SRI range of 1.36 to 1.40 a sensitivity of 506.9 nm/URI was achieved for the etched large angle TFG, which is greater than the dual resonance LPG. UV inscribed LPGs were coated with sol-gel materials with high RIs. The high RI of the coating caused an increase in cladding mode effective index which in turn caused an increase in the LPG sensitivity to SRI. LPGs of various periods of LPG were coated with sol-gel TiO2 and the optimal thickness was found to vary for each period. By coating of the already highly SRI sensitive 160µm period LPG (which is a dual resonance) with a sol-gel TiO2, the SRI sensitivity was further increased with a peak value of 1458 nm/URI, which was an almost 3 fold increase compared to the uncoated LPG. LPGs were also inscribed using a femtosecond laser which produced a highly focused index change which was no uniform throughout the core of the optical fibre. The inscription technique gave rise to a large polarisation sensitivity and the ability to couple to multiple azimuthal cladding mode sets, not seen with uniform UV inscribed gratings. Through coupling of the core mode to multiple sets of cladding modes, attenuation peaks with opposite wavelength shifts for increasing SRI was observed. Through combining this opposite wavelength shifts, a SRI sensitivity was achieved greater than any single observed attenuations peak. The maximum SRI achieved was 1680 nm/URI for a femtosecond inscribed LPG of period 400 µm. Three different types of surface plasmon resonance (SPR) sensors with a multilayer metal top coating were investigated in D shape optical fibre. The sensors could be separated into two types, utilized a pre UV inscribed tilted Bragg grating and the other employed a post UV exposure to generate surface relief grating structure. This surface perturbation aided the out coupling of light from the core but also changed the sensing mechanism from SPR to localised surface plasmon resonance (LSPR). This greatly increased the SRI sensitivity, compared to the SPR sensors; with the gold coated top layer surface relief sensor producing the largest SRI sensitivity of 2111.5nm/URI was achieved. While, the platinum and silver coated top layer surface relief sensors also gave high SRI sensitivities but also the ability to produce resonances in air (not previously seen with the SPR sensors). These properties were employed in two applications. The silver and platinum surface relief devices were used as gas sensors and were shown to be capable of detecting the minute RI change of different gases. The calculated maximum sensitivities produced were 1882.1dB/URI and 1493.5nm/URI for silver and platinum, respectively. Using a DFB laser and power meter a cheap alternative approach was investigated which showed the ability of the sensors to distinguish between different gases and flow rates of those gases. The gold surface relief sensor was coated in a with a bio compound called an aptamer and it was able to detect various concentrations of a biological compound called Thrombin, ranging from 1mM to as low as 10fM. A solution of 2M NaCl was found to give the best stripping results for Thrombin from the aptamer and showed the reusability of the sensor. The association and disassociation constants were calculated to be 1.0638×106Ms-1 and 0.2482s-1, respectively, showing the high affinity of the Aptamer to thrombin. This supports existing working stating that aptamers could be alternative to enzymes for chemical detection and also helps to explain the low detection limit of the gold surface relief sensor.
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Gibson, Richard S. "Slab-Coupled Optical Fiber Sensors for Electric Field Sensing Applications." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd3248.pdf.
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Grundling, Althea Theresa. "Evaluation of remote sensing sensors for monitoring of rehabilitated wetlands." Diss., Prtoria: [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-05132005-145705/.
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Perry, Daniel Theodore. "Directional Electric Field Sensing Using Slab Coupled Optical Fiber Sensors." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3443.
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This thesis provides the details of a multi-axis electric field sensor. The sensing element consists of three slab coupled optical fiber sensors that are combined to allow directional electric field sensing. The packaged three-axis sensor has a small cross-sectional area of 0.5 cm x 0.5 cm achieved by using an x-cut crystal. The method is described that uses a sensitivity-matrix approach to map the measurements to field components. The calibration and testing are described resulting in an average error of 1.5º.This work also includes a description of the packaging method used as well as a thorough analysis of the directional sensitivity of potassium titanyl phosphate (KTP) and electro-optic polymer: the two materials used as sensing elements. Each of the two materials is highly direction sensitive creating minimal crosstalk between the sensors.
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Shekaramiz, Mohammad. "Sparse Signal Recovery Based on Compressive Sensing and Exploration Using Multiple Mobile Sensors." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7384.
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The work in this dissertation is focused on two areas within the general discipline of statistical signal processing. First, several new algorithms are developed and exhaustively tested for solving the inverse problem of compressive sensing (CS). CS is a recently developed sub-sampling technique for signal acquisition and reconstruction which is more efficient than the traditional Nyquist sampling method. It provides the possibility of compressed data acquisition approaches to directly acquire just the important information of the signal of interest. Many natural signals are sparse or compressible in some domain such as pixel domain of images, time, frequency and so forth. The notion of compressibility or sparsity here means that many coefficients of the signal of interest are either zero or of low amplitude, in some domain, whereas some are dominating coefficients. Therefore, we may not need to take many direct or indirect samples from the signal or phenomenon to be able to capture the important information of the signal. As a simple example, one can think of a system of linear equations with N unknowns. Traditional methods suggest solving N linearly independent equations to solve for the unknowns. However, if many of the variables are known to be zero or of low amplitude, then intuitively speaking, there will be no need to have N equations. Unfortunately, in many real-world problems, the number of non-zero (effective) variables are unknown. In these cases, CS is capable of solving for the unknowns in an efficient way. In other words, it enables us to collect the important information of the sparse signal with low number of measurements. Then, considering the fact that the signal is sparse, extracting the important information of the signal is the challenge that needs to be addressed. Since most of the existing recovery algorithms in this area need some prior knowledge or parameter tuning, their application to real-world problems to achieve a good performance is difficult. In this dissertation, several new CS algorithms are proposed for the recovery of sparse signals. The proposed algorithms mostly do not require any prior knowledge on the signal or its structure. In fact, these algorithms can learn the underlying structure of the signal based on the collected measurements and successfully reconstruct the signal, with high probability. The other merit of the proposed algorithms is that they are generally flexible in incorporating any prior knowledge on the noise, sparisty level, and so on.
The second part of this study is devoted to deployment of mobile sensors in circumstances that the number of sensors to sample the entire region is inadequate. Therefore, where to deploy the sensors, to both explore new regions while refining knowledge in aleady visited areas is of high importance. Here, a new framework is proposed to decide on the trajectories of sensors as they collect the measurements. The proposed framework has two main stages. The first stage performs interpolation/extrapolation to estimate the phenomenon of interest at unseen loactions, and the second stage decides on the informative trajectory based on the collected and estimated data. This framework can be applied to various problems such as tuning the constellation of sensor-bearing satellites, robotics, or any type of adaptive sensor placement/configuration problem. Depending on the problem, some modifications on the constraints in the framework may be needed. As an application side of this work, the proposed framework is applied to a surrogate problem related to the constellation adjustment of sensor-bearing satellites.
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Ruano-Lopez, Jesus M. "Optical devices for biochemical sensing in flame hydrolysis deposited glass." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368575.
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Wang, Huan. "Crop assessment and monitoring using optical sensors." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38224.
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Doctor of Philosophy<br>Department of Agronomy<br>V. P. Vara Prasad<br>Crop assessment and monitoring is important to crop management both at crop production level and research plot level, such as high-throughput phenotyping in breeding programs. Optical sensors based agricultural applications have been around for decades and have soared over the past ten years because of the potential of some new technologies to be low-cost, accessible, and high resolution for crop remote sensing which can help to improve crop management to maintain producers’ income and diminish environmental degradation. The overall objective of this study was to develop methods and compare the different optical sensors in crop assessment and monitoring at different scales and perspectives.
At crop production level, we reviewed the current status of different optical sensors used in precision crop production including satellite-based, manned aerial vehicle (MAV)-based, unmanned aircraft system (UAS)-based, and vehicle-based active or passive optical sensors. These types of sensors were compared thoroughly on their specification, data collection efficiency, data availability, applications and limitation, economics, and adoption.
At research plot level, four winter wheat experiments were conducted to compare three optical sensors (a Canon T4i® modified color infrared (CIR) camera, a MicaSense RedEdge® multispectral imager and a Holland Scientific® RapidScan CS-45® hand-held active optical sensor (AOS)) based high-throughput phenotyping for in-season biomass estimation, canopy estimation, and grain yield prediction in winter wheat across eleven Feekes stages from 3 through 11.3. The results showed that the vegetation indices (VIs) derived from the Canon T4i CIR camera and the RedEdge multispectral camera were highly correlated and can equally estimate winter wheat in-season biomass between Feekes 3 and 11.1 with the optimum point at booting stage and can predict grain yield as early as Feekes 7. Compared to passive sensors, the RapidScan AOS was less powerful and less temporally stable for biomass estimation and yield prediction. Precise canopy height maps were generated from a CMOS sensor camera and a multispectral imager although the accuracy could still be improved. Besides, an image processing workflow and a radiometric calibration method were developed for UAS based imagery data as bi-products in this project.
At temporal dimension, a wheat phenology model based on weather data and field contextual information was developed to predict the starting date of three key growth stages (Feekes 4, 7, and 9), which are critical for N management. The model could be applied to new data within the state of Kansas to optimize the date for optical sensor (such as UAS) data collection and save random or unnecessary field trips. Sensor data collected at these stages could then be plugged into pre-built biomass estimation models (mentioned in the last paragraph) to estimate the productivity variability within 20% relative error.
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Blagoi, Gabriela. "Fluorescence resonance energy transfer (FRET) based sensors for bioanalysis." ScholarWorks@UNO, 2004. http://louisdl.louislibraries.org/u?/NOD,146.
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Thesis (Ph. D.)--University of New Orleans, 2004.<br>Title from electronic submission form. "A dissertation ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry."--Dissertation t.p. Vita. Includes bibliographical references.
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Roso, Casares Sergio. "Synthesis and gas sensing properties of single crystalline metal-oxide nanostructures." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/402468.
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A la present tesis doctoral, s'han produït diferents tipus de nanoestructures basades en òxids metàl·lics, com per exemple nanofils de ZnO i octaedros d'In2O3, utilitzant el mètode de Deposició Química de Vapor (CVD) a altes temperatures.
Per a la detecció d'òxid de nitrogen, s'ha descobert que la resposta dels nanofils d'ZnO està directament relacionada amb la quantitat de defectes presents en el material. Com més gran es el nombre de defectes, major és la resposta al diòxid de nitrogen. Tanmateix, per a la detecció d'etanol, la mostra que contenia un nombre mig de defectes, va ser la que dóna millors resultats.
Pel que fa als octaedres de In2O3, podem dir que els octaedres d'In2O3 pur són excel·lents candidats per a la detecció de NO2, ja que tenen una excel·lent sensibilitat (0.43 ppb-1) a baixes temperatures (130ºC), mentres que la resposta a altres gasos com H2 és dos ordres de magnituds inferior en les mateixes condicions. A més a més, en presencia d'humitat, s'incrementa la sensibilitat a NO2 i, a la vegada, es redueix la sensibilitat a H2, pel que la selectivitat a NO2 també es veu incrementada.
Finalment, utilitzant l'espectroscopia DRIFT, s'ha analitzat l'In2O3 expost a 1 ppm de NO2 a diferents temperatures i s'ha descobert que el mecanisme proposat per a descriure el procés de sensat es bastant més complicat del que s'ha reportat fins ara.
Com a resultat de tots aquests experiments, s'ha donat un pas edanvant en l'explicació dels mecanismes de sensat dels nanofils d'ZnO i els octaedres de In2O3 a diferents temperatures.<br>En la presente tesis doctoral, se han producido diferentes tipos de nanoestructuras basadas en oxidos metalicos, como por ejemplo nanohilos de ZnO y ocaedros de In2O3, utilizando el método de Deposición Química de Vapor (CVD) a altas temperaturas.
Para la detección de dióxido de nitrógeno, se ha descubierto que la respuesta de los nanohilos de ZnO está directamente correlacionada con la cantidad total de defectos presentes en el material. Cuanto mayor es el número de defectos, mayor es la respuesta al dióxido de nitrógeno. Sin embargo, para la detección de etanol, la muestra que contenía un número medio de defectos fue la que dio mejores resultados.
Por lo que respecta a los octaedros de In2O3, podemos decir que los octaedros de In2O3 puro son excelentes candidatos para la detección de NO2, ya que poseen una excelente sensibilidad (0.43 ppb-1) a bajas temperaturas (130ºC), mientras que la respuesta a otros gases como H2 es dos órdenes de magnitud inferior en las mismas condiciones. Además, en presencia de humedad, se incrementa la sensibilidad a NO2 y, a la vez, se reduce la sensibilidad a H2, por lo que la selectividad hacia NO2 tambien se ve incrementada.
Finalmente, utilizando la espectroscopia DRIFT, se ha analizado el In2O3 expuesto a 1 ppm de NO2 a diferentes temperaturas y se ha descubierto que el mecanismo propuesto para describir el proceso de senado es bastante más complicado que lo que se ha publicado hasta ahora.
Como resultado de todos estos experimentos, se ha arrojado luz nueva sobre los mecanismos de sensado de los nanohilos de ZnO y los octahedros de In2O3 a diferentes temperaturas.<br>In the present doctoral thesis, several metal oxide nanostructures such as ZnO nanowires and In2O3 octahedra via a chemical vapour deposition (CVD) method at high temperatures.
For the detection of nitrogen dioxide, it was found that the response of ZnO nanowires was directly correlated to the overall amount of defects of the material. The higher the number of defects is, the higher the response to nitrogen dioxide is. On the other hand, for the detection of ethanol, ZnO nanowires with an intermediate number of defects in which surface defects were dominant led to the best results.
Additionally, regarding the In2O3 octahedra, we can say that pure In2O3 octahedra are excellent for detecting NO2 gas with an outstanding sensitivity (0.43 ppb-1) at low temperatures (130ºC), while the response to H2 remains two orders of magnitude lower under the same conditions. In addition, the presence of humidity increases the sensitivity to NO2 and, at the same time, reduces the response to H2, which results in an increased selectivity.
Finally, by making use of the DRIFT spectroscopy, we have analyzed In2O3 material towards 1 ppm of NO2 at different temperatures and, it has been found that the mechanism proposed for the gas sensing is far more complicated than previously reported. As a result of these experiments, new light on the sensing mechanism of ZnO and In2O3 material towards NO2 gas at different temperatures has been shed.
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Acosta, Capilla Laura Karen. "Engineering of photonic structures based on nanoporous anodic alumina as an optical sensing platform." Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/672982.
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S'ha demostrat que les propietats òptiques de l'alúmina nanoporosa depenen intrínsecament de la seva arquitectura, el que fa possible modular la seva índex de refracció per fabricar materials avançats amb propietats òptiques úniques com les estructures fotòniques. Aquesta tesi té com a objectiu principal, la fabricació d'estructures fotòniques basades en Alúmina nanoporosa. Les estructures Fotonicas van ser fabricades amb alúmina nanoporosa (NAA-PSS) mitjançant l'anodització d'alumini amb diferents perfils de anodització (sinusoïdal i gaussià) així com la fabricació de microcavitats òptiques. Es van estudiar les seves propietats òptiques i la seva influència quan la mida de porus és més gran. Un cop fabricades i caracteritzades, les NAA-PSS van ser avaluades com a plataformes per desenvolupar sensors òptics mitjançant la tècnica d'espectroscòpia interferomètrica reflectant (rifs). Les estructures van ser analitzades utilitzant diferents concentracions de glucosa, solucions d'alcohols i clorur de sodi. Es van provar amb diferents mides de porus així com amb diferents tipus d'estructures modificant els paràmetres de fabricació. Amb els resultats obtinguts en aquesta tesi doctoral, es va demostrar que les estructures Fotonicas basada en alúmina nanoporosa tenen la capacitat de ser usades com una plataforma amb potencial per desenvolupar sensors òptics.<br>Se ha demostrado que las propiedades ópticas de la alúmina nanoporosa dependen intrínsecamente de su arquitectura, lo que hace posible modular su indice de refracción para fabricar materiales avanzados con propiedades ópticas únicas como las estructuras fotónicas. Esta tesis tiene como objetivo principal, la fabricación de estructuras fotónicas basadas en Alúmina Nanoporosa. Las estructuras fotonicas fueron fabricadas con alúmina nanoporosa (NAA-PSs) mediante la anodización de aluminio con diferentes perfiles de anodización (sinusoidal y gaussiano) así como la fabricación de microcavidades ópticas. Se estudiaron sus propiedades ópticas y su influencia cuando el tamaño de poro es mayor. Una vez fabricadas y caracterizadas, las NAA-PSs fueron evaluadas como plataformas para desarrollar sensores ópticos mediante la técnica de espectroscopia interferométrica reflectante (RIfs). Las estructuras fueron analizadas usando diferentes concentraciones de glucosa, soluciones de alcoholes y cloruro de sodio. Se probaron con diferentes tamaños de poro así como con diferentes tipos de estructuras modificando los parámetros de fabricación. Con los resultados obtenidos en esta tesis doctoral, se demostró que las estructuras fotonicas basada en alúmina nanoporosa tienen la capacidad de ser usadas como una plataforma con potencial para desarrollar sensores ópticos.<br>The optical properties of nanoporous alumina have been shown to be intrinsically dependent upon its architecture, making it possible to modulate its refractive index to fabricate advanced materials with unique optical properties such as photonic structures. This thesis has as its main objective, the manufacture of photonic structures based on Nanoporous Alumina. The photonic structures were fabricated with nanoporous alumina (NAA-PSs) by anodizing aluminum with different anodizing profiles (sinusoidal and Gaussian) as well as the fabrication of optical microcavities. Its optical properties and its influence when the pore size is larger were studied. Once manufactured and characterized, the NAA-PSs were evaluated as platforms to develop optical sensors using the reflective interferometric spectroscopy (RIfs) technique. The structures were analyzed using different concentrations of D-glucose, alcohol solutions and sodium chloride. They were tested with different pore sizes as well as with different types of structures by modifying the fabrication parameters. With the obtained results in this doctoral thesis, iwas demonstrated that photonic structures based on nanoporous alumina have the ability to be used as a potential platform to develop optical sensors.
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Martínez, Hurtado Juan Leonardo. "Gas-sensitive holographic sensors." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/244643.
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Holographic sensors are photonic layered structures contained in analyte sensitive lms that upon illumination produce monochromatic reflections (λ). The present work reports the fabrication of oxygen and ammonia sensors in Nafi on membranes and hydrocarbon and volatile organic compound sensors in poly(dimethylsiloxane) (PDMS) films. A holographic recording technique was developed to suit these materials consisting of the in situ formation of nanoparticles of 18nm average diameter and their subsequent ordered ablation with a 300mJ laser. The wavelength of the monochromatic reflections depends principally on the refractive index of the resulting layers (n) and the separation between them (Λ). Changes in these parameters are generated by the analyte-sensor interactions and their magnitude can be correlated to the analyte concentration. The strength of these interactions is determined by the thermodynamic properties of the analytes, such as the cohesive energy density (δ^2), and this, was coupled with a photonic model for the prediction of the holographic response. After exposure to different concentrations of the analytes, the kinetics of the responses were determined and the lowest detection limits (LDL) established as follows: Hydrocarbons in PDMS holograms 1% (v/v) in 3s for a range of concentrations from 0-100%; ammonia in Nafi on holograms 0.16% in 100s in the 0-12.5% range; the LDL for oxygen sensing could not be determined although the response was recorded down to 12.5% and up to 100% in 100s. Holographic sensors show competitive responses comparable to commercially available gas sensors for biomedical diagnostics and industrial process monitoring because of their facile fabrication and their shared sensing platform allowing multiplexing.
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Abhijith, N. "Semi Conducting Metal Oxide Gas Sensors: Development And Related Instrumentation." Thesis, Indian Institute of Science, 2006. https://etd.iisc.ac.in/handle/2005/281.
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A sensor is a technological device or biological organ that detects, or senses, a signal or physical condition and chemical compounds. Technological developments in the recent decades have brought along with it several environmental problems and human safety issues to the fore. In today's world, therefore, sensors, which detect toxic and inflammable chemicals quickly, are necessary. Gas sensors which form a subclass of chemical sensors have found extensive applications in process control industries and environmental monitoring.
The present thesis reports the attempt made in development of Zinc oxide thin film based gas sensors. ZnO is sensitive to many gases of interest like hydrocarbons, hydrogen, volatile organic compounds etc. They exhibit high sensitivity, satisfactory stability and rapid response. In the present work the developed sensors have been tested for their sensitivity for a typical volatile organic compound, acetone. An objective analysis of the various substrates namely borosilicate glass, sintered alumina and hard anodized alumina, has been performed as a part of this work. The substrates were evaluated for their electrical insulation and thermal diffusivity. The microstructure of the gas sensitive film on the above mentioned substrates was studied by SEM technique. The gas sensitive Zinc oxide film is deposited by D.C reactive magnetron sputtering technique with substrate bias arrangement. The characterization of the as-deposited film was performed by XRD, SEM and EDAX techniques to determine the variation of microstructure, crystallite size, orientation and chemical composition with substrate bias voltage. The thesis also describes the development of the gas sensor test setup, which has been used to measure the sensing characteristics of the sensor. It was observed that the ZnO sensors developed with higher bias voltages exhibited improved sensitivity to test gas of interest.
Gas sensors essentially measure the concentration of gas in its vicinity. In order to determine the distribution of gas concentration in a region, it is necessary to network sensors at remote locations to a host. The host acts as a gateway to the end user to determine the distribution of gas concentration in a region. However, wireless gas sensor networks have not found widespread use because of two inherent limitations:
Metal oxide gas sensors suffer from output drift over time; frequent recalibration of a
number of sensors is a laborious task.
The gas sensors have to be maintained at a high temperature to perform the task of gas
sensing. This is power intensive operation and is not well suited for wireless sensor
network.
This thesis reports an exploratory study carried out on the applicability of gas sensors in wireless gas sensor network. A simple prototype sensing node has been developed using discrete electronic components. A methodology to overcome the problem of frequent calibration of the sensing nodes, to tackle the sensor drift with ageing, is presented. Finally, a preliminary attempt to develop a strategy for using gas sensor network to localize the point of gas leak is given.
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Abhijith, N. "Semi Conducting Metal Oxide Gas Sensors: Development And Related Instrumentation." Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/281.
Full textAbstract:
A sensor is a technological device or biological organ that detects, or senses, a signal or physical condition and chemical compounds. Technological developments in the recent decades have brought along with it several environmental problems and human safety issues to the fore. In today's world, therefore, sensors, which detect toxic and inflammable chemicals quickly, are necessary. Gas sensors which form a subclass of chemical sensors have found extensive applications in process control industries and environmental monitoring.
The present thesis reports the attempt made in development of Zinc oxide thin film based gas sensors. ZnO is sensitive to many gases of interest like hydrocarbons, hydrogen, volatile organic compounds etc. They exhibit high sensitivity, satisfactory stability and rapid response. In the present work the developed sensors have been tested for their sensitivity for a typical volatile organic compound, acetone. An objective analysis of the various substrates namely borosilicate glass, sintered alumina and hard anodized alumina, has been performed as a part of this work. The substrates were evaluated for their electrical insulation and thermal diffusivity. The microstructure of the gas sensitive film on the above mentioned substrates was studied by SEM technique. The gas sensitive Zinc oxide film is deposited by D.C reactive magnetron sputtering technique with substrate bias arrangement. The characterization of the as-deposited film was performed by XRD, SEM and EDAX techniques to determine the variation of microstructure, crystallite size, orientation and chemical composition with substrate bias voltage. The thesis also describes the development of the gas sensor test setup, which has been used to measure the sensing characteristics of the sensor. It was observed that the ZnO sensors developed with higher bias voltages exhibited improved sensitivity to test gas of interest.
Gas sensors essentially measure the concentration of gas in its vicinity. In order to determine the distribution of gas concentration in a region, it is necessary to network sensors at remote locations to a host. The host acts as a gateway to the end user to determine the distribution of gas concentration in a region. However, wireless gas sensor networks have not found widespread use because of two inherent limitations:
Metal oxide gas sensors suffer from output drift over time; frequent recalibration of a
number of sensors is a laborious task.
The gas sensors have to be maintained at a high temperature to perform the task of gas
sensing. This is power intensive operation and is not well suited for wireless sensor
network.
This thesis reports an exploratory study carried out on the applicability of gas sensors in wireless gas sensor network. A simple prototype sensing node has been developed using discrete electronic components. A methodology to overcome the problem of frequent calibration of the sensing nodes, to tackle the sensor drift with ageing, is presented. Finally, a preliminary attempt to develop a strategy for using gas sensor network to localize the point of gas leak is given.
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Noren, Jonathan Robert. "Electric Field Sensing in a Railgun Using Slab Coupled Optical Fiber Sensors." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3482.
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This thesis discusses the application of Slab Coupled Optical Fiber Sensors (SCOS) in a railgun. The specific goal of these sensors is to create an electric field profile at a specific point in the gun as the armature passes. The thesis explores the theory that powers the railgun as well as the principles of the SCOS sensors. It also elaborates on the various noise sources found throughout the detection system and concludes with a summary of the various field tests that were performed throughout this project. There are many benefits to using a railgun over traditional weapons in the field. These benefits not only include both safety and cost, but also greater overall defense capabilities. Unfortunately, the velocity skin effect (VSE) causes the current railgun designs to have limited life span through wear on the rails. In order to develop superior railguns and railgun armatures, the accurate detection of the VSE through measuring the electric field is of great interest. We used a SCOS, a small directionally precise dielectric sensor, as a small sensing area is required to be able to measure the electric fields inside of the rail gun. The actual usage of the SCOS within the railgun produced an additional set of problems that are not commonly encountered in the lab. The chief amongst these was noise from strain, RF pickup, and phase noise. This thesis also reports various methods used to reduce each of these noise sources.
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Johnson, Andrea. "Sol-gel encapsulation of heterocyclic ligands for aqueous sensing applications." Thesis, Brunel University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307510.
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Smith, Ann M. "Optical and related methods of chemical sensing using substituted phthalocyanines." Thesis, University of Kent, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319229.
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Tormo, Peiró Julia Alba. "Spectrum sensing based on specialized microcontroller based white space sensors : Measuring spectrum occupancy using a distributed sensor grid." Thesis, KTH, Radio Systems Laboratory (RS Lab), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-124555.
Full textAbstract:
The continuing increase in the adoption and use of wireless technology aggravates the problem of spectrum scarcity due to the way we utilize the spectrum. The radio spectrum is a limited resource regulated by governmental agencies according to a fixed spectrum assignment policy. However, many studies show that this fixed radio frequency allocation leads to significant underutilization of the radio spectrum creating artificial scarcity, as most of the allocated spectrum is not used all of the time in every location. To meet services growing demands, efficient use of the spectrum is essential. Therefore, there is a need to estimate the radio spectrum utilization in several locations and during different periods of time in order to opportunistically exploit the existing wireless spectrum. Cognitive radio technology aims to search for those portions of the radio spectrum that are assigned to a specific service, but are unused during a specific time and at specific location in order to share these white spaces and thus to reduce the radio spectrum inefficiency. In this thesis, we study spectrum utilization in the frequency range from 790MHz to 925MHz. The spectrum sensing has been realized using a number of specialized microcontroller based white space sensors which utilize energy detection, situated in different locations of a building in Kista, Sweden. The occupancy of the frequency bands in this chunk of the spectrum is quantified as the fraction of samples with a power level greater than a threshold. The results from these spectrum measurements show that a significant amount of spectrum in this scanned range around the building is inefficiently used all the time.<br>Den senaste tidens ökning av trådlös teknik förvärrar problemet med spektrumbrist på grund av hur vi använder den. Det radiospektrum är en begränsad resurs som regleras av statliga myndigheter enligt en fast spektrumtilldelningen politik. Men många studier visar att den fasta frekvensplan leder till betydande underutnyttjande av radiospektrum och skapar en konstgjord brist eftersom de flesta av de tilldelade spektrumet inte används hela tiden i varje platsen. För att uppfylla tjänster ökade krav, är viktigt en effektiv användning av spektrumet. Därför finns det ett behov av att uppskatta användningen av radiospektrum i flera platser och i olika tidsperioder för att kunna utnyttja den befintliga trådlösa spektrumet i opportunistiskt sätt. Kognitiv radio teknologi syftar till att söka efter dessa delar av radiospektrum som tilldelas till en konkret tjänst och är oanvända i en viss tid och på viss plats för att dela dessa vita ytor och därför lösa radio spektrum ineffektivitet problem. I denna uppsats studerar vi spektrumanvändning i frekvensområdet från 790 MHz till 925 MHz. Spektrat avkänning har utförts med hjälp av ett antal specialiserade mikrokontroller blanktecken sensorer vilka utnyttjar energin upptäckt, som ligger på olika platser i en byggnad i Kista, Sverige. Uthyrningsgraden av frekvensbanden i denna del av spektrumet kvantifieras som antalet prover med en effektnivå överstiger en tröskel. Resultaten från spektrat mätningarna visar att en betydande del av spektrumet i denna scannade intervall ineffektivt används hela tiden.