Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

Analysis and design of a two-axis noncontact position sensor

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (p. 165-166).by Robert John Ritter.S.M

New spectroscopic techniques and architectures for environmental and biomedical applications

Mención Internacional en el título de doctorThe range of application of spectroscopic instruments is so broad nowadays that encompasses various areas of engineering, industry and scientific research. Consequently, different techniques and spectral analysis methods have been developed for the characterization of the numerous samples regularly targeted by spectroscopic sensors. In this doctoral dissertation, contributions have been made to virtually all of the main components that make up spectroscopic systems. Different methods, architectures and spectral data analysis algorithms have been proposed for environmental and biomedical applications particularly. In this way, novel techniques and architectures for molecular spectroscopy based on the measurement of optical dispersion have been presented (unlike most of the current methods that are based on the measurement of absorption). This approach, whereas maintain a reasonably low level of complexity, overcomes most of the limitations associated to absorption-based methods, providing an improved performance in some areas of the analyzers. Even though two of the proposed architectures for the estimation of gas concentration are based on the use of tunable lasers for the characterization of the spectral profile of the sample in the vicinity of an absorption feature, the best performances have been obtained using a dual-comb source. In fact, the development of new robust architectures for dual-comb spectrometers based on combs synthetized by the modulation of continuous wave lasers has been one of the main lines of work of this thesis. Although having a narrower spectral coverage than traditional combs, these sources provide far lower costs and complexity and the robustness of the generators is far higher. Most of the efforts have been made towards the developments of the new dual-comb architectures that allow to take advantage of the use comb-based systems out of the metrology laboratory. Finally, contributions on the integration of complete spectroscopic instrumentation systems, including spectral analysis techniques based on Blind Signal Separation have been made. For that, a non-invasive biomedical spectroscopic instrument has been developed and used as a benchmark to study the viability of diffuse spectroscopic methods and spectral data classification techniques in the monitoring of the state of angiogenesis of a bioengineered skin substitute.El ámbito de aplicación de la instrumentación basada en espectroscopía es tan amplio que abarca áreas de ingeniería, de la industrial y de investigación científica. De este modo, diferentes técnicas espectroscópicas y de análisis espectral han sido desarrolladas para la caracterización y medida de los numerosos objetivos que son habitualmente estudiados por sensores espectroscópicos. En esta tesis doctoral, se han realizado contribuciones en, prácticamente, todos los bloques constituyentes de un sistema de espectroscopía. Distintas técnicas, arquitecturas y algoritmos de análisis espectral han sido propuestos, principalmente, para aplicaciones ambientales y biomédicas. Han sido presentadas nuevas técnicas y arquitecturas para espectroscopía molecular basadas en la medida de la dispersión óptica, a diferencia de la gran mayoría de los sensores actuales que basan su funcionamiento en la medida de absorción. Esta aproximación mantiene unos niveles de complejidad de implementación razonablemente reducidos; a la vez que, soluciona la mayoría de limitaciones asociadas con los métodos basados en absorción óptica; proporcionando, además, mejores prestaciones en muchas de las áreas de funcionamiento de los analizadores moleculares. Aunque algunas de las arquitecturas que se proponen en esta tesis están basadas en la utilización de diodos sintonizables en frecuencia para la caracterización del perfil espectral de gases en las inmediaciones de transiciones moleculares, los mejores resultados se han obtenido con la utilización de fuentes duales de peines de frecuencias ópticas (dual-OFCs). De hecho, el desarrollo de arquitecturas robustas para espectrómetros basados en dual-OFCs, generados a partir de la modulación de un láser de onda continua ha sido una de las líneas principales de investigación de esta tesis. Aunque presentan una menor cobertura espectral, estas fuentes ópticas poseen niveles mucho más reducidos de coste y complejidad que los esquemas clásicos, proporcionando una gran robustez. Los principales esfuerzos de este trabajo se han dirigido a aprovechar dicha robustez para el desarrollo de nuevas arquitecturas, que permitan aprovechar las características de los peines de frecuencias ópticas en sensores desplegables fuera de un laboratorio de metrología. Del mismo modo, se han realizado contribuciones en la integración de sistemas de instrumentación espectroscópica, incluyendo técnicas de análisis espectral basadas en Separación Ciega de Fuentes. Por ello, un instrumento espectroscópico no invasivo ha sido desarrollado para ser utilizado como banco de pruebas en un estudio de la viabilidad de la utilización de métodos de espectroscopía difusa y de clasificación de datos espectrales para la monitorización del estado de angiogénesis de injertos de piel artificial.Programa Oficial de Doctorado en Ingeniería Eléctrica, Electrónica y AutomáticaPresidente: José Manuel Sánchez Pena.- Secretario: Olga María Conde Portilla.- Vocal: Bernhard Lend

Characterization of advanced materials for low-frequency Vibrational Energy Harvesting (VEH)

openNowadays sensors are among the most exploited systems in everyday life, with several applications stimulating an increasing amount of research. They generally require external power, thus adding issues such as maintenance and size constraints. The most promising energy harvesting (EH) technology for miniaturization is Reverse Electro wetting on Dielectric (REWoD). It can provide high power density by exploiting the mechanical modulation of the capacity at the liquid/dielectric interface attaining, without any external bias, power densities of µW/cm2. With respect to other EH techniques, REWoD harvests energy from low frequency vibrations (< 10Hz, human motion). I exploited low-cost materials as proof of concept of the feasibility of vibrational EH, suitable for wearable devices, using highly hydrophobic Al and PVDF coated electrodes in combination with polyacrylamide (PAAm) hydrogels loaded with LiCl solutions. The morphology at the sub-micrometer scale and the composition of the outer layers of Al have been studied as a function of the chemical etching time and have been correlated with the surface wettability. The etched Al surfaces exhibit binary structures with nanoscale block-like convexes and hollows, providing more space for air trapping. The analysis shows not only that the change in wetting behaviour correlates with the amount of Al hydroxide at the surface, but also confirms the essential role of the adsorption of airborne carbon compounds. The hydrophobic behaviour depends therefore on the combined effects of surface morphology and surface chemical composition. To compensate for the degradation of the hydrogels with time due to the microstructure of the external oxide layer, an alternative bare Al electrode covered with PVDF has been tested: PAAm hydrogels show now no degradation with time while being able to provide, at frequencies lower than 10 Hz, a peak power/unity of 0.6 Watt, higher than 0.25 Watt, obtained by using the Al oxide electrode.openXXXIII CICLO - SCIENZE E TECNOLOGIE DELLA CHIMICA E DEI MATERIALI - Scienza e tecnologia dei materialiPaolini, Giuli

Multi-Sensor Methods for Mobile Radar Motion Capture and Compensation.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017

A Novel Variable Geometry based Planar Inductor Design for Wireless Charging Application

In this thesis, the performance, modelling and application of a planar electromagnetic coil are discussed. Due to the small size profiles and their non‐contact nature, planar coils are widely used due to their simple and basic design. The uncertain parameters have been identified and simulated using ANSYS that has been run utilising a newly developed MATLAB code. This code has made it possible to run thousands of trials without the need to manually input the various parameters for each run. This has facilitated the process of obtaining all the probable solutions within the defined range of properties. The optimum and robust design properties were then determined. The thesis discusses the experimentation and the finite element modelling (FEM) performed for developing the design of planar coils and used in wireless chargers. In addition, the thesis investigates the performance of various topologies of planar coils when they are used in wireless chargers. The ANSYS Maxwell FEM package has been used to analyse the models while varying the topologies of the coils. For this purpose, different models in FEM were constructed and then tested with topologies such as circular, square and hexagon coil configurations. The described methodology is considered as an effective way for obtaining maximum Power transfer efficiency (PTE) with a certain distance on planar coils with better performance. The explored designs studies are, namely: (1) Optimization of Planar Coil Using Multi-core, (2) planar coil with an Orthogonal Flux Guide, (3) Using the Variable Geometry in a Planar coil for an Optimised Performance by using the robust design method, (4) Design and Integration of Planar coil on wireless charger. In the first design study, the aim is to present the behaviour of a newly developed planar coil, built from a Mu-metal, via simulation. The structure consists of an excitation coil, sensing coils and three ferromagnetic cores 2 located on the top, middle and bottom sections of the coil in order to concentrate the field using the iterative optimisation technique. Magnetic materials have characteristics which allows them to influence the magnetic field in its environment. The second design study presents the optimal geometry and material selection for the planar with an Orthogonal Flux Guide. The study demonstrates the optimising of the materials and geometry of the coil that provides savings in terms of material usage as well as the employed electric current to produce an equivalent magnetic field. The third design study presents the variable geometry in a planar inductor to obtain the optimised performance. The study has provided the optimum and robust design parameters in terms of different topologies such as circular, square and hexagon coil configurations and then tested, Once the best topology is chosen based on performance. The originality of the work is evident through the randomisation of the parameters using the developed MATLAB code and the optimisation of the joint performance under defined conditions. Finally, the fourth design study presents the development of the planar coil applications. Three shapes of coils are designed and experimented to calculate the inductance and the maximum power transfer efficiency (PTW) over various spacing distances and frequency

BioMEMS for cardiac tissue monitoring and maturation

Diseases of the heart have been the most common cause of death in the United States since the middle of the 20th century. The development of engineered cardiac tissue over the last three decades has yielded human induced pluripotent stem cell-derived (hiPSC) cardiomyocytes (CMs), microscale “heart-on-a-chip” platforms, optical interrogation techniques, and more. Having spawned its own scientific field, ongoing research promises lofty goals to address the heart disease burden around the world, such as patient-specific disease models, and clinical trials on chip-based platforms. The greatest academic pursuit for engineered cardiac tissues is to increase their maturity, thereby increasing relevance to native adult tissue. Investigation of cardiomyocyte maturity necessitates the development of 3D-tissue compatible techniques for measuring and perturbing cardiac biology with enhanced precision. This dissertation focuses on the development of biological microelectromechanical systems (BioMEMS) for precision measurement and perturbation of cardiac tissue. We discuss three unique approaches to interfacing MEMS-based tools with cardiac biology. The first is a high resolution magnetic sensor, which directly measures the spatial gradient of a magnetic field. This has an ideal application in magnetocardiography (MCG), as the flux of ions during cardiac contractions produces measurable magnetic signals around the tissue and can be leveraged for noncontact diagnosis. The second is a highly functionalized heart-on-a-chip platform, wherein the mechanical contractions of cardiac microtissues can be simultaneously recorded and actuated. Contractile dynamics are leading indicators of maturity in engineered cardiac tissue and mechanical conditioning has shown recent promise as a critical component of cardiac maturation. The third is the imaging of contractile nanostructures in engineered cardiomyocytes at depth in a 3D microtissue. We use small angle X-ray scattering (SAXS) to discern the periodic arrangement of myofilaments in their native 3D environment. We enable a significant structural analysis to provide insight for functional maturation. Enabling these three thrusts required developing two supporting technologies. The first is the engineered control of dynamic second order systems, a foundational element of all our MEMS and magnetic techniques. We demonstrate numerous algorithms to improve settling time or decrease dead-time such that samples with fast temporal effects can be measured. The second is a microscale gluing technique for integrating myriad of materials with MEMS devices, yielding unique sensors and actuators.2022-05-15T00:00:00

DEVELOPMENT OF PIEZORESISTIVE SILICON NANOWIRES (SINWS) AND THE APPLICATIONS IN NEMS TECHNOLOGY.

Ph.DDOCTOR OF PHILOSOPH

Physical and chemical sensing applications of polypyrrole-coated foams

We live in a world of information, and emerging technologies, which compel us to look for new ways to collect, process, and distribute information. Today we are faced with an information overload problem as users struggle to locate the right information in the right way at the right time. In my view this is an “overload” of trivial information coupled with a gap in access to important information. Digitization of information and communications has seen the rise and rise of computers to a now ubiquitous position in our society. However, the problem remains as to how to merge the digital world with sensing, and respond to changes in the real world. Ubiquitous information systems are needed that will automatically sense and importantly, respond to changes in their environment and usage in order to deliver a more intelligent, proactive and personalized information service. These systems may be wearable, enabling them to disappear into our personal space, enhancing rather than burdening our daily activities. Conventional sensors are generally unsuitable for wearable body monitoring devices either due to their physical structure or their functional requirements. This thesis examines this area of wearable sensors, detailing the development and characterisation of novel sensing materials and outlines their performance in various on-body monitoring applications