Rapid developments in microelectronics technology have allowed for phenomenal achievements in biomedical engineering. In the past few decades, an enormous amount of researches were done in the field of medical implantable microelectronic systems. The prevalence of research in this particular field have led to the design of novel systems for in-vivo applications, for example, using microelectronic systems to replace catheterization in clinical studies of urinary incontinence. In this thesis research, we study two types of wireless modules towards our goal of wireless systems for in-vivo applications. The first system, a 2.4 GHz wireless pressure sensor system, is designed as a pressure sensing module to operate as a part of a pill imaging device published in [32]. This pressure module samples pressure data and passes them to the pill imaging capsule via a serial-port-interface (SPI). The 2.4 GHz wireless pressure system has an overall system dimension of 75.0 x 20.5 x 17.5 mm3 with a current consumption of 5 mA when operating from a 3 V supply. The pressure sensitivity of this system is observed as 1.14 cmH20/LSB (least significant bit). The second system, 125kHz RFID (radio-frequency identification) dual sensor system, is designed to explore the possibility of powering the device and transmitting data using the RFID technology. The 125kHz RFID dual sensor system has an overall system dimension of 30.0 x 15.0 x 15.0 mm3 with a current consumption of 1.5 mA while operating at 3 V. The pressure sensitivity of this system is observed as 2.93 cmH20/LSB and the temperature sensitivity is observed as 0.069 °C/LSB. And, the detections of rapid pressure changes in both systems are successful. The work performed in this thesis research has provided a cost-effective method of designing medical implantable systems using off-the-shelf components as compared to full-custom designs. In this research, it is also observed that power consumption is a major issue in medical implantable systems. Finally, the possibility of transmitting data and powering such systems using RFID technology has been verified. / Thesis / Master of Applied Science (MASc)

To combat diabetes mellitus(DM), a chronicle metabolic disease, from which more than 400 million people suffered in the world, the patients must check the blood glucose level 4-5 times daily with an enzyme-based blood glucose meter and adjust blood glucose levels accordingly. The problem is that enzymatic glucose meters become unstable in the tropics. Therefore, the non-enzymatic method has been urged for blood glucose monitoring, among which the transition metal oxide electrode was found to be promising. However, despite the prolonged effort, its linear detection range is usually much smaller than the glucose level of diabetic patients, calling for an effective solution. Despite many previous attempts, none have solved the problem. Such a challenge has now been conquered by raising the NaOH concentration in the electrolyte, where amperometry, X-ray diffraction, Fourier-transform infrared spectroscopy, and Nuclear magnetic resonance measurements have been conducted. The linear range has been successfully enhanced to 40 mM in 1000 mM NaOH solution, and it was also found that NaOH affected the degree of glucose oxidation, which influenced the current response during sensing. It was expected that the alkaline concentration must be 25 times higher than the glucose concentration to enhance the linear range, much contrary to prior understanding. / Thesis / Candidate in Philosophy

The magnetoelectric (ME) effect is an electric output in response to an applied magnetic field. In a heterostructure configuration where the two-phases are engineered with close interface contact, a giant electric response to a magnetic field has been found, which is designated as the ME voltage (or charge) coefficient α^ME. This effect is mediated by a mechanical-coupling between magnetostrictive and piezoelectric phases. In this thesis, I concentrate on application study for ME sensors with respect to noise control and rejection, thermal stability, triple-axis sensor design, array imaging, DC and AC magnetic sources detection and active mode ME sensor development, which is important for future ME sensor device applications. / Ph. D.

Deep Neural Networks (DNNs) have been proposed to solve many difficult problems within the context of wireless sensing. Indoor localization and human activity recognition (HAR) are two major applications of wireless sensing. However, current fingerprint-based localization methods require massive amounts of labeled data and suffer severe performance degradation in NLOS environments. To address this challenge, we first apply DNNs to multi-modal wireless signals, including Wi-Fi, an inertial measurement unit (IMU), and ultra-wideband (UWB). By formulating localization as a multi-modal sequence regression problem, a multi- stream recurrent fusion method is developed to combine the current hidden state of each modality. This is done in the context of recurrent neural networks while accounting for the modality uncertainty directly learned from its immediate past states. The proposed method was evaluated on a large-scale open dataset and compared with a wide range of baseline methods. It is shown that the proposed approach has an average error below 20 centimeters, which is nearly three times better than classic methods. Second, in the context of activity recognition, we propose a multi-band WiFi fusion frame- work that hierarchically combines the features of sub-6 GHz channel state information (CSI) and the beam signal-to-noise ratio (SNR) at 60 GHz at different granularity levels. Specifically, we introduce three fusion methods: simple input fusion, feature fusion, and a more customized feature permutation that accounts for the granularity correspondence between the CSI and beam SNR measurements for task-specific sensing. To mitigate the problem of limited labeled training data, we further propose an autoencoder-based unsupervised fusion network consisting of separate encoders and decoders for the CSI and beam SNR. The effectiveness of the framework is thoroughly validated using an in-house experimental platform which includes indoor localization, pose recognition, and occupancy sensing. Finally, in the context of array processing, we solve the Model order estimation (MOE) problem, a prerequisite for Direction of Arrival (DoA) estimation in the presence of correlated multipath, a well-known difficult problem. Due to the limits imposed by array geometry, it is not possible to estimate spatial parameters for an arbitrary number of sources; an estimate of the signal model is required. While classic methods fail at MOE in the presence of correlated multi-path interference, we show that data-driven supervised learning models can meet this challenge. In particular, we propose the application of Residual Neural Net- works (ResNets), with grouped symmetric kernel filters to provide an accuracy over 95%, and a weighted loss function to eliminate the underestimation error of model order. The improved MOE is shown improve subsequent array processing tasks such as reducing the overhead needed for temporal smoothing, reducing the search space for signal association, and improving DoA estimation. / Doctor of Philosophy / Radio Frequency (RF) signals are used not only for wireless communication (its most well-known application), but is also commonly used to sense the environment. One specific application, localization and navigation, can require accuracy of 0.5 meters or below, which is a significant challenge indoors. To address this problem, we apply deep learning (a technique that has gains significant attention in recent years) to fuse types of RF signals, including signals and devices commonly used in smart phones (e.g., UWB, WiFi and IMUs). The result is a technique that can achieve 20cm accuracy in indoor location applications. In addition to localization, commercial WiFi signals can also be used to sense/determine human activity. The received signals from a WiFi transmitter contain sensing information about the environment, including geometric information (angles, distance and velocity) about objects. We specifically show that our proposed approach can successfully recognize human pose, whether or not a specific seat is occupied, and a person's location. Moreover, we show that this can be done with relatively little labelled data using a technique known as transfer learning. Finally, we apply the another neural network structure to solve a particular problem in multi-antenna processing, model order estimation in the presence of coherent multipath. The resulting system can deliver a 95% accuracy in complex environments greatly improving overall array processing.

To fulfill the objective of providing robust and reliable fiber optic temperature sensors capable of operating in harsh environments, a novel type of fiber optic sensor system titled self-calibrated interferometric/intensity-based (SCIIB) fiber optic temperature sensor system is presented in this thesis including the detailed research work on the principle analysis, design, modeling, implementation and performance evaluation of the system. The SCIIB fiber optic temperature sensor system shows us an innovative fiber optic sensor system compared with traditional fiber optic sensors. In addition to the general benefits of the traditional fiber optic sensors, the SCIIB fiber optic sensor system possesses several unique advantages. By taking advantage of the Split-Spectrum technique developed in Photonics Lab at Virginia Tech, the SCIIB sensor technology possesses the capability of Self-Calibration that can fully compensate for the fluctuation of optical source power and the variations of fiber losses. It combines the advantages of both the interferometric-based and the intensity-based fiber optic sensors in a single system. A multimode fiber-based SCIIB temperature sensor system is designed and successfully implemented. Comprehensive experiments are performed to evaluate the principle of SCIIB technology and the performance of the multimode fiber-based SCIIB temperature sensor system. The experiment results illustrate that the development of the SCIIB fiber optic temperature sensor system provides a reliable tool for the temperature measurement capable of operation in high temperature harsh environments. / Master of Science

No / Wireless sensor networks are an emerging technology for low-cost, unattended monitoring of a wide range of environments. Their importance has been enforced by the recent delivery of the IEEE 802.15.4 standard for the physical and MAC layers and the forthcoming ZigBee standard for the network and application layers. The fast progress of research on energy efficiency, networking, data management and security in wireless sensor networks, and the need to compare with the solutions adopted in the standards motivates the need for a survey on this field.

The word piezo in greek means \to compress". Piezoelectric sensors work on the principle of direct piezoelectric effect, where a mechanical input generates a corresponding electric charge. The advantages of these sensors are wide fre-quency range of operation, high stiffness and small size. The main limitation of a piezoelectric sensor is that it cannot be used in measurements that are truly static. When a piezoelectric sensor is subjected to a static force, a fixed amount of charge is developed which would eventually decay at a rate dependent on the external impedance of the sensor circuitry. Operating sensors at resonance have been one of the methods to overcome the limitation of using piezoelectric sensors for static measurements. However, since both actuation and sensing are done by the same piezoelectric element, this results in a cross-talk of input and output signals. The drawback of using single piezoelectric element for actuation and sensing is overcome in this work by using two identical elements|one for actuation and one for sensing. The operating frequency is about 10 % of the natural frequency of the sensor, thus enabling to operate the sensor in non resonant mode. Since the actuation and sensing mechanisms are separated, static measurement can be carried out. The output signal from the sensing element is monitored by a Lock-in amplifier which works on the principle of phase sensitive detection. The advantage of this sensor design is high sensitivity along with narrow band detection. It can be shown that the voltage output of the sensor Vout / a1 + m(b1 + b2F + b3K) + c1F + d1K, where m and K are the external mass and interaction stiffness, respectively, F is the force acting on it. By maintaining any two of these three quantities constant, the remaining one can be measured without any difficulty. The non resonant mode of operation makes it possible to explore the potential of this sensor in investigating mechanics of solid-liquid (viscous), solid-solid (inelastic) and solid-tissue(viscoelastic) interactions. High sensitivity, wide range of measurement (1 g{1 g) and high resolutio(0.1 g) of the non resonant mass sensor makes it possible to use it in measure-ment of very small masses of the order 1 g. Typically, resonant sensors such as quartz crystal microbalance (QCM) are used for mass measurements at that range. However, since the performance of resonant sensors is controlled by damp-ing, a phenomenon known as `missing mass effect' arises. Operating a sensor in non resonant mode (stiffness controlled mode) is a way to overcome this problem, especially when the mass is viscous and/or viscoelastic in nature. Drosophila fly, egg and larvae are the viscoelastic masses that are measured using this non res-onant sensor. Evaporating sessile drops of water and Cetyl trimethylammonium bromide (CTAB) surfactant solution from nominally flat surfaces are monitored to characterize the sensor for viscous mass measurement. Evaporation rate per unit surface area remains more or less constant, during the initial stages of evap-oration. When the surfactant concentration is varied, evaporation rate per unit surface area is highest for solutions around critical miscelle concentration (CMC). A study is carried out to understand the effect of concentrations on spreading of ink over inkjet printing paper. It is found that the spreading is least around CMC, since spreading is dependent on the rate of evaporation. The non resonant piezoelectric sensor which has high stiffness and quick re-sponse is also capable of measuring very small frictional forces. This sensor is configured to work as an inertial slider. Friction measurement at micro scales is important for designing microsystems such as stick-slip actuators. At such length scales, experiments have to performed at low loads and high excitation frequencies. The support stiffness of such systems should be high and the force of friction generated during slipping, when displacements are smaller than the contact radius, are of the order of few N. The displacement during slipping (S) is dependent on the amplitude of the input voltage to the actuation element. The frictional force measured during slipping by the sensor element indicates that the co-efficient of friction ( ) is independent of the sliding velocity. The developed non resonant sensor in this work under small amplitude exci-tation, can measure force gradient (i.e. stiffness). The total force generated when a needle is inserted into a viscoelastic material is a sum of force due to stiffness of the material, friction and the cutting force at the tip. The force due to stiffness is dominant when the needle is bending the tissue before the puncture occurs. Use of the non resonant sensor in tandem with strain gauge force sensor enables distinguishing the three components of the total force. The slope of the force-displacement (F -d) curve during the initial stages of needle penetration into the viscoelastic material, before puncture, is indicative of the stiffness of the mate-rial. The peak force measured during penetration is higher for needles with larger diameters and lower insertion velocities. The viscoelastic response (relaxation) of the material remains independent of the insertion velocity, for a given thickness of the material and a constant needle diameter. In summary, the sensor designed and developed in this work operates in stiffness controlled mode to eliminate the `missing mass effect' encountered dur-ing resonant mode of operation, has been clearly highlighted. Mass, force and stiffness measurements are possible over a wide range just by varying the ampli-tude of the input signal to the actuator element. The advantages such as high stiffness, small size and high response makes it advantageous to carry out in-situ micro scale studies in scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-09-16T13:29:16Z No. of bitstreams: 1 TeseRKH.pdf: 7966483 bytes, checksum: 075f420f66971bcdd35c8dbfe1d3c37c (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-16T19:45:53Z (GMT) No. of bitstreams: 1 TeseRKH.pdf: 7966483 bytes, checksum: 075f420f66971bcdd35c8dbfe1d3c37c (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-16T19:45:58Z (GMT) No. of bitstreams: 1 TeseRKH.pdf: 7966483 bytes, checksum: 075f420f66971bcdd35c8dbfe1d3c37c (MD5) / Made available in DSpace on 2016-09-16T19:46:05Z (GMT). No. of bitstreams: 1 TeseRKH.pdf: 7966483 bytes, checksum: 075f420f66971bcdd35c8dbfe1d3c37c (MD5) Previous issue date: 2015-02-26 / Não recebi financiamento / The research proposal was found low cost alternative solution to automatize the classification and selection process to recognize fruit ripeness level using biologic behavior instead of human visual inspection. The goal was to develop low cost and disposable solid state sensor made of office paper with respective equipment for odor monitoring. The concept used to development this sensor was replace the interdigitated electrode with a conductive track using office paper impregnated with an electrolyte that "turns" cellulose fiber in an electrical conductor under gas action. In order to get gas adsorbing surface property for odor monitoring were tested some electrolytes like: Magnesium Chloride, Potassium Iodide, Calcium Hydroxide and others. This configuration replaced the interdigitated electrode per cellulose fiber doped with an electrolyte, it´s the originality of this research. In the fruit ripening process, the major enzymes involved are pectinase to crack the cell walls responsible for the fruits softening, amylase which degrades carbohydrates to simple sugars responsible for the flavor and hydrolase which reduces the amount of chlorophyll responsible for the fruit color change. The reaction that produces ethylene gas (C2H4) is lipids oxidation, the main gas exhaled during the fruits ripening process. The equipment adopted to pick up electrical signal is based on resistance and capacitance measuring that showed reversible electrical signal variation basically due the track geometry and cellulose fiber doping with an electrolyte. Another feature found was the office paper sensor decrease resistivity with fruit odors presence. The sensor manufacturing process is simple, basically consist in printing a mask with a negative image of the track by laser printing and office paper impregnation by an electrolyte. / A proposta da pesquisa foi buscar uma alternativa de baixo custo para automatizar o processo de seleção e classificação do nível de maturação da banana, utilizando-se do reconhecimento de gás exalado no processo de maturação via biológica, em vez da inspeção visual humana. O objeto da pesquisa foi desenvolver um sensor de estado sólido, de baixo custo e descartável, à base de papel sulfite, com o seu respectivo equipamento de monitoramento de odor. O conceito utilizado no desenvolvimento do sensor foi eliminar o eletrodo condutor interdigitado e substitui-lo por uma trilha condutora via dopagem do papel sulfite, impregnando com um eletrólito que “transforma” a fibra de celulose em um condutor elétrico sob a ação de gás. Visando conferir a propriedade de adsorção superficial dos gases no processo de monitoramento de odor, foram testados os seguintes eletrólitos: Cloreto de Magnésio, Iodeto de Potássio, Hidróxido de Cálcio entre outros. Essa configuração de substituir o eletrodo interdigitado por fibra de celulose dopada com um eletrólito traduz a originalidade desta pesquisa. No processo de amadurecimento das frutas, as principais enzimas envolvidas foram: pectinase, que quebra as paredes celulares, responsável pelo amolecimento das frutas; amilase, que degrada carboidratos em açúcares simples, responsável pelo sabor e a hidrolase, que reduz a quantidade de clorofila responsável pela mudança de cor da fruta. A reação que produz o gás etileno (C2H4) é a oxidação de lipídios, principal gás exalado durante o processo de amadurecimento das frutas. O equipamento de captação de sinal elétrico do sensor de estado sólido foi baseado na medição de resistência e capacitância, que apresentou variação de sinal elétrico reversível, basicamente em função da geometria da trilha e da dopagem da fibra de celulose com um eletrólito. Outra característica do sensor de papel sulfite foi a queda da resistividade com a presença de odores da fruta. O processo de fabricação do sensor é simples: consiste basicamente em uma impressão a laser de uma máscara com imagem negativa da trilha e a impregnação do papel sulfite com um eletrólito.

In this thesis, an integrated flow sensor for an optogalvanic spectrometer is studied. Optogalvanic spectroscopy can be used for carbon isotope analysis when, e.g., searching life in space. At the heart of the spectrometer is a microplasma source, in which the analysis is performed. This master thesis examines the possibilities to integrate a flow sensor inside the microplasma source, to be able to improve the isotopic analysis. The report covers design, manufacturing and evaluation of both the device and the experimental setup. The device was manufactured by milling and lamination of printed circuit board, in which both the plasma source and sensors were incorporated. The final results shows that the sensor had a linear and reliable flow response in a range between 1-15 sccm, and, quite surprisingly, that is simultaneously could measure the pressure in a range between 1-6 Torr. In other words, not only one but two sensors were integrated in the spectrometer at once. The work has been done at the Ångström Space Technology Center - a research group within the Department of Engineering Science at Uppsala University.

The work described in this thesis is concerned with self-localisation (automated estimation of sensor locations) and source-localisation (location of a target) using Wireless Sensor Networks (WSNs). The motivation for the research in this thesis is the on-line localisation of marmots from their alarm calls. The application requires accurate 3D self-localisation (within a small percentage of sensor spacing) as well as timely operation. Further challenges are added by the high data-rate involved: sensor nodes acquire data at a rate that is greater than the available network bandwidth. This data cannot be streamed over a multi-hop network, implying a need for data reduction through in-network event detection and local data compression or filtering techniques. The research approach adopted in this thesis combined simulation, emulation and real-life experimentation. Real-life deployment and experimentation highlighted problems that could not be predicted in controlled experiments or simulation. Emulation used data gathered from controlled, real-life experimentation to simulate proposed system refinements; this was sufficient to provide a proof-of-concept validation for some of the concepts developed. Simulation allowed the understanding of underlying theoretical behaviour without involving the complex environmental effects caused by real-life experimentation. This thesis details contributions in two distinct aspects of localisation: acoustic ranging and end-toend deployable acoustic source localisation systems. With regard to acoustic ranging and 3D localisation, two WSN platforms were evaluated: one commercially available, but heavily constrained (Mica2) and one custom-built for accurate localisation (Embedded Networked Sensing Box (ENSBox)). A new proof of concept platform for acoustic sensing (based on the Gumstix single-board computer) was developed by the author (including the implementation of a ranging mechanism), based on experiences with the platforms above. Furthermore, the literature was found to lack a specific procedure for evaluation and comparison of self-localisation algorithms from theoretical conception to real-life testing. Therefore, an evaluation cycle for self-localisation algorithms that encompassed simulation, emulation and real-life deployment was developed. With respect to source localisation, a hardware and software platform named VoxNet was designed and implemented.