This dissertation proposes a novel packaging methodology for micro-electro-mechanical systems (MEMS) based pressure sensors by using a patterned ultra-thick (150

A MEMS piezoresistive pressure sensor provides a low-cost and accurate means of detecting and quantifying small-scale disturbances in underwater environments. A highly sensitive MEMS pressure sensor has been developed that can be packaged in two different ways – one in a cylindrical housing, and the other in a flexible, yet robust, strip configuration – enabling more freedom for the user to choose an option that fits their needs. The sensing element of each consists of four piezoresistive elements in a Wheatstone Bridge configuration arranged on a deformable buried-oxide layer, which is then bonded to a Silicon base layer with a hollow cavity carved using reactive-ion etching. Previous work has shown the survivability of these sensors in an underwater environment and also measurements of low frequency pressure changes due to flow and varying turbulence intensities. The present work is focused on evaluating these pressure sensors and testing the limits of the sensing element in the low, medium, and high frequency regime (<100Hz to >1kHz) to gain further insight into the performance. Five experimental tests were developed and conducted to guide this research objective. The sensor responses under different flow conditions were measured and analyzed with selected filtering and resampling techniques to eliminate background noises. First, the sensors were calibrated to ensure their linearity and to determine their pressure sensitivities. Then, using bench-top testing rigs and a water tunnel, the sensor performance was evaluated in submerged environments when subjected to multiple small-scale flow disturbances across the tested frequency regime. It was found that the present sensors are capable of providing more accurate measurements across a tested frequency regime of 0 to 20,000Hz when compared to other off-the-shelf products. Testing in submerged environment showed that the sensors are capable of detecting small-scale pressure fluctuations as a result of eddies which are evident in a Von Karman vortex street and a turbulent flow. Despite the presence of EMI noise within a water tunnel, the sensors demonstrated a decay of pressure fluctuations that is consistent with previous research in the field. Overall, the present work increases understanding of the sensors' performances across a broad range of frequencies and provides insight into potential uses and future work. / Master of Science / Pressure sensors are an important, if not the most important, measurement device available today. Pressure sensors play an integral role in the everyday lives for everyone around the world; from applications in medicine, aerospace, autonomy and computation, these sensors provide real-time feedback and help gain a deeper understanding of a system. However, with the technological advances in the Modern Age, there has been a growing need for smaller, cheaper, and faster sensors. As a result, engineers continued to improve sensor performance in the past century with new technologies. A micro-electromechanical system (MEMS) pressure sensor offers a low-cost and energy efficient method to quantify pressure fluctuations within a system. This work focuses on evaluating the performance of three MEMS pressure sensors for use in a submerged environment to detect small-scale pressure fluctuations across a broad range of frequencies. Five different tests were conducted to investigate this research objective. The first three were performed in a controlled underwater environment from which direct conclusions could be made. The last two were performed in an uncontrolled underwater environment from which comparisons to literature and known phenomena were used to draw conclusions. A key result showed that the sensor measurements aligned with prior research in the field. Multiple data reduction techniques were also used during post-processing to ensure accurate data was being collected. The studies showed that the developed MEMS pressure sensors provided the same capabilities as other commercially available pressure measurement devices, all the while displaying a higher sensitivity and broader frequency range. Furthermore, the survivability and robustness of the sensor was proven when subjected to large- and small-scale flow disturbances in a water tunnel.

Due to a globally aging population, there is a growing demand for smart home technology which can serve to monitor the health and safety of adults. Therefore, sleep monitoring has emerged as a crucial tool to improve the health and autonomy of adults. While polysomnography (PSG) is an effective and accurate tool for sleep monitoring, it is obtrusive as the user must wear the instruments during the experiment. Therefore, there has been a growing interest in deploying unobtrusive sleep monitoring devices, specifically for long-term patient monitoring. This thesis proposes multiple algorithms applicable to unobtrusive pressure sensitive sensor arrays in order to assess sleep quality. These algorithms can be listed as adaptive movement detection, sensor data fusion and bed occupancy detection. This thesis also investigates long-term sleep pattern changes from previously recorded data. The methods developed in the thesis can be of interest for future clinical remote patient monitoring systems.

This master thesis examines the design, manufacturing and characterization of a miniaturized ceramic pressure gauge to be integrated into a system for carbon isotope analysis. Carbon isotope analysis can be used to find traces of extraterrestrial life. Screen printing, platinum bond wire threading, milling, lamination and sintering processes have been developed in order to manufacture a robust, temperature stable and chemically inert component potentially integratable to the carbon isotope analysis system. With use of the Pirani principle, which measures the pressure dependent thermal conductivity of air, promising results have been observed. A relative resistance change of 6 % within the pressure range of 1-10 Torr has been observed. This is comparable to, and even greater than, previous studies. The device has a good response for the desired pressure range. The device sensitivity was studied with different currents and geometric parameters. The results showed that the sensitivity is highly dependent on current and air volume. The work has been done at the Ångström Space Technology Centre –­­ a research group within the Ångström Laboratory, Uppsala University – which currently researches on microscale systems for, e.g., space exploration.

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Recent industry trends toward more complex and interconnected systems have increased the demand for more reliable pressure sensors. One of the best methods to ensure reliability is by regularly calibrating the sensor, checking its functionality and accuracy. By integrating a micro-actuator with a pressure sensor, the sensor can self-calibrate, eliminating the complexities and costs associated with traditional sensor calibration methods. The present work is focused on furthering understanding and improving the thermal performance of a thermopneumatic actuated self-calibrating pressure sensor. A transient numerical model was developed in ANSYS and was calibrated using experimental testing data. The model provided insights into the sensor's performance not previously observed in experimental testing, such as the temperature gradient within the sensor and its implications. Furthermore, the model was utilized for two design studies. First, the sensor's inefficiencies were studied, and it was found that a substrate with low thermal conductivity and high thermal diffusivity is ideal for both the sensor's efficiency and a faster transient response time. The second design study showed that decreasing the size of the sealed reference cavity, decreases power consumption and transient response time. The study also showed that decreasing the cavity base dimension has a larger effect on decreasing power consumption and response time. Overall, the present work increases understanding of the self-calibrating pressure sensor and provides insight into potential design improvements, moving closer to true self-calibrating pressure sensors. / Master of Science / Pressure sensors are used in most engineering applications, and the demand is ever increasing due to emerging fields such as the Internet of things (IOT), automations, and autonomy. One drawback of current pressures sensor technology is their need to be calibrated, ensuring accuracy and function. Sensor calibration requires equipment, trained personnel, and must be done regularly, resulting in significant costs. Borrowing technology, methods, and materials from the integrated circuit industry, the costs of sensor calibration can be addressed by the development of an intelligent MEMS (micro-electromechanical system) pressure sensor with self-calibration capabilities. The self-calibrating capability is achieved by combining a micro-actuator and a micro- pressures sensor into one system. This work focuses on complementing previously obtained experimental testing data with a thermal finite element model to provide a deeper understanding and insight. The model is implemented in the commercial software ANSYS and model uncertainties were addressed via model calibration. The model revealed a temperature gradient within the sensor, and insight into its potential effects. The model is also used as a design tool to reduce energy inefficiencies, decrease the time it takes the sensor to respond, and to study the effects of reducing the sensor size. The studies showed that the power consumption can potentially be decreased up to 92% and the response time can be decreased up to 99% by changing the sensor's substrate material. Furthermore, by halving the sensor reference cavity size, the cavity temperature can be increased by 45% and the time for the sensor to respond can be decrease by 59%.

Gas turbines are widely used in power generation. Monitoring pressure variations in the combustion chamber allows for real-time assessment of the turbines performance, and can be used to optimize combustion processes, leading to reduced emissions. By analyzing pressure, patterns, potential faults or degradation in critical components can be identified, enhancing the safety and reliability of the gas turbine. Measurements close to the combustion flame put high demands on the pressure sensors and their verification method. The aim of this thesis is thus to create an automated pressure sensor verification prototype capable of operating at elevated temperature.  With the intention of increasing knowledge of how high temperature influences piezoelectric dynamic pressure sensor readings, this thesis inherits and updates an existing pressure sensor verification device. A design of thermal management system for the device is presented together with a CFD model analysis for the cooling cycle, while the heating cycle and its control algorithm is studied experimentally. This thesis also focuses on sinusoidal pressure wave generation methods used in the existing verification device to achieve reliable signals at low frequencies. An experimental study to evaluate the signal quality is performed. The results propose a feasible prototype design for automated pressure sensor verification at elevated temperature. It provides insight on how the separate parts of the thermal management system could be implemented with a PID regulator. It is concluded that air heating, even with to some extent varying mass flow, can be controlled with a PID regulator. It is also concluded that stable sinusoidal pressure waves can be generated at as low as 1Hz with the gear wheel method used in the previous verification device.

This thesis describes utilization of a nanotechnology in new pressure sensors. Detailed analysis of individual principles are carrying on. And simulations and experimental models of sensors are developed. More detailed description is provided for new capacitive pressure sensor, which is manufactured using nanotechnology, including its model and analysis in order to improve its properties. The work deals with the emission pressure sensor which uses the principle of cold emissions, including analysis comparison of the measured values of the emission current from the applied nanotubes field and analysis to improve emissions performance.