The LEAD project „Porous Materials@Work” aims on generating a deep understanding of fabrication and simulation of porous materials as well as their application in different field of areas, such as sensing or biotechnology. Our research interests include the study of nanostructured polymer thin films in terms of modeling, fabrication and application. Such thin films have the ability of reacting extremely fast to changes in ambient conditions (as temperature, humidity or pH-value), which makes them a promising material for functional layers in sensors. The deposition of thin films is done with the well-known iCVD (initiated chemical vapor deposition) technique. iCVD offers the advantage to grow those thin films on different types or shapes of substrates. Additionally, it comprises a wide variety of material compositions. For the sensor effect, the goal is to use an optical based detection method and combine it with the physical properties of the nanostructured thin film. Finally, the material we use shows a faster response time than state of the art sensors.
The icing of aircraft components is a core problem in ensuring safety in aviation and therefore a major topic in aircraft certification.
For certification of ice protection and detection systems the conditions to which an aircraft is exposed in real flight must be known and replicated on the ground as accurately as possible in icing wind tunnels. For the representative experimental simulation of clouds, the accurate determination of liquid water content (LWC) and ice water content (IWC) of large droplets is still a challenge. With recent regulatory changes, the demand for separately measuring the phases of water in icing conditions has increased.
The aim of this thesis is to develop a spectroscopic measuring device for LWC/IWC discrimination capable of measuring in harsh environments like icing wind tunnel conditions.
The first step of the work involves the design of a measurement system and experimental validation of the technology for reliable measurement of phase fractions in icing environments. Afterwards a fundamental prototype based on the developed concept will be manufactured and the measurement capacities will be evaluated in the Icing Wind Tunnel.
In recent years, silicon photonics has developed into a mature technology in the field of Datacom. The integration of a variety of optical and optoelectronic functionalities was enabled by using the possibilities of modern CMOS technology. Although applications the field telecom and Datacom dominate in the market share, there is nowadays a growing demand also in the term of small scale and highly integrated sensing applications that yearns to fully exploit the possibilities of integrated photonics. To meet the demands in terms of which needed in state of the art sensing technology for health and scientific purposes, a reliable and economically feasible process flow needs to be established.
The first part of this thesis aims at the investigation of an existing SiN waveguide process flow at ams OSRAM. The most important parameters are analysed, which influence waveguide losses, especially the surface roughness of the involved components. The critical steps are identified and unit process development is done on these. In the further course of this thesis a model which connects several roughness parameters with the waveguide loss is developed and compared to measured values. In the final step of this thesis, the gained knowledge is used to improve targeted sensing applications in terms of specificity, signal-to noise-ratio and resolution.
Biomedical analysis is shifting from lab-based analysis towards point-of-care solutions which enable a cheap, fast and, thus, more extensive monitoring of biomarkers that are critically connected to the overall health of the patient. To this end, integrated photonic sensors are unlocking the interaction of light with organic molecules and tissue for labs-on-a-chip and the internet of things. Consumer applications in particular are showing a soaring, yet unsatisfied, demand of biomarker sensor solutions. Furthermore, silicon photonics is a flourishing field with promising applications in high-speed communication, computing, sensing and scientific research. It provides highly scalable and integrated devices by wielding the same mature fabrication processes perfected by the electronics industry in the past decades.
The emphasis of this thesis lies on the system aspect of developing an integrated label-free biophotonic sensor. The goal is to engineer a versatile silicon nitride platform that can sustain cutting-edge refractometric approaches and to build a prototype device with bio-functionalized waveguides. The existing sensing architectures are to be evaluated and the current process of ams OSRAM is to be adapted for a highly sensitive design that is robust within the manufacturing and noise limitations.
Black carbon (BC) is well known for having an impact on health and our environment, whereby combustion-based vehicles are one of the main contributors. Currently, the emissions of combustion based vehicles are mainly determined during type approval or whilst periodical technical inspections (PTI) in controlled driving conditions. However, real world driving emissions can deviate substantially. Remote emission sensing (RES) is a promising approach for the non-intrusive measurement of real world emissions. With RES individual high emitters or even specific vehicle fleets can be traced. At present, a few commercialized RES systems exist which deliver accurate emission factors for gases but lack accuracy in the detection of particulate matter (PM). Concepts exist to quantify PM with non-intrusive approaches such as plume chasing or point sampling, but these methods have not been fully evaluated yet. Potential instruments must be able to capture the transient events of passing vehicles and must bring along a high sensitivity to resolve small concentrations due to exhaust dilution in air.
In this thesis, different methodologies in regard of RES are evaluated in particular concerning PM. In the course of the thesis an instrument is developed which can be employed for real time measurement of PM in RES.
Current Battery Management Systems (BMS) in larger Lithium-Ion secondary battery (LIB) packs determine the State of X, meaning, among others, the State-of-Charge (SoC) and the State-of-Health (SoH) via a single parameter or via a combination of multiple parameters derived from the electrical two pole behavior, or the history of the battery. These parameters are typically the cells’ voltage, current, impedance, and capacity, and the number of charge and discharge cycles. Structural defects like swollen or deformed batteries are difficult to recognize with current BMS. Such unnoticed mechanical damage can result in serious fires and injuries. However, with the usual parameters it is difficult to draw conclusions about the mechanical state of the battery.
This work aims to improve the estimation of the State-of-Safety (SoS) as well as the State-of-Function (SoF) by determining the mechanical properties of LIB batteries. For this, additional mechanical sensing is implemented, using small- sized and low-cost piezoelectric ultrasound transducers as emitters and sensors mounted on the surface of pouch cells. During cycling, the transmitted ultrasound signal changes its properties such as amplitude and Time of Flight (ToF), which correlate with the changing mechanical properties as well as the SOC.
The legislature on particle number emissions in combustion engine vehicles is becoming increasingly stringent. Future European emission legislation for vehicle homologation will reduce the particle size limit from 23 down to 10 nm in a first step for light-duty vehicles and subsequently for heavy-duty vehicle types. Furthermore, on-board vehicle testing is being increasingly introduced in legislations, causing new challenges for the conditioning and subsequent measurement of particle number concentration.
The aim of this thesis is to further investigate a sensor principle based on electrical diffusion charging and develop a device capable of measuring real driving emissions in motorcycle vehicles, which requires a lightweight, mobile and robust design.
In a first step, a novel piezoelectric plasma generator by TDK, called CeraPlas®, will be evaluated for its use as charging device of the aerosol particles. If the piezoelectric unit is driven in resonance mode, it provides a high output voltage, ionizing the surrounding gas and can therefore be used as an ion source for aerosol charging. A successful implementation would subsequently allow for a reduction in power consumption, cost and size of a diffusion charge based particle counter.
The photothermal spectroscopy (PTS) is a sensorial method for sensitive and selective detection of gases and/or aerosols. With this approach, this PhD thesis focuses on the development of a fast, miniaturized and robust sensor method for monitoring specific gases such as H2O or black carbon. PTS uses the effect of temperature change of air surrounding molecules/particles irradiated by light. By periodically irradiating a target with a modulated, high-intensity laser, we can detect this as a signal using via the use of an interferometer. The signal depends on the concentration of the specific target, which allows determination of the targets mass concentration. Using proper configurations, an accurate and robust measurement of the targets mass concentration therefore is achievable. As a result, this opens up possibilities for measuring a specific target of interest with the distinct advantages of low response times and small sensor size while providing a signal that shows minimal dependence upon harsh environmental influences (e.g. mechanical vibrations or environmental noise).“
Torque sensors have a vast variety of applications within the scope of the increasing automation in everyday technologies. As fundamentally important part in every servo-assisted steering system they are indispensable for the automotive sector. Moreover, precise torque data of drivetrain components allows for an elaborate analysis of engine performance, automatic transmissions or torque converters. Concerning the road towards autonomous driving, torque sensors are essential for drive control as well as in the improvement of safety systems such as traction control systems or electronic stability controls. In the emerging field of collaborative robotics, it is obligatory to have highly integrated force sensors that enable rapid reactions in the interaction with humans. Thus, it is evident that torque sensors are subject of current research with the aim of providing elaborate solutions for the increasingly complex demands in the aforementioned fields of application.
The objective of this dissertation is to develop a completely new concept of torque sensor based on tunable metamaterials. Therewith, it is expected to provide a sensor design that has a unique selling point compared to currently available products.
The first part of the work consists of an elaborate literature research in order to identify the state of the art and to determine a first target application. Thereupon, an analytical approach for the description of metamaterial structures is worked out. This serves as a basis for subsequent numerical simulations, which are an important part of the design process. Further, the experimental analysis of the measuring principle is a central topic of the work. In the final process of developing a practical torque sensor system, the challenging demands in the context of automotive industry as well as collaborative robotics have to be considered. The realization of the new torque sensor is carried out in collaboration with Infineon Technologies AG.
The increasing awareness to the impact of aerosols and trace gases such as black carbon, CO2 and CO on health and environment increases the demand for reliable, miniaturized and cheap sensor solutions. Fast growing markets for mobile applications as well as the automotive and biomedical sector, just to name a few, require high performance sensor systems while being small in size and suitable for high volume production.
In recent years photothermal spectroscopy (PTS) received a lot of scientific attention due to unprecedented sensitivities and selectivity as well as the potential for building rugged and compact sensor systems, with minute susceptibility to mechanical vibrations.
To close the gap between laboratory setups and commercially available products and to meet the aforementioned demands on gas and aerosol sensor solutions, two distinct approaches, based on PTS, are being investigated within the scope of this thesis.
On the one hand, an all-photonic aerosol sensor based on optical fiber technology will be developed in cooperation with the University of Maribor.
On the other hand, a miniaturized, large-scale producible on-chip CO2/CO sensor will be realized together with ams AG and the TU Vienna.
Lithium-ion batteries are widely used as power sources in portable devices as well as in hybrid electric vehicles and electric vehicles and the demand will increase further. To ensure a proper and safe operation of the cells in a vehicle a battery management system (BMS) is used. These systems monitor the voltage, the current and other parameters of the cell to estimate the state of charge (SOC). With these measurements, the physical state of the cell cannot be fully represented. Additional concepts are needed to get more insight in the mechanical behavior of the cell to detect failures such as thermal runaways in an early state and enhance the safety of the cell. Optical fibers are promising candidates for such sensors as they are immune to electromagnetic interference and show good performance in harsh environments.
In this thesis the mechanical properties of lithium ion cells will be observed by using optical fibers with inscribed fiber Bragg gratings (FBGs). Several FBGs can be inscribed in one fiber, so the attached and also inserted fibers can measure temperature and strain evolution spatially resolved. With these sensors deeper understanding of the chemical reactions and mechanical changes during cycling of a lithium-ion cell should be gained.
To guarantee compliance with the latest emission standards advanced and easy to use technologies for particle measurement, especially for small particles and very low concentrations, have to be designed. Electrostatic particle measurement offers great potential for the detection of charged particles in harsh environments. An aerosol is conveyed into a high voltage region between two electrodes and the resulting sensor signal is proportional to the aerosol particle concentration. Despite the simple sensor principle, the underlying effect up to now remains poorly understood.
In this dissertation a novel electrostatic particle sensor is developed incorporating an optically accessible measurement region to assess the existing ambiguity in the literature about the underlying physical effects that cause the measurement signal. Furthermore, a comprehensive characterization of the designed sensor and a commercially available sensor, including the effects of different particle species, particle sizes and charge distributions as well as different ratios of organic to elemental carbon will be conducted. The results from the characterization will be compared with an analytical model to address the question if an electrostatic sensor is suitable to be used in a mini-PEMS setup.