TY - CHAP A1 - Pangerl, Jonas A1 - Wittmann, Elisabeth A1 - Weigl, Stefan A1 - Müller, Max A1 - Bierl, Rudolf A1 - Matysik, Frank-Michael T1 - Using a Modulated Quantum Cascade Laser for Photoacoustic Spectra Recording of Exhaled Acetone and Main Breath Components T2 - Optical Sensors and Sensing Congress 2022 (AIS, LACSEA, Sensors, ES) N2 - Photoacoustic spectra of main breath components together with acetone are presented demonstrating spectral linearity towards different concentrations and compositions. The acetone 3σ detection limit at 1209 cm−1 is 0.28 ppbV Y1 - 2023 U6 - https://doi.org/10.1364/AIS.2022.ATu3G.1 PB - Optica Publishing Group ER - TY - CHAP A1 - Bartl, Mathias A1 - Buchner, Philipp A1 - Hausladen, Matthias A1 - Asgharzadehkhorasani, Ali A1 - Bachmann, Michael A1 - Schreiner, Rupert T1 - Simulations and Investigations of Silicon Nanowire Field Emitters T2 - 37th International Vacuum Nanoelectronics Conference (IVNC), 15-19 July 2024, Brno, Czech Republic N2 - The emission behavior of field emission electron sources consisting of a silicon nanowire cathode, an extraction grid electrode and a planar anode was investigated based on a particle tracing simulation using FEM. The focus was on the influence of the grid geometry as well as the positioning of the grid relative to the emitters on the electron transmission. The highest transmission can be achieved with the emitter tips protruding 10 µm trough the extraction grid openings. The transmission decreases more rapidly with increasing distance between the tip and the grid the thicker the grid is. Y1 - 2024 U6 - https://doi.org/10.1109/IVNC63480.2024.10652355 SP - 1 EP - 2 PB - IEEE ER - TY - THES A1 - Berndt, Dominik T1 - Thermische Wasserstoffsensoren für den Automobilbereich N2 - Für den sicheren Betrieb eines Brennstoffzellenfahrzeugs sind Sensoren wichtig, welche die Wasserstoffkonzentration im Fahrzeuginterieur kontinuierlich überwachen, um möglichen Entzündungen bzw. Explosionen vorzubeugen. Dafür wurden von verschiedenen nationalen und internationalen Instanzen bestimmte Kriterien definiert, die Wasserstoffsensoren für einen Einsatz in Brennstoffzellenfahrzeugen erfüllen müssen. Im Jahr 2020gab es noch keinen einzigen kommerziell erhältlichen Sensor, der alle diese Kriterien bedienen konnte. In der vorliegenden Arbeit wurde für zwei verschiedene Sensoren die Eignung des thermischen Wirkprinzips für die Detektion von Wasserstoff im Kontext dieser Sicherheitskriterien untersucht. Dabei wurden mit einem MEMS-Sensor und einem Mikrodrahtsensor zwei vergleichsweise einfache Geometrien herangezogen, welche den eindimensionalen und zylindersymmetrischen Fall abbilden sollen. Für zwei dynamische Operationsmodi (gepulste Ströme und 3ω-Methode) wurden darauf aufbauend analytische Modelle basierend auf vereinfachten Sensorgeometrien entwickelt, um die Temperaturentwicklung des Sensorelements in Abhängigkeit der Zeit zu charakterisieren. Diese Studien wurden anschließend anhand von detaillierteren Modellen mithilfe von FEM-Simulationen ergänzt und spezifiziert. Darin konnte gezeigt werden, dass für den gepulsten Betrieb sowohl die Pulshöhe als auch die Zeitkonstante des gemessenen Widerstands- bzw. Temperaturpulses als Messgröße herangezogen werden kann. Beim 3ω-Betrieb konnte zudem eine starke Frequenzabhängigkeit dieser Widerstands- bzw. Temperaturcharakteristik beobachtet werden. Die analytischen und numerischen Studien wurden anschließend durch experimentelle Ergebnisse bestätigt. Im Hinblick auf die zuvor definierten Kriterien stellte sich heraus, dass die Auswertung der Zeitkonstante beim gepulsten Betrieb im Hinblick auf Sensitivität und Auflösungsgrenze der Auswertung der Pulshöhe deutlich unterlegen ist. Beim 3ω-Betrieb können durch die hochintegrierte Messumgebung deutlich höhere Genauigkeiten und Auflösungsgrenzen erzielt werden. Für den MEMS-Sensor wurde bei einer Anregungsfrequenz von 1 Hz mit 55 ppm die bislang geringste in der Literatur berichtete Auflösungsgrenze für einen thermischen Wasserstoffsensor erreicht. Der Leistungsverbrauch ist dabei im Vergleich zum Pulsbetrieb entsprechend des jeweiligen Tastgrads leicht bis mäßig erhöht, die Ansprechzeit wird bei beiden Operationsmodi maßgeblich durch die Sensorgeometrie beeinflusst. Die geometrischen Parameter der jeweiligen Sensoren haben ferner einen starken Einfluss auf die Sensitivität, womit die Divergenz in der Performance von MEMS-Chip und Drahtsensor erklärt werden kann. Es besteht ferner eine starke Temperatur- und Feuchtigkeitsabhängigkeit des Sensorsignals, welches bei beiden Operationsmodi indirekt proportional zur Wärmeleitfähigkeit des betrachteten Gasgemischs ist. Die Abhängigkeit vom definierten Umgebungsdruck ist lediglich für die Zeitkonstante relevant, bei der Pulshöhe besteht keine Druckabhängigkeit. Es konnte eine grundsätzliche Eignung des thermischen Messprinzips für den Einsatz eines Wasserstoffsensors im Automobilbereich festgestellt werden. Für eine Anwendung müssen allerdings Referenzsensoren für Temperatur, Feuchtigkeit und Druck implementiert werden und eine Kalibrierung in Abhängigkeit dieser Größen erfolgen. Der 3ωBetrieb ist aufgrund der höheren Genauigkeit zu bevorzugen. Während der MEMSSensor im Hinblick auf Sensitivität, Ansprechzeit und Leistungsaufnahme gut abschneidet, liegen die Vorteile des Mikrodrahtsensors in seiner Robustheit und der vergleichsweise einfachen Realisierbarkeit N2 - For the safe operation of a fuel cell vehicle, sensors that continuously monitor the hydrogen concentration in the vehicle interior are crucial in order to prevent possible ignitions or explosions. For this purpose, various national and international institutions have defined certain criteria that hydrogen sensors must meet for being used in fuel cell vehicles. In 2020, there was not yet a single commercially available sensor that could serve all of these criteria. In the present work, the suitability of the thermal operating principle for the detection of hydrogen in the context of these safety criteria was investigated for two different sensors. Two relatively simple geometries, a MEMS sensor and a micro-wire sensor, were used to represent the one-dimensional and cylinder-symmetric case. Analytical models based on simplified sensor geometries were subsequently developed for two dynamic operation modes (pulsed currents and 3ω-method) to characterize the temperature response of the sensor element as a function of time. These studies were then extended and specified using more detailed models based on FEM simulations. In these studies, it was shown that for pulsed operation, both the pulse height and the time constant of the measured resistance or temperature pulse can be used as a measurand. For 3ω-operation, a strong frequency dependence of these resistance or temperature characteristics was also observed. The analytical and numerical studies were subsequently confirmed by experimental results. With respect to the previously defined criteria, the evaluation of the time constant during pulsed operation was found to be significantly inferior to the evaluation of the pulse height in terms of sensitivity and resolution limit. For 3ω-operation, significantly higher accuracies and resolution limits could be achieved due to the highly integrated measurement environment. For the MEMS sensor, at an excitation frequency of 1 Hz, the lowest resolution limit for a thermal hydrogen sensor reported in the literature to date was achieved at 55 ppm. The power consumption is slightly increased compared to the pulse mode according to the corresponding duty cycle. The response time is significantly influenced by the sensor geometry for both operation modes. Furthermore, the geometrical parameters of the individual sensors have a strong influence on the sensitivity, which can explain the divergence in the performance of the MEMS chip and the micro-wire sensor. There is also a strong temperature and humidity dependence of the sensor signal, which is indirectly proportional to the thermal conductivity of the gas mixture. The dependence on the ambient pressure is only relevant for the time constant, there is no pressure dependence for the pulse height. A fundamental suitability of the thermal measurement principle for the use of a hydrogen sensor in the automotive sector could be identified. However, for an application, reference sensors for temperature, humidity and pressure must be implemented and calibration must be performed as a function of these variables. The 3ω-operation is preferred due to its higher accuracy. While the MEMS sensor performs well in terms of sensitivity, response time and power consumption, the advantages of the microwire sensor are based on its robustness and the fact that the manufacturing process is comparably easy. KW - Kraftfahrzeugtechnik KW - Brennstoffzellenfahrzeug KW - Wasserstoff KW - Gassensor KW - Sensortechnik KW - Feuchtigkeitsabhängigkeit KW - thermischer Wasserstoffsensor Y1 - 2023 UR - https://opus.bibliothek.uni-augsburg.de/opus4/frontdoor/deliver/index/docId/105227/file/Diss_Berndt.pdf CY - Regensburg ER - TY - JOUR A1 - Hausladen, Matthias A1 - Buchner, Philipp A1 - Bartl, Mathias A1 - Bachmann, Michael A1 - Schreiner, Rupert T1 - Integrated multichip field emission electron source fabricated by laser-micromachining and MEMS technology JF - Journal of Vacuum Science & Technology B N2 - In this work, high-current field emission electron source chips were fabricated using laser-micromachining and MEMS technology. The resulting chips were combined with commercially available printed circuit boards (PCBs) to obtain a multichip electron source. By controlling the separate electron sources using an external current control circuit, we were able to divide the desired total current evenly across the individual chips deployed in the PCB-carrier. In consequence, we were able to show a decreased degradation due to the reduced current load per chip. First, a single electron source chip was measured without current regulation. A steady-state emission current of 1 mA with a high stability of ±1.3% at an extraction voltage of 250 V was observed. At this current level, a mean degradation slope of −0.7 μA/min with a nearly perfect transmission ratio of 99% ± 0.4% was determined. The measurements of a fully assembled multichip PCB-carrier electron source, using a current control circuit for regulation, showed that an even distribution of the desired total current led to a decreased degradation. This was determined by the increase in the required extraction voltage over time. For this purpose, two current levels were applied to the electron source chips of the PCB-carrier using an external current control circuit. First, 300 μA total current was evenly distributed among the individual electron source chips followed by the emission of 300 μA per electron source chip. This allows the observation of the influence of a distributed and nondistributed total current, carried by the electron source chips. Thereby, we obtained an increase in the mean degradation slope from +0.011 V/min (300 μA distributed) to +0.239 V/min (300 μA per chip), which is approximately 21 times higher. Moreover, our current control circuit improved the current stability to under 0.1% for both current levels, 300 μA distributed and 300 μA per chip. KW - MEMS technology KW - Field emitter arrays KW - Electron sources KW - Laser micromachining Y1 - 2024 U6 - https://doi.org/10.1116/6.0003233 VL - 42 IS - 1 PB - AIP Publishing ER - TY - JOUR A1 - Remškar, Maja A1 - Jelenc, Janez A1 - Czepurnyi, Nikolai A1 - Malok, Matjaž A1 - Pirker, Luka A1 - Schreiner, Rupert A1 - Hüttel, Andreas K. T1 - Modulations of the work function and morphology of a single MoS2 nanotube by charge injection JF - Nanoscale Advances N2 - Both the miniaturization of transistor components and the ongoing investigation of material systems with potential for quantum information processing have significantly increased current interest of researchers in semiconducting inorganic nanotubes. Here we report on an additional outstanding aspect of these nanostructures, namely the intrinsic coupling of electronic and mechanical properties. We observe electronic and morphology changes in a single MoS2 nanotube, exposed to charge injections by means of an atomic-force-microscopy tip. An elliptic deformation of the nanotube and helical twisting of the nanotube are visible, consistent with the reverse piezoelectric effect. Work-function changes are found to be dependent on the polarity of the injected carriers. An unexpected long-term persistence of the shape deformations is observed and explained with accumulation of structural defects and the resultant strain, which could cause a memory-like charge confinement and a long lasting modulation of the work function. Y1 - 2024 U6 - https://doi.org/10.1039/d4na00490f SN - 2516-0230 PB - Royal Society of Chemistry (RSC) ER - TY - BOOK A1 - Galka, Stefan T1 - AutoStore - was Nutzer über das System berichten können BT - Ergebnisse einer Online-Umfrage KW - Kleinteil KW - Lager KW - Intralogistik KW - Umfrage Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-6463 SN - 978-3-9818209-9-7 CY - Regensburg ER - TY - CHAP A1 - Escher, Lukas A1 - Rück, Thomas A1 - Jobst, Simon A1 - König, Martin A1 - Bierl, Rudolf T1 - Design and Characterization of a Low-Cost Photoacoustic Sensor for NO2 Using Lateral Illumination and Background Suppression T2 - Imaging and Applied Optics Congress 2022 (3D, AOA, COSI, ISA, pcAOP): 11–15 July 2022, Vancouver, British Columbia, Canada N2 - We introduce a low-cost photoacoustic NO2 sensor based on lateral LED illumination and optical background signal compensation. The 3σ limit of detection (LOD) was identified to be 24 ppbV. Y1 - 2022 SN - 978-1-957171-09-8 U6 - https://doi.org/10.1364/3D.2022.JTu2A.10 PB - Optica Publishing Group ER - TY - INPR A1 - Pangerl, Jonas A1 - Sukul, Pritam A1 - Rück, Thomas A1 - Escher, Lukas A1 - Miekisch, Wolfram A1 - Bierl, Rudolf A1 - Matysik, Frank-Michael T1 - Photoacoustic Trace-Analysis of Breath Isoprene and Acetone Via Interband- and Quantum Cascade Lasers N2 - This research presents two laser-based photoacoustic approaches for analyzing exhaled breath isoprene and acetone. The integration of a PTR-ToF-MS as a reference device ensured the reliability and accuracy of the PAS systems that is based on an ICL for isoprene and a QCL for acetone detection. The calibration yielded limits of detection of 26.9 ppbV and 1.7 ppbV, respectively, and corresponding normalized noise equivalent absorption coefficients (NNEAs) of 5.0E-9 Wcm-1Hz-0.5 and 4.9E-9 Wcm-1Hz-0.5. Laboratory as well as real breath sample measurements from alveolar breath revealed a robust system performance, with only one outlier within the static isoprene measurements. However, discrepancies emerged under dynamic breath sampling conditions, emphasizing the need for further optimization. Especially by knowing the dynamic nature and endogenous origin of exhaled isoprene our findings highlight the potential of breath analysis for non-invasive physio-metabolic and pathophysiological monitoring towards point-of-care devices. KW - photoacoustic spectroscopy KW - breath analysis/profiling KW - real-time mass spectroscopy KW - isoprene KW - acetone Y1 - 2024 U6 - https://doi.org/10.2139/ssrn.4834735 PB - Elsevier / SSRN ER - TY - JOUR A1 - Pangerl, Jonas A1 - Sukul, Pritam A1 - Rück, Thomas A1 - Escher, Lukas A1 - Miekisch, Wolfram A1 - Bierl, Rudolf A1 - Matysik, Frank-Michael T1 - Photoacoustic trace-analysis of breath isoprene and acetone via interband- and Quantum Cascade Lasers JF - Sensors and Actuators: B. Chemical N2 - This research presents two laser-based photoacoustic approaches for analyzing exhaled breath isoprene and acetone. The integration of a PTR-ToF-MS as a reference device ensured the reliability and accuracy of the photoacoustic systems that is based on an ICL for isoprene and a QCL for acetone detection. The calibration yielded limits of detection of 26.9 ppbV and 1.7 ppbV, respectively, and corresponding normalized noise equivalent absorption coefficients (NNEAs) of 5.0E-9 Wcm 1Hz 0.5 and 4.9E-9 Wcm 1Hz 0.5. Laboratory as well as real breath sample measurements from alveolar breath revealed a robust system performance, with only one outlier within the static isoprene measurements. However, discrepancies emerged under dynamic breath sampling conditions, emphasizing the need for further optimization. Especially by knowing the dynamic nature and endogenous origin of exhaled isoprene our findings highlight the potential of breath analysis for non-invasive physio-metabolic and pathophysiological monitoring towards point-of-care devices KW - Photoacoustic spectroscopy KW - Breath analysis/profiling KW - Real-time mass spectrometry KW - Isoprene KW - Acetone Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-77024 N1 - Corresponding author der OTH Regensburg: Jonas Pangerl VL - 424 PB - Elsevier ER - TY - GEN A1 - Esper, Lukas A1 - Noster, Ulf A1 - Schultheiss, Ulrich A1 - Bund, Andreas T1 - Quasi-in-Situ Analysis of Electropolished Additively Manufactured Stainless Steel Surfaces T2 - ECS Meeting Abstracts, F01: Advances in Industrial Electrochemistry and Electrochemical Engineering N2 - Progress in additive manufacturing is leading to the emergence of new areas of application. Laser Powder Bed Fusion (L-PBF) is increasingly used for the development of metallic medical implants, but for high-risk implants like vascular support structures (stents), surface quality is critical to ensure successful implantation without harming the surrounding tissue and ensure the patients’ health. Therefore, enhancing the surface quality is crucial. Electropolishing is a method for removing surface roughness by smoothing out micro-peaks and valleys. However, L-PBF structures have a high surface roughness due to metal particles adhering on the surface. To achieve a smooth surface for additively manufactured implants like stents using electropolishing, the removal of these particles needs to be studied in more detail. The objective of this study is to examine the electropolishing mechanism of 316L stainless steel samples additively manufactured through Laser Powder Bed Fusion (L-PBF). The main objective is to investigate the removal properties and surface characteristics during electropolishing. To achieve this, various surfaces were characterized for morphology and roughness during Hull cell experiments. Markings are utilized on the Hull cell sample surfaces to identify points of interest during quasi-in-situ measurements. The surfaces are then analyzed after multiple time steps, applying different currents to investigate particle dissolution. The surface characteristics are analyzed through scanning electron microscopy, and surface roughness is analyzed using laser scanning microscopy. The results show that the electropolishing process preferentially removes the adhering particles present on the surface of the samples. Increasing the current density results in faster particle dissolution and a smoother surface (see Figure 1a and b). The mechanism of material removal of various surface features, as shown in Figure 1 (red circle, yellow arrow and red square), was assessed based on the experimental results of the surface structures seen on the SEM images. It was found that different surface features were removed during the experiment at different polishing times and current densities. The amount of charge flowed was found to correlate with surface morphology. Based on the obtained results, various surface features (such as large adherent particles, agglomerates of smaller particles, and valleys) and their changes with increasing test duration and current density were observed by quasi-in situ analyses. A reduction in the diameter of round particles adhering to the surface was observed at both low and higher current densities (see Figure 1a red circle a). Increasing the polishing time resulted in leveling of both large particles and valleys (see Figure 1b red square). Also, dissolution of agglomerates of smaller particles occurred at different polishing times as a function of current density and polishing time (see Figure 1a yellow arrow) are observed. Smoothed surface structures can be observed in regions with equivalent surface charge density (see Figure 2). As a result, comparable surface morphologies may appear at the same area charge density, irrespective of a specific current density. So, it may be adequate to only consider the amount of charge flowed to describe the electropolishing of additive materials. In conclusion, comprehending the dissolution characteristics of particles on L-PBF surfaces is essential for attaining satisfactory surface finish in electropolishing. The results of this study offer valuable perspectives into the electropolishing mechanism of additively manufactured 316L stainless steel and can guide future investigations on surface finishing and polishing of additive manufactured implants like stents. Figure 1 KW - General Earth and Planetary Sciences KW - General Environmental Science Y1 - 2023 U6 - https://doi.org/10.1149/MA2023-02241342mtgabs SN - 2151-2043 VL - MA2023-02 SP - 1342 EP - 1342 PB - The Electrochemical Society ER -