@article{PangerlMuellerRuecketal., author = {Pangerl, Jonas and M{\"u}ller, Max and R{\"u}ck, Thomas and Weigl, Stefan and Bierl, Rudolf}, title = {Characterizing a sensitive compact mid-infrared photoacoustic sensor for methane, ethane and acetylene detection considering changing ambient parameters and bulk composition (N2, O2 and H2O)}, series = {Sensors and Actuators B: Chemical}, volume = {352,1}, journal = {Sensors and Actuators B: Chemical}, publisher = {Elsevier}, doi = {10.1016/j.snb.2021.130962}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-25868}, pages = {1 -- 12}, abstract = {We present a sensitive and compact interband cascade laser (ICL) based photoacoustic setup for the detection of gaseous hydrocarbons and discuss its applicability towards trace gas analysis. We investigated the performance of the sensor for trace concentrations of methane, ethane and acetylene diluted in nitrogen. The excitation of methane and ethane was accomplished using one tunable diode laser, covering a range from 3360 to 3372 nm, which was replaced by a separate ICL at 3025 nm for acetylene detection. The influence of ambient parameters such as temperature, flow rate and pressure as well as potential cross-sensitivities towards O2 and H2O have been examined in terms of methane and acetylene detection. A series of simulations proved several of these influences to be attributed to relaxation effects. With a 3σ limit of detection (LoD) of 6.8 parts per billion (ppbV) in case of methane, 2.3 ppbV regarding ethane and 3.6 ppbV in terms of acetylene, the sensor demonstrates a great potential for applications in the field of trace gas analysis.}, language = {en} } @article{MuellerRueckJobstetal., author = {M{\"u}ller, Max and R{\"u}ck, Thomas and Jobst, Simon and Pangerl, Jonas and Weigl, Stefan and Bierl, Rudolf and Matysik, Frank-Michael}, title = {An Algorithmic Approach to Compute the Effect of Non-Radiative Relaxation Processes in Photoacoustic Spectroscopy}, series = {Photoacoustics}, volume = {26}, journal = {Photoacoustics}, publisher = {Elsevier}, doi = {10.1016/j.pacs.2022.100371}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-39935}, abstract = {Successful transfer of photoacoustic gas sensors from laboratory to real-life applications requires knowledge about potential cross-sensitivities towards environmental and gas matrix changes. Multi-dimensional calibration in case of cross-sensitivities can become very complex or even unfeasible. To address this challenge, we present a novel algorithm to compute the collision based non-radiative efficiency and phase lag of energy relaxation on a molecular level (CoNRad) for photoacoustic signal calculation. This algorithmic approach allows to calculate the entire elaxation cascade of arbitrarily complex systems, yielding a theoretical photoacoustic signal. In this work the influence of varying bulk compositions, i.e. nitrogen (N2), oxygen (O2) and water (H2O) on the photoacoustic signal during methane (CH4) detection is demonstrated. The applicability of the algorithm to other photoacoustic setups is shown exemplary by applying it to the relaxational system investigated in [1]. Hayden et al. examined the effect of water on photoacoustic carbon monoxide (CO) detection.}, language = {en} } @inproceedings{SchererVitzthumeckerBierl, author = {Scherer, Leo and Vitzthumecker, Thomas and Bierl, Rudolf}, title = {Capacitive PCB sensor for the detection of insects in intelligent traps}, series = {Applied Research Conference 2022 Conference Proceedings: 4th July 2022, University of Applied Sciences Ansbach (Onsite Conference)}, booktitle = {Applied Research Conference 2022 Conference Proceedings: 4th July 2022, University of Applied Sciences Ansbach (Onsite Conference)}, editor = {Uhl, Christian and Walter, Michael and Stiehl, Annika}, publisher = {Hochschule Ansbach}, address = {Ansbach}, doi = {10.25929/qbwt-zf40}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-55837}, pages = {519 -- 523}, abstract = {Reliable and fast detection of pest in the food processing and pharmaceutical industry is crucial to ensure hygienically safe, pure and healthy products. This is why intelligent traps, that are able to detect insects automatically are needed. For this, a capacitive PCB sensor is developed and tested, which could be a simplistic, low power solution to the problem. This includes design, footprint generation and simulation as well as testing different types of capacitve sensing against noise immunity and sensitivity to Blattella germanica, the German cockroach. It is shown that a single specimen can very well and reliably be detected by the developed sensor.}, language = {en} } @misc{vanderWeerdBierlMatysik, author = {van der Weerd, Bastiaan and Bierl, Rudolf and Matysik, Frank-Michael}, title = {A Conductivity Probe for Determination of the Carbon Dioxide Tension at the Oxygenator Exhaust Outlet during Extracorporeal Membrane Oxygenation (ECMO)}, series = {Proceedings of the 9th ISC Modern Analytical Chemistry 2013, Prag}, journal = {Proceedings of the 9th ISC Modern Analytical Chemistry 2013, Prag}, language = {en} } @misc{RueckHofmannBierl, author = {R{\"u}ck, Thomas and Hofmann, Matthias and Bierl, Rudolf}, title = {Development of a miniaturized photoacoustic multigas sensing system for trace gas measurement}, series = {17th International Conference on Photoacoustic and Photothermal Phenomena, Oct. 20-24, 2013, Suzhou China}, journal = {17th International Conference on Photoacoustic and Photothermal Phenomena, Oct. 20-24, 2013, Suzhou China}, language = {en} } @misc{RueckMatysikBierl, author = {R{\"u}ck, Thomas and Matysik, Frank-Michael and Bierl, Rudolf}, title = {Development of a miniaturized photoacoustic multigas sensing system for trace gas measurement}, series = {analytica conference 2014, 1. bis 4. April, M{\"u}nchen}, journal = {analytica conference 2014, 1. bis 4. April, M{\"u}nchen}, language = {en} } @misc{RueckMatysikBierl, author = {R{\"u}ck, Thomas and Matysik, Frank-Michael and Bierl, Rudolf}, title = {Comparison of acoustic detectors for use in miniaturized photoacoustic devices designed for nitrogen dioxide trace gas measurement}, series = {ANAKON, 23.-26.3.2015, Graz}, journal = {ANAKON, 23.-26.3.2015, Graz}, language = {en} } @article{PangerlSukulRuecketal., author = {Pangerl, Jonas and Sukul, Pritam and R{\"u}ck, Thomas and Fuchs, Patricia and Weigl, Stefan and Miekisch, Wolfram and Bierl, Rudolf and Matysik, Frank-Michael}, title = {An inexpensive UV-LED photoacoustic based real-time sensor-system detecting exhaled trace-acetone}, series = {Photoacoustics}, volume = {38}, journal = {Photoacoustics}, publisher = {Elsevier}, issn = {2213-5979}, doi = {10.1016/j.pacs.2024.100604}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-71279}, pages = {12}, abstract = {n this research we present a low-cost system for breath acetone analysis based on UV-LED photoacoustic spectroscopy. We considered the end-tidal phase of exhalation, which represents the systemic concentrations of volatile organic compounds (VOCs) - providing clinically relevant information about the human health. This is achieved via the development of a CO2-triggered breath sampling system, which collected alveolar breath over several minutes in sterile and inert containers. A real-time mass spectrometer is coupled to serve as a reference device for calibration measurements and subsequent breath analysis. The new sensor system provided a 3σ detection limit of 8.3 ppbV and an NNEA of 1.4E-9 Wcm 1Hz 0.5. In terms of the performed breath analysis measurements, 12 out of 13 fell within the error margin of the photoacoustic measurement system, demonstrating the reliability of the measurements in the field.}, language = {en} } @article{EscherRueckJobstetal., author = {Escher, Lukas and R{\"u}ck, Thomas and Jobst, Simon and Pangerl, Jonas and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Photodissociation-Driven Photoacoustic Spectroscopy with UV-LEDs for Ozone Detection}, series = {Photoacoustics}, volume = {43}, journal = {Photoacoustics}, publisher = {Elsevier BV}, issn = {2213-5979}, doi = {10.1016/j.pacs.2025.100718}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-80076}, pages = {16}, abstract = {This study presents the development and evaluation of a UV-LED based photoacoustic (PA) measurement system for ozone (O3) detection to demonstrate its potential for low-cost and accurate sensing while for the first time addressing the importance of photodissociation for PA signal generation for O3 in the UV range. With a detection limit of 7.9 ppbV, the system exhibits a significant advancement over state-of-the-art UV-PA O3 detection and is on par with laser-based setups. Following a novel discussion of the PA signal arising from photodissociation and its products, cross-sensitivity effects due to environmental factors such as temperature and gas composition were systematically analyzed. A digital twin driven compensation for these influences was implemented and evaluated. Despite the challenges associated with modeling the effects of H2O and CO2, the PA system shows considerable potential, though further studies in real world applications must be conducted.}, language = {en} } @article{HauslerHolznerEhrnspergeretal., author = {Hausler, Peter and Holzner, Lukas and Ehrnsperger, Matthias and Bierl, Rudolf}, title = {Evaluation of the creep strength of samples produced by fused deposition modeling}, series = {Open Engineering}, volume = {14}, journal = {Open Engineering}, number = {1}, publisher = {de Gruyter}, doi = {10.1515/eng-2024-0084}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-79760}, pages = {10}, abstract = {Data sheets for 3D printing materials typically include softening temperature, impact strength, tensile strength, and stiffness. However, creep strength, an important parameter for components used over an extended period, is usually not included. Nevertheless, this parameter is of significant importance for components that are used over an extended period of time.This study compares the long-term creep behavior of a selection of materials that are commonly used in fused deposition modeling 3D printing. The materials under investigation are acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, polylactic acid, and polycarbonate. In addition, the influence of fiber reinforcements on these materials is also examined. A simple, reproducible test procedure is proposed for users to determine and compare creep resistance of materials. This enables developers to select materials suitable for their own requirements on creep resistance and allows 3D-printing users to compare different materials. Results suggest that fiber reinforcement generally improves creep stability in 3D-printing materials, with GreenTEC Pro Carbon and add:north PC Blend HT LCF showing the most promise in this study.}, language = {en} } @article{ReinkerBlaesingBierletal., author = {Reinker, Lukas and Bl{\"a}sing, Dominic and Bierl, Rudolf and Ulbricht, Sabina and Dendorfer, Sebastian}, title = {Correlation of Acceleration Curves in Gravitational Direction for Different Body Segments during High-Impact Jumping Exercises}, series = {sensors}, volume = {23}, journal = {sensors}, number = {4}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/s23042276}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-58217}, abstract = {Osteoporosis is a common disease of old age. However, in many cases, it can be very well prevented and counteracted with physical activity, especially high-impact exercises. Wearables have the potential to provide data that can help with continuous monitoring of patients during therapy phases or preventive exercise programs in everyday life. This study aimed to determine the accuracy and reliability of measured acceleration data at different body positions compared to accelerations at the pelvis during different jumping exercises. Accelerations at the hips have been investigated in previous studies with regard to osteoporosis prevention. Data were collected using an IMU-based motion capture system (Xsens) consisting of 17 sensors. Forty-nine subjects were included in this study. The analysis shows the correlation between impacts and the corresponding drop height, which are dependent on the respective exercise. Very high correlations (0.83-0.94) were found between accelerations at the pelvis and the other measured segments at the upper body. The foot sensors provided very weak correlations (0.20-0.27). Accelerations measured at the pelvis during jumping exercises can be tracked very well on the upper body and upper extremities, including locations where smart devices are typically worn, which gives possibilities for remote and continuous monitoring of programs.}, language = {en} } @inproceedings{BierlBoehmFraunhofferetal., author = {Bierl, Rudolf and Boehm, M. and Fraunhoffer, Judith and Gardeia, Armin and Mottok, J{\"u}rgen and Schneider, Ralph and Streubel, J.}, title = {"Regensburger Modell zu den P-Seminaren" - Ein Konzept zur Gestaltung der Schnittstelle Gymnasium - Hochschule und zur Praxis einer kooperativen Lehr-Lern-Didaktik f{\"u}r Informationstechnik}, series = {3rd Embedded Software Engineering Congress, 7. bis 9. Dezember, Sindelfingen}, booktitle = {3rd Embedded Software Engineering Congress, 7. bis 9. Dezember, Sindelfingen}, publisher = {Vogel Business Media}, address = {W{\"u}rzburg}, language = {de} } @article{WeiglFeldmeierBierletal., author = {Weigl, Stefan and Feldmeier, Florian and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Photoacoustic detection of acetone in N2 and synthetic air using a high power UV LED}, series = {Sensors Actuators B Chemical}, volume = {316}, journal = {Sensors Actuators B Chemical}, number = {August}, publisher = {Elsevier}, doi = {10.1016/j.snb.2020.128109}, pages = {1 -- 11}, abstract = {The performance of a photoacoustic trace gas sensor for the detection of acetone in N2 and synthetic air is reported. The sensor system utilises an amplitude modulated UV LED. The light source has an emission maximum at 278 nm and a maximum CW output power of 300 mW according to the datasheet. Three different collimating and focusing approaches have been investigated to guide the highly divergent LED light into the acoustic resonator of the photoacoustic measurement cell. A 3D printed aluminium cell was designed to optimize light coupling by simultaneously minimizing the photoacoustic background signal generation. Hence, the diameter of the resonator was set to a comparable large diameter of 10 mm and the inner walls of the resonator were mirror polished. The additive manufacturing procedure allowed for integration of a spirally formed gas channel, enabling gas heating prior to detection. The sensor performance was investigated by measuring acetone in N2 and synthetic air at different concentrations. The UV LED current was set to 86 \% of the maximum value according to the datasheet of the light source in order to increase the lifetime and thermal stability. An Allan-Werle deviation analysis validates a stable sensor performance. The limit of detection (LoD) was determined at a 3σ noise level with a 10 s lock-in amplifier time constant by sampling data points over 20 s with a data acquisition rate of 5 Hz. LoDs of 80.8 ppbV and 19.6 ppbV were obtained for acetone in N2 and synthetic air, respectively.}, language = {en} } @article{WeiglWittmannRuecketal., author = {Weigl, Stefan and Wittmann, Elisabeth and R{\"u}ck, Thomas and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Effects of ambient parameters and cross-sensitivities from O2, CO2 and H2O on the photoacoustic detection of acetone in the UV region}, series = {Sensors Actuators B Chemical}, journal = {Sensors Actuators B Chemical}, number = {328}, publisher = {Elsevier}, issn = {0925-4005}, doi = {10.1016/j.snb.2020.129001}, abstract = {We present a sensitive UV LED photoacoustic setup for the detection of gaseous acetone and discuss its applicability towards breath analysis. We investigated the performance of the sensor for low acetone concentrations down to 0.1 parts per million (ppmV). The influences of temperature, flow, pressure, optical power and LED duty cycle on the measured signal have been examined. To gain a better understanding of the different effects on the photoacoustic signal, correlation analysis was applied and feature importance was determined using a large measured dataset. Furthermore, the cross-sensitivities towards O2, CO2 and H2O have been studied extensively. Finally, the sensor's performance to detect acetone between 0.1-1 ppmV within gas mixtures simulating breath exhale conditions has been investigated, too. With a limit of detection (LoD) of 12.5 parts per billion (ppbV) (3σ) measured under typical breath exhale gas mixture conditions, the sensor demonstrated a high potential for the application of acetone detection in human breath analysis.}, language = {en} } @inproceedings{HauslerJobstFischeretal., author = {Hausler, Peter and Jobst, Simon and Fischer, Johannes and Roth, Carina and Bierl, Rudolf}, title = {Homogeneous Light Source for Surface Plasmon Resonance Imaging}, series = {PHOTOPTICS 2020: proceedings of the 8th International Conference on Photonics, Optics and Laser Technology, Valletta, Malta, February 27-29, 2020}, booktitle = {PHOTOPTICS 2020: proceedings of the 8th International Conference on Photonics, Optics and Laser Technology, Valletta, Malta, February 27-29, 2020}, publisher = {SCITEPRESS - Science and Technology Publications}, doi = {10.5220/0009168701630167}, pages = {163 -- 167}, abstract = {We describe how to build a homogeneous light source for Surface Plasmon Resonance Imaging (SPRi) which mainly finds its applications in pharmaceutical screening and biotechnology so far. SPR spectroscopy is a label-free, non-destructive and highly sensitive measurement principle for detecting changes in the refractive index in close vicinity of a gold surface. A transfer of this technology to a miniaturized sensor will broaden the range of possible applications. Commercial SPR assays are mainly working with a small number of sensing spots. In contrast, the SPR imaging system shown here will allow the use of an array of many sensing spots. In combination with chemical receptors designed as an artificial nose or an electronic tongue, the simultaneous detection of many analytes is envisioned. So far, lasers or other inhomogeneous light sources were used to illuminate the sensing surface, which is decreasing the systems sensitivity. We show a compact ( 300mm2) homogeneous top hat profile. The combination of a high bit-resolution camera with our new light source enables a reflectivity based surface plasmon resonance imaging system with a high refractive index unit (RIU) resolution.}, language = {en} } @inproceedings{GschossmannJobstMottoketal., author = {Gschossmann, Andreas and Jobst, Simon and Mottok, J{\"u}rgen and Bierl, Rudolf}, title = {A Measure of Confidence of Artificial Neural Network Classifiers}, series = {ARCS Workshop 2019; 32nd International Conference on Architecture of Computing Systems, 20-21 May 2019, Copenhagen, Denmark}, booktitle = {ARCS Workshop 2019; 32nd International Conference on Architecture of Computing Systems, 20-21 May 2019, Copenhagen, Denmark}, publisher = {VDE-Verlag}, address = {Berlin}, pages = {153 -- 157}, abstract = {Confidence in results of an Artificial Neural Networks (ANNs) is increased by preferring to reject data, that is not trustful, instead of risking a misclassification. For this purpose a model is proposed that is able to recognize data, which differs significantly from the training data, during inference. The proposed model observes all activations of the hidden layers, as well as input and output layers of an ANN in a grey-box view. To make ANNs more robust in safety critical applications, this model can be used to reject flawed data, that is suspected to decrease the accuracy of the model. If this information is logged during inference, it can be used to improve the model, by training it specifically with the missing information. An experiment on the MNIST dataset is conducted and its results are discussed.}, language = {en} } @inproceedings{RomanoMicklitzOlbrichetal., author = {Romano, Marco and Micklitz, Matthias and Olbrich, Florian and Bierl, Rudolf and Ehrlich, Ingo and Gebbeken, Norbert}, title = {Experimental investigation of damping properties of unidirectionally and fabric reinforces plastics by the free decay method}, series = {Proceeding of the 15th International Materials Symposium (IMSP´2014), Pamukkale University (Denizli, Turkey), 15./17. October 2014}, booktitle = {Proceeding of the 15th International Materials Symposium (IMSP´2014), Pamukkale University (Denizli, Turkey), 15./17. October 2014}, pages = {665 -- 679}, language = {en} } @unpublished{PangerlSukulRuecketal., author = {Pangerl, Jonas and Sukul, Pritam and R{\"u}ck, Thomas and Fuchs, Patricia and Weigl, Stefan and Miekisch, Wolfram and Bierl, Rudolf and Matysik, Frank-Michael}, title = {An Inexpensive Uv-Led Photoacoustic Based Real-Time Sensor-System Detecting Exhaled Trace-Acetone}, publisher = {Elsevier}, doi = {10.2139/ssrn.4724198}, abstract = {In this research we present a low-cost system for breath acetone analysis based on UV-LED photoacoustic spectroscopy. We considered the end-tidal phase of exhalation, which represents the systemic concentrations of volatile organic compounds (VOCs) - providing clinically relevant information about the human health. This is achieved via the development of a CO2-triggered breath sampling system, which collected alveolar breath over several minutes in sterile and inert containers. A real-time mass spectrometer is coupled to serve as a reference device for calibration measurements and subsequent breath analysis. The new sensor system provided a 3σ detection limit of 6.4 ppbV and an NNEA of 1.1E-9 Wcm-1Hz-0.5. In terms of the performed breath analysis measurements, 12 out of 13 fell within the error margin of the photoacoustic measurement system, demonstrating the reliability of the measurements in the field.}, language = {en} } @article{RueckBierlMatysik, author = {R{\"u}ck, Thomas and Bierl, Rudolf and Matysik, Frank-Michael}, title = {NO2 trace gas monitoring in air using off-beam quartz enhanced photoacoustic spectroscopy (QEPAS) and interference studies towards CO2, H2O and acoustic noise}, series = {Sensors and Actuators B: Chemical}, volume = {255}, journal = {Sensors and Actuators B: Chemical}, number = {Part 3, February}, publisher = {Elsevier}, doi = {10.1016/j.snb.2017.09.039}, pages = {2462 -- 2471}, abstract = {We present the development and characterization as well as comprehensive interference studies of a photoacoustic NO2 trace gas detection system. The system is based on an off-beam quartz enhanced photoacoustic scheme (off-beam QEPAS) and signal generation was initiated by amplitude modulating a low-cost diode laser emitting at 450 nm. The QEPAS sensor element features double-resonant amplification, still it is only ∼ 5 × 5 × 2.5 mm in size. The individual and combined resonance characteristics were investigated and specified to 52 dB amplification, adding up 15 dB acoustic- and 37 dB mechanical-resonance amplification. The linearity of the photoacoustic signal dependency on the analyte concentration was verified from 200 ppbV to 100 ppmV NO2 in synthetic air. The detection limit (3σ) was determined to 1.8 ppbV using a lock-in time constant of 10 s and an averaging time of 20 s. The normalized noise equivalent absorption coefficient was specified to 2.5·10-8 W cm-1 Hz-0.5. The stability of the signal was investigated over time and a slight drift by 1 per mille was observed after 30 min without temperature stabilizing the photoacoustic cell (PAC). Noise analysis was performed by means of Allan deviation and the inverse dependency of response time and precision of the system on the lock-in time constant was outlined. We performed interference analyses towards N2, O2, CO2, H2O and acoustic noise, respectively. Although neither spectral interferences nor losses due to slow NO2 VT-relaxation were observed, O2 was identified to cause a 15\% signal drop due to VVNO2-O2-relaxation. Changing H2O concentrations were found to cause acoustic detuning, which cannot be compensated by adjusting the frequency of modulation, because of the double-resonant feature of the PAC. However, alternative approaches of compensation were discussed. Finally, we carried out heavy traffic noise simulations and determined the QEPAS setup to be 46 times less susceptible towards ambient noise compared to standard microphone-based photoacoustic setups.}, language = {en} } @article{RueckBierlMatysik, author = {R{\"u}ck, Thomas and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Development and characterization of a laboratory setup for photoacoustic NO2 determination based on the excitation of electronic 2B2 and 2B1 states using a low-cost semiconductor laser}, series = {Sensors and Actuators A: Physical}, volume = {258}, journal = {Sensors and Actuators A: Physical}, publisher = {Elsevier}, address = {Amsterdam, Niederlande}, doi = {10.1016/j.sna.2017.03.024}, pages = {193 -- 200}, abstract = {This work gives a detailed characterization of a laboratory setup for photoacoustic NO2 trace gas detection at the ppb level. The signal generation is based on the excitation of electronic 2B2 and 2B1 states using a low-cost semiconductor laser emitting at 450 nm. An acoustic resonator was used for signal amplification and the modulation frequency of the laser was determined to 3395 Hz in order to gain maximum signal amplification. The quality of resonant amplification was determined to 7.9. The gas samples were NO2 calibration gases diluted with pure nitrogen. The signal-to-noise ratio (SNR) dependency on the flow rate Q and the lock-in time constant τLIA was investigated, respectively, and the optimum values were specified to Q = 500 mL/min and τLIA = 2 s. In case of ambient noise, increasing τLIA to 10 s was evaluated as sufficient for SNR preservation. The noise level was measured in the absence of NO2 and it was determined to be composed of 51\% electronic noise and 49\% gas flow noise. With the analyte concentration ranging from 300 ppbV to 100 ppmV, the linear dependency of the photoacoustic amplitude on the NO2 concentration was specified, the sensitivity was determined to 110 μV/ppmV and the maximum measurement error was calculated to ±0.8\%. The detection limit was determined to 2.0 ppbV. Furthermore, the stability of the signal was investigated and a maximum drift of ±1\% was observed within a measuring period of 30 min. The response time τ90 was specified to 58 s. All results considered, this photoacoustic measuring system, which is based on low-cost signal generation and detection units, provides an excellent basis in view of developing a portable device for photoacoustic trace gas detection.}, language = {en} } @article{RueckBierlMatysik, author = {R{\"u}ck, Thomas and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Low-cost photoacoustic NO2 trace gas monitoring at the pptV-level}, series = {Sensors and Actuators A: Physical}, volume = {263}, journal = {Sensors and Actuators A: Physical}, publisher = {Elsevier}, address = {Amsterdam, Niederlande}, doi = {10.1016/j.sna.2017.06.036}, pages = {501 -- 509}, abstract = {We present the development and the characterization of a photoacoustic NO2 trace gas detection system. The system is based on the implementation of low-cost components, i.e. a mass-produced blue diode laser and a standard MEMS microphone which is commonly built into smartphones, for example. An optimized cell design was realized by means of 3D printing. The linearity of the photoacoustic signal dependency on the analyte concentration was verified from 200 ppbV to 100 ppmV NO2. The detection limit (1σ) was determined to 33 pptV and the normalized noise equivalent absorption coefficient was calculated to 7.0 ∙ 10-10 W cm-1 Hz-1/2. The dynamic range of the system was verified to be linear over three magnitudes of order and the sensitivity was calculated to 814 μV/ppmV. The system was characterized in view of optimal operating parameters, i.e. lock-in time constant τLIA and total mass flow rate, optical performance and signal stability. The mass flow dependend response time of the system was specified to 19 s and an idealized step response to a quasi-Heaviside step function was quantified as a function of τLIA. The quality factor of acoustic resonance was determined to 21.9 and an empirical expression regarding acoustic node shifting is provided. The expression takes into account the radius of the resonator pipe and the radius of the hole, which was drilled into the pipe for microphone coupling. Furthermore, we studied the cross-sensitivity of the photoacoustic signal towards H2O and CO2, respectively.}, language = {en} } @misc{WeiglMatysikBierl, author = {Weigl, Stefan and Matysik, Frank-Michael and Bierl, Rudolf}, title = {Development of a sensor system for analysis of human breath exhale}, series = {BayWISS Herbstakademie 2018, Plankstetten}, journal = {BayWISS Herbstakademie 2018, Plankstetten}, abstract = {Atemgasanalyse ist ein junges und vielversprechendes Feld im Bereich der diagnostischen Medizin. Der Ansatz verspricht einfach zug{\"a}ngliche und leicht wiederholbare Probennahme die zum einen non-invasiv ist und zugleich R{\"u}ckschl{\"u}sse auf Vorg{\"a}nge im menschlichen K{\"o}rper und bspw. dessen Gesundheitszustand zul{\"a}sst. Seit Ende des 20. Jahrhunderts gibt es Massenspektrometer die es erm{\"o}glicht haben mehrere Tausend verschiedene Stoffe in der Ausatemluft nachzuweisen. Diese Technologien verbessern sich stetig und erm{\"o}glichen es die Vorg{\"a}nge und Zusammenh{\"a}nge zwischen Zusammensetzung der Ausatemluft und systemischen Prozessen besser zu verstehen. Die bei Studien mit Massenspektrometern ermittelten Biomarker, deren qualitative und quantitative Detektion Gesundheitsdiagnosen erm{\"o}glichen, haben aber noch nicht den Weg in den klinischen Alltag gefunden. Das Problem sind meistens die hohen Anschaffungskosten, komplizierte Datenauswertung und zumeist geringe Verf{\"u}gbarkeit und Immobilit{\"a}t dieser Messger{\"a}te. Die photoakustische Spektroskopie ist eine selektive und hochsensitive Messmethode, die es erm{\"o}glichen soll den Biomarker „Aceton", der grunds{\"a}tzlich die Metabolisierung von Fetten widerspiegelt, schnell und reproduzierbar quantitativ zu detektieren. Dabei m{\"u}ssen Hindernisse wie Querempfindlichkeiten, ausgel{\"o}st durch die komplexe Zusammensetzung der Messmatrix Atemgas, bei gleichzeitig kleine Aceton Konzentrationen (200-800 parts-per-billion) {\"u}berwunden werden. Verschiedene Wellenl{\"a}ngenbereiche mit unterschiedlichen Lichtquellen, akustisch resonante sowie innovative Messzellendesigns und anspruchsvolle Datenauswertung mittels komplexer Algorithmik sind n{\"o}tig um das Ziel, die Entwicklung eines kompakten, g{\"u}nstigen und zuverl{\"a}ssigen Acetonsensors, zu erreichen.}, language = {en} } @inproceedings{RothHauslerBierl, author = {Roth, Carina and Hausler, Peter and Bierl, Rudolf}, title = {Einbindung eines 2D-Photodetektors in einen hochintegrierten SPR-Imaging-Sensor}, series = {118. Jahrestagung der deutschen Gesellschaft f{\"u}r angewandte Optik (DGaO), 6.-10. Juni 2017, Dresden}, booktitle = {118. Jahrestagung der deutschen Gesellschaft f{\"u}r angewandte Optik (DGaO), 6.-10. Juni 2017, Dresden}, abstract = {Mit der Oberfl{\"a}chenplasmonenresonanzspektroskopie (SPR) k{\"o}nnen Brechungsindex{\"a}nderungen eines Analyten von bis zu 10-6 RIU detektiert werden. Das SPR-Imaging bietet heute gegen{\"u}ber der konventionellen SPR-Analyse die M{\"o}glichkeit, mehrere einzelne Messungen parallel durchf{\"u}hren zu k{\"o}nnen. Mit Hilfe eines zweidimensionalen Sensorchips und einer leistungsf{\"a}higen Boardlevelkamera k{\"o}nnen die Abbildungen des Chips direkt an einen Rechner {\"u}bertragen und dort verarbeitet werden. Aufgrund unterschiedlicher Winkelstellungen und der Geometrie des Aufbaus entstehen Stauchungen und Streckungen des abgebildeten Sensorchips, die mit verschiedenen Ans{\"a}tzen aus der Bildverarbeitung ausgeglichen werden, um die Bilder miteinander vergleichen zu k{\"o}nnen. Zudem wird die G{\"u}te der Referenz- und Messbereiche des Chips bestimmt. Diese Algorithmen sind nur m{\"o}glich aufgrund der heutigen, leistungsf{\"a}higen Rechner und der immer gr{\"o}ßer werdenden Durchsatzraten der Kameras. Dabei kommt in dieser Anwendung der relativ neue Kamerastandard USB3 Vision zum Einsatz. Dieser zeichnet sich zus{\"a}tzlich durch das Plug and Play und seinen Standardstecker, der an (fast) jedem Rechner vorhanden ist, aus.}, language = {de} } @inproceedings{ZhouLandgrafRuecketal., author = {Zhou, Qi and Landgraf, Ferdinand and R{\"u}ck, Thomas and Bierl, Rudolf}, title = {Resonance frequency tuning and process design of a micromechanical capacitive cantilever in a photoacoustic trace-gas sensing device}, series = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, booktitle = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, publisher = {VDE-Verlag}, address = {Berlin}, isbn = {978-3-8007-4491-6}, abstract = {Photoacoustic spectroscopy is an efficient method to detect the concentration of trace gases with following advantages: short response time, high sensitivity, continuous and real-time monitoring and the option of miniaturization without the need of complex mirror-based multi-pass cell designs. A micromechanical cantilever is used as a key component in a two-part "Cantilever-Resonator" system that detects the weak photoacoustic signal. The resonance frequency of cantilever needs to be tuned to match the resonance frequency of resonator in order to achieve the maximum vibration amplitude of the "Cantilever-Resonator" system. This paper reports a post-fabrication method to tune the resonance frequency of cantilevers via focused ion beam (FIB) and a capacitive solution for the cantilever to transform the acoustic signal to electrical signal.}, language = {en} } @article{vanderWeerdBierlMatysik, author = {van der Weerd, Bastiaan and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Trends in Electrochemical Sensing of Blood Gases}, series = {Bioanalytical Reviews}, volume = {6}, journal = {Bioanalytical Reviews}, publisher = {Springer}, address = {Berlin}, doi = {10.1007/11663_2016_1}, pages = {263 -- 280}, abstract = {The monitoring of partial pressures of the blood gases carbon dioxide (pCO2) and oxygen (pO2) is of great importance in clinical diagnostics. The measure of pCO2 and pO2 provides essential information about the patient's metabolism, gas exchange, ventilation, and acid-base homeostasis. The conventional electrochemical methods for clinical blood gas analysis are based on the potentiometric Severinghaus sensor for carbon dioxide and the amperometric Clark sensor for oxygen. These techniques are well established and are only shortly discussed in this overview. However, in recent years a variety of modifications of these classical sensor concepts and new approaches of electrochemical sensing of pCO2 and pO2 have been introduced. This review summarizes recent developments in this field and discusses the potential for future applications in clinical blood gas analysis.}, language = {en} } @inproceedings{RueckLaeppleBierl, author = {R{\"u}ck, Thomas and L{\"a}pple, I. and Bierl, Rudolf}, title = {Photoakustische Spurengasanalytik von NO2 im ppt-Bereich (10^-12) bei Verwendung kosteng{\"u}nstiger Einzelkomponenten}, series = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, booktitle = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, publisher = {VDE-Verlag}, address = {Berlin}, isbn = {978-3-8007-4491-6}, language = {de} } @article{ZaglerLandgrafRuecketal., author = {Zagler, Andreas and Landgraf, Ferdinand and R{\"u}ck, Thomas and Bierl, Rudolf}, title = {Entwicklung eines mikromechanischen kapazitiven Schalldetektors im resonanten Betrieb f{\"u}r die photoakustische Spurengasanalyse}, series = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, journal = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, publisher = {VDE-Verlag}, address = {Berlin}, language = {de} } @inproceedings{GaidaWeiglRuecketal., author = {Gaida, Peter and Weigl, Stefan and R{\"u}ck, Thomas and Bierl, Rudolf}, title = {Portable photoakustische Messeinheit zur NO2 Detektion im Spurenbereich}, series = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, booktitle = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, publisher = {VDE-Verlag}, address = {Berlin}, isbn = {978-3-8007-4491-6}, language = {de} } @misc{HauslerRothVitzthumeckeretal., author = {Hausler, Peter and Roth, Carina and Vitzthumecker, Thomas and Fischer, Johannes and Bierl, Rudolf}, title = {Motionless SPR-angle scan with a miniaturized device}, series = {Europtrode XIV, Naples, 25-28 March 2018}, journal = {Europtrode XIV, Naples, 25-28 March 2018}, language = {en} } @inproceedings{WeiglGaidaRuecketal., author = {Weigl, Stefan and Gaida, Peter and R{\"u}ck, Thomas and Bierl, Rudolf}, title = {Portable Measurement Unit for NO2 Trace Gas Detection}, series = {PHOTOPTICS 2018, 6th International Conference on Photonics, Optics and Laser Technology, 25 - 27 January 2018, Funchal Madeira}, booktitle = {PHOTOPTICS 2018, 6th International Conference on Photonics, Optics and Laser Technology, 25 - 27 January 2018, Funchal Madeira}, language = {en} } @techreport{UngerRueckLandgrafetal., author = {Unger, J. and R{\"u}ck, Thomas and Landgraf, Ferdinand and Bierl, Rudolf}, title = {Herstellung und Analyse der Resonanzfrequenz eines MEMS Cantilever f{\"u}r das CEPAS Verfahren}, abstract = {Diese Abhandlung beschreibt das Konzept eines mikroeletromechanischen Systems (MEMS), das im Messverfahren der cantilever enhanced photoacoustic spectroscopy (CEPAS) Verwendung finden soll. Es wird die Herstellung eines einseitig eingespannten Biegebalkens aus Silizium mittels deep reactiv ion etching (DRIE) beschrieben. Des Weiteren wird die Resonanzfrequenz dieses Cantilevers mit Hilfe Laservibrometertechnik untersucht. Die resultierenden resonanten Schwingungen 0.Ordnung werden mit den Ergebnissen einer vereinfachten theoretischen N{\"a}herung verglichen. Die Messergebnisse stehen in gutem Zusammenhang mit den theoretischen Werten. Solche Cantilever, die aus silicon on insula tor (SOI) Wafer angefertigt wurden, weisen bei einer Zielfrequenz ein mittlere Abweichung von Δf = 118±26Hz (bzw.Δf =0,76±0,17\%) auf.}, language = {de} } @inproceedings{HollerHauslerRothetal., author = {Holler, Sven and Hausler, Peter and Roth, Carina and Bierl, Rudolf}, title = {Gestapelte Au-Al-Au und Au-Ag-Au Schichten als aktive Schichten f{\"u}r die Oberfl{\"a}chenplasmonenresonanzspektroskopie}, series = {5. Landshuter Symposium Mikrosystemtechnik, M{\"a}rz 2016}, booktitle = {5. Landshuter Symposium Mikrosystemtechnik, M{\"a}rz 2016}, publisher = {Fachhochschule Landshut}, address = {Landshut}, isbn = {978-3-9812696-9-7}, pages = {192 -- 198}, language = {de} } @inproceedings{RothHauslerBierl, author = {Roth, Carina and Hausler, Peter and Bierl, Rudolf}, title = {Einbindung eines CMOS-Detektors in einen hochintegrierten SPR-Sensor}, series = {5. Landshuter Symposium Mikrosystemtechnik, M{\"a}rz 2016}, booktitle = {5. Landshuter Symposium Mikrosystemtechnik, M{\"a}rz 2016}, publisher = {Fachhochschule Landshut}, address = {Landshut}, isbn = {78-3-9812696-9-7}, pages = {200 -- 205}, language = {de} } @article{RomanoMicklitzOlbrichetal., author = {Romano, Marco and Micklitz, Matthias and Olbrich, Florian and Bierl, Rudolf and Ehrlich, Ingo and Gebbeken, Norbert}, title = {Experimental investigation of damping properties of unidirectionally and fabric reinforced plastics by the free decay method}, series = {Journal of Achievements in Materials and Manufacturing Engineering}, volume = {63}, journal = {Journal of Achievements in Materials and Manufacturing Engineering}, number = {2}, pages = {65 -- 80}, abstract = {Purpose: of this paper is experimental investigation of damping properties of unidirectionally and fabric reinforced plastics by the free decay method. Design/methodology/approach: For the evaluation of the presumed effect experimental structural dynamic investigations comparing unidirectionally and fabric reinforced plastics are carried out. In detail the free decay behaviour of flat beamlike specimens under fixed-free boundary conditions and relatively constant and reproducible displacement excitation is investigated. Findings: The vibrating structure has been measured by a laser scanning vibrometer PSV 400 from POLYTEC. In both cases evaluation of the results yields enhanced damping properties of the specimens with fabric reinforcement compared to the unidirectionally reinforced specimens. The results justify the presumed acting of a mesomechanic kinematic. Research limitations/implications: The results show that in either case the material damping in terms of the logarithmic decrement of the fabric reinforced material is higher than the material damping in of the unidirectionally reinforced material. Additionally, when the fabric reinforced specimens are addressed, in each case the plain weave reinforced specimens exhibited higher values of the material damping as the twill weave 2/2 reinforced ones. Originality/value: Ondulations in fabrics as a textile semi-finished product are caused by the alternating crossing of warp and fill yarns. In the mesoscopic scale the acting of a mesomechanic kinematic is presumed to enhance the damping properties under cyclic elastic deformation. For the evaluation of the presumed effect experimental structural dynamic investigations comparing unidirectionally and fabric reinforced plastics are carried out.}, language = {en} } @inproceedings{JobstBierl, author = {Jobst, Simon and Bierl, Rudolf}, title = {A Comparison of Correlation and Zero-Crossing Based Techniques in Ultrasonic Measurement}, series = {10th International Symposium on Applied Reconfigurable Computing (ARC'2014), Vilamoura, Algarve, Portugal, 14 - 16 April, 2014}, booktitle = {10th International Symposium on Applied Reconfigurable Computing (ARC'2014), Vilamoura, Algarve, Portugal, 14 - 16 April, 2014}, abstract = {Ultrasound measurement technology has advancedin previous decades due to positive developments in computing power and lower cost for the necessary hardware. Correlation-based processing can be advantageous for high-accuracy measurements, especially in noisy environments. Higher computational load makes correlation less attractive for industrialapplications, though, favouring traditional processing techniques. A platform for comparing various processing techniques hasbeen developed. It was found that both zero-crossing detectionas well as correlation can achieve very high accuracy over a hightemperature range but that correlation-based processing can lead to a significant precision bias depending on system bandwidth.}, language = {en} } @inproceedings{HofmannBierlRueck, author = {Hofmann, Matthias and Bierl, Rudolf and R{\"u}ck, Thomas}, title = {Implementation of a dual-phase lock-in amplifier on a TMS320C5515 digital signal processor}, series = {Proceedings of the 5th European DSP Education and Research Conference (EDERC), 13-14 Sept. 2012, Amsterdam}, booktitle = {Proceedings of the 5th European DSP Education and Research Conference (EDERC), 13-14 Sept. 2012, Amsterdam}, doi = {10.1109/EDERC.2012.6532217}, abstract = {A digital dual-phase lock-in amplifier that is capable to run on a low-cost, low-power platform comprising a 16-bit fixed-point digital signal processor was developed. This is achieved by a set of optimised digital filters including an exponential averager to adjust the time constant of the overall filter. The reference frequency is generated using a direct digital synthesis source utilising angle decomposition with a resolution of 1 Hz. The digital lock-in algorithm is described and the performance of the algorithm is analysed. The experimental results show that the developed lock-in amplifier achieves similar performance to a commercially available lock-in amplifier.}, language = {en} } @inproceedings{RueckLandgrafLaeppleetal., author = {R{\"u}ck, Thomas and Landgraf, Ferdinand and L{\"a}pple, I. and Unger, J. and Matysik, Frank-Michael and Bierl, Rudolf}, title = {Specification of an improved photoacoustic setup for high-sensitive, low-cost NO2 trace gas detection}, series = {18th International Conference on Photoacoustic and Photothermal Phenomena (ICPPP18), 2015, September 6-10, Novi Sad, Serbia}, booktitle = {18th International Conference on Photoacoustic and Photothermal Phenomena (ICPPP18), 2015, September 6-10, Novi Sad, Serbia}, language = {en} } @inproceedings{vanderWeerdBierlMatysik, author = {van der Weerd, Bastiaan and Bierl, Rudolf and Matysik, Frank-Michael}, title = {A Conductivity Probe for the Determination of Carbon Dioxide Tension at the Oxygenator Exhaust Outlet during Extracorporeal Membrane Oxygenation (ECMO)}, series = {analytica Conference 2014, 1. bis 4. April, M{\"u}nchen}, booktitle = {analytica Conference 2014, 1. bis 4. April, M{\"u}nchen}, language = {en} } @inproceedings{vanderWeerdBierlMatysik, author = {van der Weerd, Bastiaan and Bierl, Rudolf and Matysik, Frank-Michael}, title = {A Conductivity Probe for the Determination of Carbon Dioxide Tension at the Oxygenator Exhaust Outlet during Extracorporeal Membrane Oxygenation (ECMO)}, series = {Electrochemistry 2014, September 22 - 24, Mainz}, booktitle = {Electrochemistry 2014, September 22 - 24, Mainz}, language = {en} } @inproceedings{vanderWeerdBierlMatysik, author = {van der Weerd, Bastiaan and Bierl, Rudolf and Matysik, Frank-Michael}, title = {A Planar Conductivity Probe for CO2 Determination at the Oxygenator Outlet}, series = {Doktorandenseminar GDCh Prozessanalytik 2014, Berlin}, booktitle = {Doktorandenseminar GDCh Prozessanalytik 2014, Berlin}, language = {en} } @article{WunderlichHauslerMaerkletal., author = {Wunderlich, Lukas and Hausler, Peter and Maerkl, Susanne and Bierl, Rudolf and Hirsch, Thomas}, title = {Nanoparticle Determination in Water by LED-Excited Surface Plasmon Resonance Imaging}, series = {Chemosensors}, volume = {9}, journal = {Chemosensors}, number = {7}, publisher = {MDPI}, issn = {2227-9040}, doi = {10.3390/chemosensors9070175}, pages = {1 -- 9}, abstract = {The increasing popularity of nanoparticles in many applications has led to the fact that these persistent materials pollute our environment and threaten our health. An online sensor system for monitoring the presence of nanoparticles in fresh water would be highly desired. We propose a label-free sensor based on SPR imaging. The sensitivity was enhanced by a factor of about 100 by improving the detector by using a high-resolution camera. This revealed that the light source also needed to be improved by using LED excitation instead of a laser light source. As a receptor, different self-assembled monolayers have been screened. It can be seen that the nanoparticle receptor interaction is of a complex nature. The best system when taking sensitivity as well as reversibility into account is given by a dodecanethiol monolayer on the gold sensor surface. Lanthanide-doped nanoparticles, 29 nm in diameter and with a similar refractive index to the most common silica nanoparticles were detected in water down to 1.5 mu g mL(-1). The sensor can be fully regenerated within one hour without the need for any washing buffer. This sensing concept is expected to be easily adapted for the detection of nanoparticles of different size, shape, and composition, and upon miniaturization, suitable for long-term applications to monitor the quality of water.}, language = {en} } @inproceedings{HauslerRothVitzthumeckeretal., author = {Hausler, Peter and Roth, Carina and Vitzthumecker, Thomas and Bierl, Rudolf}, title = {Miniaturized Surface Plasmon Resonance Based Sensor Systems}, series = {Optics, Photonics and Laser Technology 2018}, booktitle = {Optics, Photonics and Laser Technology 2018}, editor = {Ribeiro, Paulo and Raposo, Maria}, publisher = {Springer Nature}, address = {Cham}, isbn = {978-3-030-30112-5}, doi = {10.1007/978-3-030-30113-2_8}, pages = {169 -- 195}, abstract = {Surface Plasmon Resonance (SPR) is a well-known and established technology in bioanalysis and pharmaceutical sciences. Due to the expensive instrumentation and the need of trained people, it is mainly limited to applications in laboratories. However, there are some areas like environmental monitoring, chemical processing and civil infrastructure, which urgently need new sensor technologies. SPR has the potential to serve these fields. In order to be qualified for a use in these areas SPR has to overcome some hurdles. The instrumentation has to be robust, small in size and cheap. A device, which fits these needs, will be a micro-opto-electro-mechanical system (MOEMS) with integrated intelligent algorithms. In this book chapter, examples of miniaturized SPR devices are introduced, the limitations which have to be overcome as well as the possibilities for future applications are proposed. Due to the manifold advantages of this technology and the dropping prices for imaging sensors, Surface Plasmon Resonance imaging (SPRi) might become one of the leading technologies for SPR smart sensor systems.}, language = {en} } @unpublished{RueckMuellerJobstetal., author = {R{\"u}ck, Thomas and M{\"u}ller, Max and Jobst, Simon and Weigl, Stefan and Pangerl, Jonas and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Digital Twin of a Photoacoustic Trace Gas Sensor for Monitoring Methane in Complex Gas Compositions}, publisher = {Elsevier / SSRN}, doi = {10.2139/ssrn.4215170}, pages = {22}, abstract = {The digitalization of industrial processes requires smart sensor systems. Photoacoustic spectroscopy is well suited for this purpose as it allows for small-sized and low-cost trace gas analysis. However, the method is susceptible to changes in measurement conditions and standard calibration routines often fail to correct for all changes. We therefore created a Digital Twin (DT) of a photoacoustic trace gas sensor for methane and evaluated it regarding variations in gas composition (CH4, N2, O2, CO2, H2O), temperature and pressure. With a mean absolute percentage error of 0.8 \% the accuracy of the sensor after DT compensation significantly exceeds the 24 \% achieved based on standard calibration in nitrogen. For the first time, we can fully analytically compute the photoacoustic signal under moderate ambient conditions with an error in the ppbV range by taking a holistic approach. Assuming knowledge of the underlying energy transfer processes, the model of this Digital Twin can be adapted to any microphone based photoacoustic sensor for monitoring any analyte species.}, language = {en} } @inproceedings{MuellerRueckJobstetal., author = {M{\"u}ller, Max and R{\"u}ck, Thomas and Jobst, Simon and Pangerl, Jonas and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Creating a Digital Twin of a Photoacoustic Gas Sensor for Methane Detection in Complex Gas Matrices}, series = {Proceedings Optical Sensors and Sensing Congress 2022 (AIS, LACSEA, Sensors, ES): 11-15 July 2022, Vancouver, British Columbia, Canada}, booktitle = {Proceedings Optical Sensors and Sensing Congress 2022 (AIS, LACSEA, Sensors, ES): 11-15 July 2022, Vancouver, British Columbia, Canada}, publisher = {Optica Publishing Group}, isbn = {978-1-957171-10-4}, doi = {10.1364/LACSEA.2022.LW4D.2}, abstract = {We present the calculation results from a digital twin (DT) of our photoacoustic (PA) sensor for methane detection, regarding gas composition, temperature and pressure variations.}, language = {en} } @unpublished{MuellerWeiglMuellerWilliamsetal., author = {M{\"u}ller, Max and Weigl, Stefan and M{\"u}ller-Williams, Jennifer and Lindauer, Matthias and R{\"u}ck, Thomas and Jobst, Simon and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Ambient methane monitoring at Hohenpeißenberg utilizing photoacoustic spectroscopy and cavity ring down spectroscopy}, doi = {10.5194/egusphere-2023-1010}, abstract = {With an atmospheric concentration of approximately 2000 parts per billion (ppbV, 10-9) methane (CH4) is the second most abundant greenhouse gas (GHG) in the atmosphere after carbon dioxide (CO2). The task of long-term and spatially resolved GHG monitoring to verify whether climate policy actions are effective, is becoming more crucial as climate change progresses. In this paper we report the CH4 concentration readings of our photoacoustic (PA) sensor over a five day period at Hohenpeißenberg, Germany. As a reference device a calibrated cavity ringdown spectrometer Picarro G2301 from the meteorological observatory was employed. Trace gas measurements with photoacoustic instruments promise to provide low detection limits at comparably low costs. However, PA devices are often susceptible to cross-sensitivities related to environmental influences. The obtained results show that relaxation effects due to fluctuating environmental conditions, e.g. ambient humidity, are a non-negligible factor in PA sensor systems. Applying algorithm compensation techniques, which are capable of calculating the influence of relaxational effects on the photoacoustic signal, increase the accuracy of the photoacoustic sensor significantly. With an average relative deviation of 1.11 \% from the G2301, the photoacoustic sensor shows good agreement with the reference instrument.}, language = {en} } @article{RueckMuellerJobstetal., author = {R{\"u}ck, Thomas and M{\"u}ller, Max and Jobst, Simon and Weigl, Stefan and Pangerl, Jonas and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Digital Twin of a Photoacoustic Trace Gas Sensor for Monitoring Methane in Complex Gas Compositions}, series = {Sensors and Actuators B: Chemical}, journal = {Sensors and Actuators B: Chemical}, number = {378}, doi = {10.1016/j.snb.2022.133119}, abstract = {The digitalization of industrial processes requires smart sensor systems. Photoacoustic spectroscopy is well suited for this purpose as it allows for small-sized and low-cost trace gas analysis. However, the method is susceptible to changes in measurement conditions and standard calibration routines often fail to correct for all changes. We therefore created a Digital Twin (DT) of a photoacoustic trace gas sensor for methane and evaluated it regarding variations in gas composition (CH4, N2, O2, CO2, H2O), temperature and pressure. With a mean absolute percentage error of 0.8 \% the accuracy of the sensor after DT compensation significantly exceeds the 24 \% achieved based on standard calibration in nitrogen. For the first time, we can fully analytically compute the photoacoustic signal under moderate ambient conditions with an error in the ppbV range by taking a holistic approach. Assuming knowledge of the underlying energy transfer processes, the model of this Digital Twin can be adapted to any microphone based photoacoustic sensor for monitoring any analyte species.}, language = {en} } @inproceedings{PangerlWittmannWeigletal., author = {Pangerl, Jonas and Wittmann, Elisabeth and Weigl, Stefan and M{\"u}ller, Max and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Using a Modulated Quantum Cascade Laser for Photoacoustic Spectra Recording of Exhaled Acetone and Main Breath Components}, series = {Optical Sensors and Sensing Congress 2022 (AIS, LACSEA, Sensors, ES)}, booktitle = {Optical Sensors and Sensing Congress 2022 (AIS, LACSEA, Sensors, ES)}, publisher = {Optica Publishing Group}, doi = {10.1364/AIS.2022.ATu3G.1}, abstract = {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}, language = {en} } @inproceedings{EscherRueckJobstetal., author = {Escher, Lukas and R{\"u}ck, Thomas and Jobst, Simon and K{\"o}nig, Martin and Bierl, Rudolf}, title = {Design and Characterization of a Low-Cost Photoacoustic Sensor for NO2 Using Lateral Illumination and Background Suppression}, series = {Imaging and Applied Optics Congress 2022 (3D, AOA, COSI, ISA, pcAOP): 11-15 July 2022, Vancouver, British Columbia, Canada}, booktitle = {Imaging and Applied Optics Congress 2022 (3D, AOA, COSI, ISA, pcAOP): 11-15 July 2022, Vancouver, British Columbia, Canada}, publisher = {Optica Publishing Group}, isbn = {978-1-957171-09-8}, doi = {10.1364/3D.2022.JTu2A.10}, abstract = {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.}, language = {en} } @unpublished{PangerlSukulRuecketal., author = {Pangerl, Jonas and Sukul, Pritam and R{\"u}ck, Thomas and Escher, Lukas and Miekisch, Wolfram and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Photoacoustic Trace-Analysis of Breath Isoprene and Acetone Via Interband- and Quantum Cascade Lasers}, publisher = {Elsevier / SSRN}, doi = {10.2139/ssrn.4834735}, abstract = {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.}, language = {en} } @article{PangerlSukulRuecketal., author = {Pangerl, Jonas and Sukul, Pritam and R{\"u}ck, Thomas and Escher, Lukas and Miekisch, Wolfram and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Photoacoustic trace-analysis of breath isoprene and acetone via interband- and Quantum Cascade Lasers}, series = {Sensors and Actuators: B. Chemical}, volume = {424}, journal = {Sensors and Actuators: B. Chemical}, publisher = {Elsevier}, doi = {10.1016/j.snb.2024.136886}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-77024}, pages = {12}, abstract = {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}, language = {en} }