Neuromorphic acoustic sensing using an adaptive microelectromechanical cochlea with integrated feedback. - In: Nature electronics, ISSN 2520-1131, Bd. 6 (2023), 5, S. 370-380
Many speech processing systems struggle in conditions with low signal-to-noise ratios and in changing acoustic environments. Adaptation at the transduction level with integrated signal processing could help to address this; in human hearing, transduction and signal processing are integrated and can be adaptively tuned for noisy conditions. Here we report a microelectromechanical cochlea as a bio-inspired acoustic sensor with integrated signal processing functionality. Real-time feedback is used to tune the sensing and processing properties, and dynamic switching between linear and nonlinear characteristics improves the detection of signals in noisy conditions, increases the sensor dynamic range and enables adaptation to changing acoustic environments. The transition to nonlinear behaviour is attributed to a Hopf bifurcation and we experimentally validate its dependence on sensor and feedback parameters. We also show that output-signal coupling between two coupled sensors can increase the frequency coverage.
https://doi.org/10.1038/s41928-023-00957-5
CO2 conversion toward real-world applications: electrocatalysis versus CO2 batteries. - In: Advanced functional materials, ISSN 1616-3028, Bd. 33 (2023), 32, 2300926, S. 1-38
Electrochemical carbon dioxide (CO2) conversion technologies have become new favorites for addressing environmental and energy issues, especially with direct electrocatalytic reduction of CO2 (ECO2RR) and alkali metal-CO2 (M-CO2) batteries as representatives. They are poised to create new economic drivers while also paving the way for a cleaner and more sustainable future for humanity. Although still far from practical application, ECO2RR has been intensively investigated over the last few years, with some achievements. In stark contrast, M-CO2 batteries, especially aqueous and hybrid M-CO2 batteries, offer the potential to combine energy storage and ECO2RR into an integrated system, but their research is still in the early stages. This article gives an insightful review, comparison, and analysis of recent advances in ECO2RR and M-CO2 batteries, illustrating their similarities and differences, aiming to advance their development and innovation. Considering the crucial role of well-designed functional materials in facilitating ECO2RR and M-CO2 batteries, special attention is paid to the development of rational design strategies for functional materials and components, such as electrodes/catalysts, electrolytes, and membranes/separators, at the industrial level and their impact on CO2 conversion. Moreover, future perspectives and research suggestions for ECO2RR and M-CO2 batteries are presented to facilitate practical applications.
https://doi.org/10.1002/adfm.202300926
Influence of environment on self-propagating reactions in Al/Ni multilayer foils. - In: MRS advances, ISSN 2059-8521, Bd. 8 (2023), 9, S. 477-483
Reactive aluminum-nickel multilayer system shows exothermic energetic materials which act as a heat source for packaging and bonding of microsystems. The main challenge is controlling the self-propagation reaction velocity and temperature generated by thermal management through different thermal conductive substrate materials. The current work investigates the heat distribution of Al/Ni multilayer foils from different thermal conductive substrates which act as heat sink materials during the self-propagating reaction. A two-dimensional numerical model was developed to study thermal conductive heat loss and substrate thermal properties on the self-propagating reaction in Al/Ni multilayer foils. The self-propagating reaction was introduced on the surface of the foils by an electrical spark. Here we investigate the minimum critical thickness of Al/Ni multilayer foils which shows the self-propagation reaction on different substrates and verified from the two-dimensional numerical model. The outcomes of this investigation will facilitate the integration of Al/Ni multilayer foils on different substrates as intrinsic heat sources for different applications of micro/nanodevices.
https://doi.org/10.1557/s43580-023-00574-6
Systemic conception of the data acquisition of Digital Twin solutions for use case-oriented development and its application to a gearbox. - In: Systems, ISSN 2079-8954, Bd. 11 (2023), 5, 227, S. 1-17
Digital Twins are being used more and more frequently and provide information from the Real Twin for different applications. Measurements on the Real Twin are required to obtain information, which in many cases requires the installation of supplementary sensors. For their conception and design, it is particularly important that the measuring principles are selected purposefully and the appropriate sensors are integrated at the goal-oriented measuring positions without impairing the functions and other properties of the Real Twin by the integration of these sensors. In this article, a "Design for Digital Twin" approach is discussed for the systematic procedure and demonstrated using a multi-staged gearbox as a concrete example. The approach focuses on the mechanical and hardware side of the Real Twin. For the systematic conception and design of the Digital Twin solution, an understanding of the stakeholder demands and the expected use cases is necessary. Based on the stakeholder demands and use cases, the relevant product properties can be determined. Using the relevant properties, an iterative process of conception, design, and analysis takes place. The conception is carried out by means of target-oriented cause-effect analyses, taking into account systemic interrelations of the Real Twin components and systematics for the selection of measurement principles. Systemic considerations, combined with an effect graph, allow for the analysis and evaluation of disturbing factors.
https://doi.org/10.3390/systems11050227
Effects of ultrashort pulsed direct laser writing on Ni/Al reactive multilayer foils. - In: Applied Sciences, ISSN 2076-3417, Bd. 13 (2023), 7, 4313, S. 1-13
Reactive multilayer foils (RMFs) for joining processes have attracted a great deal of attention over the last few years. They are capable of exothermic self-propagating reactions and can serve as localized heat sources for joining applications when ignited by suitable means. Using short and ultrashort pulsed lasers with carefully selected parameters, cutting and shaping of RMFs makes it possible to tailor heat release characteristics without triggering the reaction. The present study is an investigation of microstructural changes induced by femtosecond laser machining of a commercially available Ni/Al-based RMF. The effects of the specific laser parameters pulse duration and repetition rate on the heat-affected zone (HAZ) are investigated by scanning and transmission electron microscopy. Debris consisting of oxide deposits can be found at a distance of several tens of microns from the cut edge. A negligible HAZ extending to less than 100 nm was observed for all parameters tested and no signs of ignition of a self-propagating reaction were observed. These results underline the suitability of femtosecond lasers for metal machining with minimal heat input.
https://doi.org/10.3390/app13074313
Facile microwave plasma driven 3D-WSe2 2H-1T phase modulation for improving NO2 gas sensing performance. - In: Sensors and actuators, ISSN 0925-4005, Bd. 387 (2023), 133822
In recent years, transition metal dichalcogenides (TMDs) have been widely used for gas sensors. Here, three-dimensional (3D) WSe2 nanosheet arrays were surface treated by microwave plasma. Based on the original 3D structure, a 1T/2H hybrid phase structure was constructed by phase modulation, and Se vacancies were introduced to effectively improve its gas sensing performance. After only 60 s of treatment, the response (52.24 %), response/recovery time of the sample for 1 ppm NO2 were significantly improved with excellent stability and selectivity at room temperature. The intrinsic mechanism of its performance enhancement was elicited through various characterizations and molecular model construction. It is demonstrated that microwave plasma is a promising treatment method to improve the gas-sensitive performance of TMDs.
https://doi.org/10.1016/j.snb.2023.133822
Archaeal and extremophilic bacteria from different archaeological excavation sites. - In: International journal of molecular sciences, ISSN 1422-0067, Bd. 24 (2023), 6, 5519, S. 1-18
Beside natural factors, human activities are important for the development of microbiomes. Thus, local soil bacterial communities are affected by recent activities such as agriculture, mining and industry. In addition, ancient human impacts dating back centuries or millennia have changed soils and can emboss the recent bacterial communities up to now, representing a certain long-term "memory of soil". Soil samples from five different archaeological excavation places were investigated for the presence of Archaea with a Next Generation Sequencing (NGS) analysis of the DNA coding for 16S r-RNA sequences. It was found that the abundance of Archaea differs strongly between less than one and more than 40 percent of bacteria. A Principal Component Analysis (PCA) of all samples shows that the archaeological excavation places can be distinguished from each other by the archaeal component of soil bacterial communities, which presents a typical pattern for each place. Most samples are marked by the dominance of Crenarchaeota, which are presented mainly by ammonia-related types. High contents of Nanoarchaeaota have been observed in one ash deposit of a historical saline and all samples of a historical tannery area. These samples are also marked by a significant presence of Dadabacteria. The specific abundancies of special Archaea - among them ammonia-oxidizing and sulphur-related types - are due obviously to former human activities and support the concept of the "ecological memory of soil".
https://doi.org/10.3390/ijms24065519
Three-dimensional immersion scanning technique: a scalable low-cost solution for 3D scanning using water-based fluid. - In: Sensors, ISSN 1424-8220, Bd. 23 (2023), 6, 3214, S. 1-14
Three-dimensional scanning technology has been traditionally used in the medical and engineering industries, but these scanners can be expensive or limited in their capabilities. This research aimed to develop low-cost 3D scanning using rotation and immersion in a water-based fluid. This technique uses a reconstruction approach similar to CT scanners but with significantly less instrumentation and cost than traditional CT scanners or other optical scanning techniques. The setup consisted of a container filled with a mixture of water and Xanthan gum. The object to be scanned was submerged at various rotation angles. A stepper motor slide with a needle was used to measure the fluid level increment as the object being scanned was submerged into the container. The results showed that the 3D scanning using immersion in a water-based fluid was feasible and could be adapted to a wide range of object sizes. The technique produced reconstructed images of objects with gaps or irregularly shaped openings in a low-cost fashion. A 3D printed model with a width of 30.7200 ± 0.2388 mm and height of 31.6800 ± 0.3445 mm was compared to its scan to evaluate the precision of the technique. Its width/height ratio (0.9697 ± 0.0084) overlaps the margin of error of the width/height ratio of the reconstructed image (0.9649 ± 0.0191), showing statistical similarities. The signal-to-noise ratio was calculated at around 6 dB. Suggestions for future work are made to improve the parameters of this promising, low-cost technique.
https://doi.org/10.3390/s23063214
An in-depth understanding of photophysics in organic photocatalysts. - In: Journal of semiconductors, ISSN 2058-6140, Bd. 44 (2023), 3, 030401, S. 1-4
https://doi.org/10.1088/1674-4926/44/3/030401
Configurable pseudo noise radar imaging system enabling synchronous MIMO channel extension. - In: Sensors, ISSN 1424-8220, Bd. 23 (2023), 5, 2454, insges. 27 S.
In this article, we propose an evolved system design approach to ultra-wideband (UWB) radar based on pseudo-random noise (PRN) sequences, the key features of which are its user-adaptability to meet the demands provided by desired microwave imaging applications and its multichannel scalability. In light of providing a fully synchronized multichannel radar imaging system for short-range imaging as mine detection, non-destructive testing (NDT) or medical imaging, the advanced system architecture is presented with a special focus put on the implemented synchronization mechanism and clocking scheme. The core of the targeted adaptivity is provided by means of hardware, such as variable clock generators and dividers as well as programmable PRN generators. In addition to adaptive hardware, the customization of signal processing is feasible within an extensive open-source framework using the Red Pitaya® data acquisition platform. A system benchmark in terms of signal-to-noise ratio (SNR), jitter, and synchronization stability is conducted to determine the achievable performance of the prototype system put into practice. Furthermore, an outlook on the planned future development and performance improvement is provided.
https://doi.org/10.3390/s23052454