Recent Submissions
From two‐photon grayscale lithography to scalable replication : enabling complex aspherical micro‐optics for mass production
(2025) Wagner, Stefan; Siegle, Leander; Haeusler, Stephan; Flad, Philipp; Henschel, Mario; Guenther, Thomas; Zimmermann, André; Giessen, Harald
The evolution of complex micro‐optics from prototyping to scalable manufacturing is a key challenge for modern imaging, sensing, and photonic systems. Two‐photon polymerization grayscale lithography (2GL) revolutionized the fabrication of micro‐optics by combining aspherical lenses with micro‐features enabling performance increases, weight reduction, aberration correction, and beam shaping. Its scalability for mass production, however, remains a key limitation. In this study, the replication and integration of 3D printed optics are demonstrated through electroplating and injection molding processes, enabling high‐volume production without sacrificing precision. Advancements in replicating complex micro‐optics fabricated via 2GL are presented by designing and 3D printing a diffractive, aspherical micro‐lens array. In relation to their size, these optics are almost impossible to produce with common techniques such as precision turning. The topography, beam profiles, and imaging quality of the 3D printed master are compared to the replicated lens array. By combining 2GL 3D printing and injection molding, micro‐optical mass production of arbitrary geometries is enabled. It is highlighted how this approach unlocks new opportunities for scalable production, addressing disparities between rapid prototyping and industrial manufacturing of micro‐optics.
Direct recycling of all‐solid‐state batteries with a halide solid electrolyte via water‐based separation : interactions of electrode materials in aqueous Li3InCl6 solutions
(2025) Jacob, Martine; Moreno Fernández, Harol; Haben, Aaron; Waidha, Aamir Iqbal; Özel, Simay; Hofmann, Jan P.; Kautenburger, Ralf; Clemens, Oliver; Wissel, Kerstin
Despite extensive research in the field of all‐solid‐state batteries, there has been limited attention to their recycling, which is crucial for achieving long‐term sustainability. Different electrolyte and electrode combinations must be considered for the recycling of these batteries, each requiring a detailed investigation of potential recycling approaches. The halide‐based solid electrolyte, Li3InCl6, has attracted significant attention due to its high‐room‐temperature lithium‐ion conductivity and its ability to recover its initial crystal structure after dissolution in water without significant electrochemical deterioration. This structural reversibility could potentially enable a direct recycling approach, allowing for the separation of the electrolyte from active electrode materials when dissolved in H2O. To assess the recycling compatibility, the interactions of Li3InCl6 with different electrode materials (Li4Ti5O12, LiCoO2, LiMn2O4, carbon‐coated LiFePO4, LiNi0.8Mn0.1Co0.1O2, and LiNi0.8Co0.15Al0.05O2) are studied during dissolution. Interactions arising from Lewis‐acid and Lewis‐base reactions can be identified using a combination of X‐ray diffraction, X‐ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry. Depending on the material combination, these interactions significantly impact the electrochemical properties of both recycled Li3InCl6 and the electrode materials compared to the pristine samples.
Electrochemical doping for absorption and conductivity tuning of P(NDI2OD‐T2) films
(2025) Neusser, David; Sun, Xiuming; Jena, Sushri Soumya; Tan, Wen Liang; Thomsen, Lars; McNeill, Christopher R.; Ghosh, Sarbani; Zozoulenko, Igor; Ludwigs, Sabine
Electrochemical doping of thin films of poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2)) is shown as straightforward method to achieve different degrees of doping both during in situ electrochemical experiments as well as in the solid state. Results obtained from cyclic voltammetry and absorption spectroscopy upon reduction can be explained by the presence of the neutral state as well as polaron and bipolaron species, including neutral/polaron and polaron/bipolaron mixed valence states. The UV‐vis‐NIR spectra are analyzed and explained based on the calculated electronic structure and the corresponding transitions between different states, this includes features such as numbers and positions of the peaks and their evolution during reduction. Most intruingly, doped films are stable after transfer in the solid state, as evidenced by absorption spectroscopy. Conductivity measurements of films with different degrees of doping show a bell‐shaped conductivity profile, which underlines the classification of P(NDI2OD‐T2) as a conjugated redox polymer with mixed valence transport. Maximum conductivities of up to 2 × 10 -4 S cm -1 are obtained at intermediate doping levels under the coexistence of neutral state and polarons. Conductivity measurements of blade‐coated films point to anisotropic charge transport with the highest charge transport along the blade /polymer chain direction and an anisotropic conductivity ratio of 4.1.
Shielding the mind with flow : attention allocation and auditory event‐related potentials under varying mental workload
(2025) Lingelbach, Katharina; Vorreuther, Anna; Moll, Elias; Vukelić, Mathias
Attention allows individuals to prioritize and effectively process relevant information while ignoring task‐irrelevant distractions. It plays a critical role in task performance, learning, and creativity. This study examines how varying levels of workload influence auditory attention, cognitive resource allocation, and the experience of flow. Thirteen participants engaged in a game‐based electroencephalographic study designed to induce states of mental underload, overload, and flow. To assess available attentional resources, an implicit auditory oddball task was integrated as a secondary task. Spatiotemporal cluster analyses revealed significant differences in event‐related potentials when comparing flow and overload to underload. Multivariate pattern analysis successfully decoded all three conditions above chance level, particularly in centroparietal regions. Subjective measures, including the NASA Task Load Index and Flow Short Scale, along with behavioral performance metrics, confirmed the effective induction of flow and distinct levels of workload. Notably, participants demonstrated significantly higher performance and subjectively perceived valence during the flow condition compared to the overload condition, albeit with similar levels of neural engagement. Our results support the notion that experiencing flow may act as a “shielding mechanism,” enhancing the effective allocation of attentional resources to the game and improving task engagement and performance efficiency.
Non‐invasive imaging of solute redistribution below evaporating surfaces using 23Na‐MRI
(2026) Chaudhry, M. A.; Kiemle, Stefanie; Pohlmeier, Andreas; Helmig, Rainer; Huisman, Johan Alexander
Saline water evaporation from porous media is a key phenomenon in the terrestrial environment and is linked to problems such as soil salinization and weathering of building materials. Recent modeling studies suggest the development of local instabilities due to density differences during evaporation in case of saturated porous media with high permeability. To experimentally investigate this and improve our understanding of near surface solute accumulation, we performed evaporation experiments on two types of porous media (F36 and W3) with intrinsic permeabilities that differed by two orders of magnitude. Using magnetic resonance imaging ( 23 Na‐MRI), we monitored the development of solute accumulation and subsequent redistribution during evaporation under wicking conditions. The F36 sample showed an initial enrichment at the surface, but soon after a downwards moving plume developed that redistributed NaCl into the column. Average depth profiles of Na concentrations obtained from 3D imaging showed that the surface concentration reached only 2.5 mol L -1 , well below the solubility limit. In contrast, the W3 sample with lower permeability showed enrichment in a shallow near‐surface zone reaching a concentration of over 6 mol L -1 . No fingering occurred although the mean evaporation rate was similar to that of F36 sand. Comparison of experimental results with numerical simulations using DuMu x for both samples showed qualitative agreement between measured and modeled solute concentrations. This study experimentally confirms the importance of density‐driven redistribution of solutes in case of evaporating saturated porous media, carrying implications for predicting evaporation rates and the time to start of salt crust formation.
Phase stabilities and influence on magnetic and electrical properties of the system (MgxMn4‐x)MnVO8
(2025) Fraune, Jonas; Bredow, Thomas; Kunz, Sylvia; Blaschkowski, Björn; Clemens, Oliver
Manganese vanandates have a wide range of interesting material properties, covering magnetic, electrical, and catalytic aspects. Among them, Mn5VO8 is a compound containing manganese in both its trivalent as well as divalent oxidation states with ordering of the different manganese species on different crystallographic sites. In this article, we show that the divalent manganese can be replaced by magnesium fully up to a composition of Mg4MnVO8. For low magnesium content, this results in a change of symmetry from triclinic to monoclinic, whereas for Mg4MnVO8, a trigonal modification can be found in addition to a monoclinic phase. Density Functional Theory based calculations reveal that for magnesium rich compositions, monoclinic and trigonal modifications are energetically similar. Magnetic characterization reveals that the materials are paramagnetic around room temperature. Further, the magnesium substitution results in a strong decrease of electrical conductivity with an increase of the activation energy determined by electrochemical impedance spectroscopy.
Filling voids : cubic carbodiimide nitride nitridometalates (Ba6Nx)2[MN4][CN2]6 of M = Zr, Hf, Nb, Ta, Mo, and W
(2026) Höhn, Peter; Link, Lukas; Reckeweg, Olaf; Prots, Yurii; Niewa, Rainer
Cubic carbodiimide nitride nitridometalates (Ba6Nx)2[MN4][CN2]6 of M = Zr, Hf, Nb, Ta, Mo, and W are synthesized by various high-temperature reactions and their respective crystal structures were investigated using X-ray diffraction. Red transparent crystals (Ba6N5/6)2[NbVN4][CN2]6 in space group Im3 as aristotype exhibit site disorder of the [NbN4]7 anion and an about 42% occupation of a further nitride ion site for charge balance. Upon reduced nitrogen content on the latter site, dark gray (Ba6Nx)2[NbN4][CN2]6 with x=0.55(7) crystallizes in the direct subgroup I23 with fully ordered tetrahedra. This structure is also observed for crystals of red (Ba6N2/3)2[HfIVN4][CN2]6 with ordered tetrahedra [HfN4]8. Dark red (Ba6N)2[WVIN4][CN2]6 with enlarged nitride content balancing the higher charge of the transition metal in oxidation state þ6 crystallizes in the different direct subgroup Pn3, and shows an unlike site order for the nitride ions. Depending on the (dis)order of the nitride ions, the nitridometalate ions (dis)order in different patterns. Powder diffraction data of microcrystalline samples indicate identical structures of the zirconium and hafnium compounds in I23, but realization of space group Pn3 of the red compounds of not only molybdenum and tungsten but also niobium and tantalum. The IR spectra corroborate the identity of the carbodiimide anion.
An acidic patch in the unstructured N‐terminus modulates LSD1 activity
(2025) Dukatz, Franziska; Timofeev, Hermann; Schnee, Philipp; Rathert, Philipp
Lysine‐specific demethylase 1 (LSD1) plays a crucial role in chromatin organization and gene regulation by removing methyl groups from histone and non‐histone substrates. While its catalytic core is well characterized, the functional contributions of its intrinsically disordered N‐terminal region remain less understood. Here, we identify a conserved acidic patch within this unstructured domain as a key regulator of LSD1 activity. Our findings suggest that this region influences enzymatic efficiency and interactions with regulatory cofactors, shedding new light on the mechanistic control of LSD1 function in epigenetic modulation.
Measuring entrepreneurial ecosystems across levels : a district approach
(2025) Hess, Sophia; Wahl, Andreas; Johnson, Alan R.
Entrepreneurial ecosystem measures should combine archival civic and self-reported entrepreneur data. This combination helps to overcome the limitations of aggregated archival data that affect our collective capacity to derive actionable insights for research and policy. Previous measurement approaches lack consistency with entrepreneurial ecosystem theory because they do not capture data at a sufficiently local level or data about entrepreneurs’ values, beliefs, and attitudes. This paper proposes a new measurement approach for EE elements at the district level (NUTS-3), facilitating comparisons of local geographic EE properties and measuring relations between entrepreneurs, new ventures, and their ecosystems. Using confirmatory factor analysis, we combine self-reported and archival data to connect the micro and macro dimensions of the entrepreneurial ecosystem phenomenon. Analyzing survey data from 257 founders of innovative startups across 29 NUTS-3 districts in Baden-Württemberg, Germany, our findings support the “substitutability logic” among ten entrepreneurial ecosystem elements and uncover district-level geographic properties. Our study offers replication possibilities, recommendations for entrepreneurs’ actions, and policy monitoring.
An SPH approach to model the influence of assist gas forces in laser cutting
(2025) Anjana, Ishan; Baumann, Andreas; Sollich, Daniel; Eberhard, Peter
Laser cutting is a non-contact thermal-based material removal technique that offers various advantages over conventional machining processes. The workpiece is melted by a high-powered laser beam and the resulting melt is blown away by a jet of gas. The laser assist gas is crucial as it influences the cutting speed, edge quality, and thermal effects, ultimately affecting the overall efficiency and accuracy of the process. However, modeling the laser assist gas is highly challenging due to the immense computational costs associated when dealing with shock waves, turbulence, and high speed jet dynamics. An approach is presented to model the formation of the cutting front and the dynamics of the melt film, influenced by the cutting assist gas forces acting upon it, using the Smoothed Particle Hydrodynamics (SPH) method. SPH is able to deal with large material displacements and moving boundaries occurring in the laser cutting process. The forces applied to the melt film and cutting kerf are modeled using the Continuum Surface Force approach and boundary particle detection. Consequently, the effects of the assist gas are calculated without modelling the assist gas phase domain, saving a significant amount of computational cost and reducing the complexity of the model. The SPH model is coupled with a ray-tracing scheme and a Fresnel absorption model to determine the laser-material interaction. The presented approach is compared against experimental data from literature, showing good agreement with the experimentally observed cutting front formation, melt ejection, phase transition, dross formation, and striation patterns. The results show that SPH can be effectively applied in applications related to laser cutting, showing its potential to design precise and accurate numerical models. Moreover, the proposed parameterized model can help to optimize process parameters to maximize material utilization and reduce energy consumption, operational cost, and processing time during laser cutting.