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Item type:Publication, Access status: with files , Lagrangian μ-particle tracking velocimetry analysis of microscale flow over structured surfaces(American Chemical Society (ACS), 2026-10-08); ; ; ; This work aims to provide an experimental basis for the improvement of (bio)reactors by studying flow over micro- and nanostructured surfaces, with a focus on microscale mass transport toward and away from the surface. μ-Particle tracking velocimetry is employed in a microreactor to experimentally obtain Lagrangian trajectories of flow-following tracer particles. The method also resolves three-dimensional, time-dependent velocity fields. The derived mean velocity profiles agree well with the theory of flow over porous walls. Beyond averaged Eulerian velocities, the Lagrangian framework captures near-surface interactions. The Lagrangian analysis of different surfaces indicates that rectangular structured microgrooves increase the wall contact of the tracer particles, especially when the flow is oriented perpendicular to the microgrooves. Particularly, this approach enables resolution of trapping phenomena and localized recirculation dynamics. Nanostructuring by growing a carbon nanotube forest increases surface area and modifies local fluid dynamics, thereby enhancing contact with (bio)catalysts that are potentially functionalized on the nanotubes in future applications.Publicationtype: Journal Article43 18 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Aerographite vs Graphite: Investigating the role of electrode architecture in H2-mediated electroautotrophic biofilms(American Chemical Society (ACS), 2026-08-07); ; ; ; Oxic microbial electrosynthesis using aerobic hydrogenotrophic bacteria requires productive cathodic biofilm formation, yet reactive oxygen species (ROS) generated at the electrode surface present a critical barrier to initial colonization. This study investigates biofilm development by Cupriavidus necator H16 on Aerographite, an ultralow-density carbon foam (3–12 mg cm–3, porosity > 99%) with a hierarchical tetrapodal pore network, as a cathode material in microfluidic bioelectrochemical systems and compares it to graphite (a composite material consisting of graphite and polypropylene (PPG86)). A biphasic cultivation strategy, in which heterotrophic biofilm establishment preceded a switch to electroautotrophic conditions at −45.45 μA cm–2, successfully overcame the ROS barrier on both electrode materials. Noninvasive optical coherence tomography revealed a final biovolume of 0.086 mm3 mm–2 on graphite after 14 days, representing the first continuous kinetic characterization of C. necator cathode biofilm formation under defined flow conditions. Despite lower absolute biovolume per projected area, Aerographite supported higher biomass per unit electrode mass, reflecting its 585-fold higher mass-specific electroactive surface area relative to graphite. Scanning electron microscopy confirmed C. necator colonization of internal pore regions up to 500 μm below the electrode surface under laminar flow-over conditions. The macropore dimensions substantially exceed documented self-limiting biofilm thicknesses, indicating that pore occlusion is unlikely even at full biofilm development, and positioning Aerographite as a structurally enabling electrode material for smart, scalable, flow-through CO2 valorization systems.Publicationtype: Journal Article71 25 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Impact of permeability of triply periodic minimal surface-based substrates on multiwalled carbon nanotube growth(American Chemical Society (ACS), 2026-08-05); ; ; ; Lumpp, DominiqueDue to their excellent thermal and electrical properties combined with pronounced porosity, carbon nanotube forests are promising as catalyst support materials for smart reactors. To maximize catalytic turnover, it is essential to increase the available surface while maintaining precise control over reactant flow and heat distribution. In this work, multiwalled carbon nanotubes are grown on three-dimensional substrates based on triply periodic minimal surfaces, which offer superior mechanical properties alongside controlled flow dynamics and enhanced heat transfer rates. The substrates are fabricated via laser powder bed fusion and subsequently coated using injection chemical vapor deposition. To evaluate the design limitations of the three-dimensional substrates for CNT growth, the impact of a decreasing permeability on the coating’s morphology is investigated. As the permeability decreases with the unit cell size of the triply periodic minimal surfaces and the introduction of an external wall, the characteristic CNT forest structure gradually transforms. Provided that permeability and precursor accessibility to the internal surfaces remain sufficiently high, the morphology and composition of CNT forests closely resemble those grown on flat substrates. Introducing the wall leads to a transition from vertically aligned CNT forests to horizontally oriented CNT networks due to enhanced laminar-like flow characteristics. While less dense, it offers an increased CNT quality. Below a critical minimal permeability, carbon nanostructures with numerous defects form. The successful coating and control of its morphology enable the utilization of the CNT for further smart tailoring of the reactor.Publicationtype: Journal Article88 30 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Investigations on the role of support and synthesis procedure for the Rux–Cuy/CNT‐catalysed hydrogenolysis of glycerol to 1,2‐propanediol(Wiley, 2026-07-14); ; ; Tailoring support effects plays an important role for controlling activity and selectivity in heterogeneously catalyzed gas–liquid reactions. Sophisticated carbon supports like single‐ and multiwall carbon nanotubes (CNTs) as well as in house produced Globugraphite were used for the synthesis of bimetallic Ru–Cu catalysts, which were tested in a multibatch reactor setup for the chemical hydrogenolysis of glycerol to 1,2‐propanediol (1,2‐PDO) in aqueous solution. In‐depth characterization using multiple tools like inductively coupled plasma optical emission spectrometry, CHNS‐O analysis, N₂‐physisorption, scanning electron microscopy, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, powder X‐ray diffraction, H₂‐temperature programmed reduction, laser diffraction, and point of zero charge measurements revealed the dominating effects that the various carbon supports exert on the catalytic performance. The best‐performing catalyst synthesized by wetness impregnation consisted of Ru–Cu₃ nanoparticles (NPs) from mixed RuCl₃ and Cu(NO₃)₂ precursors dispersed on multiwall CNT Baytubes with a productivity of p = 12.74 g₁,₂‐PDO gactive metal ⁻¹ h⁻¹ . Its superior activity combined with high 1,2‐PDO selectivity (S= 75%) can be explained both by the nature of the highly dispersed Ru and Cu NPs showing the lowest reduction peak temperature on entangled tubes of CNT agglomerates demonstrating a high mesopore volume for optimal reactant accessibility and the highest specific surface area of all investigated materials. This lays the foundation for implementing this highly active and selective catalyst in a future SMART reactor for glycerol valorisation.Publicationtype: Journal Article58 43 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Vibrational fingerprints of strained polymers: a spectroscopic pathway to mechanical state prediction(IOP Publishing, 2026-06-01); ; ; ; The vibrational response of polymer networks under load provides a sensitive probe of molecular deformation and enables non-destructive diagnostics. Machine-learned force fields reproduce these spectroscopic fingerprints with quantum-level fidelity in realistic epoxy thermosets. Using MACE-OFF23 molecular dynamics, the experimentally observed redshifts of para-phenylene stretching modes under tensile load are captured, in contrast to predictions from the harmonic OPLS-AA model. The shifts correlate with molecular elongation and alignment, consistent with Badger’s rule, thereby establishing a direct link between vibrational features and local stress. Infrared intensities are predicted through a symmetry-adapted dipole moment model trained on representative epoxy fragments, enabling quantitative validation of strain-dependent responses. The combined approach yields chemically accurate and computationally efficient predictions of vibrational spectra under deformation. These results identify vibrational fingerprints as predictive markers of mechanical state in polymer networks and outline a spectroscopic route to stress mapping and structural-health diagnostics in advanced materials.Publicationtype: Journal Article49 17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Network topology governs cryogenic mechanical response in isocyanate-modified epoxy networks(American Chemical Society, 2026-05-11); ; ; High-performance epoxy-based polymers are increasingly deployed in space applications, where cryogenic service conditions impose stringent demands on mechanical performance over a wide temperature range. Modification of epoxy resins is commonly employed to improve fracture toughness and to mitigate brittle behavior. In this study, isocyanate-modified epoxy networks were investigated by combining molecular dynamics simulations with dynamic mechanical thermal analysis. Structural descriptors such as radius of gyration and hydrogen-bond statistics were correlated with elastic and thermal properties to establish molecular-level structure–property relationships. The simulations reveal homogeneous chain extension for systems containing up to 20% isocyanate, whereas further addition contributes little to backbone elongation. Hydrogen bonds provide a secondary stabilization mechanism at low temperatures, but selectively disabling hydrogen bonding demonstrates that covalent network topology dominates stiffness. The β-transition is consistently identified in simulation and experiment and shifts to lower temperature upon isocyanate incorporation. The corresponding transition temperature Tβ marks a change in the dominant stiffening mechanism. Analysis of molecular fluctuations shows that below Tβ stiffness is governed primarily by network compactness, while above Tβ enhanced segmental mobility leads to accelerated softening despite hydrogen-bond formation.Publicationtype: Journal Article76 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , CNT-modified globugraphite carbon foam for hydrogen peroxide generation: structural and electrochemical characterisation(Elsevier, 2026-05-11); ; ; ; Three-dimensional (3D) porous carbon architectures offer unique advantages for electrochemical processes due to their high surface area, interconnected porosity, and intrinsic conductivity. In this study, a carbon nanotube-modified Globugraphite composite (CNT-GG) is developed to achieve efficient electrogeneration of hydrogen peroxide (H₂O₂). The composite exhibits exceptionally high porosity (98%), ultralow density (0.04–0.05 g·cm−3), and a hierarchical porous structure, providing enhanced active surface exposure and mass transport. Incorporation of carbon nanotubes (CNTs), consistent with a multi-walled structure, within the GG matrix modifies the pore architecture and promotes a more interconnected network enhancing mass transport and charge-transfer processes, thereby improving electrochemical activity. It significantly improves effective bulk conductivity (up to 662 S/m), mechanical strength as determined by higher flexural and modulus values, and slight enhancement in thermal stability. The optimized CNT-GG structure also exhibits reduced tortuosity (from 4.29 to 1.21), facilitating efficient charge-transfer pathways. Electrochemical evaluation demonstrates that CNT-GG electrodes markedly enhance the in-situ generation of H₂O₂, reaching concentrations up to 48 μmol·L−1 within 30 min while achieving a high specific H₂O₂ productivity of 2.64 μmol·cm−2·min−1. These results demonstrate that CNT modification synergistically improves porosity, conductivity, defect-rich carbon structure contributing to electrochemical activity, positioning CNT-GG as a promising electrode material for H₂O₂ electrogenaration systems.Publicationtype: Journal Article54 46 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Non-destructive testing of CFRP laminates for aerospace structures: acoustic emission and ultrasonic longitudinal wave (ULW) evaluation under Mode II loading with destructive validationCarbon Fiber Reinforced Polymer (CFRP) laminates are widely used in aerospace structures. However, understanding their damage mechanisms under Mode II loading and establishing reliable non-destructive testing (NDT) techniques remain critical challenges for structural health monitoring. This study investigates the fracture behavior and damage evolution of thin CFRP laminates with two stacking sequences, [0°/+45°/−45°]2S and [+45°/−45°/0°]2S, using End-Notched Flexure (ENF) testing combined with Acoustic Emission (AE) and Ultrasonic Longitudinal Wave (ULW) evaluation. The results show that the [0°/+45°/−45°]2S laminates exhibit higher flexural stiffness and delayed crack initiation with sudden catastrophic crack propagation, whereas the [+45°/−45°/0°]2S laminates demonstrate earlier crack initiation and more progressive crack growth during loading. The average Mode II interlaminar fracture toughness values were approximately 1.70 kJ/m² for [0°/+45°/−45°]2S, and 1.78 kJ/m² for [+45°/−45°/0°]2S, indicating that stacking sequence significantly influences delamination resistance and energy dissipation. AE signal parameters, including absolute energy, duration, and average frequency, reveal distinct damage evolution stages, while ultrasonic scanning confirms different damage distributions where [0°/+45°/−45°]2S laminates show broader delamination zones and [+45°/−45°/0°]2S laminates exhibit more localized defects. This study provides valuable insights into the structural health monitoring of aerospace composite structures and demonstrates the potential of integrated NDT systems for developing damage-detection methods for advanced lightweight composite components.Publicationtype: Journal Article71 27 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Bio-based poly(furfuryl alcohol) resin as a sustainable matrix alternative for prepregsDespite their ecological superiority and competitive thermo-mechanical performance compared to petrochemical matrices, furan resins based on poly(furfuryl alcohol) (PFA) have so far played a minor role in composite applications. This is due to a demanding manufacturing process, which involves long curing cycles and specialized equipment for removing water from polycondensation to produce low-porosity parts. This work employs resin pre-curing (B-staging) to tailor PFA bio-resin properties for prepreg applications, while reducing the porosity in a fully cured state. A PFA prepolymer with a bio-content of 98 wt% was synthesized before heat treatments were applied for B-staging and final curing of the acid-catalyzed prepreg resin. The influences on viscosity, resin reactivity and chemistry, molecular weight, volatile separation, density, and porosity were investigated. It was found that an isothermal 120-minute B-staging procedure at 60 °C resulted in rheological behavior matching the processing properties of commercial, aerospace-grade epoxy prepregs. It was demonstrated that B-staging reduces volatile separation and associated void formation in the final curing step. Fully cured PFA samples with a porosity of less than 3 % could be produced employing short curing cycles. The findings advance the understanding of sustainable lightweight materials by tailoring PFA resins as potential polymer matrices for bio-prepregs.Publicationtype: Journal Article82 26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Experimental and numerical investigation of bio-inspired CFRP structures with layer thickness gradients(Elsevier, 2026-03-15); ; ; ; Throughout evolutionary history, mineralised tissues have developed remarkable skeletal microstructures that combine exceptional damage tolerance with adaptation to challenging environmental conditions. These tissues typically feature composite architectures with spatially varying fibre orientations and layer thicknesses. This study utilises the microstructure of deep-sea sponge spicules and the cuticle of the lobster Homarus americanus as bioinspiration. Sponge spicules, found at depths between 1100 m and 2100 m, consist of radially arranged layers of hydrated silicon dioxide. Their curvature adapts to ocean currents, and analyses reveal graded layer thickness from 0.6 µm to 10 µm. Thinner layers in tensile regions enhance tensile strength due to scaling relationship with layer thickness h<sup>−1/2</sup>, while thicker layers in compressive zones improve stability and reduce buckling. Unlike this microstructure, the cuticle of Homarus americanus comprises epicuticle, exocuticle, and endocuticle, with the latter two forming helicoidal fibre architecture. In the claws, exocuticular layers are thinner, facilitating energy absorption under impact, whereas thicker endocuticular layers provide structural stabilisation through increased stiffness. Inspired by these biological systems, thin-ply carbon fibre reinforced polymer laminates were designed for out-of-plane loading conditions. A quasi-isotropic layup 45°,90°,-45°,0° was chosen to reflect amorphous nature of hydrated silica. To mimic natural gradients, layers of varying thin-ply thickness were employed within thermally balanced laminate sequence. Layer configurations were initially optimised using finite element three-point bending simulations and subsequently validated experimentally. The graded design approach resulted in improved flexural performance and reduced damage propagation under impact loading, demonstrating potential of bio-inspired layer thickness gradation for development of advanced composite structures.Publicationtype: Journal Article91 35