INMdok (Leibniz Institute for New Materials)
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Reconstruction of 3D Conductive Networks in Metal‐Filled Elastomer Composites Indicates Dominance of Contact Resistances
Full text linkConductive polymer composites (CPCs) combine the stretchability of an elastomeric matrix with the electrical conductivity of a metallic filler. The 3D structure of this filler particle network (FPN) and the contact resistances between particles above percolation, key factors in the conductivity, are not well understood. Here, we introduce 3D reconstructions of FPNs of micron‐sized spherical silver particles in polydimethylsiloxane from focused ion beam scanning electron microscopy tomography. Analysis of the tomographic images provides the length and number of parallel conductive paths. The results show that the average contact resistance drops five orders of magnitude when increasing the silver loading from to , highlighting its dominating role for macroscopic conductivity rather than network structure. This links to 33% larger average area‐equivalent diameters of the contact spots. Diffusional tortuosity, a metric that quantifies flow restriction through narrow contact spots, proves that higher contact forces decrease current flow restrictions and thus, increase overall electrical conductivity. These conclusions are verified using a segregated CPC, and it is found that the addition of of insulating fillers at a constant silver loading of increases the conductivity 37‐fold and decreases the average contact resistance by two orders of magnitude
A novel lipopolyplex platform for dual mRNA delivery via core- and surface-loading
Full text linkThe approval of Onpattro® (2018) and Comirnaty (2020) has driven interest in nanoparticulate nucleotide delivery. Newer concepts in gene therapy however, require not only the delivery of one, but multiple nucleotides. Examples are CRISPR/Cas9 gene editing and cancer immunotherapy. However, the current gold standard for nucleotide delivery – lipid nanoparticles – faces significant challenges, including limitations for co-encapsulation and nucleotide-nucleotide interactions. Aim of this study was to design a core-shell system featuring separate encapsulation of two nucleotides via a two-step formulation process. Six distinct cationic polymers were combined with three anionic polymers, resulting in 18 core compositions. Screening of these formulations identified three potent lipopolyplexes (LPPs), which were further evaluated and compared in terms of transfection efficiency, expression kinetics, storage stability, and nebulization performance. Among them, the combination of poly-L-arginine and poly-L-glutamic acid demonstrated the highest overall performance. Our systems enabled precise co-delivery of two model mRNAs in a controlled ratio, demonstrating potential for advanced therapeutic applications. Additionally, the role of mRNA localization within the LPP was investigated. Surface-loaded mRNA demonstrated superior transfection efficiency and shear resistance compared to core-loaded mRNA, which lost functionality under nebulization
Electrode engineering of metal-oxide-based materials for optimized lithium-ion batteries
Full text linkThis dissertation explores the advancements in the design and manufacturing of lithium-ion batteries (LIB), with a focus on metal oxide-based materials and techniques used to enhance their performance. It discusses the processes to boost efficiency and environmental friendliness. The primary goal is to address the challenges of metal oxide electrodes in LIBs, particularly capacity degradation at high charge/discharge rates and expanding their operating voltage range. We are confident in our ability to enhance the characteristics of these electrodes through preparation methods. Our research investigates how different mixing techniques and variables can improve the performance and durability of these electrodes. Furthermore, this thesis describes our efforts to digitize the battery manufacturing process by introducing the DigiBatMat platform, a platform for battery materials and manufacturing processes. DigiBatMat drives advancements in battery technology by optimizing LIBs through data gathering and analysis, highlighting its crucial role in this field. Ultimately, this thesis provides insights into battery electrode engineering and supports initiatives to improve energy storage technologies and advance sustainability efforts.Diese Dissertation befasst sich mit den Fortschritten bei der Entwicklung und Herstellung von Lithium-Ionen-Batterien (LIB), wobei der Schwerpunkt auf Materialien auf Metalloxidbasis und Techniken zur Verbesserung ihrer Leistung liegt. Es werden die Verfahren zur Steigerung der Effizienz und der Umweltfreundlichkeit erörtert. Das Hauptziel besteht darin, die Herausforderungen von Metalloxidelektroden in LIBs anzugehen, insbesondere die Kapazitätsverschlechterung bei hohen Lade-/Entladeraten und die Erweiterung ihres Betriebsspannungsbereichs. Wir sind zuversichtlich, dass wir die Eigenschaften dieser Elektroden durch Präparationsmethoden verbessern können. Unsere Forschung untersucht, wie verschiedene Mischtechniken und Variablen die Leistung und Haltbarkeit dieser Elektroden verbessern können. Darüber hinaus beschreibt diese Arbeit unsere Bemühungen, den Herstellungsprozess von Batterien zu digitalisieren, indem wir die DigiBatMat-Plattform einführen, eine Plattform für Batteriematerialien und Herstellungsprozesse. DigiBatMat treibt den Fortschritt in der Batterietechnologie voran, indem es die LIBs durch Datenerfassung und -analyse optimiert, was seine entscheidende Rolle in diesem Bereich hervorhebt. Letztendlich bietet diese Arbeit Einblicke in die Batterieelektrodenentwicklung und unterstützt Initiativen zur Verbesserung von Energiespeichertechnologien und zur Förderung von Nachhaltigkeitsbestrebungen
Polyelectrolyte metallopolymer particles for efficient PFAS capture and release
Full text linkIn technologies for PFAS removal, one of the biggest challenges is combining high adsorption capacity with excellent regeneration capabilities. In recent years, metallopolymer-based materials have shown promising potential in both aspects. In this work, we present two convenient ways to functionalize organic microparticles with charged, functional moieties (cobaltocenium), either through a one-pot reaction via siloxane-condensation or by straightforward ring-opening reaction of epoxides. After characterization of the novel adsorbent materials by state-of-the-art analytics to verify the successful functionalization, their performance for PFAS adsorption and regeneration was investigated. To gain insight into the adsorption mechanism, experiments were first conducted at low concentrations (20 μg L−1) and in equilibrium, showing adsorption for both materials of up to 97 % for PFOA and PFOS. Furthermore, an increase in adsorption within an ionic matrix of commercial drinking water and an adsorbent preference at different pH values was demonstrated. Analysis of the influence of the concentration indicates multilayer adsorption beyond simple ion-paring, best described by a Brunauer-Emmett-Teller mechanism. Moreover, utilizing a straightforward column setup, the total PFOA capacity is analyzed, revealing a 4–5-fold increase upon functionalization, leading to 215 mg g−1 and 296 mg g−1 PFOA adsorption. Overall, column-based adsorption experiments showed promising results at low (20 μg L−1) and medium (2.25 mg L−1) PFAS concentrations. Finally, reusability and regeneration studies further revealed an excellent desorption performance upon multiple cycles and PFAS elution of up to 88 ± 4 %
Solution structure and synaptic analyses reveal determinants of bispecific T cell engager potency
Full text linkBispecific T cell engagers (TcEs) link T cell receptors to tumor-associated antigens on cancer cells, forming cytotoxic immunological synapses (IS). Close membrane-to-membrane contact (≤13 nm) has been proposed as a key mechanism of TcE function. To investigate this and identify potential additional mechanisms, we compared four immunoglobulin G1-based (IgG1) TcE Formats (A–D) targeting CD3ε and Her2, designed to create varying intermembrane distances (A B = C > D. In a minimal system for IS formation on SLBs, TcE performance followed the trend A = B = C > D. Addition of close contact requiring CD58 costimulation revealed phospholipase C-γ activation matching cytotoxicity with A > B = C > D. Our findings suggest that when adhesion is equivalent, TcE potency is determined by two parameters: contact distance and flexibility. Both the close/far-contact formation axis and the low/high flexibility axis significantly impact TcE potency, explaining the similar potency of Format B (close contact/high flexibility) and C (far contact/low flexibility)
Hybrid System in Foil Containing Secure Identification and Temperature Sensing Units
Full text linkFlexible hybrid electronics allow for seamless integration of sensing functionalities within materials, non-conformal surfaces and products and thus can enable novel value chains. Next to new functionalities, product authenticity plays a crucial role in complex global supply chains. This holds especially true, when products are deployed in critical environments, such as the industrial or automotive sector, where product failure can be fatal. In this work, we present a secure hybrid system, which contains a custom-designed, thinned ASIC in foil, as well as two printed temperature sensing elements that are seamlessly embedded in an industrial process fabricated automotive coolant hose and an inkjet-printed unique identifier in the form of a physically unclonable function to derive the system’s authenticity. We show the results of the standalone hose-integrated temperature sensors, the bulk ASIC verification results prior to thinning and foil integration, as well as the fully assembled integrated hybrid system. The thinned ASIC in foil communication interfaces, its circuit building blocks, as well as the integrated printed components were successfully commissioned. We show the obtained temperature response as well as the unique identification by generating the challenge response pairs of the physically unclonable function over 1000 repetitions. The security circuit shows only 0.0084% of flipped bits at T = 25 °C, which makes it well suited to be used as physically unclonable function
Mechanical property measurements enabled by short-term Fourier-transform of atomic force microscopy thermal deflection analysis
Full text linkContact resonance atomic force microscopy (CR-AFM) has been used in many studies to characterize variations in the elastic and viscoelastic constants of materials along a heterogeneous surface. In almost all experimental work, the quantitative modulus of the surface is calculated in reference to a known reference material, rather than calculated directly from the dynamics models of the cantilever. We measured the cantilever displacement with very high sampling frequencies over the course of the experiment and captured its oscillations that result from thermal energy. Using short-term Fourier transformations, it was possible to fit the thermal resonance peak of the normal displacement to track the frequency and Q-factor of the cantilever during an experiment, using a similar process to that used to calibrate the normal bending stiffness of cantilevers. With this quantitative data, we have used the dynamic mechanics models relating the contact stiffness of the tip/cantilever pressing into a surface with the oscillation frequency of the cantilever and show that they did not accurately model the experiment. Several material combinations of tip and sample were examined; tip size and cantilever stiffness demonstrate that existing models cannot capture the physics of this problem. While concrete solutions to use analytical models to interpret CR-AFM data have not been found, a possible solution may include revisiting the analytical model to capture a potentially more complex system than the current model, improved matching the cantilever/sample stiffness to obtain a larger variation in contact stiffness with frequency, or investigating the use of higher-order modes that may achieve this improved match
Elucidating Structural Disorder in a Polymeric Layered Material: The Case of Sodium Poly(heptazine imide) Photocatalyst
Full text linkStructurally heterogeneous materials present major challenges for characterization due to their complex nanoscale order. Sodium poly(heptazine imide) (NaPHI), a layered carbon nitride photocatalyst, exemplifies this complexity, with its precise structure remaining unresolved. Here, we uncover new structural insights into NaPHI using energy-filtered four-dimensional scanning transmission electron microscopy combined with machine-learning-based diffraction image segmentation, supported by transmission electron microscopy, atomic force microscopy, X-ray diffraction, and Raman spectroscopy. At the mesoscale, NaPHI flakes display bent morphologies, while nanodiffraction patterns reveal features characteristic of stacking disorder. Based on these insights, we modeled a NaPHI-layered structure incorporating out-of-plane undulations (waves) with amplitudes of ∼0.5 Å and wavelengths of 2–3 nm. This model reproduces the observed line features in nanodiffraction patterns and agrees with powder X-ray diffraction data, thereby bridging local and bulk structural information. The introduced approach uses data-driven machine learning to identify statistically significant features, offering a robust framework for structural analysis of semi-crystalline materials
Emotional time lengthening carries over to subsequent neutral events
Full text linkThe perceived time can shrink or expand for emotional stimuli. Converging evidence suggests that emotional time distortions are rooted in the emotional states of the timing agents because emotional stimuli can influence the timing of simultaneous neutral events. As emotional states are transitory, we investigated if time modulating emotional states also influence timing of subsequent neutral events. In each trial, we induced different valence and arousal levels by using affective vibrotactile patterns before participants judged the duration of neutral auditory tones. Compared to neutral patterns, affective patterns modulated participants’ time perception of the subsequent tones. We observed an interaction between arousal and valence: Pleasant-Low arousal patterns expanded the timing of subsequent neutral events more than Unpleasant-Low arousal patterns while Pleasant and Unpleasant-High arousal led to a similar temporal expansion. Our results indicate time modulating effects of emotional stimuli are due to changed emotional states and influence time perception likely until the underlying state decays
Hybrid Ultrathin Gold Nanowire Gels: Formation and Mechanical Properties
Full text linkThis report is about the chemical formation of gels from ultrathin gold nanowires (AuNWs) and the gels’ properties. An excess of triphenylphosphine (PPh3) initiated the gelation of AuNWs with core diameters below 2 nm and an oleylamine (OAm) ligand shell dispersed in cyclohexane. The ligand exchange of OAm by PPh3 changes the AuNW-solvent interactions and leads to phase separation of the solvent to form a macroscopic gel. Small angle X-ray scattering and transmission electron microscopy indicate that hexagonal bundles in the original dispersion are dispersed, and the released nanowires entangle. Rheological analyses indicate that the resulting gel is stabilized both by physical entanglement and crosslinking of AuNWs by Van der Waals and π–π interactions. Chemically formed AuNW gels have solid-like properties and crosslinks that distinguish them from highly concentrated non-crosslinked AuNW dispersions. The AuNW gel properties can be tuned via the Au:PPh3 ratio, where smaller ratios led to stiffer gels with higher storage moduli