INMdok (Leibniz Institute for New Materials)
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Surface polarization, field homogeneity, and dielectric breakdown in ordered and disordered nanodielectrics based on gold–polystyrene superlattices
Get PDFHybrid dielectrics were prepared from dispersions of nanoparticles with gold cores (diameters from 2.9 nm to 8.2 nm) and covalently bound thiol-terminated polystyrene shells (5000 Da and 11 000 Da) in toluene. Their microstructure was investigated with small angle X-ray scattering and transmission electron microscopy. The particles arranged in nanodielectric layers with either face-centered cubic or random packing, depending on the ligand length and core diameter. Thin film capacitors were prepared by spin-coating inks on silicon substrates, contacted with sputtered aluminum electrodes, and characterized with impedance spectroscopy between 1 Hz and 1 MHz. The dielectric constants were dominated by polarization at the gold–polystyrene interfaces that we could precisely tune via the core diameter. There was no difference in the dielectric constant between random and supercrystalline particle packings, but the dielectric losses depended on the layer structure. A model that combines Maxwell–Wagner–Sillars theory and percolation theory described the relationship of the specific interfacial area and the dielectric constant quantitatively. The electric breakdown of the nanodielectric layers sensitively depended on particle packing. A highest breakdown field strength of 158.7 MV m−1 was found for the sample with 8.2 nm cores and short ligands that had a face-centered cubic structure. Breakdown apparently is initiated at the microscopic maxima of the electric field that depends on particle packing. The relevance of the results for industrially produced devices was demonstrated on inkjet printed thin film capacitors with an area of 0.79 mm2 on aluminum coated PET foils that retained their capacity of 1.24 ± 0.01 nF@10 kHz during 3000 bending cycles
Reversibly growing crosslinked polymers with programmable sizes and properties
Get PDFGrowth constitutes a powerful method to post-modulate materials’ structures and functions without compromising their mechanical performance for sustainable use, but the process is irreversible. To address this issue, we here report a growing-degrowing strategy that enables thermosetting materials to either absorb or release components for continuously changing their sizes, shapes, compositions, and a set of properties simultaneously. The strategy is based on the monomer-polymer equilibrium of networks in which supplying or removing small polymerizable components would drive the networks toward expansion or contraction. Using acid-catalyzed equilibration of siloxane as an example, we demonstrate that the size and mechanical properties of the resulting silicone materials can be significantly or finely tuned in both directions of growth and decomposition. The equilibration can be turned off to yield stable products or reactivated again. During the degrowing-growing circle, material structures are selectively varied either uniformly or heterogeneously, by the availability of fillers. Our strategy endows the materials with many appealing capabilities including environment adaptivity, self-healing, and switchability of surface morphologies, shapes, and optical properties. Since monomer-polymer equilibration exists in many polymers, we envision the expansion of the presented strategy to various systems for many applications
Bifunctional Carbanionic Synthesis of Fully Bio-Based Triblock Structures Derived from β-Farnesene and ll-Dilactide: Thermoplastic Elastomers
Get PDFCurrent environmental challenges and the shrinking fossil-fuel feedstock are important criteria for the next generation of polymer materials. In this context, we present a fully bio-based material, which shows promise as a thermoplastic elastomer (TPE). Due to the use of β-farnesene and L-lactide as monomers, bio-based feedstocks, namely sugar cane and corn, can be used. A bifunctional initiator for the carbanionic polymerization was employed, to permit an efficient synthesis of ABA-type block structures. In addition, the “green” solvent MTBE (methyl tert-butyl ether) was used for the anionic polymerisation, enabling excellent solubility of the bifunctional anionic initiator. This afforded low dispersity (Đ=1.07 to 1.10) and telechelic polyfarnesene macroinitiators. These were employed for lactide polymerization to obtain H-shaped triblock copolymers. TEM and SAXS revealed clearly phase-separated morphologies, and tensile tests demonstrated elastic mechanical properties. The materials featured two glass transition temperatures, at - 66 °C and 51 °C as well as gyroid or cylindrical morphologies, resulting in soft elastic materials at room temperature
Relaxation times of ionic liquids under electrochemical conditions probed by friction force microscopy
Get PDFIonic liquids (ILs) represent an important class of liquids considered for a broad range of applications such as lubrication, catalysis, or as electrolytes in batteries. It is well-known that in the case of charged surfaces, ILs form a pronounced layer structure that can be easily triggered by an externally applied electrode potential. Information about the time required to form a stable interface under varying electrode potentials is of utmost importance in many applications. For the first time, probing of relaxation times of ILs by friction force microscopy is demonstrated. The friction force is extremely sensitive to even subtle changes in the interfacial configuration of ILs. Various relaxation processes with different time scales are observed. A significant difference dependent on the direction of switching the applied potential, i.e., from a more cation-rich to a more anion-rich interface or vice versa, is found. Furthermore, variations in height immediately after the potential step and the presence of trace amounts of water are discussed as well
Evolutionary design of explainable algorithms for biomedical image segmentation
Get PDFAn unresolved issue in contemporary biomedicine is the overwhelming
number and diversity of complex images that require annotation, analysis and interpretation. Recent advances in Deep Learning have revolutionized the field of computer vision, creating algorithms that compete with human experts in image segmentation tasks. However, these frameworks require large human-annotated datasets for training and the resulting “black box” models are difficult to interpret. In this study, we introduce Kartezio, a modular Cartesian Genetic Programming-based computational strategy that generates fully transparent and easily interpretable image processing pipelines by iteratively assembling and parameterizing computer vision functions. The pipelines thus generated exhibit comparable precision to state-of-the-art Deep Learning approaches on instance segmentation tasks, while requiring drastically smaller training datasets. This Few-Shot Learning method confers tremendous flexibility, speed, and functionality to this approach. We then deploy Kartezio to solve a series of semantic and instance segmentation problems, and demonstrate its utility across diverse images ranging from multiplexed tissue histo-pathology images to high resolution microscopy images. While the flexibility, robustness and practical utility of Kartezio make this fully explicable evolutionary designer a potential game-changer in the field of biomedical image processing, Kartezio remains complementary and potentially auxiliary to mainstream Deep Learning approaches
Self-Healing Iron Oxide Polyelectrolyte Nanocomposites: Influence of Particle Agglomeration and Water on Mechanical Properties
Get PDFSelf-healing nanocomposites can be generated by organic functionalization of inorganic nanoparticles and complementary functionalization of the polymer matrix, allowing reversible interactions between the two components. Here, we report on self-healing nanocomposites based on ionic interactions between anionic copolymers consisting of di(ethylene glycol) methyl ether methacrylate, sodium 4-(methacryloyloxy)butan-1-sulfonate, and cationically functionalized iron oxide nanoparticles. The materials exhibited hygroscopic behavior. At water contents 85%) at higher particle contents
Abschlussbericht zum Forschungsprojekt PLASIOBIO : Plasmonenresonanz für Sicherheitsmerkmale, integrierte Optik und Biophotonik ; gefördert vom Bundesministerium für Bildung und Forschung im Rahmen der Fördermaßnahme Wissenschaftliche Vorprojekte (WiVoPro) : Photonik und Quantentechnologien
Get PDFEin am INM entwickeltes Verfahren zur lichtinduzierten Silberabscheidung sollte verwendet werden, um Mikro- und Submikrostrukturen mit optischer Funtionalität für photonische Bauelemente herzustellen. Unter Ausnutzung von Effekten der Oberflächenplasmonenresonanz sollten dabei insbesondere diffraktive Elemente und Wellenleiter gezeigt werden, um daraus eine Plattform für unterschiedliche Anwendungen, wie z.B. optische Sicherheitsmerkmale, aber auch integrierte Optik oder Biosensoren zu entwickeln. Das erwähnte Verfahren beruht auf der durch UV-Licht initiierten Zersetzung eines gelösten Silberkomplexes an einer mit photokatalytischen Anatas-Nanopartikeln belegten Oberfläche. Hierdurch wird unlösliches elementares Silber freigesetzt, das sich am Ort der Belichtung niederschlägt. Diese Silberabscheidung erfolgt zunächst in Form kolloidaler Silbernanopartikel, die mit zunehmender Belichtungsdosis zu leitfähigen Silberflächen zusammenwachsen können. Durch örtliche Modulation der Lichtverteilung kann die Verteilung des Silbers auf der photokatalytischen Grenzfläche mit beugungsbegrenzter Auflösung strukturiert werden. In diesem Vorhaben sollte primär der kolloidale Zustand genutzt werden. Edelmetallkolloide zeigen eine charakteristische Oberflächenplasmonenresonanz, die sich sowohl in einer starken Absorption und Lichtstreuung bei der Resonanzfrequenz als auch in einer Änderung des Brechungsindex des aus kolloidalen Partikeln und der umgebebenden Matrix bestehenden Kompositmaterials äußert. Die durch Strukturierung der Silberverteilung erreichte örtliche Modulation der optischen Materialeigenschaften sollte demnach die Erzeugung photonischer Bauelemente wie z.B. optischer Beugungsgitter erlauben. Da die Änderung des Brechungsindex auch Frequenzbereiche fernab der eigentlichen Resonanzfrequenz betrifft, in denen die durch die Resonanz bedingte Absorption gering ist, sollten auch indexgeführte planare Welleneleiter ("photonische Wellenleiter") auf diesem Weg möglich werden. Zudem sollte die Option, auch strukturierte leitfähige Flächen herzustellen, die Integration mit plasmonischen Wellenleitern erlauben. Das Ziel dieses Vorhabens bestand in der Realisierung der oben skiziierten Möglichkeiten, um die Grundlagen einer neuen Technologieplattform zur Herstellung photonischer Bauelemente zu schaffen. Neben kolloidbasierten Beugungsgittern sollten auch photonische und plasmonische Wellenleiter gezeigt werden und auf dieser Basis Prototypen einzelner anwendungsbezogener Devices hergestellt werden
Light-regulated pro-angiogenic engineered living materials
Get PDFThe role of growth factors is important to stimulate regenerative cellular changes to rejuvenate damaged cells, tissues, and organs. Growth factor engineering and delivery systems are developed quite a lot for example, emergence of small protein like chains (peptidomimetics) and matrices for controlled release of growth factors. Despite these advancements, the use of growth factors in regenerative medicine is limited because of their low stability. In this thesis, angiogenesis inducing Engineered Living Materials (ELMs) are used as the strategy to overcome the limitations associated with traditional GF delivery methods. These ELMs contain living bacteria programmed to synthesize angiogenic protein in response to light. This thesis describes challenges and successes in developing light regulated Engineered Living Material that releases angiogenic protein. The bacteria were ontogenetically engineered to synthesize and secrete a Vascular Endothelial Growth Factor (VEGF) mimetic peptide (QK) attached to a Collagen Binding Domain (CBD). To create an ELM, the engineered bacteria were safely encapsulated in a bilayer hydrogel designed to help aid survival and to prevent bacterial escape from the material. It is proven that in-situ control over production of pro-angiogenic protein can be attained with light. Secreted protein can bind to collagen and promote endothelial cell network formation which is a hallmark of angiogenesis. These results highlight the potential of this light inducible ELM to support vascularization in endothelial cells.Wachstumsfaktoren spielen eine wichtige Rolle bei der Stimulierung regenerativer zellulärer Veränderungen zur Verjüngung geschädigter Zellen, Gewebe und Organe. Die Entwicklung von Systemen zur Herstellung und Verabreichung von Wachstumsfaktoren ist weit fortgeschritten, z. B. die Entwicklung von kleinen proteinhaltigen Ketten (Peptidomimetika) und Matrizen zur kontrollierten Freisetzung von Wachstumsfaktoren. Trotz dieser Fortschritte ist die Regenerationsfähigkeit von Wachstumsfaktoren aufgrund ihrer geringen Stabilität im menschlichen Körper und der Notwendigkeit, ihre lokale Konzentration sorgfältig zu regulieren, um schädliche Auswirkungen zu vermeiden, begrenzt. In dieser Arbeit werden Angiogenese-induzierende lebende Materialien (ELMs) als Strategie zur Überwindung der mit den herkömmlichen GF-Verabreichungsmethoden verbundenen Einschränkungen verwendet. Diese ELMs enthalten lebende Bakterien, die darauf programmiert sind, als Reaktion auf Licht angiogenes Protein zu synthetisieren. In dieser Arbeit werden die Herausforderungen und Erfolge bei der Entwicklung eines ELMs beschrieben, das ein Angiogenese-induzierendes Protein auf lichtregulierte Weise freisetzt. Die Bakterien wurden ontogenetisch so verändert, dass sie ein mimetisches Peptid (QK) des vaskulären endothelialen Wachstumsfaktors (VEGF) synthetisieren und absondern, das an eine kollagenbindende Domäne (CBD) gebunden ist. Um ein ELM herzustellen, wurden die manipulierten Bakterien sicher in einem zweischichtigen Hydrogel eingekapselt, das das Überleben der Bakterien unterstützt und ihr Entweichen aus dem Material verhindert. Es wurde gezeigt, dass das Freisetzungsprofil des pro-angiogenen Proteins in-situ mit Hilfe von Licht gesteuert werden kann. Das sezernierte Protein kann an Kollagen binden und die Endothel
Antibodies generated in vitro and in vivo elucidate design of a thermostable ADDomer COVID-19 nasal nanoparticle vaccine
No full textAbstractCOVID-19 continues to damage populations, communities and economies worldwide. Vaccines have reduced COVID-19-related hospitalisations and deaths, primarily in developed countries. Persisting infection rates, and highly transmissible SARS-CoV-2 Variants of Concern (VOCs) causing repeat and breakthrough infections, underscore the ongoing need for new treatments to achieve a global solution. Based on ADDomer, a self-assembling protein nanoparticle scaffold, we created ADDoCoV, a thermostable COVID-19 candidate vaccine displaying multiple copies of a SARS-CoV-2 receptor binding motif (RBM)-derived epitope.In vitrogenerated neutralising nanobodies combined with molecular dynamics (MD) simulations and electron cryo-microscopy (cryo-EM) established authenticity and accessibility of the epitopes displayed. A Gigabody comprising multimerized nanobodies prevented SARS-CoV-2 virion attachment with picomolar EC50. Antibodies generated by immunising mice cross-reacted with VOCs including Delta and Omicron. Our study elucidates nasal administration of ADDomer-based nanoparticles for active and passive immunisation against SARS-CoV-2 and provides a blueprint for designing nanoparticle reagents to combat respiratory viral infections
SEC14-GOLD protein PATELLIN2 binds IRON-REGULATED TRANSPORTER1 linking root iron uptake to vitamin E
Get PDFOrganisms require micronutrients, and Arabidopsis (Arabidopsis thaliana) IRON-REGULATED TRANSPORTER1 (IRT1) is essential for iron (Fe2+) acquisition into root cells. Uptake of reactive Fe2+ exposes cells to the risk of membrane lipid peroxidation. Surprisingly little is known about how this is avoided. IRT1 activity is controlled by an intracellular variable region (IRT1vr) that acts as a regulatory protein interaction platform. Here, we describe that IRT1vr interacted with peripheral plasma membrane SEC14-Golgi dynamics (SEC14-GOLD) protein PATELLIN2 (PATL2). SEC14 proteins bind lipophilic substrates and transport or present them at the membrane. To date, no direct roles have been attributed to SEC14 proteins in Fe import. PATL2 affected root Fe acquisition responses, interacted with ROS response proteins in roots, and alleviated root lipid peroxidation. PATL2 had high affinity in vitro for the major lipophilic antioxidant vitamin E compound α-tocopherol. Molecular dynamics simulations provided insight into energetic constraints and the orientation and stability of the PATL2-ligand interaction in atomic detail. Hence, this work highlights a compelling mechanism connecting vitamin E with root metal ion transport at the plasma membrane with the participation of an IRT1-interacting and α-tocopherol-binding SEC14 protein