INMdok (Leibniz Institute for New Materials)
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Annual report 2020 / Leibniz Institute for New Materials
Get PDFVorwort:
Hinter uns liegt ein schwieriges Jahr, das mit seinen Einschränkungen die Arbeit an unserem Institut wesentlich beeinflusst hat. Umso mehr haben wir uns über das Verständnis, die Disziplin und die Resilienz unserer Mitarbeiterinnen und Mitarbeiter gefreut, die 2020 trotz allem zu einem erfolgreichen Jahr für das INM gemacht haben.
Eine besondere Premiere war für uns die Bewilligung des Leibniz-WissenschaftsCampus "Living Therapeutic Materials", der zum 1. Juli seine Arbeit aufnahm. Mit ihm verstärken wir gezielt unsere Arbeiten im biologisch-medizinischen Bereich und vertiefen die Kooperation am Campus der Universität des Saarlandes.
Auch junge Forscherinnen und Forscher konnten in diesem Jahr wieder punkten. Der Dissertationspreis der Leibniz-Gemeinschaft ging erneut an das INM: Der Dr. Pattarachai Srimuk wurde für seine Arbeit zur Wasserentsalzung ausgezeichnet, für die er außerdem den UMSICHT-Wissenschaftspreis erhielt. Den ersten Starting Grant des European Research Council für das INM konnte Frau Dr. Lola González-García einwerben. Sie leitet ab Januar 2021 eine neue Juniorforschungsgruppe Elektrofluide. Und schließlich belegen Humboldt-Stipendien an Frau Dr. Xuan Zhang und Frau Dr. Gülistan Kocer die ungebrochene Attraktivität des INM für hochqualifizierte internationale Kolleginnen und Kollegen.
Eine neue Juniorforschungsgruppe finden Sie bereits in diesem Bericht: Seit Januar 2020 verstärkt die Gruppe Bioprogrammierbare Materialien unter der Leitung von Herrn Dr. Shrikrishnan Sankaran unsere Forschung.
Wir wünschen Ihnen viel Spaß dabei, auf den folgenden Seiten noch mehr Neues und Spannendes zu entdecken, und freuen uns, wenn Sie uns auch in Zukunft gewogen bleibe
Graphene Acid for Lithium-Ion Batteries—Carboxylation Boosts Storage Capacity in Graphene
Get PDFEnvironmentally sustainable, low-cost, flexible, and lightweight energy storage technologies require advancement in materials design in order to obtain more efficient organic metal-ion batteries. Synthetically tailored organic molecules, which react reversibly with lithium, may address the need for cost-effective and eco-friendly anodes used for organic/lithium battery technologies. Among them, carboxylic group-bearing molecules act as high-energy content anodes. Although organic molecules offer rich chemistry, allowing a high content of carboxyl groups to be installed on aromatic rings, they suffer from low conductivity and leakage to the electrolytes, which restricts their actual capacity, the charging/discharging rate, and eventually their application potential. Here, a densely carboxylated but conducting graphene derivative (graphene acid (GA)) is designed to circumvent these critical limitations, enabling effective operation without compromising the mechanical or chemical stability of the electrode. Experiments including operando Raman measurements and theoretical calculations reveal the excellent charge transport, redox activity, and lithium intercalation properties of the GA anode at the single-layer level, outperforming all reported organic anodes, including commercial monolayer graphene and graphene nanoplatelets. The practical capacity and rate capability of 800 mAh g−1 at 0.05 A g−1 and 174 mAh g−1 at 2.0 A g−1 demonstrate the true potential of GA anodes in advanced lithium-ion batteries
Supra-Molecular Assemblies of ORAI1 at Rest Precede Local Accumulation into Puncta after Activation
Get PDFThe Ca2+ selective channel ORAI1 and endoplasmic reticulum (ER)-resident STIM proteins form the core of the channel complex mediating store operated Ca2+ entry (SOCE). Using liquid phase electron microscopy (LPEM), the distribution of ORAI1 proteins was examined at rest and after SOCE-activation at nanoscale resolution. The analysis of over seven hundred thousand ORAI1 positions revealed a number of ORAI1 channels had formed STIM-independent distinct supra-molecular clusters. Upon SOCE activation and in the presence of STIM proteins, a fraction of ORAI1 assembled in micron-sized two-dimensional structures, such as the known puncta at the ER plasma membrane contact zones, but also in divergent structures such as strands, and ring-like shapes. Our results thus question the hypothesis that stochastically migrating single ORAI1 channels are trapped at regions containing activated STIM, and we propose instead that supra-molecular ORAI1 clusters fulfill an amplifying function for creating dense ORAI1 accumulations upon SOCE-activation
Bioinspired Underwater Adhesion to Rough Substrates by Cavity Collapse of Cupped Microstructures
Get PDFUnderwater or wet adhesion is highly desirable for numerous applications but is counteracted by the liquids in the contact which weaken intermolecular attraction. The problem is exacerbated in conjunction with surface roughness when liquids partially remain in grooves or dimples of the substrate. In the present study, a cupped microstructure with a cavity inspired by suction organs of aquatic animals is proposed. The microstructures (cup radius of 100 µm) are made from polyurethane using two-photon lithography followed by replica molding. Adhesion to rough substrates is emulated experimentally by a micropatterned model substrate with varying channel widths. Pull-off stresses are found to be about 200 kPa, i.e., twice atmospheric pressure. Evaluation of force–displacement curves together with in situ observations reveal the adhesion mechanism, which involves adaptation to surface roughness and an elastic force induced by the collapse of the cavity that holds sealed contact with the substrate during retraction. This new microarchitecture may pave the way for next generation microstructures applicable to real, rough surfaces under wet conditions
Functional surface microstructures inspired by nature – from adhesion and wetting principles to sustainable new devices
Get PDFIn the course of evolution nature has arrived at startling materials solutions to ensure survival. Investigations into biological surfaces, ranging from plants, insects and geckos to aquatic animals, have inspired the design of intricate surface patterns to create useful functionalities. This paper reviews the fundamental interaction mechanisms of such micropatterns with liquids, solids, and soft matter such as skin for control of wetting, self-cleaning, anti-fouling, adhesion, skin adherence, and sensing. Compared to conventional chemical strategies, the paradigm of micropatterning enables solutions with superior resource efficiency and sustainability. Associated applications range from water management and robotics to future health monitoring devices. We finally provide an overview of the relevant patterning methods as an appendix
Comparative Transcriptomics of Lowland Rice Varieties Uncovers Novel Candidate Genes for Adaptive Iron Excess Tolerance
Get PDFIron (Fe) toxicity is a major challenge for plant cultivation in acidic waterlogged soil environments, where lowland rice is a major staple food crop. Only few studies have addressed the molecular characterization of excess Fe tolerance in rice, and these highlight different mechanisms for Fe tolerance. Out of 16 lowland rice varieties, we identified a pair of contrasting lines, Fe-tolerant Lachit and -susceptible Hacha. The two lines differed in their physiological and morphological responses to excess Fe, including leaf growth, leaf rolling, reactive oxygen species generation and Fe and metal contents. These responses were likely due to genetic origin as they were mirrored by differential gene expression patterns, obtained through RNA sequencing, and corresponding gene ontology term enrichment in tolerant vs. susceptible lines. Thirty-five genes of the metal homeostasis category, mainly root expressed, showed differential transcriptomic profiles suggestive of an induced tolerance mechanism. Twenty-two out of these 35 metal homeostasis genes were present in selection sweep genomic regions, in breeding signatures, and/or differentiated during rice domestication. These findings suggest that Fe excess tolerance is an important trait in the domestication of lowland rice, and the identified genes may further serve to design the targeted Fe tolerance breeding of rice crops
The influence of vimentin on actin dynamics and force generation in RPE1 cells
Get PDFThe cytoskeleton is a network of filaments in cells, it consists of actin filaments, intermediate filaments and microtubules. It is very dynamic and plays a key role in many biological processes such as cell migration and cell division. Actin stress fibers are involved in force generation, cell retraction and cell protrusion during migration. The polymerization and depolymerization of actin filaments regulate cell migration and are influenced by the activity of actin binding proteins. Even though no motor molecules bind to vimentin, and it does not generate forces, its role is important in the regulation of cell migration. To better understand the mechanism of cell migration, it is important to understand how cytoskeleton filaments interplay. Therefore, understanding the role of vimentin on actin dynamics, and its implication in actin force generation are the two main interests of my Ph.D. thesis. I first measure actin dynamics in vimentin depleted cells using fluorescence recovery after photobleaching. I show that silencing of vimentin expression slows down actin dynamics but does not affect the fraction of actin monomers that participate. In addition, I show that plectin as a vimentin-actin cross-linker protein does not have the same effect. Finally, I study actin force generation using traction force microscopy. I show that silencing of vimentin disarranges the distribution of traction forces and adhesion sites but does not impact the magnitude of traction forces
Oscillatory Microrheology, Creep Compliance and Stress Relaxation of Biological Cells Reveal Strong Correlations as Probed by Atomic Force Microscopy
Get PDFThe mechanical properties of cells are important for many biological processes, including wound healing, cancers, and embryogenesis. Currently, our understanding of cell mechanical properties remains incomplete. Different techniques have been used to probe different aspects of the mechanical properties of cells, among them microplate rheology, optical tweezers, micropipette aspiration, and magnetic twisting cytometry. These techniques have given rise to different theoretical descriptions, reaching from simple Kelvin-Voigt or Maxwell models to fractional such as power law models, and their combinations. Atomic force microscopy (AFM) is a flexible technique that enables global and local probing of adherent cells. Here, using an AFM, we indented single retinal pigmented epithelium cells adhering to the bottom of a culture dish. The indentation was performed at two locations: above the nucleus, and towards the periphery of the cell. We applied creep compliance, stress relaxation, and oscillatory rheological tests to wild type and drug modified cells. Considering known fractional and semi-fractional descriptions, we found the extracted parameters to correlate. Moreover, the Young’s modulus as obtained from the initial indentation strongly correlated with all of the parameters from the applied power-law descriptions. Our study shows that the results from different rheological tests are directly comparable. This can be used in the future, for example, to reduce the number of measurements in planned experiments. Apparently, under these experimental conditions, the cells possess a limited number of degrees of freedom as their rheological properties change
Emerging Biofabrication Techniques: A Review on Natural Polymers for Biomedical Applications
Get PDFNatural polymers have been widely used for biomedical applications in recent decades. They offer the advantages of resembling the extracellular matrix of native tissues and retaining biochemical cues and properties necessary to enhance their biocompatibility, so they usually improve the cellular attachment and behavior and avoid immunological reactions. Moreover, they offer a rapid degradability through natural enzymatic or chemical processes. However, natural polymers present poor mechanical strength, which frequently makes the manipulation processes difficult. Recent advances in biofabrication, 3D printing, microfluidics, and cell-electrospinning allow the manufacturing of complex natural polymer matrixes with biophysical and structural properties similar to those of the extracellular matrix. In addition, these techniques offer the possibility of incorporating different cell lines into the fabrication process, a revolutionary strategy broadly explored in recent years to produce cell-laden scaffolds that can better mimic the properties of functional tissues. In this review, the use of 3D printing, microfluidics, and electrospinning approaches has been extensively investigated for the biofabrication of naturally derived polymer scaffolds with encapsulated cells intended for biomedical applications (e.g., cell therapies, bone and dental grafts, cardiovascular or musculoskeletal tissue regeneration, and wound healing
Stabilization of ultrathin nanowires by self-assembly into bundles
Get PDFThe relative tendency of freely dispersed and bundled gold nanowires to break up along their length by the Rayleigh–Plateau instability is investigated both experimentally and theoretically. Small angle X-ray scattering, in combination with transmission electron microscopy, reveal that the bundling of nanowires can enhance their stability. The experimental observation is rationalized by a linear perturbation analysis of a representative unit cell of bundled wires. A stability map is constructed for a bundle of nanowires to display the sensitivity of the Rayleigh–Plateau instability to the number and size of contacts with nearest neighbors per nanowire, and to the ratio of interfacial energy to surface energy. Stabilisation is enhanced by allowing the bundle of wires to sinter freely: a criterion for this kinetically-based stabilisation is given in terms of the ratio of pinch-off time for the instability to the sintering time to form the necks between nanowires