Nanoscale building blocks of many materials exhibit extraordinary mechanical properties due to their defect-free molecular structure. Translation of these high mechanical properties to macroscopic ...materials represents a difficult materials engineering challenge due to the necessity to organize these building blocks into multiscale patterns and mitigate defects emerging at larger scales. Cellulose nanofibrils (CNFs), the most abundant structural element in living systems, has impressively high strength and stiffness, but natural or artificial cellulose composites are 3–15 times weaker than the CNFs. Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment. Efficient stress transfer from macroscale to individual CNF due to cross-linking and high degree of order enables their Young’s modulus to reach up to 86 GPa and a tensile strength of 1.57 GPa, exceeding the mechanical properties of known natural or synthetic biopolymeric materials. The specific strength of our CNF fibers engineered at multiscale also exceeds that of metals, alloys, and glass fibers, enhancing the potential of sustainable lightweight high-performance materials with multiscale self-organization.
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IJS, KILJ, NUK, PNG, UL, UM
Reticulate ridges of reefs and sediment in Holocene lagoons are usually interpreted as an inheritance of antecedent karst topography. Satellite imagery served as a template for integrating plan‐view ...geometry with published data from coring, drilling and seismic surveys to test the antecedent‐karst hypothesis. The link between karst morphology and overlying reef patterns can be demonstrated convincingly for a rather limited number of examples, particularly those on a substrate of tower karst with high relief. On very young limestones, doline karst with reticulate patterns develops very slowly because of the high porosity. Moreover, karst control can be ruled out for the significant number of reticulate reefs that are founded on terrigenous sediment or on demonstrably flat pre‐Holocene rock surfaces. One likely cause of reticulate patterns is biotic self‐organization that has been shown to generate reticulate and labyrinthic patterns of mussel beds on tidal flats and tree cover of arid ecosystems. Another pathway to reticulate reefs may be the colonization of reticulate hydrodynamic bedforms by reef builders. Thus, reticulate patterns of Holocene reef‐sediment ridges are highly ambiguous indicators of antecedent karst.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Maintaining the performance of infrastructure‐dependent systems in the face of surprises and unknowable risks is a grand challenge. Addressing this issue requires a better understanding of enabling ...conditions or principles that promote system resilience in a universal way. In this study, a set of such principles is interpreted as a group of interrelated conditions or organizational qualities that, taken together, engender system resilience. The field of resilience engineering identifies basic system or organizational qualities (e.g., abilities for learning) that are associated with enhanced general resilience and has packaged them into a set of principles that should be fostered. However, supporting conditions that give rise to such first‐order system qualities remain elusive in the field. An integrative understanding of how such conditions co‐occur and fit together to bring about resilience, therefore, has been less clear. This article contributes to addressing this gap by identifying a potentially more comprehensive set of principles for building general resilience in infrastructure‐dependent systems. In approaching this aim, we organize scattered notions from across the literature. To reflect the partly self‐organizing nature of infrastructure‐dependent systems, we compare and synthesize two lines of research on resilience: resilience engineering and social‐ecological system resilience. Although some of the principles discussed within the two fields overlap, there are some nuanced differences. By comparing and synthesizing the knowledge developed in them, we recommend an updated set of resilience‐enhancing principles for infrastructure‐dependent systems. In addition to proposing an expanded list of principles, we illustrate how these principles can co‐occur and their interdependencies.
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BFBNIB, FSPLJ, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Acoustic levitation, which allows contactless manipulation of micro‐objects with ultrasounds, is a promising technique for spheroids formation and culture. This acoustofluidic technique favors ...cell–cell interactions, away from the walls of the chip, which leads to the spontaneous self‐organization of cells. Using this approach, we generated spheroids of mesenchymal stromal cells, hepatic and endothelial cells, and showed that long‐term culture of cells in acoustic levitation is feasible. We also demonstrated that this self‐organization and its dynamics depended weakly on the acoustic parameters but were strongly dependent on the levitated cell type. Moreover, spheroid organization was modified by actin cytoskeleton inhibitors or calcium‐mediated interaction inhibitors. Our results confirmed that acoustic levitation is a rising technique for fundamental research and biotechnological industrial application in the rapidly growing field of microphysiological systems. It allowed easily obtaining spheroids of specific and predictable shape and size, which could be cultivated over several days, without requiring hydrogels or extracellular matrix.
Formation of spheroids in acoustic levitation depends weakly on the acoustic and strongly on cell–cell interactions. The dynamic of self‐organization is cell‐type dependent. Spheroids formed and cultivated in this manner for several days are viable. Cytoskeletal and cell–cell adhesion inhibitors can disrupt self‐organization. Created with Biorender.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Designing complex local properties that seamlessly integrate efficient functions into processed materials presents a formidable challenge. A promising solution has emerged in the form of ultrafast ...laser‐surface structuring. Through time‐controlled polarization ultrafast irradiation at the picosecond timescale, spontaneous self‐organization of surfaces can be induced. The thermal gradient length scale unfolds on the micro‐ and nanoscale, instigating thermoconvection that leads to structured surfaces upon quenching. Convective instabilities dynamically shape intricate yet self‐regulated periodic relief structures. The ability to achieve laser‐induced self‐organization in both surface dimensions holds immense scientific importance, as it unlocks the potential to create uniform periodic 2D patterns by harnessing the inherent regulation of nonlinear dynamics processes in fluids. This comprehensive review explores recent advances in understanding and leveraging ultrafast laser‐induced self‐organization for precise patterning across versatile scales and applications. The insights herein hold the potential to drive significant advancements in nanoscale manufacturing through 2D laser‐induced periodic surface structures.
Ultrafast laser structuring offers a promising solution for creating a wide array of complex surface morphologies. Through time‐controlled polarization ultrafast irradiation, surfaces can spontaneously self‐organize at the micro‐ and nanoscale. Explored in a comprehensive review, this technique unlocks the potential to create precise 2D patterns, propelling advancements in nanoscale manufacturing.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Polyaniline (PANI) is prepared by the oxidation of aniline. Depending on the acidity conditions during the chemical oxidation, different types of products can be identified. The aniline dimers, ...semidines, are the first oxidation products. In the next step, aniline trimers containing a phenazine moiety, the nucleates, are produced. At moderate acidity, pH
>
3.5, the reaction pathway further leads to higher brown non-conducting aniline oligomers. Alternatively, when the acidity is sufficiently high, pH
<
2.5, the nucleates convert to initiation centers that start the subsequent propagation of PANI chains.
The model of phenazine nucleates is offered to explain the various supramolecular nanostructures produced by PANI. It is proposed that the hydrophobic nucleates randomly aggregate in the aqueous phase or become organized to form one-dimensional stacks stabilized by π–π interactions. This step is followed by the growth of PANI chains from the self-assembled nucleates. The evolution of the nanostructures is conveniently observed by the combination of microscopic and spectroscopic techniques. The random agglomeration of nucleates gives rise to PANI granules and regular self-assembly into stacks subsequently leads to PANI nanofibers. The growth of other nanostructures requires a starting template. A model of a flowing template combined with a helical nanotubular growth is proposed to account for the formation of nanotubes, monomer droplets serve as templates for microspheres. The detailed chemical structure of nucleates has still to be elucidated.
The nucleates adsorb and self-assemble along various interfaces giving subsequently rise to additional conducting polymer morphologies. The adsorption of nucleates at solid surfaces immersed in the reaction mixture leads to PANI nanofilms or coatings of various substrates. The competition between nucleate adsorption and nucleate self-assembly may lead to more complex morphologies combining one-dimensional and three-dimensional features, such as nanobrushes, hairy spheres,
etc. The control of nucleates self-assembly and of PANI growth, the involvement of various interfaces in this process, and the role of PANI conductivity are discussed.
The nanostructures produced by other conducting polymers, especially by substituted PANI, polypyrrole, or poly(3,4-ethylenedioxythiophene) are also considered. Two potential extensions to the preparation of related materials, such as nitrogen-containing carbonized PANI nanostructures or the composites of conducting polymers with noble metals are outlined. The present review accounts for the latest development in the realm of PANI nanostructures in past few years and provides an upgrade in the models proposed for their formation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Tissue folds are structural motifs critical to organ function. In the intestine, bending of a flat epithelium into a periodic pattern of folds gives rise to villi, finger-like protrusions that enable ...nutrient absorption. However, the molecular and mechanical processes driving villus morphogenesis remain unclear. Here, we identify an active mechanical mechanism that simultaneously patterns and folds the intestinal epithelium to initiate villus formation. At the cellular level, we find that PDGFRA+ subepithelial mesenchymal cells generate myosin II-dependent forces sufficient to produce patterned curvature in neighboring tissue interfaces. This symmetry-breaking process requires altered cell and extracellular matrix interactions that are enabled by matrix metalloproteinase-mediated tissue fluidization. Computational models, together with in vitro and in vivo experiments, revealed that these cellular features manifest at the tissue level as differences in interfacial tensions that promote mesenchymal aggregation and interface bending through a process analogous to the active dewetting of a thin liquid film.
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•Mesenchymal aggregates generate forces that fold the mammalian intestinal epithelium•Active and fluid-like properties of aggregates program tissue geometry and pattern•Matrix metalloproteinases fluidize the subepithelial mesenchyme to initiate aggregation•Mesenchymal patterning conceptually resembles water dewetting from a hydrophobic surface
Subepithelial mesenchyme behaves like a dewetting fluid to pattern and fold the intestinal epithelium, initiating the formation of villi.
New class of turbulence in active fluids Bratanov, Vasil; Jenko, Frank; Frey, Erwin
Proceedings of the National Academy of Sciences - PNAS,
12/2015, Volume:
112, Issue:
49
Journal Article
Peer reviewed
Open access
Turbulence is a fundamental and ubiquitous phenomenon in nature, occurring from astrophysical to biophysical scales. At the same time, it is widely recognized as one of the key unsolved problems in ...modern physics, representing a paradigmatic example of nonlinear dynamics far from thermodynamic equilibrium.Whereas in the past, most theoretical work in this area has been devoted to Navier–Stokes flows, there is now a growing awareness of the need to extend the research focus to systems with more general patterns of energy injection and dissipation. These include various types of complex fluids and plasmas, as well as active systems consisting of self-propelled particles, like dense bacterial suspensions. Recently, a continuum model has been proposed for such “living fluids” that is based on the Navier–Stokes equations, but extends them to include some of the most general terms admitted by the symmetry of the problem Wensink HH, et al. (2012)Proc Natl Acad Sci USA109:14308–14313. This introduces a cubic nonlinearity, related to the Toner–Tu theory of flocking, which can interact with the quadratic Navier–Stokes nonlinearity. We show that as a result of the subtle interaction between these two terms, the energy spectra at large spatial scales exhibit power laws that are not universal, but depend on both finite-size effects and physical parameters. Our combined numerical and analytical analysis reveals the origin of this effect and even provides a way to understand it quantitatively. Turbulence in active fluids, characterized by this kind of nonlinear self-organization, defines a new class of turbulent flows.
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Landscapes of facilitation Cornacchia, Loreta; Van De Koppel, Johan; Van Der Wal, Daphne ...
Ecology (Durham),
April 2018, Volume:
99, Issue:
4
Journal Article
Peer reviewed
Open access
Spatial heterogeneity plays a crucial role in the coexistence of species. Despite recognition of the importance of self-organization in creating environmental heterogeneity in otherwise uniform ...landscapes, the effects of such self-organized pattern formation in promoting coexistence through facilitation are still unknown. In this study, we investigated the effects of pattern formation on species interactions and community spatial structure in ecosystems with limited underlying environmental heterogeneity, using self-organized patchiness of the aquatic macrophyte Callitriche platycarpa in streams as a model system. Our theoretical model predicted that pattern formation in aquatic vegetation – due to feedback interactions between plant growth, water flow and sedimentation processes – could promote species coexistence, by creating heterogeneous flow conditions inside and around the plant patches. The spatial plant patterns predicted by our model agreed with field observations at the reach scale in naturally vegetated rivers, where we found a significant spatial aggregation of two macrophyte species around C. platycarpa. Field transplantation experiments showed that C. platycarpa had a positive effect on the growth of both beneficiary species, and the intensity of this facilitative effect was correlated with the heterogeneous hydrodynamic conditions created within and around C. platycarpa patches. Our results emphasize the importance of self-organized patchiness in promoting species coexistence by creating a landscape of facilitation, where new niches and facilitative effects arise in different locations. Understanding the interplay between competition and facilitation is therefore essential for successful management of biodiversity in many ecosystems.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
Light-activated self-propelled colloids Palacci, J.; Sacanna, S.; Kim, S.-H. ...
Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences,
11/2014, Volume:
372, Issue:
2029
Journal Article
Peer reviewed
Open access
Light-activated self-propelled colloids are synthesized and their active motion is studied using optical microscopy. We propose a versatile route using different photoactive materials, and ...demonstrate a multiwavelength activation and propulsion. Thanks to the photoelectrochemical properties of two semiconductor materials (α-Fe2O3 and TiO2), a light with an energy higher than the bandgap triggers the reaction of decomposition of hydrogen peroxide and produces a chemical cloud around the particle. It induces a phoretic attraction with neighbouring colloids as well as an osmotic self-propulsion of the particle on the substrate. We use these mechanisms to form colloidal cargos as well as self-propelled particles where the light-activated component is embedded into a dielectric sphere. The particles are self-propelled along a direction otherwise randomized by thermal fluctuations, and exhibit a persistent random walk. For sufficient surface density, the particles spontaneously form ‘living crystals’ which are mobile, break apart and reform. Steering the particle with an external magnetic field, we show that the formation of the dense phase results from the collisions heads-on of the particles. This effect is intrinsically non-equilibrium and a novel principle of organization for systems without detailed balance. Engineering families of particles self-propelled by different wavelength demonstrate a good understanding of both the physics and the chemistry behind the system and points to a general route for designing new families of self-propelled particles.
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