基於二甲基銨陽離子添加劑的中間相工程用於穩定鈣鈦礦太陽能電池The stability of halide perovskite solar cells, determined by film morphology, is paramount to their commercialization. Here, the authors introduce a high-temperature DMSO-free method that enables better control of the grain size, texturing, orientation and crystallinity to achieve improved device operational stability.
Intermediate-phase engineering via dimethylammonium cation additive for stable perovskite solar cellsAchieving the long-term stability of perovskite solar cells is arguably the most important challenge required to enable widespread commercialization. Understanding the perovskite crystallization process and its direct impact on device stability is critical to achieving this goal. The commonly employed dimethyl-formamide/dimethyl-sulfoxide solvent preparation method results in a poor crystal quality and microstructure of the polycrystalline perovskite films. In this work, we introduce a high-temperature dimethyl-sulfoxide-free processing method that utilizes dimethylammonium chloride as an additive to control the perovskite intermediate precursor phases. By controlling the crystallization sequence, we tune the grain size, texturing, orientation (corner-up versus face-up) and crystallinity of the formamidinium (FA)/caesium (FA)yCs1–yPb(IxBr1–x)3 perovskite system. A population of encapsulated devices showed improved operational stability, with a median T80 lifetime (the time over which the device power conversion efficiency decreases to 80% of its initial value) for the steady-state power conversion efficiency of 1,190 hours, and a champion device showed a T80 of 1,410 hours, under simulated sunlight at 65 °C in air, under open-circuit conditions. This work highlights the importance of material quality in achieving the long-term operational stability of perovskite optoelectronic devices.Impact of hydrohalic acids on the morphology, crystal quality and electronic disorder of the FA0.83Cs0.17Pb(I0.6Br0.4)3 perovskite film.
David P. McMeekin, Philippe Holzhey, Sebastian O. Fürer, Steven P. Harvey, Laura T. Schelhas, James M. Ball, Suhas Mahesh, Seongrok Seo, Nicholas Hawkins, Jianfeng Lu, Michael B. Johnston, Joseph J. Berry, Udo Bach & Henry J. Snaith
doi:10.1038/s41563-022-01399-8
Liquid crystal (LC) applications typically rely on defining the non-topological spatial patterns of the optical axis. Here, the authors demonstrate the topological steering of light by LC nematic vortices, futher establishing an analogy between topological light steering by LC vortices and cosmic strings.
Topological steering of light by nematic vortices and analogy to cosmic stringsLiquid crystals are widely known for their technological uses in displays, electro-optics, photonics and nonlinear optics, but these applications typically rely on defining and switching non-topological spatial patterns of the optical axis. Here, we demonstrate how a liquid crystal’s optical axis patterns with singular vortex lines can robustly steer beams of light. External stimuli, including an electric field and light itself, allow us to reconfigure these unusual light–matter interactions. Periodic arrays of vortices obtained by photo-patterning enable the vortex-mediated fission of optical solitons, yielding their lightning-like propagation patterns. Predesigned patterns and spatial trajectories of vortex lines in high-birefringence liquid crystals can steer light into closed loops or even knots. Our vortex lattices might find technological uses in beam steering, telecommunications, virtual reality implementations and anticounterfeiting, as well as possibly offering a model system for probing the interaction of light with defects, including the theoretically predicted, imagination-capturing light-steering action of cosmic strings, elusive defects in cosmology.Topological steering of light by LC vortices.Cuiling Meng, Jin-Sheng Wu & Ivan I. Smalyukh
doi:10.1038/s41563-022-01414-y
Viscoelasticity is a universal mechanical feature of the extracellular matrix. Here the authors show that the extracellular matrix viscoelasticity guides tissue growth and symmetry breaking, a fundamental process in morphogenesis and oncogenesis.
Matrix viscoelasticity controls spatiotemporal tissue organizationBiomolecular and physical cues of the extracellular matrix environment regulate collective cell dynamics and tissue patterning. Nonetheless, how the viscoelastic properties of the matrix regulate collective cell spatial and temporal organization is not fully understood. Here we show that the passive viscoelastic properties of the matrix encapsulating a spheroidal tissue of breast epithelial cells guide tissue proliferation in space and in time. Matrix viscoelasticity prompts symmetry breaking of the spheroid, leading to the formation of invading finger-like protrusions, YAP nuclear translocation and epithelial-to-mesenchymal transition both in vitro and in vivo in a Arp2/3-complex-dependent manner. Computational modelling of these observations allows us to establish a phase diagram relating morphological stability with matrix viscoelasticity, tissue viscosity, cell motility and cell division rate, which is experimentally validated by biochemical assays and in vitro experiments with an intestinal organoid. Altogether, this work highlights the role of stress relaxation mechanisms in tissue growth dynamics, a fundamental process in morphogenesis and oncogenesis.Matrix viscoelasticity determines symmetry breaking, tissue branching and EMT.
Alberto Elosegui-Artola, Anupam Gupta, Alexander J. Najibi, Bo Ri Seo, Ryan Garry, Christina M. Tringides, Irene de Lázaro, Max Darnell, Wei Gu, Qiao Zhou, David A. Weitz, L. Mahadevan & David J. Mooney
doi:10.1038/s41563-022-01414-y
Screening of hundreds of nanoparticle polymers identifies an effective and low-toxicity formulation for the functional delivery of RNA to the lungs of distinct animal species.
Species-agnostic polymeric formulations for inhalable messenger RNA delivery to the lungMessenger RNA has now been used to vaccinate millions of people. However, the diversity of pulmonary pathologies, including infections, genetic disorders, asthma and others, reveals the lung as an important organ to directly target for future RNA therapeutics and preventatives. Here we report the screening of 166 polymeric nanoparticle formulations for functional delivery to the lungs, obtained from a combinatorial synthesis approach combined with a low-dead-volume nose-only inhalation system for mice. We identify P76, a poly-β-amino-thio-ester polymer, that exhibits increased expression over formulations lacking the thiol component, delivery to different animal species with varying RNA cargos and low toxicity. P76 allows for dose sparing when delivering an mRNA-expressed Cas13a-mediated treatment in a SARS-CoV-2 challenge model, resulting in similar efficacy to a 20-fold higher dose of a neutralizing antibody. Overall, the combinatorial synthesis approach allowed for the discovery of promising polymeric formulations for future RNA pharmaceutical development for the lungs.Functional screening of polymers for nebulized mRNA delivery.
Laura Rotolo, Daryll Vanover, Nicholas C. Bruno, Hannah E. Peck, Chiara Zurla, Jackelyn Murray, Richard K. Noel, Laura O』Farrell, Mariluz Araínga, Nichole Orr-Burks, Jae Yeon Joo, Lorena C. S. Chaves, Younghun Jung, Jared Beyersdorf, Sanjeev Gumber, Ricardo Guerrero-Ferreira, Santiago Cornejo, Merrilee Thoresen, Alicia K. Olivier, Katie M. Kuo, James C. Gumbart, Amelia R. Woolums, Francois Villinger, Eric R. Lafontaine, …Philip J. Santangelo
doi:10.1038/s41563-022-01404-0
This Review discusses recent progress in bioinspired nanocomposite design, emphasizing the role of hierarchical structuring at distinct length scales to create multifunctional, lightweight and robust structural materials for diverse technological applications.
Hierarchically structured bioinspired nanocompositesNext-generation structural materials are expected to be lightweight, high-strength and tough composites with embedded functionalities to sense, adapt, self-repair, morph and restore. This Review highlights recent developments and concepts in bioinspired nanocomposites, emphasizing tailoring of the architecture, interphases and confinement to achieve dynamic and synergetic responses. We highlight cornerstone examples from natural materials with unique mechanical property combinations based on relatively simple building blocks produced in aqueous environments under ambient conditions. A particular focus is on structural hierarchies across multiple length scales to achieve multifunctionality and robustness. We further discuss recent advances, trends and emerging opportunities for combining biological and synthetic components, state-of-the-art characterization and modelling approaches to assess the physical principles underlying nature-inspired design and mechanical responses at multiple length scales. These multidisciplinary approaches promote the synergetic enhancement of individual materials properties and an improved predictive and prescriptive design of the next era of structural materials at multilength scales for a wide range of applications.Keratin-based hierarchical structures in different animal species.
Dhriti Nepal, Saewon Kang, Katarina M. Adstedt, Krishan Kanhaiya, Michael R. Bockstaller, L. Catherine Brinson, Markus J. Buehler, Peter V. Coveney, Kaushik Dayal, Jaafar A. El-Awady, Luke C. Henderson, David L. Kaplan, Sinan Keten, Nicholas A. Kotov, George C. Schatz, Silvia Vignolini, Fritz Vollrath, Yusu Wang, Boris I. Yakobson, Vladimir V. Tsukruk & Hendrik Heinz
doi:10.1038/s41563-022-01384-1
Picture story: Transform to deformCeramics with covalent bonding are mostly hard and brittle at ambient temperature, unlike metals that are much easier to deform through the shifting or sliding of atoms. Now, Jie Zhang and colleagues report that silicon nitride (Si3N4) ceramics can deform via a phase transformation mediated by coherent interfaces in a dual-phase structure giving rise to notable compression plasticity (Science 378, 371–376; 2022).
doi:10.1038/articles/s41563-022-01439-3
Picture Story: Setting stable catalystsSingle-atom catalysts (SACs) can present improved catalytic properties with respect to more commonly used catalytic nanoparticles. Now, Jingyue Liu and colleagues present a strategy that prevents deactivation of these systems in challenging conditions (Nature 611, 284–288; 2022).
doi:10.1038/s41563-022-01440-w
Meeting Report: Materials for a changing planetAbout 700 scientists from 45 countries gathered in Dresden for the first time since the start of the COVID-19 pandemic to share their latest findings on metal–organic frameworks and open frameworks compounds.
Veronique Van Speybroeck & Guillaume Maurin
doi:10.1038/s41563-022-01419-7
Q&A: Caution on trace impuritiesZhi-Wei Shan, a professor at Xi』an Jiaotong University (School of Materials Science and Engineering), talks to Nature Materials about the non-negligible impact of trace impurities in metallic structural materials.
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What are the origins of the trace impurities?Impurities in metals and alloys are mainly derived from ores and their subsequent smelting and preparation processes. In the case of pure magnesium prepared through the silicon thermal process, some impurities are inherited from the mineral material itself, and some are derived from the additives in the refining process of crude magnesium. For alloys, both impurities in the parent element and in the alloying element can be inherited into the final product. Depending on the smelting equipment and smelting technology, some impurities may also be introduced during the alloy smelting process.There are often many kinds of impurities in metals and alloys with their content fluctuating in quite a large range. For example, we randomly sampled 12 batches of the 3N grade (99.9%, N represents 9) pure magnesium from a leading company. To our surprise, the highest content of the same impurities (such as Si and Cu) was 2 to 10 times higher than the lowest content, even though they were all 3N grade pure magnesium samples. These fluctuations mainly come from the variations of raw materials and production processes. Downstream products are very likely to inherit at least part of the large and uncontrollable content fluctuation of these impurities.
What do you think about the impact of these impurities on material properties?These impurities can have a significant impact on the properties of the materials themselves, which include, but are not limited to, corrosion resistance, strength and ductility.Trace impurities can change the corrosion rate of a material dramatically. Previous studies have shown that in the presence of a certain amount of silicon, the corrosion rate of magnesium containing 25 ppm iron can be 1,000 times higher than that of magnesium containing 3 ppm iron. In sharp contrast, if the content of impurities in a magnesium alloy can be controlled well (for example, iron content less than 50 ppm, nickel content less than 20 ppm), the salt spray corrosion rate of these highly clean magnesium alloys will not only be 1–2 orders of magnitude lower than that of ordinary magnesium alloys, but also lower than that of typical steel and aluminium alloys. In fact, as early as the 1940s, in the classic paper 『Corrosion studies of magnesium and its alloys』, Hanawalt et al. pointed out, 「This basic behavior (excellent corrosion resistance) is often marked because of their extreme sensitivity of these alloys to certain impurities and combinations of impurities」 (Trans. AIME 147, 273–299; 1942).The impurities may also seriously affect the mechanical properties of materials. Pure magnesium was asserted to have poor ductility, and the chief culprit was thought to be pyramidal dislocations because of their inability to accommodate plasticity. However, our results, published in 2019 in Science, showed that the 「poor ductility」 of pure magnesium is not due to pyramidal dislocations (B.-Y. Liu et al. Science 365, 73–75; 2019). Then, there must be other reasons. Subsequently, we used the same method to prepare pure magnesium with different purities, and found that the tensile elongation of magnesium can increase from less than 10% to about 45% when the purity of magnesium changes from 3N to 4N grade. This indicates that impurities can affect the mechanical properties of materials significantly.
doi:10.1038/s41563-022-01434-8
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