Communications Materials最新文献

The integrity of structural materials is oftentimes defined by their resistance against catastrophic failure through dissipative plastic processes at the crack tip, commonly quantified by the J-integral concept. However, to date the experimental stress and strain fields necessary to quantify the J-integral associated with local crack propagation in its original integral form were inaccessible. Here, we present a multi-method nanoscale strain- and stress-mapping surrounding a growing crack tip in two identical miniaturized fracture specimens made from a nanocrystalline FeCrMnNiCo high-entropy alloy. The respective samples were tested in situ in a scanning electron microscope and a synchrotron X-ray nanodiffraction setup, with detailed analyzes of loading states during elastic loading, crack tip blunting and general yielding, corroborated by a detailed elastic-plastic finite element model. This complementary in situ methodology uniquely enabled a detailed quantification of the J-integral along different integration paths from experimental nanoscale stress and strain fields. We find that conventional linear-elastic and elastic-plastic models, typically used to interpret fracture phenomena, have limited applicability at micron to nanoscale distances from propagating cracks. This for the first time unravels a limit to the path-independence of the J-integral, which has significant implications in the development and assessment of modern damage-tolerant materials and microstructures.

The sustainability of vascular access for hemodialysis is limited by frequent interventions and the inability of synthetic grafts to self-heal. Tissue engineering offers a solution through biodegradable grafts that remodel into autologous tissue. Here we assess electrospun polycarbonate-bis urea (PC-BU) vascular scaffolds (6mm-inner-Ø), reinforced with 3D-printed polycaprolactone coils, in a goat model, and compared them to expanded polytetrafluoroethylene (ePTFE) controls. The tissue-engineered grafts were repeatedly cannulated starting two weeks after implantation and were evaluated using computed tomography and histological analyses. By 12 weeks, the PC-BU grafts remodel into autologous tissue while maintaining structural integrity, maintaining integrity without dilations, ruptures, or aneurysms. Cannulation does not interfere with scaffold degradation or neo-tissue formation. Although the patency rate is lower for the PC-BU grafts (50%) compared to ePTFE (100%), the engineered grafts exhibit a self-healing response not seen in ePTFE. These findings demonstrate the potential of PC-BU tissue-engineered grafts as healing, functional vascular access solutions for hemodialysis, supporting cannulation during tissue transformation.

Iron-based superconductors exhibit various magnetic and electronic phases that are highly sensitive to structural and chemical modifications. Elucidating the origins of these phases remains a central challenge. Here, using neutron and x-ray diffraction, we uncover a universal phase diagram that identifies disorder as a hidden tuning parameter governing these phase transitions. By analyzing nine hole-doped phase diagrams, we observe the emergence of a double-Q tetragonal magnetic phase in proximity to ideal FeAs₄ tetrahedral configurations, thereby demonstrating a strong link between bond-angle stabilization and magnetic transitions. Beyond stabilizing the double-Q phase, atomic disorder also influences charge doping and magnetic anisotropy. We further observe similar scaling behavior of the transition temperatures of the double-Q and the more prevalent orthorhombic single-Q magnetic phases, evidencing a unified origin of structural and magnetic properties linked to itinerant nesting instability. Our findings establish a comprehensive basis for understanding how chemical disorder, charge doping, and structural features collectively shape the magnetic and superconducting properties of iron-based superconductors.

A cell's ability to sense and respond to the mechanical properties of the extracellular matrix (ECM) is essential for maintaining tissue homeostasis, and its disruption contributes to diseases such as fibrosis, cardiovascular disorders, and cancer. Effective mechanical coupling between the plasma membrane, the underlying filamentous actin (F-actin) cytoskeleton, and integrin-based adhesion complexes (IACs) is required to link ECM mechanics to cell morphology, yet the underlying mechanisms remain incompletely understood. Here, we combine computational modeling and high-resolution imaging to show that integrin-ECM bonds determine F-actin cytoskeleton organization. On soft substrates, short-lived IACs bonds allow rapid actin retrograde flow and dense branching, restricting protrusion and limiting cell spreading. In contrast, stiff substrates or Mn²⁺-mediated integrin activation stabilize adhesions, promote filament alignment, and drive membrane protrusion for cell spreading. These cytoskeletal transitions arise from feedback between adhesion strength and the spatial positioning of the F-actin barbed ends relative to the leading-edge membrane. This positioning determines whether filaments polymerize into linear bundles or branch into dendritic networks, each generating distinct protrusive forces that regulate cell spreading. Collectively, our findings establish integrin-ECM bond stability as a key regulator of F-actin cytoskeleton organization and cell morphology.

The carnivorous Drosera species employ hair-like appendages called trichomes that secrete a deadly adhesive consisting of an acidic polysaccharide, sugars, organic acids, and water to capture prey insects. Here, we develop a sustainable alternative to chemical pesticides using hyaluronic acid in a sugar-based natural deep eutectic solvent to mimic the composition and trapping mechanism of the Drosera mucilage. We formulate trichome biomimetic adhesives that become sprayable with added water to lower their viscosity, which can then regain the required adhesiveness as water evaporates up to the equilibrium content. Using a custom indentation setup, we measure promising adhesion energies between 9.5-14.5 µJ over one week, along with the formation of elongated fibrils (>2.3 cm) for the best-performing sample. Additionally, the material shows no phytotoxicity for over two weeks and effectively immobilizes western flower thrips through multiple contact points with the material in Petri dish bioassays, highlighting its efficacy and trapping mechanism akin to natural trichomes.

Radiochromic crystals have many suitable features for dosimetry across a broad range of radiotherapy modalities, yet the study of these materials within the medical physics community has been limited. Here, we study three types of radiochromic pentacosa-10,12-diynoic acid-based formulations: two analogues of commercially available materials and one newly developed. Formulations coated on polyethylene are irradiated with photon (6 and 10 MV) and proton (74 MeV) beams (0-25 Gy) using custom fibre-optic setups that enable real-time transmission measurements at 1.5-2 cm depth to maintain dosimetric accuracy. The dose response to ionizing radiation is compared between the formulations and all formulations were characterized using a variety of analytical methods. The response of radiochromic crystals to ionizing radiation is complex and influenced by factors such as monomer composition and resulting macroscopic crystal morphology. By optimizing these parameters, it could be possible to develop dosimeters suitable for a variety of clinical applications.

Quantum light sources, particularly single-photon emitters (SPEs), are critical for quantum communications and computing. Among them, III-V semiconductor quantum dots (QDs) have demonstrated superior SPE metrics, including near-unity brightness, high photon purity, and indistinguishability, making them especially suitable for quantum applications. However, their overall quantum efficiency-determined by a product of the internal, excitation, and outcoupling efficiencies-remains limited, primarily due to low (typically below 0.1%) excitation efficiency. To mitigate the low efficiency under non-resonant pumping, here we realize liquid droplet etched GaAs QDs in a microscale 3D AlGaAs charge-carrier funnel. The funnel channels charge carriers to the QD and enhances the overall emission efficiency by over one order of magnitude while preserving the SPE behavior. We reveal that a modified energy landscape around the QD leads to the excitation efficiency improvement. These energy landscape-modified QDs can be operated with optical excitation up to 10 μm away, raising the promise of efficient electrically driven QD SPEs for quantum information systems.

Ultra-pure materials are highly valued as model systems for the study of intrinsic physics. Frequently, however, the crystal growth of such pristine samples requires significant optimization. PtSn₄ is a rare example of a material that naturally forms with a very low concentration of crystalline defects. Here, we investigate the origin of its low defect levels using a combination of electrical resistivity measurements, computational modeling, and scanning tunneling microscopy imaging. While typical flux-grown crystals of PtSn₄ can have residual resistivity ratios (RRRs) that exceed 1000, we show that even at the most extreme formation speeds, the RRR cannot be suppressed below 100. This aversion to defect formation extends to both the Pt and Sn sublattices, which contribute with equal weight to the conduction properties. Direct local imaging with scanning tunneling microscopy further substantiates the rarity of point defects, while the prohibitive energetic cost of forming a defect is demonstrated through density functional theory calculations. Taken together, our results establish PtSn₄ as an intrinsically defect-intolerant material, making it an ideal platform to study other properties of interest, including extreme magnetoresistance and topology.

Topological Insulators (TIs) present an interesting materials platform for nanoscale, high frequency devices because they support high mobility, low scattering electronic transport within confined surface states. However, a robust methodology to control the properties of surface plasmons in TIs has yet to be developed. Surface doping of TIs with molecules may provide tunable control of the two-dimensional plasmons in Bi₂Se₃, but exploration of such heterostructures is still at an early stage and usually confined to monolayers. We have grown heterostructures of Bi₂Se₃/C₆₀ with exceptional crystallinity. Electron energy loss spectroscopy (EELS) reveals significant hybridisation of π states at the interface, despite the expectation for only weak van der Waals interactions, including quenching of 2D plasmons. Momentum-resolved EELS measurements are used to probe the plasmon dispersion, with Density Functional Theory predictions providing an interpretation of results based on interfacial charge dipoles. This work provides growth methodology and characterization of highly crystalline TI/molecular interfaces that can be engineered for plasmonic applications in energy, communications and sensing.