High-throughput measurement of elastic moduli of microfibers by rope coiling.

There are many fields where it is of interest to measure the elastic moduli of tiny fragile fibers, such as filamentous bacteria, actin filaments, DNA, carbon nanotubes, and functional microfibers. The elastic modulus is typically deduced from a sophisticated tensile test under a microscope, but the throughput is low and limited by the time-consuming and skill-intensive sample loading/unloading. Here, we demonstrate a simple microfluidic method enabling the high-throughput measurement of the elastic moduli of microfibers by rope coiling using a localized compression, where sample loading/unloading are not needed between consecutive measurements. The rope coiling phenomenon occurs spontaneously when a microfiber flows from a small channel into a wide channel. The elastic modulus is determined by measuring either the buckling length or the coiling radius. The throughput of this method, currently 3,300 fibers per hour, is a thousand times higher than that of a tensile tester. We demonstrate the feasibility of the method by testing a nonuniform fiber with axially varying elastic modulus. We also demonstrate its capability for in situ inline measurement in a microfluidic production line. We envisage that high-throughput measurements may facilitate potential applications such as screening or sorting by mechanical properties and real-time control during production of microfibers.

The driving force behind tool-stone selection in the African Middle Stone Age.

In the Stone Age, the collection of specific rocks was the first step in tool making. Very little is known about the choices made during tool-stone acquisition. Were choices governed by the knowledge of, and need for, specific properties of stones? Or were the collected raw materials a mere by-product of the way people moved through the landscape? We investigate these questions in the Middle Stone Age (MSA) of southern Africa, analyzing the mechanical properties of tool-stones used at the site Diepkloof Rock Shelter. To understand knapping quality, we measure flaking predictability and introduce a physical model that allows calculating the relative force necessary to produce flakes from different rocks. To evaluate their quality as finished tools, we investigate their resistance during repeated use activities (scraping or cutting) and their strength during projectile impacts. Our findings explain tool-stone selection in two emblematic periods of the MSA, the Still Bay and Howiesons Poort, as being the result of a deep understanding of these mechanical properties. In both cases, people chose those rocks, among many others, that allowed the most advantageous trade-off between anticipated properties of finished tools and the ease of acquiring rocks and producing tools. The implications are an understanding of African MSA toolmakers as engineers who carefully weighed their choices taking into account workability and the quality of the tools they made.

Nanocolloidal hydrogel mimics the structure and nonlinear mechanical properties of biological fibrous networks.

Fibrous networks formed by biological polymers such as collagen or fibrin exhibit nonlinear mechanical behavior. They undergo strong stiffening in response to weak shear and elongational strains, but soften under compressional strain, in striking difference with the response to the deformation of flexible-strand networks formed by molecules. The nonlinear properties of fibrous networks are attributed to the mechanical asymmetry of the constituent filaments, for which a stretching modulus is significantly larger than the bending modulus. Studies of the nonlinear mechanical behavior are generally performed on hydrogels formed by biological polymers, which offers limited control over network architecture. Here, we report an engineered covalently cross-linked nanofibrillar hydrogel derived from cellulose nanocrystals and gelatin. The variation in hydrogel composition provided a broad-range change in its shear modulus. The hydrogel exhibited both shear-stiffening and compression-induced softening, in agreement with the predictions of the affine model. The threshold nonlinear stress and strain were universal for the hydrogels with different compositions, which suggested that nonlinear mechanical properties are general for networks formed by rigid filaments. The experimental results were in agreement with an affine model describing deformation of the network formed by rigid filaments. Our results lend insight into the structural features that govern the nonlinear biomechanics of fibrous networks and provide a platform for future studies of the biological impact of nonlinear mechanical properties.

Ultrastrong spinodoid alloys enabled by electrochemical dealloying and refilling.

We present an extreme case of composition-modulated nanomaterial formed by selective etching (dealloying) and electrochemical refilling. The product is a coarse-grain polycrystal consisting of two interwoven nanophases, with identical crystal structures and a cube-on-cube relationship, separated by smoothly curved semicoherent interfaces with high-density misfit dislocations. This material resembles spinodal alloys structurally, but its synthesis and composition modulation are spinodal-independent. Our Cu/Au "spinodoid" alloy demonstrates superior mechanical properties such as near-theoretical strength and single-phase-like behavior, owing to its fine composition modulation, large-scale coherence of crystal lattice, and smoothly shaped three-dimensional (3D) interface morphology. As a unique extension of spinodal alloy, the spinodoid alloy reported here reveals a number of possibilities to modulate the material's structure and composition down to the nanoscale, such that further improved properties unmatchable by conventional materials can be achieved.

Bioinspired stretchable molecular composites of 2D-layered materials and tandem repeat proteins.

Protein based composites, such as nacre and bone, show astounding evolutionary capabilities, including tunable physical properties. Inspired by natural composites, we studied assembly of atomistically thin inorganic sheets with genetically engineered polymeric proteins to achieve mechanically compliant and ultra-tough materials. Although bare inorganic nanosheets are brittle, we designed flexible composites with proteins, which are insensitive to flaws due to critical structural length scale (∼2 nm). These proteins, inspired by squid ring teeth, adhere to inorganic sheets via secondary structures (i.e., ß-sheets and α-helices), which is essential for producing high stretchability (59 ± 1% fracture strain) and toughness (54.8 ± 2 MJ/m3). We find that the mechanical properties can be optimized by adjusting the protein molecular weight and tandem repetition. These exceptional mechanical responses greatly exceed the current state-of-the-art stretchability for layered composites by over a factor of three, demonstrating the promise of engineering materials with reconfigurable physical properties.

Achieving the theoretical limit of strength in shell-based carbon nanolattices.

Recent developments in mechanical metamaterials exemplify a new paradigm shift called mechanomaterials, in which mechanical forces and designed geometries are proactively deployed to program material properties at multiple scales. Here, we designed shell-based micro-/nanolattices with I-WP (Schoen's I-graph-wrapped package) and Neovius minimal surface topologies. Following the designed topologies, polymeric microlattices were fabricated via projection microstereolithography or two-photon lithography, and pyrolytic carbon nanolattices were created through two-photon lithography and subsequent pyrolysis. The shell thickness of created lattice metamaterials varies over three orders of magnitude from a few hundred nanometers to a few hundred micrometers, covering a wider range of relative densities than most plate-based micro-/nanolattices. In situ compression tests showed that the measured modulus and strength of our shell-based micro-/nanolattices with I-WP topology are superior to those of the optimized plate-based lattices with cubic and octet plate unit cells and truss-based lattices. More strikingly, when the density is larger than 0.53 g cm-3, the strength of shell-based pyrolytic carbon nanolattices with I-WP topology was found to achieve its theoretical limit. In addition, our shell-based carbon nanolattices exhibited an ultrahigh strength of 3.52 GPa, an ultralarge fracture strain of 23%, and an ultrahigh specific strength of 4.42 GPa g-1 cm3, surpassing all previous micro-/nanolattices at comparable densities. These unprecedented properties can be attributed to the designed topologies inducing relatively uniform strain energy distributions and avoiding stress concentrations as well as the nanoscale feature size. Our study demonstrates a mechanomaterial route to design and synthesize micro-/nanoarchitected materials.

Supramolecularly Connected Armor-like Nanostructure Enables Mechanically Robust Radiative Cooling Materials.

Passive daytime radiative cooling (PDRC) is a promising practice to realize sustainable thermal management with no energy and resources consumption. However, there remains a challenge of simultaneously integrating desired solar reflectivity, environmental durability, and mechanical robustness for polymeric composites with nanophotonic structures. Herein, inspired by a classical armor shell of a pangolin, we adopt a generic design strategy that harnesses supramolecular bonds between the TiO2-decorated mica microplates and cellulose nanofibers to collectively produce strong interfacial interactions for fabricating interlayer nanostructured PDRC materials. Owing to the strong light scattering excited by hierarchical nanophotonic structures, the bioinspired film demonstrates a desired reflectivity (92%) and emissivity (91%) and an excellent temperature drop of 10 °C under direct sunlight. Notably, the film guarantees high strength (41.7 MPa), toughness (10.4 MJ m-3), and excellent environmental durability. This strategy provides possibilities in designing polymeric PDRC materials, further establishing a blueprint for other functional applications like soft robots, wearable devices, etc.

A New Strategy for the Design of Triple-Phase Eutectic High-Entropy Alloys Based on Infinite Solid Solution and Pseudo-Ternary Method.

Eutectic high-entropy alloys (EHEAs) have combined both high-entropy alloys and eutectic alloy contributions, with excellent castability and high-temperature application potential. Yet, multielement/triple-phase eutectic high-entropy alloy (TEHEA) designs remain puzzling. This work proposed a new strategy based on an infinite solid solution and pseudo-ternary model to reveal the puzzle of TEHEAs. The designed triple-phase eutectic high-entropy alloys (TEHEAs) with more than seven elements were identified as face-centered cubic (FCC), ordered body-centered cubic (B2), and Laves phase structures. In this work, the alloy C showcases outstanding comprehensive mechanical properties, offering a novel avenue for the design of high-performance EHEAs.

Supertough MXene/Sodium Alginate Composite Fiber Felts Integrated with Outstanding Electromagnetic Interference Shielding and Heating Properties.

The development of multifunctional MXene-based fabrics for smart textiles and portable devices has garnered significant attention. However, very limited studies have focused on their structure design and associated mechanical properties. Here, the supertough MXene fiber felts composed of MXene/sodium alginate (SA) fibers were fabricated. The fracture strength and bending stiffness of felts can be up to 97.8 MPa and 1.04 N mm2, respectively. Besides, the fracture toughness of felts was evaluated using the classic Griffith theory, yielding to a critical stress intensity factor of 1.79 MPam. In addition, this kind of felt presents outstanding electrothermal conversion performance (up to 119 °C at a voltage of 2.5 V), high cryogenic and high-temperature tolerance of photothermal conversion performance (-196 to 160 °C), and excellent electromagnetic interference (EMI) shielding effectiveness (54.4 dB in the X-band). This work provides new structural design concepts for high-performance MXene-based textiles, broadening their future applications.

Mechanics of neural tube morphogenesis.

The neural tube is an important model system of morphogenesis representing the developmental module of out-of-plane epithelial deformation. As the embryonic precursor of the central nervous system, the neural tube also holds keys to many defects and diseases. Recent advances begin to reveal how genetic, cellular and environmental mechanisms work in concert to ensure correct neural tube shape. A physical model is emerging where these factors converge at the regulation of the mechanical forces and properties within and around the tissue that drive tube formation towards completion. Here we review the dynamics and mechanics of neural tube morphogenesis and discuss the underlying cellular behaviours from the viewpoint of tissue mechanics. We will also highlight some of the conceptual and technical next steps.

Root growth of monocotyledons and dicotyledons is limited by different tissues.

Plant growth and morphogenesis are determined by the mechanical properties of its cell walls. Using atomic force microscopy, we have characterized the dynamics of cell wall elasticity in different tissues in developing roots of several plant species. The elongation growth zone of roots of all species studied was distinguished by a reduced modulus of elasticity of most cell walls compared to the meristem or late elongation zone. Within the individual developmental zones of roots, there were also significant differences in the elasticity of the cell walls of the different tissues, thus identifying the tissues that limit root growth in the different species. In cereals, this is mainly the inner cortex, whereas in dicotyledons this function is performed by the outer tissues-rhizodermis and cortex. These differences result in a different behaviour of the roots of these species during longitudinal dissection. Modelling of longitudinal root dissection using measured properties confirmed the difference shown. Thus, the morphogenesis of monocotyledonous and dicotyledonous roots relies on different tissues as growth limiting, which should be taken into account when analyzing the localization of associated molecular events. At the same time, no matrix polysaccharide was found whose immunolabelling in type I or type II cell walls would predict their mechanical properties. However, assessment of the degree of anisotropy of cortical microtubules showed a striking correlation with the elasticity of the corresponding cell walls in all species studied.

Role of tubulin C-terminal tail on mechanical properties of microtubule.

Tubulin C-terminal tail (CTT) is a disordered segment extended from each tubulin monomer of αß tubulin heterodimers, the building blocks of microtubules. The tubulin CTT contributes to the cellular function of microtubules such as intracellular transportation by regulating their interaction with other proteins and cell shape regulation by controlling microtubule polymerization dynamics. Although the mechanical integrity of microtubules is crucial for their functions, the role of tubulin CTT on microtubule mechanical properties has remained elusive. In this work, we investigate the role of tubulin CTTs in regulating the mechanical properties of microtubules by estimating the persistence lengths and investigating the buckling behavior of microtubules with and without CTT. We find that microtubules with intact CTTs exhibit twice the rigidity of microtubules lacking tubulin CTTs. Our study will widen the scope of altering microtubule mechanical properties for its application in nano bio-devices and lead to novel therapeutic approaches for neurodegenerative diseases with altered microtubule properties.

DFT insights into LaFeO3 with Mn substitution: A promising path to energy-efficient magneto-optical applications.

In recent years, the demand for electronic materials has significantly increased, driven by industrial needs and the pursuit of cost-efficient alternatives. This comprehensive study investigates the effects of Mn substitution on LaFeO3 through the implementation of the GGA approach in density functional theory. The research findings demonstrate remarkable consistency with the experimental outcomes reported in the existing literature pertaining to the studied compounds. However, this study unveils novel insights into the mechanical and optical characteristics of the doped structures, which have not been previously reported. The structural stability is rigorously examined through multiple stability criteria, encompassing structural optimization, tests of elastic stability, and enthalpy of formation calculations. Furthermore, the electronic and optical properties of the compounds exhibit exceptional improvements in conductivity and reflectivity as a result of the doping process. The band structure analysis reveals the presence of a Moss-Burstein shift. Investigation of the magnetic properties indicates an increase in the magnetic moment value due to the Fe-Mn degeneracy resulting from increased Mn content. Mechanical analysis of the elastic moduli B, G, and Y demonstrates an enhanced strength and metal-like conductivity, attributed to the induced anharmonicity. Moreover, the internal strain factor suggests a higher degree of bond flexibility, implying potential applications of these compounds in flexible electronics.

A systematic first-principles investigation of the structural, electronic, mechanical, optical, and thermodynamic properties of Half-Heusler ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) for spintronics and optoelectronics applications.

This paper is the first to look at the structural, electronic, mechanical, optical, and thermodynamic properties of the ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) half-Heusler (HH) using DFT based first principles method. The lattice parameters that we have calculated are very similar to those obtained in prior investigations with theoretical and experimental data. The positive phonon dispersion curve confirm the dynamical stability of ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn). The electronic band structure and DOS confirmed that the studied materials ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) are direct band gap semiconductors. The investigation also determined significant constants, including dielectric function, absorption, conductivity, reflectivity, refractive index, and loss function. These optical observations unveiled our compounds potential utilization in various electronic and optoelectronic device applications. The elastic constants were used to fulfill the Born criteria, confirming the mechanical stability and ductility of the solids ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn). The calculated elastic modulus revealed that our studied compounds are elastically anisotropic. Moreover, ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) has a very low minimum thermal conductivity (Kmin), and a low Debye temperature (θD), which indicating their appropriateness for utilization in thermal barrier coating (TBC) applications. The Helmholtz free energy (F), internal energy (E), entropy (S), and specific heat capacity (Cv) are determined by calculations derived from the phonon density of states.

Hysteresis-Free, Elastic, and Tough Hydrogel with Stretch-Rate Independence and High Stability in Physiological Conditions.

Many existing synthetic hydrogels are inappropriate for repetitive motions because of large hysteresis, and their mechanical properties in warm and saline physiological conditions remain understudied. In this study, a stretch-rate-independent, hysteresis-free, elastic, and tough nanocomposite hydrogel that can maintain its mechanical properties in phosphate-buffered saline of 37 °C similar to warm and saline conditions of the human body is developed. The strength, stiffness, and toughness of the hydrogel are simultaneously reinforced by biomimetic silica nanoparticles with a surface of embedded circular polyamine chains. Such distinctive surfaces form robust interfacial interactions by local topological folding/entanglement with the polymer chains of the matrix. Load transfer from the soft polymer matrix to stiff nanoparticles, along with the elastic sliding/unfolding/disentanglement of polymer chains, overcomes the traditional trade-off between strength/stiffness and toughness and allows for hysteresis-free, strain-rate-independent, and elastic behavior. This robust reinforcement is sustained in warm phosphate-buffered saline. These properties demonstrate the application potential of the developed hydrogel as a soft, elastic, and tough bio-strain sensor that can detect dynamic motions across various deformation speeds and ranges. The findings provide a simple yet effective approach to developing practical hydrogels with a desirable combination of strength/stiffness and toughness, in a fully swollen and equilibrated state.

Elastic SiC Aerogel for Thermal Insulation: A Systematic Review.

SiC aerogels with their lightweight nature and exceptional thermal insulation properties have emerged as the most ideal materials for thermal protection in hypersonic vehicles; However, conventional SiC aerogels are prone to brittleness and mechanical degradation when exposed to complex loads such as shock and mechanical vibration. Hence, preserving the structural integrity of aerogels under the combined influence of thermal and mechanical external forces is crucial not only for stabling their thermal insulation performance but also for determining their practicality in harsh environments. This review focuses on the optimization of design based on the structure-performance of SiC aerogels, providing a comprehensive review of the inherent correlations among structural stability, mechanical properties, and insulation performance. First, the thermal transfer mechanism of aerogels from a microstructural perspective is studied, followed by the relationship between the building blocks of SiC aerogels (0D particles, 1D nanowires/nanofibers) and their compression performance (including compressive resilience, compressive strength, and fatigue resistance). Moreover, the strategy to improve the high-temperature oxidation resistance and insulation performance of SiC aerogels is explored. Lastly, the challenges and future breakthrough directions for SiC aerogels are presented.

Architecture Controls Phonon Propagation in All-Solid Brush Colloid Metamaterials.

Brillouin light scattering and elastodynamic theory are concurrently used to determine and interpret the hypersonic phonon dispersion relations in brush particle solids as a function of the grafting density with perspectives in optomechanics, heat management, and materials metrology. In the limit of sparse grafting density, the phonon dispersion relations bear similarity to polymer-embedded colloidal assembly structures in which phonon dispersion can be rationalized on the basis of perfect boundary conditions, i.e., isotropic stiffness transitions across the particle interface. In contrast, for dense brush assemblies, more complex dispersion characteristics are observed that imply anisotropic stiffness transition across the particle/polymer interface. This provides direct experimental validation of phonon propagation changes associated with chain conformational transitions in dense particle brush materials. A scaling relation between interface tangential stiffness and crowding of polymer tethers is derived that provides a guideline for chemists to design brush particle materials with tailored phononic dispersion characteristics. The results emphasize the role of interfaces in composite materials systems. Given the fundamental relevance of phonon dispersion to material properties such as thermal transport or mechanical properties, it is also envisioned that the results will spur the development of novel functional hybrid materials.

Unprecedented Multifunctionality in Novel Monophase Micro/Nanostructured Ti-Zn Alloy.

It is always challenging to integrate multiple functions into one material system. However, those materials/devices will address society's critical global challenges and technological demands if achieved with innovative design strategies and engineering. Here, one such material with a broader spectrum of desired properties appropriate for seven applications is identified and explored, and a glucose-sensing-triggered energy-storage mechanism is demonstrated. To date, the Titanium (Ti)-Zinc (Zn) binary alloys are investigated only as mixed phases and for a maximum of three applications. In contrast, the novel single phase of structurally stable 50 Ti-50 Zn (Ti0.5 Zn0.5 ) is synthesized and proven suitable for seven emerging applications. Interestingly, it is thermally stable up to 750 °C and possesses excellent mechanical, tribological properties and corrosion resistance. While exceptional biocompatibility is evident even up to a concentration of 500 µg mL-1 , the antibacterial activity against E. coli is also seen. Further, rapid detection and superior selectivity for glucose, along with supercabattery behavior, unambiguously demonstrate that this novel monophase is a remarkable multifunctional material than the existing mixed-phase Ti-Zn compounds. The coin-cell supercapacitor shows outstanding stability up to 30 000 cycles with >100% retention capacity. This allows us to prototype a glucose-sensing-triggered energy-storage-device system for wearable point-of-care diagnostic applications.

Amorphous Materials for Lithium-Ion and Post-Lithium-Ion Batteries.

Lithium-ion and post-lithium-ion batteries are important components for building sustainable energy systems. They usually consist of a cathode, an anode, an electrolyte, and a separator. Recently, the use of solid-state materials as electrolytes has received extensive attention. The solid-state electrolyte materials (as well as the electrode materials) have traditionally been overwhelmingly crystalline materials, but amorphous (disordered) materials are gradually emerging as important alternatives because they can increase the number of ion storage sites and diffusion channels, enhance solid-state ion diffusion, tolerate more severe volume changes, and improve reaction activity. To develop superior amorphous battery materials, researchers have conducted a variety of experiments and theoretical simulations. This review highlights the recent advances in using amorphous materials (AMs) for fabricating lithium-ion and post-lithium-ion batteries, focusing on the correlation between material structure and properties (e.g., electrochemical, mechanical, chemical, and thermal ones).  We  review both the conventional and the emerging characterization methods for analyzing AMs and present the roles of disorder in influencing the performances of various batteries such as those based on lithium, sodium, potassium, and zinc. Finally,  we  describe the challenges and perspectives for commercializing rechargeable AMs-based batteries.

Strong Yet Tough Transparent Paper with Superb Foldability.

Transparent paper manufactured from wood fibers is emerging as a promising, cost-effective, and carbon-neutral alternatives to plastics. However, fully exploring their mechanical properties is one of the most pressing challenges. In this work, a strong yet tough transparent paper with superior folding endurance is prepared by rationally altering the native fiber structure. Microwave-assisted choline chloride/lactic acid deep eutectic solvent (DES) pulping is first utilized to isolate wood fibers from spruce wood. During this process, the S1 layer within the fibers is partially disrupted, forming protruding microfibrils that play a crucial role in enhancing cellulose accessibility. Subsequently, carboxymethylation treatment is applied to yield uniformly swollen carboxymethylated wood fibers (CM fibers), which improves the interaction between CM fibers during papermaking. The as-prepared transparent paper not only shows a 90% light transmittance (550 nm) but also exhibits impressive mechanical properties, including a folding endurance of over 26 000, a tensile strength of 248.4 MPa, and a toughness of 15.6 MJ m-3. This work provides a promising route for manufacturing transparent paper with superior mechanical properties from wood fibers and can extend their use in areas normally dominated by high-performance nonrenewable plastics.