Intrinsic Deformation Research Articles

Hypothetical molecular mechanism of a novel class of bacteriocin-based antivirals for the inhibition of respiratory Syncytial Virus (RSV)

Respiratory Syncytial Virus (RSV) is a serious pathogen in vulnerable individuals and a major cause of hospitalization and death. With limited access to effective biotherapeutics for RSV treatment, antimicrobial peptides (AMPs) have been explored, including bacteriocins such as labyrinthopeptins (Labys) produced by Actinomadura namibiensis. Labys have demonstrated antiviral activity against RSV and are believed to interact with phosphatidylethanolamine (PE) in the capsid to form pores in the viral membrane. However, a greater understanding of the interaction mechanism of these bacteriocins with phospholipids like PE is needed. Our hypothesis suggests that, due to the structural plasticity of Labys, these peptides can undergo changes in their intrinsic deformability and thus bind stably to PE, mediating subsequent disruption of the lipid envelope as a new therapeutic target. Findings from modeling, classical dynamics, and ENM suggest that some Labys, such as Laby A1, interact favorably and stably with PE, with computationally predictable experimental inhibitory kinetics, and can even interact with more complex membranes rich in PE. Additionally, Laby A1 can undergo allosteric conformational changes based on its interaction with PE, adopting a “toroidal” folded conformation. This conformation is associated with peptide-lipid interactions, where the embedding of the peptide into the membrane, due to its affinity for PE, may lead to the formation of toroidal pores. This could explain the mechanism of RSV inhibition. The results support the need for further research in the development of antivirals against RSV based on Labys-like bacteriocins.

Room- and elevated-temperature strength of as-cast Mg-Sn-Y alloys mediated by Sn and Y solubility via intrinsic stability and deformation resistance

Microstructure evolution and first-principles calculations were adopted to explore alloying elements Sn and Y proportion influence on room- and elevated-temperature mechanical properties of as-cast Mg-Sn-Y alloy in the present study. The results show that the room- and elevated-temperature compression yield strength and ultimate compression strength of Mg-1Sn-yY alloy simultaneously improves with Y addition from 0.5 wt.% to 2 wt.%. Decreasing Sn to 0.5 wt.% in Mg-1Sn-2Y alloy, Mg-0.5Sn-2Y alloy yields comparable room-temperature strength to Mg-1Sn-1.5Y alloy with similar alloying element addition. Notably, the elevated-temperature strength of Mg-0.5Sn-2Y alloy is even greater than that of counterpart Mg-1Sn-1.5Y alloy and achieves increment by ∼42 MPa at 200 °C, 48 MPa at 250 °C, and 29 MPa at 300 °C, respectively. Combined with microstructure analysis and first-principles calculations, the mechanism behind this is mainly attributed to increased Y solubility in the matrix. Sn content reduction leads to the MgSnY ternary phase (4.97%) in Mg-1Sn-1.5Y alloy being replaced by the low-content Sn3Y5 phase (2.30%) so as to high Y solid solution in the Mg-0.5Sn-2Y alloy. Raised Y solubility is more favorable to decrease cohesive energy and increase bulk modulus, shear modulus and Young’s modulus, which avails enhancing intrinsic cohesive strength and deformation resistance of alloy other than Sn solubility. Thus, improvement of cohesive strength and deformation resistance by Y solubility promotes Mg-0.5Sn-2Y alloy to endure high loading at elevated temperatures.

MODIFICATION OF THE EXTENDED TUBE MODEL (METM) FOR THE CHARACTERIZATION OF FILLED VULCANIZATES

ABSTRACT The aim of this study is to develop a material model for filled vulcanizates that is physically justifiable. This model builds upon the established extended tube model and is incorporated into a finite element program. The research demonstrates that the intrinsic deformation concept is inadequate for describing nonlinear deformation behavior under the assumption of incompressible, isotropic materials. Consequently, an alternative approach is proposed, employing a strain function rather than direct use of principal strains, to characterize reinforcement behavior. This strain function aligns with the first invariant of the right Cauchy-Green strain tensor over a wide deformation range. At minor deformations, the entanglements’ contribution is considered through an additional reinforcement term. The novel reinforcement function is depicted as a sum of three elements, each representing reinforcement at different strain levels: low, medium, and high. Experimental comparisons show that the Modified Extended Tube Model (METM) effectively captures the stress-strain response of filled systems across all deformation levels. Furthermore, the reinforcement function parameters, derived from fitting the METM to experimental data, offer a quantitative assessment of the fillers’ reinforcing effects, while the extended tube model parameters reflect the network characteristics.

Optical coherence tomography quantifies gradient refractive index and mechanical stiffness gradient across the human lens

BackgroundAs a key element of ocular accommodation, the inherent mechanical stiffness gradient and the gradient refractive index (GRIN) of the crystalline lens determine its deformability and optical functionality. Quantifying the GRIN profile and deformation characteristics in the lens has the potential to improve the diagnosis and follow-up of lenticular disorders and guide refractive interventions in the future.MethodsHere, we present a type of optical coherence elastography able to examine the mechanical characteristics of the human crystalline lens and the GRIN distribution in vivo. The concept is demonstrated in a case series of 12 persons through lens displacement and strain measurements in an age-mixed group of human subjects in response to an external (ambient pressure modulation) and an intrinsic (micro-fluctuations of accommodation) mechanical deformation stimulus.ResultsHere we show an excellent agreement between the high-resolution strain map retrieved during steady-state micro-fluctuations and earlier reports on lens stiffness in the cortex and nucleus suggesting a 2.0 to 2.3 times stiffer cortex than the nucleus in young lenses and a 1.0 to 7.0 times stiffer nucleus than the cortex in the old lenses.ConclusionsOptical coherence tomography is suitable to quantify the internal stiffness and refractive index distribution of the crystalline lens in vivo and thus might contribute to reveal its inner working mechanism. Our methodology provides new routes for ophthalmic pre-surgical examinations and basic research.

Mean-field-derived IBM-1 Hamiltonian with intrinsic triaxial deformation

Mean-field-derived IBM-1 Hamiltonian with intrinsic triaxial deformation

Residual deformation analysis of laser powder bed fusion-fabricated lattice structures

ABSTRACT Lattice structures are crucial for weight reduction, and laser powder bed fusion (LPBF) is an efficient fabrication method. However, there's a notable research gap in understanding the residual deformation of LPBF-fabricated lattice structures. This study investigates the residual deformation of three basic lattice structures, body centre cell (BCC), face centre cell (FCC), and diamond cell (DC), fabricated via LPBF to reveal their deformation mechanisms. Analysis covers horizontal direction, building direction, and total deformations, unveiling complex structural responses. Lower relative densities exhibit a prevalent structural deformation mode (SDM) causing significant deformations, while higher densities shift to an intrinsic deformation mode (IDM) dominated by contraction during fabrication. The FCC structure shows optimal stability with minimal residual deformation across most densities. This study offers insightful findings and a detailed mechanistic analysis of residual deformation in LPBF-fabricated lattice structures, applicable across various configurations, ensuring design process uniformity and reliability.

A strain components-based Mohr–Coulomb fracture criterion for proportional loading

Ductile fracture criteria are crucial in the application of elastoplastic materials like advanced high-strength steels, particularly due to their tendency to fail without significant localized necking. It is aimed to figure out the unified mechanism for ductile fracture and accurately describe it with phenomenological criteria. In this study, the effect of the stress triaxiality and the Lode parameter is analyzed mathematically. The maximum shear strain and the normal strain to fracture are emphasized in the proposed strain components-based Mohr–Coulomb fracture criterion particularly designed for plane stress states, and it is assumed that fracture occurs when the combination of the maximum shear strain and the normal strain reaches the critical value. It is then extended to describe fracture with the equivalent plastic strain and the normal strain to fracture. The experimental fracture data of AA 2024-T351 and the additively manufactured Ti-6Al-4V titanium alloy are used to verify the proposed models. A fracture forming limit diagram comprising forming limit curves calibrated from stress states under different stress triaxialities is proposed based on the proposed fracture criteria for plane stress states. This study shows that a strong correlation between the maximum shear strain and the normal strain to fracture has been observed, and it can be described piecewise-linearly. Besides, the orientation of the fracture surface under both tension (including plane strain tension) and compression (including plane strain compression) can be qualitatively explained by the Mohr’s strain circles. The results provide a new insight into the intrinsic deformation and fracture mechanism of materials that fail without severe localized necking.

Force-regulated chaperone activity of BiP/ERdj3 is opposite to their homologs DnaK/DnaJ.

Polypeptide chains experience mechanical tension while translocating through cellular tunnels, which are subsequently folded by molecular chaperones. However, interactions between tunnel-associated chaperones and these emerging polypeptides under force is not completely understood. Our investigation focused on mechanical chaperone activity of two tunnel-associated chaperones, BiP and ERdj3 both with and without mechanical constraints and comparing them with their cytoplasmic homologs: DnaK and DnaJ. While BiP/ERdj3 have been observed to exhibit robust foldase activity under force, DnaK/DnaJ showed holdase function. Importantly, the tunnel-associated chaperones (BiP/ERdj3) transitioned to a holdase state in the absence of force, indicating a force-dependent chaperone behavior. This chaperone-driven folding event in the tunnel generated an additional mechanical energy of up to 54 zJ, potentially aiding protein translocation. Our findings align with strain theory, where chaperones with higher intrinsic deformability act as mechanical foldases (BiP, ERdj3), while those with lower deformability serve as holdases (DnaK and DnaJ). This study thus elucidates the differential mechanically regulated chaperoning activity and introduces a novel perspective on co-translocational protein folding.

Composite patch with negative Poisson's ratio mimicking cardiac mechanical properties: Design, experiment and simulation

Developing patches that effectively merge intrinsic deformation characteristics of cardiac with superior tunable mechanical properties remains a crucial biomedical pursuit. Currently used traditional block-shaped or mesh patches, typically incorporating a positive Poisson's ratio, often fall short of matching the deformation characteristics of cardiac tissue satisfactorily, thus often diminishing their repairing capability. By introducing auxeticity into the cardiac patches, this study is trying to present a beneficial approach to address these shortcomings of the traditional patches. The patches, featuring the auxetic effect, offer unparalleled conformity to the cardiac complex mechanical challenges. Initially, scaffolds demonstrating the auxetic effect were designed by merging chiral rotation and concave angle units, followed by integrating scaffolds with a composite hydrogel through thermally triggering, ensuring excellent biocompatibility closely mirroring heart tissue. Tensile tests revealed that auxetic patches possessed superior elasticity and strain capacity exceeding cardiac tissue's physiological activity. Notably, Model III showed an equivalent modulus ratio and Poisson's ratio closely toward cardiac tissue, underscoring its outstanding mechanical potential as cardiac patches. Cyclic tensile loading tests demonstrated that Model III withstood continuous heartbeats, showcasing outstanding cyclic loading and recovery capabilities. Numerical simulations further elucidated the deformation and failure mechanisms of these patches, leading to an exploration of influence on mechanical properties with alternative design parameters, which enabled the customization of mechanical strength and Poisson's ratio. Therefore, this research presents substantial potential for designing cardiac auxetic patches that can emulate the deformation properties of cardiac tissue and possess adjustable mechanical parameters.

Fabrication and characterization of in-situ Ti(C, N) – CoCrFeNi cermets via mechanical alloying and spark plasma sintering

Ti(C, N) cermets were prepared by adding CoCrFeNiTi to g-C3N4 and using mechanical alloying and spark plasma sintering techniques. The evolution of microstructure and the systematic analysis of the influence of different binder content on mechanical properties were investigated. This result demonstrates that with an increase in binder content, the grain size of Ti(C, N) in the cermets decreases, and the formation of spheroidal small grains becomes more prominent while the occurrence of large grains decreases. Additionally, the relative density and hardness of Ti(C, N) metal ceramics have slightly decreased. The fracture toughness of Ti(C, N)/HEA cermet is codetermined by the intrinsic sintering property and deformability of HEA binders. The Ti(C, N) cermets (CH3) exhibits excellently bending strength and fracture toughness，which are 1941 MPa and 11.2 MPa m1/2 respectively. The study aims to enhance the mechanical properties and toughness of Ti(C, N) and proposes a novel approach for the synthesis of Ti(C, N) cermet.

Effect of compressive strain on electronic and optical properties of Cr-doped monolayer WS2.

The electronic properties and optical properties of Cr-doped monolayer WS2 under uniaxial compressive deformation have been investigated based on density functional theory. In terms of electronic structure properties, both intrinsic and doped system bandgaps decrease with the increase of compression deformation, and the values of the bandgap under the same compression deformation after Cr doping are reduced compared with the corresponding intrinsic states. When the compressive deformation reaches 10%, both the intrinsic and doped system band gaps are close to zero. New electronic states and impurity energy levels appear in the WS2 system when doped with Cr atoms. For the optical properties, the calculation and analysis of the dielectric function under each deformation regime of monolayer WS2 show that the compression deformation affects the dielectric function, and when the compression deformation is 10%, the un-doped and Cr-doped regimes show a decrease in ε1(ω) compared to the compression deformation of 8%. For each deformation system, the peak reflections occur in the ultraviolet region. Near the position where the second peak of the absorption spectrum appears, it can be seen that the ability of each system to absorb light gradually decreases with the increase of the amount of deformation and appears to be red-shifted to varying degrees. This study follows the initial principles of the density functional theory framework and is based on the CASTEP module of Materials-Studio software GGA and PBE generalizations are used to perform computations such as geometry optimization of the model. We have calculated the energy band structure of monolayer WS2 with intrinsic and compressive deformations of 2% and 4% using PBE and HSE06, respectively. The band gap values calculated using PBE are 1.802 eV, 1.663 eV, and 1.353 eV, respectively, and the band gap values calculated with HSE06 are 2.267 eV, 2.034 eV, 1.751 eV. The results show that the bandgap values calculated by HSE06 are significantly higher than those calculated by PBE, but the bandgap variations calculated by the two methods have the same trend, and the shape characteristics of the energy band structure are also the same. However, it is worth noting that the computation time required for the HSE06 calculation is much longer than that of the PBE, which is far beyond the capability of our computer hardware, and the purpose of this paper is to investigate the change rule of the effect of deformation on the bandgap value, so to save the computational resources, the next calculations are all calculated using the PBE. The Monkhorst-Pack special K-point sampling method is used in the calculations. The cutoff energy for the plane wave expansion is 400 eV, and the K-point grid is assumed to be 5 × 5 × 1. Following geometric optimization, the iterative precision converges to a value of less than 0.03 eV/Å for all atomic forces and at least 1 × 10-5 eV/atom for the total energy of each atom. The vacuum layer's thickness was selected at 20 Å to mitigate the impact of the interlayer contact force.

Molecular insights into reversible and irreversible kinks formed in nanocellulose

Kink defects in nanocellulose are common, yet questions remain open regarding the unclear microstructure-mechanical property relationship. Various kink patterns without molecular-scale resolution cause confusion about how nanocellulose forms different kinks and what the fundamental mechanisms of reversible and irreversible kinks are. In atomic force microscopy images, bent nanofibrils usually exhibit small curvatures, while kinked nanofibrils feature sharp bends, in which kinks are notable due to their distinct disordered configurations. To identify the incipient kink defects formed in nanocellulose, molecular dynamics simulations of cellulose nanocrystals (CNCs) under curvature-dependent bending were subsequently carried out. Five typical bending/kinking modes were found, depending on the anisotropic microstructure and size of CNCs. More importantly, two contrasting cases of kinks were demonstrated, providing evidence that kink defects in nanocellulose depend mainly on the microstructure at the molecular scale. Kinks in CNCs with the (100) and (11¯0) crystal plane are recoverable with a few residual defects. While kinks in CNCs with the (010) crystal plane are irreversible with permanent microstructural damage. Compressive stresses accumulated in the bottom chains of CNC contribute to the main mechanism for forming incipient kinks in nanocellulose. The results can fundamentally answer the confusion in recent experiments why bond breakage did not necessarily occur even at high kink angles. The insights present intrinsic deformation mechanisms for understanding the widespread but mysterious kinks arising in nanocellulose.

Bending deformation modulation of the optoelectronic properties of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, O): a first-principles study.

A first-principles approach based on density functional theory was used to explore the effect of bending deformation on the electrical structure of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, and O). The study included alternate doping of nonmetallic atoms, as well as a comparison of the effects of intrinsic bending deformation and nonmetallic doping deformation. The results demonstrate that boron atom doping raises the Fermi energy level. Examining the energy band structure indicates that the intrinsic molybdenum ditelluride is a direct band gap semiconductor, which is transformed from a direct band gap to an indirect band gap after doping. We selected boron-doped systems for bending deformation and compared them with the intrinsic systems. With increasing deformation, all systems start to shift from semiconductor to metal. When the deformation reaches 8°, the energy levels fill and the electron energy increases. The intrinsically bent systems transition from direct band gap to indirect band gap and eventually to metal. The indirect band gap semiconductor-to-metal transition process occurs after the bending deformation of the boron-doped atoms. The analytical results show that the absorption and reflection peaks of the molybdenum ditelluride system are blue-shifted after the bending deformation of the boron-doped atoms. Under fundamental principles, this research depends on the density functional theory framework (DFT) using the CASTEP module in the Materials-Studio software. The plane-wave pseudopotential approach with modified gradient approximation and the Perdew-Burke-Ernzerhof (PBE) generalized function is used for structure optimization and total energy calculations of the X-doped (X = B, C, N, O) MoTe2 system at different shape variables. Geometry optimization of the 27-atom superlattice MoTe2 was carried out, followed by alternative doping of tellurium atoms in the molybdenum ditelluride with B, C, N, and O. In this paper, the intrinsic bending deformation and B-doping of molybdenum ditelluride were selected for deformation analysis. Intrinsic bending deformations and boron-doped molybdenum ditelluride with bending angles ranging from 2° to 8° were employed for deformation investigation. In Fig.1, pink is used to represent doped B atoms, orange is used to describe Te atoms, and green is used to represent Mo atoms. For the degree of deformation of molybdenum ditelluride, in this paper, it is expressed by the bending angle, i.e., the angle of the plane of molybdenum ditelluride after bending and deformation of a single layer of molybdenum ditelluride concerning the angle of the plane folded for the deformed plane. How to do it: For ease of presentation, the atomic chains are set to different colors. The purple part on both sides of the figure is bent and deformed, 3-5 atoms are fixed appropriately, and the middle part is deformed. On this basis, the bending deformation of intrinsically doped and boron-doped MoTe2 is comparatively analyzed. The effect of boron-doped atoms on the structure of MoTe2 is systematically investigated to study its structural stability and electronic structure. Fig.1 a1 and a2 The main and side views of intrinsic MoTe2; b1 and (b2) the main and side views of MoTe2 doped with boron atoms bent by 8°.

Twisted-layer boron nitride ceramic with high deformability and strength.

Moiré superlattices formed by twisted stacking in van der Waals materials have emerged as a new platform for exploring thephysics of strongly correlated materials and other emergent phenomena1-5. However, there remains a lack of research on the mechanical properties of twisted-layer van der Waals materials, owing to a lack of suitable strategies for making three-dimensional bulk materials. Here we report the successful synthesis of a polycrystalline boron nitride bulk ceramic with high room-temperature deformability and strength. This ceramic, synthesized from an onion-like boron nitride nanoprecursor with conventional spark plasma sintering and hot-pressing sintering, consists of interlocked laminated nanoplates in which parallel laminae are stacked with varying twist angles. The compressive strain of this bulk ceramic can reach 14% before fracture, about one order of magnitude higher compared with traditional ceramics (less than 1% in general), whereas the compressive strength is about six times that of ordinary hexagonal boron nitride layered ceramics. The exceptional mechanical properties are due to a combination of theelevated intrinsic deformability of the twisted layering in the nanoplates and the three-dimensional interlocked architecture that restricts deformation from propagating across individual nanoplates. The advent of this twisted-layer boron nitride bulk ceramic opens a gate to the fabrication of highly deformable bulk ceramics.

Design and characterization of a variable-stiffness ankle-foot orthosis.

Ankle-foot orthoses (AFOs) are a type of assistive device that can improve the walking ability of individuals with neurological disorders. Adjusting stiffness is a common way to customize settings according to individuals' impairment. This study aims to design a variable-stiffness AFO by stiffness module and characterize the AFO stiffness range to provide subject-specific settings for the users. We modeled AFO using bending beams with varying fulcrum positions to adjust the stiffness. To characterize the stiffness range and profile, we used the superposition method to generate the theoretical model to analyze the AFO numerically. The intrinsic deformation of the bending beam in the AFO is considered a combination of 2 bending deformations to replicate actual bending conditions. The corresponding experiments in different fulcrum positions were performed to compare with and optimize the theoretical model. The curve fitting method was applied to tune the theoretical model by adding a fulcrum position-related coefficient. The AFO stiffness increased as the fulcrum moved to the proximal position. The maximum stiffness obtained was 1.77 Nm/° at a 6-cm fulcrum position, and the minimum stiffness was 0.82 Nm/° at a 0.5-cm fulcrum position with a 0.43-cm thick fiberglass beam. The corresponding theoretical model had maximum and minimum stiffness of 1.71 and 0.80 Nm/°, respectively. The theoretical model had a 4.08% difference compared with experimental values. The stiffness module can provide adjustable stiffness with the fulcrum position and different kinds of fiberglass bars, especially the thickness and material of the beam. The theoretical model with different fulcrum positions can be used to profile the real-time stiffness of the AFO in a dynamic motion and to determine the appropriate dimensions of the bending beam.

Orientation dependent magnetocapacitance tuning in epitaxial (La,Sr)MnO3/(K,Na)NbO3-based heterostructures

We fabricated multiferroic heterostructures composed of La0.67Sr0.33MnO3 (LSMO) and (K0.48Na0.48Li0.04) (Nb0.81Ta0.15Sb0.04)O3 (KNN-LTS) on (001)-, (110)-, and (111)-oriented SrTiO3 substrates using pulsed laser deposition technique. X-ray diffraction confirmed the coherent growth of LSMO layers, while KNN-LTS layers exhibited partial relaxation in the heterostructures, with relaxation increasing from (001) to (111) orientations. Notably, the (111)-oriented LSMO, which displayed the highest out-of-plane lattice relaxation, exhibited superior magnetic properties. On the other hand, (001)-oriented sample showcased the maximum ferroelectric and piezoelectric properties due to its high elastic deformation, whereas (111)-oriented sample, characterized by higher intrinsic lattice deformation, demonstrated better dielectric properties. Our elemental analysis confirmed interface charge transfer, indicating the presence of magnetoelectric coupling within the heterostructures. Then, the magnetocapacitance effect was attributed to a combination of interface magnetoelectric coupling and magnetoresistance in LSMO. The (111)-oriented sample displayed a remarkable MC value of approximately 62% near the transition temperature (around 352 K) of LSMO, while the (110)-oriented sample reached the highest MC of approximately 65% at 300 K. These findings suggest that engineered ferroelectric/ferromagnetic heterostructures hold promise for high MC performance at room temperature and offer opportunities for modulation with crystallographic orientation, making them potentially valuable for applications in multiferroic devices.

Omnidirectionally Strain‐Unperturbed Tactile Array from Modulus Regulation in Quasi‐Homogeneous Elastomer Meshes

AbstractSkin‐like stretchable tactile arrays are of paramount significance for perceiving physical interactions in dynamic biological tissues, prosthetic limbs, and robots. However, mechanical strain‐induced interference invariably degrades the pressure‐sensing accuracy of tactile arrays. In this work, an omnidirectionally strain‐unperturbed tactile array is prepared through modulus regulation in quasi‐homogeneous elastomer meshes. By varying fiber orientations, the proportion of intrinsic elastic and structural deformations in quasi‐homogeneous elastomer meshes can be adjusted, and the modulus can be regulated from 0.23 to 8.23 MPa. The tactile array combined with low‐ and high‐modulus elastomer meshes enables strain‐unperturbed pressure sensing through local stiffening and controllable deformation. Remarkably, the tactile array exhibits 97% strain insensitivity when stretched 100% along the omniplane directions. Moreover, the quasi‐homogeneous structure endows the tactile array with high robustness, even after 5000 cycles of severe stretching or pressing. By integrating the tactile array with a microcontroller, a tactile visualization system is built to achieve accurate tactile interaction even under multiaxial tensile strain. This work provides an alternative insight into the design of omnidirectionally strain‐unperturbed electronic devices for wide applications on dynamic surfaces.

Effect of biaxial cyclic loading path on the mechanical and microstructure properties of articular cartilage

Cyclic loading stimulation has the potential to change both the mechanical properties and microstructure of cartilage, subsequently damaging the articular cartilage and contributing to joint osteoarthritis. This study focuses on investigating the behavior of knee articular cartilage under biaxial cyclic loading and analyzing the associated microstructural changes at the ultrastructural level. We studied the in-plane biaxial cyclic loading behavior of cartilage with a particular emphasis on understanding the effects of loading paths, taking into consideration the complex loading conditions encountered during daily activities. The experimental results reveal a clear influence of the constraints in the Y-direction (orthogonal direction) on the strain evolution in the X-direction. Furthermore, the variation in orthogonal stress corresponding to the loading path significantly impacts the biaxial mean strain of the test sample. To be specific, the uniaxial path, characterized by no constraints in the Y-direction, demonstrates the highest mean strain of 25.08 ± 0.88% in the X-direction, while the proportional path exhibits the lowest mean strain (10.77 ± 0.49%) in the X-direction due to the Y-direction's largest stress constraint. We explored the effects of stress amplitude and peak stress holding time on mean strain under a square path. Our observations indicate that the mean strain of cartilage increases with the higher stress amplitude or the longer peak stress holding time. Additionally, we analyzed the collagen fibril networks before and after biaxial cyclic loading to reveal the intrinsic deformation mechanism. The rearrangement of collagen fibril networks is closely associated with the stress state of cartilage, where higher stress levels lead to more severe fibril damage.

Strength-ductility synergy in 3D-printed (TiB + TiC)/Ti6Al4V composites with unique dual-heterogeneous structure

The 3D-printed (TiB + TiC)/Ti6Al4V composite with tailored network reinforcement architecture and heterogeneous α lamellae structure (i.e., a dual-heterogeneous structure) possesses simultaneously improved tensile strength and uniform ductility. To reveal the fundamentals behind the strengthening and deformation mechanisms, the microstructural evolution and tensile deformation behavior of as-printed (TiB + TiC)/Ti6Al4V composite were carefully examined under in-situ tensile testing together with as-printed Ti6Al4V. The heterogeneous structure in the composites induced significant constraint effect, affording deformation compatibility via strain partitioning throughout the composite. Importantly, owing to the heterogeneous α lamellae structure and the pinning effect of reinforcements, the hetero-deformation induced additional strengthening effect and strain-hardening potential, leading to much enhanced plastic deformation capacity and improved strengthening efficiency. Furthermore, the microcracks arresting stabilized the plastic deformation at the later deformation stage and offered extra ductility. Based on these investigations, the intrinsic strengthening and deformation mechanisms behind the synergetic strength-ductility over the whole deformation process were elucidated. This work highlights the importance of heterogeneous structure design strategy in the development of discontinuous metal matrix composites.

GelMap: intrinsic calibration and deformation mapping for expansion microscopy

Expansion microscopy (ExM) is a powerful technique to overcome the diffraction limit of light microscopy by physically expanding biological specimen in three dimensions. Nonetheless, using ExM for quantitative or diagnostic applications requires robust quality control methods to precisely determine expansion factors and to map deformations due to anisotropic expansion. Here we present GelMap, a flexible workflow to introduce a fluorescent grid into pre-expanded hydrogels that scales with expansion and reports deformations. We demonstrate that GelMap can be used to precisely determine the local expansion factor and to correct for deformations without the use of cellular reference structures or pre-expansion ground-truth images. Moreover, we show that GelMap aids sample navigation for correlative uses of expansion microscopy. Finally, we show that GelMap is compatible with expansion of tissue and can be readily implemented as a quality control step into existing ExM workflows.