Search

The tilt grain boundaries can be used to absorb energy and shield dynamic wrinkle propagation.

Origami, such as Miura-ori, is the art of folding two-dimensional materials into complex, elaborate, and multifunctional three-dimensional objects. In this paper, SMP MO sheet are prepared, and the accuracy of deployable process is verified by experiments. The folding and deployable process of SMP MO sheet is divided into 4 stages, and each stage is described in detail. The stiffness of smart deployable stage is characterized by an exponential decline at the beginning and a gradual decrease to 0, and this is similar to the theoretical shear equivalent modulus in the Y direction. The effects of various parameters on strain and stress are also explored. The purpose of studying these mechanical characteristics is to provide driving force reference in application; In terms of application, the flow field and electromagnetic characteristics of MO sheet in different directions are studied. The aerodynamic drag and RCS reduction of MO unit cell and graded MO sheet during the deployable process are evaluated. When the dihedral fold angle is about 45°, the RCS reduction and drag reduction characteristics of MO sheet are relatively optimal, which is most beneficial to morphing aircraft.

Twisted bilayer graphene can demonstrate extraordinary optical and electrical characteristics due to its interlayer interactions. The strong coupling of normal and tangential van der Waals interactions at the interface results in inhomogeneous interlayer deformations and further changes the bilayer graphene’s physical properties. Herein, theoretical and numerical models are established to study the torsional deformation behaviour of twisting a graphene flake over a rigid graphene substrate. It is found that in-plane deformations have significant influences on the interlayer potential energy density of AA stacking, but seldom affect other stacked domains. The deformation process is thus approximated by first twisting the graphene flake rigidly, and then relaxing the rigid constraints. The bilayer graphene system minimizes its energy by reducing (enlarging) the size of high-energy (low-energy) domains through additional rotations. The additional angles of the graphene flake are derived analytically based on a mechanical model following the principle of minimum potential energy. Results show that the influences of graphene film deformations get significant at small-twist-angles (typically less than 2 ∘ ). This work reveals the torsional deformation evolution mechanism of bilayer graphene and provides beneficial guidance on achieving intriguing physical properties.

A floating air weapon system (such as airborne floating mines) plays an important role in modern air defense operations. This paper focuses on aerodynamic characteristics of airborne floating mine named inflated pillow. Firstly, the dynamic deployable process of the pillow and characteristics of the local instability of the edge are studied, and the evolution mechanism of wrinkles and kinks is analyzed. Secondly, in the cruising stage, the fluid-structural-thermal coupling analysis is performed on the pillow, and the aerodynamic characteristics are studied. Thirdly, the shape-preserving effect of the inflated pillow during the “negative pressure” slow landing stage is evaluated. It is found that when the wind velocity is higher, the pillow has a collapsed instability (surface extrusion and contact), and when the wind velocity is lower, snap-through instability occurs. Finally, for the collapsed instability, a carbon fiber skeleton is added to discrete the large global collapsed fold into small local folds, thus achieving shape-preserving effect of pillow. For snap-through instability, the critical internal pressure and different shape evolution under different wind velocity are evaluated. Through the analysis of the mechanical mechanism and control of the structural morphological evolution, it provides theoretical guidance for the application of the curved shell structure in floating air weapon system.

Owing to the unique advantages in flight altitude, dwelling time and wide coverage area, stratospheric airships provide permanent monitoring and surveillance for both civil and military applications. Here we propose a semi-rigid stratosphere airship design with circumferential high-pressure inflatable rings and a longitudinal carbon fiber skeleton supported inside. We perform numerical simulations to analyze the deformation characteristics during the whole ascending and descending process. An equivalent internal gradient pressure model of helium is established based on the capsule shape and buoyancy-weight equilibrium conditions. The implicit dynamic method is used to deal with the large deformation of the airship capsule under a low negative pressure condition. Deformation and load-bearing performance of the airship capsule, inflatable ring, skeleton, and suspension line are obtained under different working conditions. The results show that the airship, supported with the inflatable rings and the suspension lines, effectively maintains the shape and ensures the stiffness during the ascending, dwelling, and descending stages, especially suffering from negative pressure.

Hypoxia plays a crucial role in pulmonary vascular remodelling at the early stage of chronic obstructive pulmonary disease (COPD). Circle RNA (circRNA) has been identified to play a critical role in multiple diseases. However, the role of circRNAs in pulmonary vascular remodelling in COPD remains unclear. In this study, we aim to investigate the role of circRNAs in pulmonary arterial smooth muscle cell proliferation and pulmonary vascular remodelling in COPD. COPD patients show lower partial pressure of arterial oxygen and pulmonary arterial remodeling as compared with controls. circRNA microarray and real-time PCR analyses show significantly higher level of circ-BPTF and lower miR-486-5p level in the pulmonary arteries of COPD patients as compared with controls. Hypoxia suppresses miR-486-5p expression but promotes expressions of circ-BPTF and cell migration inducing protein (CEMIP) in human pulmonary arterial smooth muscle cells (PASMCs)

Graphene oxide (GO) is widely used to improve the pore structure, dispersion capacity, adsorption selectivity, resistance to acids and bases, and thermal stability of metal-organic frameworks (MOFs). However, it remains a daunting challenge to enhance selectivity simply by modifying the pore surface polarity and producing a suitable pore structure for CO2 molecules through a combination of GO with MOFs. Herein, we demonstrate a novel porous hyper-cross-linked polyimide-UiO-graphene composite adsorbent for CO2 capture via in situ chemical knitting and condensation reactions. Specifically, a network of polyimides rich in carbonyl and nitrogen atoms with amino terminations was synthesized via the reaction of 4,4'-oxydiphthalic anhydride (ODPA) and 2,4,6-trimethyl-1,3-phenylenediamine (DAM). The product plays a crucial role in the separation of CO2 from N2. As expected, the resulting composite (PI-UiO/GO-1) exhibited a 3-fold higher CO2 capacity (8.24 vs 2.8 mmol·g-1 at 298 K and 30 bar), 4.2 times higher CO2/N2 selectivity (64.71 vs 15.43), and significantly improved acid-base resistance stability compared with those values of pristine UiO-66-NH2. Furthermore, breakthrough experiments verified that the porous composites can effectively separate CO2 from simulated fuel gas (CO2/N2 = 15/85 vol %) with great potential in industrial applications. More importantly, this strategy can be extended to prepare other MOF-based composites. This clearly advances the development of MOF-polymer materials for gas capture.

Metastructures based on kirigami (the Japanese art of paper folding and cutting) have great potential for applications in stretchable electronics, bioprobes, and controllable optical and thermal devices. However, a theoretical framework for understanding the physics of their buckling behavior and to facilitate the search for ultrahigh stretchability has yet to be developed. Here, we present such a framework based on an energy approach. Closed-form analytical solutions and scaling laws are obtained for some key mechanical quantities, including flexibility, normalized flexibility, critical buckling strain, maximum tensile strain, elastic stretchability, normalized stretchability, and out-of-plane stiffness. Both experiments and numerical calculations are performed to validate the accuracy and scalability of the theoretical model. Systematic analyses of key mechanical quantities reveal how it is possible to bridge the gap between kirigami design by experience and by mechanically guided design, as well as how various dimensionless geometric parameters can be used to regulate buckling responses. Illustrative applications show that the ability to predict and tune the mechanical programmability of the proposed theoretical framework enables stable electromechanical conversion and programmable electromechanical kirigami with domino-like buckling. This work provides a foundation for further research and can also aid in the design of kirigami for use in programmable metastructures and metamaterials and energy harvesting.

This study investigated dynamic surface wrinkle propagation across a series of flower-like rotational grain boundaries (GBs) in graphene using theoretical solutions and atomistic simulations. It was found that there was significantly less out-of-plane displacement of dynamic wrinkles when curvature of rotational GBs was reduced, which can be explained by a defect shielding effect of flower-like GBs. Potential energy evolved via different modes for pristine graphene and graphene with various GBs. With external excitation, the distinctly different patterns of wrinkle propagation in graphene with various GBs demonstrated how dynamic wrinkling can reveal defects. These results can provide a theoretical basis for guiding the design and implementation of graphene-based nano-mechanical devices such as protectors and detectors.

This paper studies the unfolding mechanical behavior of a creased membrane with different crease characteristics under tensile load. The three-dimensional unfolding shape measured by a noncontact test system reflects both panel bending and crease opening. The rotational stiffness of the crease can be characterized based on the test shape. A finite deformation crease–beam model is developed to describe this unfolding mechanism. The predicted results show that the unfolding behavior of the creased membrane is affected by the ratio of the rotational stiffness of the crease to the bending stiffness of the panel. Analysis of the unfolding mechanism for the creased membrane reveals the contributions of three deformation styles—namely panel bending, panel tension, and crease opening—during different unfolding stages. The present results can be used to guide the controllable unfolding of crease-based deployable structures by adjusting the crease characteristics.

A stratospheric airship is an essential flight vehicle in the aviation field. In this paper, optimal design approach of stratospheric airships is developed to optimize envelope shape considering three failure modes and multidisciplinary analysis models, and could also reduce the mass of a stratospheric airship to be deployed at a specific location. Based on a theoretical analysis, three failure modes of airships including bending wrinkling failure, hoop tearing failure and bending kink failure, are given to describe and illustrate the failure mechanism of stratospheric airships. The results show that the location, length and size of the local uniform load and the large fineness ratio are easier to lead to bending wrinkling failure and bending kink failure. The small fineness ratio and the increasing differential pressure are more prone to cause hoop tearing failure for an airship hull. The failure probability is sensitive to the wind field. From an optimization design, the reliability analysis is essential to be carried out based on the safety of the airship. The solution in this study can provide economical design recommendations.

Articulated surface wrinkling patterns can be induced through the mechanical instability of patterned stiff films with periodic stiffness distributions (including periodic material and/or film thickness distributions) on a compliant substrate. To explore this articulated surface wrinkling, the governing equations are established by energy minimization, and the theoretical results are consistent with those from experiment and finite-element simulations. Morphology transitions from articulated wrinkling to trapezoidal or sine–trapezoid hybrid wrinkling are observed when the geometrical or material property parameters beyond a specific interval. Phase diagrams are established for the formation of articulated wrinkling morphology with respect to the geometrical and material parameters. The results show that articulated wrinkling is observed for a patterned film on a compliant substrate, depending on the periodic segment dimensions of the patterned film compared to the sinusoidal wrinkle wavelength of the corresponding homogeneous film. Compared to the sinusoidal wrinkling of a homogeneous film, articulated wrinkling has notably larger wrinkling wavelength and normal traction at the interface (approximately double when L 1 = L 2 ), however, has slightly smaller amplitude and film strains (membrane and bending peak strains). This study is a good reference for designing articulated surfaces with potential applications in many areas, especially energy harvesting devices, because of the controlled deformation location and strain distribution of such surfaces.

Lithium-ion batteries (LIBs) often suffer from capacity fading and poor cyclic performance due to mechanical degradation of the solid-electrolyte interphase (SEI). Here we perform numerical simulations and theoretical analysis to elucidate the role of plasticity in wrinkling and ratcheting behaviors of an SEI/electrode system. A coupled diffusion and finite deformation framework is formulated and numerically implemented as a user-element subroutine (UEL) to describe transient lithium diffusion and accompanying elastic–viscoplastic deformation of the electrode. It is found that concentration dependent properties and plastic deformation facilitate wrinkling in such a system. A wrinkled morphology may further lead to ratcheting and related failure under cycling. A phase diagram of four types of cyclic behaviorsis identified in terms of the charging rate and time. Our analysis suggests several potential strategies to avoid wrinkling and ratcheting instabilities, such as charging/discharging the electrode at a sufficiently slow rate, and/or introducing a thick artificial SEI with a pre-tension.

A robust and general theory is of great importance to understanding the mechanism of wrinkling, describing its behaviors and guiding the design of thin sheets. Two widely accepted theories, tension-field theory (Wagner, 1929) and thin-film theory (Cerda and Mahadevan, 2003), have been successfully used in predicting the location and pattern of wrinkling and defining critical conditions for its onset, but they have failed to describe the post-buckling behaviors (i.e., bifurcations, increasing wavenumber, and corresponding changes in morphology). In this paper, we propose a new theory of wrinkling that considers the effects of both mechanical and geometrical characteristics of thin sheets on the spatial variation in wrinkles and is valid for the general problems of post-buckling analyses. By circumventing the Föppl–von Kármán equations, the theory offers a compelling complement to thin-film theory and provides analytical details of wrinkles, especially for closed form of post-buckling behaviors. An energy barrier is introduced to assess the configurational changes of wrinkles as they evolve. Three typical examples are selected for validating the robustness of the theory and exploring its implications. More broadly, the present work provides important guidelines for eliminating wrinkles in thin sheet structures.

BACKGROUND: Pembrolizumab and sintilimab have both been approved by the China National Medical Products Administration (NMPA) for the first-line treatment of advanced non-small cell lung cancer (NSCLC). These two drugs have several differences in biological characteristics and population in clinical trials. The current retrospective study was conducted to compare the efficacy and safety of sintilimab and pembrolizumab as first-line treatments in patients with advanced NSCLC. METHODS: Consecutive patients with advanced NSCLC who received sintilimab or pembrolizumab as first-line therapy, with or without chemotherapy, from November 2018 to October 2021 in the First Affiliated Hospital of Soochow University and Dushu Lake Hospital Affiliated to Soochow University were retrospectively reviewed. Clinical data and treatment response were collected and survival was followed up. Kaplan-Meier method was used to estimate survival curves. The patients were divided into the sintilimab group and the pembrolizumab group according to the PD-1 inhibitors they received during treatment. The primary objective was to compare objective response rate (ORR) and progression-free survival (PFS) between the two groups. The secondary objectives were to compare disease control rate (DCR) and analyze adverse events (AEs) of the two groups. RESULTS: A total of 124 patients were enrolled, including 68 patients (54.8%) in the sintilimab group and 56 patients (45.2%) in the pembrolizumab group. The baseline characteristics of the patients were comparable between the two groups. The ORR was 50% in the sintilimab group and 46.4% in the pembrolizumab group (P=0.69). The DCR was 89.7% and 89.3% in the sintilimab group and the pembrolizumab group, respectively (P=0.94). The median PFS time was 9.9 months in patients treated with sintilimab compared to 10.8 months in patients on pembrolizumab treatment [hazard ratio (HR) =0.960; 95% confidence interval (CI): 0.574–1.606; P=0.875]. The median OS time was not reached in either group of patients. The incidence of grade 3–4 treatment-related adverse events (TRAEs) was 25% (17/68) in the sintilimab group and 21.4% (12/56) in the pembrolizumab group. CONCLUSIONS: Sintilimab has similar efficacy to pembrolizumab as a first-line treatment option for patients with advanced NSCLC in clinical practice, with manageable AEs.

This paper lays stress on the normalized stiffness and stretchability of planar ribbon kirigami. A dimensionless analytical model is proposed based on plane strain beam theory, in which the large curvature curved beam (LCCB) model is considered. The tensile experiments and simulations are performed and compared to validate the analytical model based on four dimensionless parameters. It is found that not all kirigami-based design is conducive to the enhancement of normalized stretchability. Remarkable long arm effect can enhance the normalized stretchability or reduce the normalized stiffness by several orders of magnitude. Finally, an optimization method is used to obtain the maximum normalized stretchability. The results in this paper can be used to guide the kirigami design in future application.

The surface of large deployable reflectors has to be carefully adjusted to achieve the required accuracy, which is an effective way to compensate for manufacturing and assembly errors or other impe...

A tiny spherical cavity will expand unboundedly in a homogenous incompressible neo-Hookean solid when the applied hydrostatic tension reaches five times of the shear modulus of the solid. Such phen...

In this letter, nanodirectional motion due to intrinsic warping edge of graphene nanoribbon is demonstrated using theoretical analysis and molecular dynamics (MD) simulation. Simulation model is established and the underlying physical insights of intrinsic nanodirectional motion are investigated. It is found that nanodirectional motion of carbon fullerene is gradient-dependent. Directional motion with +z-warping graphene edge is energetically favorable over the −z-warping configuration. As a result, a novel nanodirectional motion actuator inspired by intrinsic edge warping with Gaussian curvature can be designed. The obtained results in current research are fundamental and general, similar intrinsic properties and design paradigms can be applied to other 2D materials beyond graphene.

This paper studies the toughness, strength and interfacial bonding effect of graphene kirigami silicon-based nanocomposite (GKSN) using molecular dynamics (MD) simulation. The GKSN model is proposed based on a hybrid potential. It is found that the toughness and maximum strength of GKSN are related to the number of interior cuts and density of kirigami patterns for graphene kirigami. Mechanical response of GKSN has four typical stages, including initial wrinkling, linear increasing, ratcheting and failure. Locking effect can significantly enhance the toughness and maximum strength of GKSN with some rare expectations. With increasing interfacial bonding strength of GKSN, toughness and maximum strength increase steadily. Finally, two novel nanocomposites based on graphene kirigami can be designed. The obtained results in this paper can provide a fundamental understanding of the maximum strength and an insight for enhancing the toughness of graphene kirigami nanocomposite. The proposed mechanisms may have general significances for the design of the next generation “super-tough” and “super-strong” nanocomposites.

The chief aim of this paper is to control groove morphology precisely. In this paper, a 2D temperature field model for ultrafast picosecond laser grooving was set up on the foundation of the two-temperature model coupled with the phase change model. Then, a series of simulations were executed to investigate the influence of laser parameters such as laser power, scanning speed and repetition rate on ultrafast picosecond laser grooving. Finally, a number of experiments were performed to verify the model. The results suggest that the laser power has an obvious influence on the groove width and depth because the heat-affected zone area and single-pulse laser energy increase when the laser power varies from 2 W to 5 W. Obvious impacts of scanning speed on the groove depth and quality are observed in the present simulation due to the variation of overlap between sequential pulses and pulse numbers. The groove width and quality depend on the repetition rate. This is because the increase in the repetition rate has a certain contribution to increasing the temperature of heat residue and pulse number. This research contributes to present theoretical guidance on laser grooving.

Miura-ori is a form of origami and is widely used in aerospace. The aerodynamic characteristics of Miura-ori composite structure are greatly influenced by its configuration. In this paper, ...

Graphene oxide (GO) is widely used to improve the pore structure, dispersion capacity, adsorption selectivity, resistance to acids and bases, and thermal stability of metal-organic frameworks (MOFs). However, it remains a daunting challenge to enhance selectivity simply by modifying the pore surface polarity and producing a suitable pore structure for CO

A fundamental understanding of the interactions between one-dimensional nanomaterials and the cell membrane is of great importance for assessing the hazardous effects of viruses and improving the performance of drug delivery. Here, we propose a finite element-based coarse-grained model to describe the cell entry of nanomaterials based on an absolute nodal coordinate formula and Brownian dynamics. The interactions between nanoparticles and lipid membrane are described by the Lennard–Jones potential, and a contact detection algorithm is used to determine the contact region. Compared with the theoretical and published experimental results, the correctness of the model has been verified. We take two examples to test the robustness of the model: the endocytosis of nanorods grafted with polymer chains and simultaneous entry of multiple nanorods into a lipid membrane. It shows that the model can not only capture the effect of ligand–receptor binding on the penetration but also accurately characterize the cooperative or separate entry of multiple nanorods. This coarse-grained model is computationally highly efficient and will be powerful in combination with molecular dynamics simulations to provide an understanding of cell–nanomaterial interactions.