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Shape transformation offers the possibility of realizing devices whose 3D shape can be altered to adapt to different environments. Many applications would profit from reversible and actively controllable shape transformation together with a self‐locking capability. Solutions that combine such properties are rare. Here, a novel class of meta‐structures that can tackle this challenge is presented thanks to multi‐stability. Results demonstrate that the multi‐stability of the meta‐structure is strictly tied to the use of highly anisotropic materials. The design rules that enable large‐shape transformation, programmability, and self‐locking are derived, and it is proven that the shapes can be actively controlled and harnessed to realize inchworm‐inspired locomotion by strategically actuating the meta‐structure. This study provides routes toward novel shape adaptive lightweight structures where a metamaterial‐inspired assembly of anisotropic components leads to an unforeseen combination of properties, with potential applications in reconfigurable space structures, building facades, antennas, lenses, and soft robots. A novel class of meta‐structures that combines large and reversible shape reconfiguration with self‐locking property is presented. This combination of properties is reached by realizing a multi‐stable periodic structure where unit cells can possess up to nine stable states. The multi‐stability is strictly tied to the anisotropy of the materials and can be harnessed to realize a crawling soft robot.

We theoretically study the nature of parametrically driven dissipative Kerr soliton (PD-DKS) in a doubly resonant degenerate micro-optical parametric oscillator (DR-DμOPO) with the cooperation of and nonlinearities. Lifting the assumption of close-to-zero group velocity mismatch (GVM) that requires extensive dispersion engineering, we show that there is a threshold GVM above which single PD-DKS in DR-DμOPO can be generated deterministically. We find that the exact PD-DKS generation dynamics can be divided into two distinctive regimes depending on the phase matching condition. In both regimes, the perturbative effective third-order nonlinearity resulting from the cascaded quadratic process is responsible for the soliton annihilation and the deterministic single PD-DKS generation. We also develop the experimental design guidelines for accessing such deterministic single PD-DKS state. The working principle can be applied to different material platforms as a competitive ultrashort pulse and broadband frequency comb source architecture at the mid-infrared spectral range.

This work presents a framework for designing self-locking 3D compliant structures using elasto-plastic topology optimization. Design updates are generated using the gradient-based method of moving asymptotes, while the material behavior is modeled under small strain elasto-plasticity. To accurately capture the Bauschinger effect that occur during reversed loading, kinematic hardening is a crucial component of the formulation. Unlike previous studies, our approach optimizes the unloaded and permanently deformed state, enabling the realization of self-locking functionality that relies on plastic deformation. Numerical results demonstrate the effectiveness of the proposed method in designing mechanisms with the desired self-locking behavior, highlighting its potential for practical applications.

The increasing integrated manufacturing of composite components required efficiency and reliable one-sided connection. In this paper, the effect of riveting displacement on the mechanical behavior of CFRP single-lap bolted joints with a new type of one-sided connected fastener named elliptical-head non-lug self-locking (EHNL) rivet nut was studied. A three-dimensional FE model considering CFRP damage and nut material plastic deformation was developed. The whole process of the joint from nut forming to static tensile could be simulated by the FE model. The unique load-drop phenomenon in the tensile response of the joint with the EHNL rivet nut was explained. The forming quality, tensile, and fatigue behavior of joints and progressive damage of CFRP with five riveting displacements were comprehensively studied by experiments and numerical simulations. The results showed that the tensile strength increased with the increase of the riveting displacement, while the fatigue life decreased due to the larger residual stress and damage of CFRP caused by the larger riveting displacement in the nut-forming process. The fatigue life of the joint should be considered more significantly in the selection of the riveting displacement.

Achieving a fabric with good mechanical performance and breathability is significant for the development of protective clothing. The leno structure is a desirable fabric design for enhancing these properties due to its advantageous characteristics, such as flexibility, lightness, diamond-shaped structure, and increased yarn interlacing. However, there is a lack of studies focused on developing novel leno structures because of the difficulty of weaving and exploring the mechanical behavior and breathability of various leno fabrics with different structural characteristics. In this study, we leveraged advanced weaving techniques with improved needle-shaped heald frames to develop a programmed mesh-like four-warp leno cotton fabric that offers outstanding mechanical performance and breathability. The efficacy of the self-locking effects, achieved by manipulating the yarn interweaving to simultaneously regulate yarn friction and fabric porosity, is experimentally demonstrated. Compared to plain structures of the same density, the four-warp leno (FL) fabric exhibits nearly twice the tensile strength and strain in the warp direction. Additionally, the four-warp leno fabric demonstrates greater displacements to reach the junction rupture force point than plain structure of the same density in the yarn pull out tests, owing to the self-locked interweaving of the warp yarns. The yarn pull-out behavior of the FL was analyzed to illustrate the variation in load and displacement. Moreover, the high porosity of the four-warp leno woven fabric results in excellent air permeability, thermal conductivity, and water vapor transmission. This study provides an effective strategy for designing and fabricating four-warp leno fabric with outstanding mechanical performance and breathability for diverse applications.

This study explores the valorization of rice husk and plastic waste through the design of self-locking blocks for construction. The objective is to model and numerically simulate the mechanical behavior of blocks composed of two composites: rice husk concrete and melted plastic. The blocks, named RHCP Blocks (Rice Husk, Cement, Plastic Blocks), consist of three 4 cm thick rice husk concrete plates, with the intermediate plate offset and assembled to the other two using a 1.5 cm thick layer of melted plastic. The results show that RHCP blocks exhibit a compressive strength of 4.1 MPa, more than twice that of rice husk concrete alone, which is 1.75 MPa. The tensile strength reaches 2.53 MPa, an increase of more than 2.5 times compared to rice husk concrete alone, which is 1 MPa. The RHCP block has a density of 914.17 kg/m³ and a thermal conductivity between 0.119 and 0.126 W/m·K, indicating insulating performance superior to traditional materials like brick or concrete. These characteristics make RHCP blocks as promising composite for applications requiring robustness and thermal insulation in sustainable construction.

Self-locking structures are often studied in macroscopic energy absorbers, but the concept of self-locking can also be effectively applied at the nanoscale. In particular, we can engineer self-locking mechanisms at the molecular level through careful shape selection or chemical functionalisation. The present work focuses on the use of collapsed carbon nanotubes (CNTs) as self-locking elements. We start by inserting a thin CNT into each of the two lobes of a collapsed larger CNT. We aim to create a system that utilises the unique properties of CNTs to achieve stable configurations and enhanced energy absorption capabilities at the nanoscale. We used molecular dynamics simulations to investigate the mechanical properties of periodic systems realised with such units. This approach extends the application of self-locking mechanisms and opens up new possibilities for the development of advanced materials and devices.

Myocardial infarction (MI) is the leading cause of human death. Conductive patches have emerged as a promising alternative for MI repair. However, due to the epicardium and the scar tissue blocking the electrical connection between the patch and the myocardium, the immediate and effective electrical integration of the patch with the host myocardium remains a great challenge. Here, we report a conductive barbed microneedle-integrated conductive patch (CBMN-CP). The microneedle can not only self-anchor robustly to the myocardium, but also penetrate the epicardium into the inner myocardium enabling patch to bridge non-infarcted myocardium across the infarcted area immediately and to re-establish the electrical pathways in the infarcted myocardium. The rat MI model experiments demonstrated CBMN-CP significantly improved early cardiac function on day 3 post-infarction compared with traditional conductive patch. CBMN-CP enhanced myocardial repair efficacy by re-establishing intercellular electrical connections, promoting angiogenesis and regulating inflammatory responses. RNA sequencing showed that CBMN-CP mediated cardiac functions mainly through regulating early cardiac conduction and calcium handling-related gene expressions. Overall, the strategy of providing an immediate electrical integration through CBMN-CP demonstrated promising results and would be valuable in practical applications. [Display omitted] •The PPy-coated patch consists of an anisotropic substrate and barbed microneedles.•The patch can re-establish electrical pathways in myocardium immediately.•The microneedles allow for sutureless implantation of the patch.•The patch significantly improve cardiac function 3 days after infarction.•We propose an immediate electrical integration strategy for cardiac repair.

The demand for high-performance energy-absorbing structures has been on the rise in various sectors such as transportation, intelligent equipment, and emergency protection. The investigation of the self-locking properties and energy-absorbing capabilities of novel structures holds significant importance. Drawing on the body shape of weightlifters and the self-locking characteristics of the mortise and tenon structure, this paper introduces a biconical snap-fit spatial self-locking thin-walled structure. This structure offers the benefits of being adjustable, easy to install rapidly, and providing all-round self-locking in space. The findings from the quasi-static compression test conducted on a singular thin-walled tube are compared with the outcomes of finite element simulation. The overall error is maintained within a 10% margin, and the experimental and simulation results demonstrate a relatively high level of consistency, thus confirming the viability of subsequent investigations into the overall structure. The spatial self-locking ability and energy absorption (EA) characteristics of the structure under uniform impact load are confirmed using the finite element method. The study examines the impact of different stacking methods and various impact speeds on EA characteristics of the structure. The findings indicate that the biconical snap-fit spatial self-locking thin-walled structure is capable of withstanding uniform impact loads from all spatial directions. The self-locking characteristics and EA are most effective when the impact direction is α  = 0°, β  = 0°.

Inter-module connections are the critical load-transfer components in modular steel buildings (MSBs), whose mechanical behavior directly governs the overall safety and seismic performance of the entire structural system. To address the unresolved issue that the influence of complex loading conditions, especially the coupling effect of biaxial bending, on the load-transfer mechanism and degradation law of bayonet-type self-locking and unlockable connections remains poorly understood, two groups of full-scale quasi-static tests were conducted in this study. Specimen S1 (0°) was designed for the in-plane compression–bending–shear loading condition, while Specimen S2 (45°) was designed for the spatial compression–biaxial bending–shear loading condition. The test results demonstrate that both groups of specimens exhibit typical three-stage mechanical characteristics. The average initial stiffness of Specimen S1 (0°) is 5.47 kN/mm, while that of Specimen S2 (45°) is 6.08 kN/mm. The average ultimate load of S1 (0°) reaches 162.8 kN, and that of S2 (45°) is 164.85 kN. The average ductility coefficient of S1 (0°) and S2 (45°) is 2.79 and 2.14, respectively. Comparative analysis indicates that Specimen S1 (0°) presents superior energy dissipation capacity and ductility, while Specimen S2 (45°) has higher initial stiffness accompanied by faster stiffness degradation in the late loading stage. A high-fidelity refined FE model of the bayonet-type self-locking and unlockable connection was established. The FE analysis results are in good agreement with the test results, with the relative error of the positive flexural bearing capacity controlled within 5%. On this basis, parametric FE analysis was carried out to explore the influence of axial compression ratio on the mechanical performance of the connection. Furthermore, theoretical calculation formulas for the ultimate flexural bearing capacity of the connection under in-plane compression–bending–shear loading and spatial compression–biaxial bending–shear loading were proposed respectively. The calculated results are compared with the test data, with all relative errors within 5%, which verifies that the proposed formulas have favorable prediction accuracy for the ultimate flexural bearing capacity of the connection under both aforementioned complex loading conditions.