Room-temperature compressive creep deformation threatens the long-term reliability of deep-sea pressure hulls. Its distinct stress states and thermal activation energies make conventional high-temperature or tensile creep mechanisms inadequate for this scenario. This study investigates the compressive creep mechanism of Ti80 alloy, focusing on microstructural evolution and dislocation behavior under prolonged near-yield stress conditions. Using multiscale characterization techniques from the micron to atomic scale, including quasi in-situ and in-situ methods, we demonstrate that premature dislocation nucleation at interfaces-the primary mechanism for roomtemperature compressive creep-is linked to nanoscale gamma phases at alpha/(3 interfaces, which have lower critical resolved shear stress (CRSS) for dislocation activation and serve as bridges for dislocations transmission. Our findings provide mechanistic insight into room-temperature compressive creep and offer guidance for alloy design and service life prediction of deep-sea pressure hulls.

In crystals, grains with different orientations form grain boundaries (GBs), while the meeting of three neighboring GBs gives rise to triple junctions (TJs). TJs are therefore ubiquitous crystalline defects in polycrystals and bear effect to the microstructural evolution of GB network via modulating GB migration and grain growth kinetics. Since the plastic deformation of TJs depend inherently on their atomic structures and migration pathways, it is crucial to establish a direct connection between the TJ kinetics and the grain growth of polycrystals. We propose a multiscale formulation to incorporate molecular dynamics (MD), kinetic Monte Carlo (kMC) simulation, and theoretical modeling of TJ kinetics to unravel the importance of structure-dependent TJ migration mechanisms in regulating GB network evolution in polycrystals. At an atomic scale, MD simulations have demonstrated that both the TJ disclinations and asymmetry can inhibit the glide of disconnections into TJs and thus obstruct the migration of TJs. Based on the atomistic insights, a theoretical model has been developed to describe the structure-dependent TJ migration kinetics, differing from the infinite TJ mobility hypothesis frequently utilized in existing formulations. The migration of an individual TJ, which is featured by the flux and accumulation of disconnections and their interactions with disclinations, can be captured by our model using kMC simulations, furnishing a dataset of TJ structure-mobility relationship. The atomistically-informed TJ kinetics and TJ mobility dataset are incorporated into a polycrystalline kMC model, which is capable of modelling TJ-influenced grain growth kinetics and grain size distribution evolution. Our work not only provides physical insights into the TJ-mediated GB migration mechanisms, but also offers a multiscale formulation for predicting the evolution of GB network in polycrystalline metals.

Cracking represents a fundamental mode of failure in solids and structures, with mechanisms from catastrophic cleavage to fully ductile separation, as extensively investigated in materials spanning brittle ceramics and rocks to ductile metals and composites. However, for superhard materials, extreme hardness and brittleness result in exceptionally formidable challenges to mechanical testing and microstructural characterization, leaving their underlying cracking mechanisms and corresponding mechanical models largely unexplored. Herein, by employing a homemade in situ transmission electron microscopy mechanical stage, we observed two distinct cracking mechanisms in superhard cubic boron nitride (cBN), including the conventional brittle cleavage and a fundamentally different layered decohesion mechanism characterized by the formation of stacked hexagonal planes formed via a cubic-to-graphitic phase transition on the crack surfaces. Combining experimental observations and molecular dynamics simulations, it was revealed that the activation of the two cracking mechanisms depends on the surface flaw depth, with mechanistically distinct layered decohesion pathway occurring only when the flaw depth is below the critical flaw size. Building on the elucidated cracking mechanisms in cBN, a double-phase field model including both the descriptions of cleavage and the transition from cubic to graphitic phases is proposed. The presented phase field model endeavors to predict brittle or ductile fractures as occurred in cBN under severe strain, and provides a novel methodology to simulate the cracking in superhard covalent materials.

Functional skins represent a transformative platform for diverse applications, yet their highly conformal deployment and maintenance remain challenging on substrates with arbitrary geometries, complex microstructures and dynamic deformation. Herein, we present a material-form shift for functional skin fabrication, utilizing spray-deposited polyacrylic acid/polyethyleneimine (PAA/PEI) lyophilized hydrogel powders embedded with functional components. Upon rehydration, these powders instantaneously coalesce into conformal hydrogel skins (<5 s). Their micron-scale particle size enables high-fidelity deposition that preserves substrate topography, including microstructural features. The resulting functional hydrogel skins exhibit exceptional mechanical properties: a magnetoactive variant demonstrates softness (Young's modulus approximate to 140 kPa), high toughness (approximate to 800 J/m(2)), and strong interfacial adhesion (approximate to 600 J/m(2)) to various substrates. Soft robots are constructed by conformally coating magnetic hydrogel skins onto elastomer films, maple leaves, or liquid metal balls, capable of flapping, grasping, locomotion, and therapeutic operation. The versatility of the platform is further exemplified through integrated bioinspired functionalities such as thermochromic response and fluorescence. Leveraging convenience, versatility, and broad applicability, this strategy presents an enticing pathway for engineering functional surfaces in devices and robotics.

Fracture mechanics, originating from Griffith’s pioneering theory, has evolved into a foundational framework for understanding and predicting material failure across scales. Over the past century, it has expanded from linear elasticity to encompass nonlinear, dynamic, and stochastic behaviors—capturing fracture, fatigue, rupture, damage, and fragmentation in materials ranging from metals and ceramics to polymers, composites, soft matter, and biological tissues. Despite these advances, the field is far from complete. As modern materials and structures operate under unprecedented extremes of size, rate, and environment, classical assumptions—continuum validity, small-scale yielding, and singular field dominance—are increasingly challenged. This Perspective identifies 25 outstanding issues that delineate the current and emerging frontiers of fracture mechanics. Organized across three interrelated domains—theoretical foundations, material behavior, and engineering applications—these issues span the limits of continuum theory, attainable fracture toughness, multiscale crack coalescence, fracture under extreme environments, and the integration of artificial intelligence for data-driven modeling. Collectively, they highlight a paradigm shift toward multiscale, multiphysics, and information-rich approaches that bridge atomistic processes and macroscopic failure. Far from a mature or closed discipline, fracture mechanics remains an evolving science—one that will continue to play a central role in designing materials and structures with unprecedented strength, toughness, and resilience in the century ahead.

Crosslinked functional polymers exhibit exceptional mechanical and chemical properties critical for applications spanning biomedical engineering, advanced adhesives, and self-healing materials. However, challenges in recycling, either due to irreversible crosslinks or, in the case of covalent adaptable networks (CANs), limited solid-state plasticity that typically requires catalysts, significantly restrict sustainability. To address these limitations, we present a novel water-mediated polymerization strategy inspired by the radical-generating mechanism of the Maillard reaction, utilizing maltose as both an initiator and a functional side group in a simple, catalyst-free, aqueous reaction with acrylamide (AAm). This mild, one-pot reaction occurs below 100 °C, forming adaptively functionalized supramolecular networks (AFSNs) that form supramolecular networks through hydrogen bonding and display dynamic imine linkages to the maltose side chains supporting self-healing and re-shaping. These elastomers are characterized by impressive mechanical strength (up to 5 MPa tensile strength), high elongation (up to 1000%), notable fracture energy (36 kJ m-2), robust adhesive performance (up to 4.8 MPa), and rapid self-healing capability at room temperature. Crucially, the elastomer's supramolecular network can be fully and repeatedly dissolved and reprocessed using only water, preserving mechanical integrity without chemical degradation. This sustainable approach provides a practical solution for synthesizing and recycling high-performance crosslinked materials while eliminating environmental hazards, guiding the future development of green polymer chemistry and functional material design.

Architected materials derive functionality from geometry, yet conventional unit cell-based design limits functional heterogeneity, geometric adaptability, and robustness to defects. Inspired by natural morphogenesis, we introduce RDGenCAD, a morphogenetic design framework that translates programmable growth rules into reaction-diffusion dynamics to generate self-organized, CAD-ready architectures. A database of 120,000 morphogenetic structures reveals statistically deterministic and continuous tunability of elastic properties across auxetic and conventional regimes, despite pronounced geometric irregularity. These architectures further exhibit emergent flaw insensitivity and crack deflection through stress compartmentalization, leading to synergistic gains in strength and toughness relative to regular lattices. By shifting architected material design from unit-cell tessellation to programmable morphogenetic growth, this work establishes self-organization as a generative principle for designing materials that are irregular yet predictable, heterogeneous yet "coherent," and directly manufacturable.

A novel Co42Ni26Cr20Al6Ti3Si2Mo1 medium entropy alloy (MEA) with low stacking fault energy (SFE) and long-range ordered (LRO) L1₂ domains was fabricated by arc-melting. Its tensile properties and deformation mechanisms at room temperature (RT – 25 °C) and cryogenic temperature (CT - −196 °C) were investigated in detail. The results showed a pronounced temperature-dependent mechanical behavior. As the testing temperature decreased from RT to CT, the yield strength and ultimate tensile strength increased from 550 MPa and 1025 MPa to 790 MPa and 1390 MPa, respectively, while the ductility improved from 60% to 63%. This MEA exhibits an exceptional strength-ductility synergy along with superior work-hardening capability at CT. Although the predominant deformation mechanism remains planar slip at both temperatures, the mechanism transfers from dislocation-dominated at RT to stacking fault-dominated at CT. Compared to RT, the narrower slip band spacing, combined with the earlier activation of stacking faults (SF) and the synergistic interactions among Lomer-Cottrell (L-C) locks and deformation twins (DTs), collectively contribute to the outstanding work-hardening capability at CT. This study provides theoretical basis into the deformation mechanisms of LRO alloys at CT.

Replicating biological systems’ agile locomotion remains challenging in legged robotics, evidenced by substantial performance gaps between humans and the state-of-the-art bipedal robots in running. Analysis of intrinsic speed limits in bipedal running remains less developed, despite progress in controller design. Inspired by human biomechanics, the present work proposed the power-bounded inverted pendulum (PBIP) model that incorporates the leg power saturation effect. The PBIP model characterizes the maximum running speed of bipedal robots over a complete set of gait parameters, revealing two distinct speed-limiting mechanisms: geometry constraints dominate at low-frequency gaits, and power saturation dictates speed limitation at high-frequency gaits. Simulation of LimX Dynamics Tron, Unitree-G1, and Unitree-H1 robots verified the universality of the dual speed constraint mechanism in physical robot systems. Applying the PBIP model to optimize joint motor parameters, we reduced leg power consumption by 18.0

Enabling robots to perform musical instruments with human-level expressivity represents a frontier in bridging the gap between mechanical precision and artistic interpretation. Despite advances in robotic dexterity, replicating the fluid finger transitions and nuanced dynamic control characteristic of human pianists remains a significant challenge. Through a reinforcement learning-based control framework, we demonstrate that a dexterous robotic hand can achieve high-fidelity performance across a diverse piano repertoire. Central to our approach is a graph-based optimization strategy that guides the robot to generate natural pre-press and key-press fingering strategies that closely resemble human movement patterns. To achieve expressive sound production, the control system is coupled with a physics-inspired acoustic model that modulates keypress velocity to accurately reproduce the dynamic variations specified in musical scores. Quantitative evaluations demonstrate that our expressive control model significantly outperforms baseline methods in both finger morphology similarity and dynamic velocity accuracy. In a perceptual test involving participants from diverse listener groups, performances generated by our system are significantly preferred over baseline robotic performances and are indistinguishable from human performances for non-professional audiences. Furthermore, extensive experiments across multiple musical styles confirm that our method maintains high note-level accuracy while achieving expressive performance. Our approach provides a robust pathway for robotic systems to move beyond mere mechanical accuracy, elevating robotic musicianship to a level of expressive performance comparable to human pianists.

Water in hydrogels has often been overlooked or deemed detrimental to the mechanical properties of hydrogels due to the plasticizing effect of water, which weakens interchain interactions and accelerates crack propagation. Here, we propose a slow-water strategy that imparts enhanced fracture resistance to hydrogels. By converting free water into slowly migrating intermediate water, we suppress excess chain mobility by reducing the free volume around polymer chains, thereby enhancing interchain interactions and substantially extending the load-transfer length. Notably, even with only 13% polymer content and without additional network design, the hydrogels achieve orders-of-magnitude improvements in fracture toughness and fatigue threshold solely through medium design, and these enhancements are demonstrated to be dominated by the intermediate water. The strategy demonstrates versatility, providing insights into the role of intermediate water in biological systems and enabling innovative approaches to reinforcing biomimetic materials under complex stress conditions. The high water content of hydrogels can lead to limited mechanical robustness, but is also key to favourable properties. Here, the authors report the development of a water strategy with free water converted to intermediate water, suppressing chain mobility and improving properties.

Cavitation is an undesirable phenomenon in hydrodynamic systems, leading to surface erosion, efficiency degradation, and intense acoustic emissions. Existing research efforts have primarily focused on mitigating cavitation-induced impacts but have rarely addressed cavitation initiation. Here, we propose a hydrogel coating that raises the energy barrier for heterogeneous nucleation while retaining the capability to dissipate impact energy during bubble collapse. When applied uniformly to hydrodynamic surfaces, it exhibits robust adhesion, durability, and structural stability under hydrated conditions. The hydrogel coating maintains a thrust enhancement of approximately 3.4% under cavitating flow and elevates the onset speeds for incipient and developed cavitation, resulting in a 31.3% increase in maximum thrust under cavitation-free operation and a 27.8% increase before developed cavitation. Additionally, the coating attenuates broadband noise by up to 12.8 dB. This hydrogel-based strategy may be extended to other hydrodynamic systems where cavitation suppression is required.

Inspired by the structure of Setaria viridis and based on guidance of molecular dynamics simulations, a hierarchical nanospike structure on micrometer-sized coaxial fibers has been designed at the molecular scale. A piezoresistive composite membrane of in situ-grown PDA-PPy on a TPU@PES coaxial fiber has been prepared, exhibiting good anticreep performance, high sensitivity, and fast response. The matrix material is designed as coaxial fibers, which consist of an inner PES core that provides anticreep mechanical support and an outer thermoplastic polyurethane shell that offers a large specific surface area and rich graft reaction sites. The nanospike semiconductor phase constructs an interlocking structured composite by forming a multihierarchical conducting network. The piezoresistive sensor constructed with this composite exhibits ultrahigh sensitivity (27.1 kPa-1) and quick response (23.1 ms response time and 26.3 ms recovery time). Furthermore, the chemical grafting process ensures a stable interface between the semiconductor phase and matrix material by creating covalent and hydrogen bonds. This interface not only prevents instability but also demonstrates excellent signal recovery performance and dynamic stability (10,000 cycles). Monitoring changes in renal pelvic pressure with a 3D-printed artificial renal pelvis was performed, confirming its practicality for medical monitoring.

Mechanical transmission is essential in force-related activities ranging from the daily tying of shoe laces1 to sophisticated surgical2 and robotic operations3,4. Modern machines and robots typically use complex electronic devices designed to sense and limit force5, some of which still face challenges when operating space is limited (for example, in minimally invasive surgeries)6 or when resources are scarce (for example, operations in remote areas without electricity). Here we describe an alternative slipknot-based mechanical transmission mechanism to control the intelligent operation of both human and robotic systems. Through topological design, slipknot tying and release can encode and deliver force with a consistency of 95.4% in repeating operations, which circumvents the need for additional sensors and controllers. When applied to surgical repair, this mechanism helped inexperienced surgeons to improve their knotting-force precision by 121%, enabling them to perform surgical knots as good as those of experienced surgeons. Moreover, blood supply and tissue healing after surgery were improved. The mechano-intelligence exhibited in slipknots may inspire investigations of knotted structures across multiple length scales. This slipknot-gauged mechanical transmission strategy can be widely deployed, opening up opportunities for resource-limited healthcare, science education and field exploration.

Acoustic microrobots offer an easy-to-operate approach for microobject manipulation in biomedical and nanotechnology applications. However, microobject transportation tasks require synergistic handling and movement, which poses a challenge for solely acoustically powered microrobots. These systems often require additional actuation mechanisms, such as magnetic control, for assistance. To address this challenge, we developed an acoustically powered micro-clampbot capable of clamping objects using claws actuated by acoustically induced secondary Bjerknes forces and moving via flagella that oscillate under acoustic input. The robot’s actions are governed by distinct acoustic frequencies, enabling precise and independent control of clamping and locomotion. The micro-clampbot can pick a single particle from a cluster and navigate delicately through narrow channels, with narrow necks (~2.1 times the width of the micro-clampbot). This system facilitates the targeted transportation of microscale objects, including live cells, without causing damage. This versatile design highlights the potential of solely acoustically powered microrobots for advanced clinical therapies and microscale operations.

Gallium-based liquid metals,when combined with magnetic agents,emerge as intelligent materials with potential applications in soft robotics within biomedical engineering.However,concerns have arisen from the residual presence of liquid metal,raising long-term biological risks.Herein,we propose a containment method that involves the rolling of magnetic liquid-metal droplets in lyophilized powders,resulting in the formation of intact hydrogel coatings upon hydration.These hydrogel coatings adhere to the liquid-metal surface,forming a cohesive network through hydrogen bonding between carboxylic acid groups and siloxane linkages from silanol groups.This synergy of physical and chemical interactions enables hydrogel coatings with exceptional stretchability,fracture energy and interfacial bonding to liquid metals.Consequently,the hydrogel-coated containment capsule of magnetic liquid metal exhibits remarkable resilience to cyclic compression,enduring strains of ≤85%,while also withstanding impacts from heights of> 14 m.Moreover,the containment capsules demonstrate large deformation capabilities,dexterous locomotion and wireless heating under the control of static and alternating magnetic fields.They showcase the capability for remote thermal ablation operations on ex vivo porcine stomachs and in vivo rabbit models.

For deep-sea submersibles, the service life of titanium alloys in lightweight pressure hulls is dictated by roomtemperature creep deformation. Under high stress in deep-sea, the mechanism for room-temperature creep is primarily dominated by dislocation slip in the soft grains. Guided by the principles of dislocation pile-up and back stress hardening, a pre-compression treatment was applied to Ti80 alloy. Via pre-compression, the dislocation density increased significantly by 1.9-2.5 times in some softer grains whereas the average dislocation density only experienced a 22 % increase. This treatment effectively elevated the critical resolved shear stress (CRSS) and enhanced the resistance to dislocation motion. Accordingly, the creep stress threshold is raised by at least 14 % and the total creep strain is reduced by 80 % after 1000 h of creep at 90 % the yield strength. A creep constitutive model based on back stress evolution was developed to accurately describe the creep behavior of Ti80 alloy. That model incorporates an estimation of the initial back stress induced by pre-compression treatment and its effect on dislocation slip. The results demonstrate crucial insights into the optimization of materials for deep-sea pressure hulls and their long-term performance prediction.

Biodegradable hydrogels are promising for tissue adhesives and implantable coatings, but are often limited by harsh degradation triggers and uncontrolled breakdown. Here, we present a biodegradable hydrogel design strategy that leverages a redox-responsive crosslinker with a low activation threshold, enabling spatiotemporally controlled degradation in response to trace levels of reactive oxygen species (ROS). The hydrogel undergoes rapid and complete degradation, even under low redox stress, disassembling entirely within 2 h under 0.1% (w/w) ROS, and 24 h at concentrations as low as 0.0001% (w/w) (37°C). Functioning as a tissue adhesive, the hydrogel forms bonds within 5 s, maintains strong wet adhesion (200 J/m²), and exhibits excellent sealing performance in both in vitro and in vivo models, with complete degradation under physiological ROS concentrations [∼0.0000001% (w/w)] occurring over 3 weeks-well aligned with the natural wound healing process. Notably, initial mild degradation triggers chain growth, which reinforces wet adhesion by actively compensating for swelling-induced interfacial weakening. The strategy demonstrates remarkable generality and biocompatibility, facilitating the clinical application of biodegradable materials and minimizing the risk of synthetic residue and contamination.

Solids in nano-scales hold the promise to exhibit extreme strength and elasticity due to the absence of interior defects and the designability of micro-arrangements. A nano-scaled bulk sample can be produced by diamond, ice, metallic twins, high entropy alloy (HEA), or cubic boron nitride (cBN). A loading stage capable of 4-DoF movements was designed and built to achieve multi-axial mechanical loading inside a transmission electronic microscope chamber with sub-nanometer loading precision. For single crystal diamond in the shape of nano-needles, we were able to achieve an extreme bending strength of 125 GPa at the tensile side, approaching the theoretical strength of diamond. For ice fibers of sub-micron radius, an extreme elastic strain of 10.9

Precipitate-strengthened copper alloys are widely used in lead frames and high-speed railway wires due to the enhanced strength and electrical conductivity conferred by nano-precipitates. However, the exploration of novel copper alloys only by data faces the dilemma of insufficient samples. Here we proposed a dual-drive design strategy that integrates knowledge and data for ternary precipitate-strengthened copper alloys. The knowledge from phase diagrams (PD) and open-source databases can be regarded as a dataset for machine learning (ML) models, and alloy candidates predicted by the model can be screened with maximum information using PD. The average compound formation energy, a key factor in the precipitation ability of alloying elements from the matrix, was screened out by the PD/ML dual-drive model. By exploring the composition space of 15 ternary alloys formed by the combination of 6 alloying elements and copper, we developed a Cu-0.44Ti-0.26Si alloy with tensile strength, electrical conductivity, and elongation of 741 MPa, 35.1 %IACS, and 14.0 %. This strategy can improve efficiency and accuracy in the design of precipitation-strengthened alloys with only ML or PD.