In this paper, we investigate the nonlinear behaviour of ribbons subjected to coaxial compression and twisting through theoretical, numerical, and experimental approaches. Using anisotropic Kirchhoff rod theory and continuation techniques, we construct global bifurcation diagrams and identify stability transition points via the conjugate-point test. Here, we show that the twist induces supercritical pitchfork bifurcations in ribbons, giving rise to a rich landscape of multi-stability with up to four coexisting stable states. With increasing twist, we observe stability transitions between the fundamental and second Euler buckling modes. Moreover, gravity triggers a global bifurcation reconstruction characterized by the emergence of saddle-node bifurcations. These gravity-induced transformations allow for multiple, controllable snap-through pathways between stable states. We extend a mixed-curvature-based numerical optimization method to predict snap-through destinations and propose a general path-planning framework to navigate between stable configurations. Experiments on ribbons with varied aspect ratios corroborate the theoretical predictions and demonstrate the viability of programmable transitions in multi-stable systems. Our findings provide new insights into bifurcation and snap-through behaviour in slender structures, with potential applications in mechanical metamaterials, flexible electronics, and soft robotics.

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.

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.

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.

Background: Food quality and safety issues have garnered extensive attention globally, making it essential to adopt effective ways to avoid such problems. Emerging two-dimensional nanomaterials (2DNMs) have demonstrated exceptional potential in advancing food quality and safety due to their unique physicochemical properties and versatile functionalities. Over the past decade, significant breakthroughs have been achieved in leveraging 2DNMs for applications in the food industry. Scope and approach: This review provides a comprehensive overview of recent progress of 2DNMs in the food industry. Classical synthesis techniques and critical structural features are systematically explored. Special attention is given to the mechanisms underlying their roles in food preservation, intelligent packaging, and safety enhancement. Finally, the review concludes by highlighting future perspectives and challenges. This review not only provides theoretical insights for optimizing high-performance 2DNMs but also presents new avenues for inventive development in the food industry. Key findings and conclusions: 2DNMs exhibit unique layered structures, large specific surface areas, and tunable physicochemical properties, which confer significant advantages for various food applications. The fabrication techniques for 2DNMs are diverse, ranging from simple and efficient co-precipitation to high-precision etching strategies and low-cost, multifunctional one-pot methods. Through structural adjustments (such as defect control, pore structure, surface modification, etc.), 2DNMs exhibit enhanced multiple functions such as catalytic, electronic, and adsorption. 2DNMs can enhance food quality and safety through antimicrobial action, encapsulation of natural active substances, regulation of gases, intelligent monitoring, management of temperature and humidity, and the removal of hazardous substances, providing novel perspectives to advance this field.

3D printing has been highly pursued owing to its effortless fabrication of custom-defined geometries, yet the integration of multi-material with diverse properties in one printed object remains challenging. In this work, a digital light 3D-printed polymer network that is capable of heterogeneous growth to seamlessly integrate multi-material is designed. This is accomplished through orthogonal photochemistry design, where visible light is utilized to initiate radical polymerization of acrylates for 3D printing. Inspired by plants' phototropism due to uneven auxin distribution, UV light is employed to induce spatiotemporal catalyst generation for promoting network heterogeneous growth. In this process, it is found that the UV-generated catalyst effectively facilitates the hydrolysis of ketals to produce hydroxyls, which can further serve as "growing sites" to initiate the ring-opening polymerization of polycaprolactone. This enables precise manipulation of both shape and mechanical properties in 3D-printed objects. The distinctive heterogeneous growth mechanism of 3D printing enables the production of multi-material components using a single resin.

Solanine is a toxic glycoalkaloid naturally present in potatoes and other Solanaceae crops, and its accumulation during storage poses a serious risk to food safety. However, current detection methods such as high-performance liquid chromatography, and mass spectrometry, are costly, labor-intensive, and unsuitable for rapid on-site analysis. In this study, we present a fast, green, and cost-effective colorimetric sensing platform for solanine detection based on a biomimetic papain-CuSO₄@SiO₂ nanozyme. The nanozyme was synthesized in water via a one-step reaction at room temperature, completing within 10 min without the use of precious metals, volatile organic solvents, or high-temperature treatments. The nanozyme mimics natural CuS enzyme active sites, promoting hydroxyl radical (·OH) generation through Fenton-like reactions to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Incorporation of SiO₂ improves nanozyme dispersion, stability, and active site exposure. The nanozyme was further immobilized within a hydrogel, which can be freeze-dried into an aerogel-like format for long-term storage and rehydrated on demand. A cascade sensing strategy was developed using solanine's inhibition of acetylcholinesterase (ACHE) to modulate H₂O₂ production and control the TMB colorimetric signal. Integrated with smartphone-based RGB analysis, the system achieved sensitive and selective solanine detection with a detection limit of 0.0335 mg L-1 in 40 min. The platform was successfully validated using potato and lake water samples, demonstrating excellent potential for portable, real-time food safety monitoring.

Magnetically responsive soft smart materials have garnered significant academic attention due to their flexibility, remote controllability, and reconfigurability. However, traditional soft materials used in the construction of these magnetically responsive systems typically exhibit low density and poor thermal and electrical conductivities. These limitations result in suboptimal performance in applications such as medical radiography, high-performance electronic devices, and thermal management. To address these challenges, magnetically responsive gallium-based liquid metals have emerged as promising alternatives. In this review, we summarize the methodologies for achieving magnetically responsive liquid metals, including the integration of magnetic agents into the liquid metal matrix and the utilization of induced Lorentz forces. We then provide a comprehensive discussion of the key physicochemical properties of these materials and the factors influencing them. Additionally, we explore the advanced and potential applications of magnetically responsive liquid metals. Finally, we discuss the current challenges in this field and present an outlook on future developments and research directions.

The oriented actuation of biological muscles that relies on the contraction and relaxation of sarcomeres in myofibrils is the foundation of animal movement. Dielectric elastomers (DEs), which are deemed as a kind of promising artificial muscles, can effectively transfer electric energy to mechanical energy within milliseconds under a stimulation of external electric field. Herein, the state-of-art in bioinspired oriented electroactuation of dielectric elastomer actuators (DEAs) is reviewed. The oriented electroactuation of DEAs shows directional movement with larger stroke, directional output, and higher energy transformation efficiency. In general, most of the DEs are mechanically isotropic with uniform expansion deformation, yet in practical applications they usually utilize deformation in limited direction, leading to energy waste in other directions. Thus, we have principally reviewed the efforts from physical engineering mainly based upon mechanically isotropic DEs to material preparation for mechanically anisotropic DEs, aimed at achieving oriented electroactuation of DEAs. Meanwhile, the typical bionic applications of DEAs with oriented electroactuation are introduced, the main challenges are summarized, and some perspectives for promoting this area are also proposed. We firmly believe that the development of DEAs with oriented electroactuation can significantly impact the fields of artificial muscles for flexible actuators and soft robotics.

Leveraging the rich stimuli-response of polymers represents a promising direction towards optical communication/encryption. Sign language, which relies on specific geometric change for secured communication, has been widely used for the same purpose since ancient time. We report a strategy that combines both in a validated manner with a hydrogel that not only carries encrypted optical information but also has the hidden behavior to morph geometrically. In particular, the shape morphing behavior is programmable by controlling the oriented state of the polymer chain in the thermo-responsive network. Whether the shape morphing direction is positive (bending) or negative (flattening) cannot be predicted when the polymerization methods are not informed, revealing a hidden manner. Through deciphering the coupling of chain elastic stresses and thermo-induced deswelling stress, the hydrogel can perform designed and diversified 4D morphing which represents evolution of 3D geometries with time as the fourth dimension. Consequently, the corresponding optical information can be gated based on these geometric features, thereby decrypting the correct permutation of information. Our approach that utilizes the geometric 4D morphing for gated verification of optical information offers a strategy for enhancing the security of communication in ways that are quite different from existing strategies.

Achieving homogeneous dispersion of graphene oxide (GO) within silk fibroin (SF) matrices remains a significant challenge due to solvent incompatibility and GO aggregation. In this study, SF-GO composite films were fabricated using a binary solvent system comprising 1-butyl-3-methylimidazolium chloride (BMIM Cl), an ionic liquid (IL) and dimethyl sulfoxide (DMSO). BMIM Cl contains an imidazolium cation (BMIM+) and chloride anion (Cl-), which are effective in disrupting the hydrogen bonds in SF's beta-sheet regions, promoting the transition to a more flexible random coil or alpha-helical conformation. This structure also enhances the compatibility of BMIM Cl with the oxygenated functional groups on GO. DMSO reduces solution viscosity and prevents GO restacking, thus enabling homogeneous GO dispersion and controlled modulation of SF's secondary structure. At low GO loading (0.1 wt. %), pi-pi stacking, hydrogen bonding, and hydrophobic interactions facilitated beta-sheet formation, leading to composites with enhanced mechanical strength, increased elongation at break (26.12% +/- 1.64%), superior flexibility, and improved thermal stability. The improvement was found to correlate closely with molecular alignment and interfacial interaction strength. This study highlights the importance of nanofiller dispersion and secondary structure control in engineering high-performance biopolymer nanocomposites, with potential for biomedical, flexible electronics, and sustainable packaging applications.

Hydrogels consist of cross-linked polymers that are highly swollen with water. Water evaporation or freezing during temperature changes may lead to stiff and brittle hydrogels. We introduce a strategy called "hydro-locking," which involves immobilizing the water molecules within the polymer network of the hydrogel. This is accomplished by establishing robust connections between water molecules and the polymer by using sulfuric acid. A sacrificial network is introduced to shield the prime polymer network from collapsing. Under the hydro-locking mode, an alginate-polyacrylamide double-network hydrogel remains soft and stretchable within a temperature range that spans from -115 degrees to 143 degrees C. The strategy works with a range of hydrogels and solutions and may enable the preservation and observation of materials or even living organisms at extreme temperatures.

Hydrogel actuators with controllable deformation and excellent biocompatibility are widely used in soft robot, valve, drug delivery and lenses. However, the stimulation response performance of existing hydrogel actuators mostly focuses on a single active layer, which greatly affects its driving performance and service life. In this work, we integrate temperature-responsive hydrogel (Poly (N-isopropyl acrylamide), PNIPAM) and pH-responsive hydrogel (polyacrylic acid, PAAc) into one system to fabricate a dual active layer composite hydrogel actuator with high performance. Based on the PAAc hydrogels achieving contract or expand at different pH values, the obtained actuator exhibits admirable bidirectional bending characteristics. In addition, the anisotropic bamboo sheet endows the hydrogel actuator with programmable 3 D complex deformation. Benefitting from the synergy and different responsiveness between the two active layers, the hydrogel actuator not only has multiple response performance, but also greatly improves its deformation degree and response speed. More importantly, these promising properties of the actuator have broad application prospects in the development of pattern design and intelligent switch. This work proposes a promising strategy for the structural design of hydrogel actuators with excellent performance, and encourages more exploration of the application range of the actuator.

The buoyancy adjustment capability is crucial for underwater robots. Dielectric elastomer (DE) is promising to be designed as inflatable actuators to achieve quiet, fast, and effective buoyancy adjustment. However, the buoyancy adjustment of DE actuators is limited by voltage amplification and controllability. This paper presents to solve the limitation of the DE buoyancy adjustment actuator by magnetic enhancement. An actuator is designed with a two-stage buoyancy adjustment capability. The two-stage adjustment strategy allows the actuator to achieve higher buoyancy adjustment at low voltage and controllable buoyancy adjustment at high voltage, where the switch between the two stages is achieved by tuning the snap of the magnet. A theoretical model is developed to assess the performance of the actuator in the two stages and describe the snap behavior. The experiment results agree with the simulation, and the actuator demonstrates the ability to adjust attitude by changing buoyancy at high voltages and rapidly ascending at low voltages. The multiple buoyancy adjustment capabilities of this actuator have the potential to enable the underwater robot to fulfill various complex task demands.

Soft robot incarnates its unique advantages in deep-sea exploration,but grapples with high hydrostatic pressure's unpredictable impact on its mechanical performances.In our previous work,a self-powered soft robot showed excellent work performance in the Mariana Trench at a depth of 11 000 m,yet experienced notable degradation in deforming capability.Here,we propose a magnetic loading method for characterizing elastomer's mechanical properties under extremely high hydrostatic pressure of up to 120 MPa.This method facilitates remote loading and enables in-situ observation,so that the dimensions and deformation at high hydrostatic pressure are obtained and used for calculations.The results reveal that the Young's modulus of Polydimethylsiloxane(PDMS)monotonously increases with pressure.It is found that the relative increase in Young's modulus is determined by its initial value,which is 8％for an initial Young's modulus of 2200 kPa and 38％for 660 kPa.The relation between initial Young's modulus and relevant increase can be fitted by an exponential function.The bulk modulus of PDMS is about 1.4 GPa at 20 ℃ and is barely affected by hydrostatic pressure.The method can quantify alterations in the mechanical properties of elastomers induced by hydrostatic pressure,and provide guidance for the design of soft robots which serve in extreme pressure environment.

Acoustic metamaterials, especially the topological insulators, have garnered substantial research attention due to their unique wave properties. Recent research emphasizes the crucial role of imperfect interfaces in accurately simulating and understanding wave propagation within these metamaterials. This paper studies the mechanical properties of soft imperfect interfaces and derives the effects of finite deformations on their stiffness. We present a comprehensive model of a soft Rayleigh beam system that incorporates these interfaces, allowing for the observation of the topological phase transition by altering the distance between them. Our investigation into the impacts of finite deformations and interface stiffness adjustment reveals that longitudinal waves' phase transition points are mainly influenced by interface stiffness. In contrast, transverse waves are predominantly affected by finite deformations. The decisive parameters driving these phenomena are also identified theoretically. The transmission studies of supercells further confirm the presence of topologically protected interface modes and their extensive tunability. Overall, this study offers a novel methodology and framework for managing topological phase transition in composite and soft topological insulator systems.

Underwater robots desire versatile, water -adaptive, untethered, and rapidly actuating soft artificial muscles. Existing artificial muscles compromise between high water compatibility and untethered rapid actuation. Taking inspiration from the watery and fast contraction characteristics of jellyfish, we present a jelly -like muscle design that features an extremely soft (elastic modulus, 66.9 kPa) and watery (water content, 83.3%) structure. The jelly -like muscle can instantly respond to electrical stimuli and provide underwater propulsion. The muscle can shift propulsion direction by simply tuning the voltage signal and quickly recover from electromechanical failures through repair. An untethered robot can be assembled by stimulating the muscle with an onboard power system. The robot reaches a maximum speed of 0.91 cm/s (0.3 body length per second) and has an endurance of 15.7 min with a 500-mAh lithium -ion battery. Robots can be constructed in different forms by tailoring the jelly -like muscle, which is promising for various applications.

Three-dimensional (3D) printing has emerged as an attractive manufacturing technique because of its exceptional freedom in accessing geometrically complex customizable products. Its potential for mass manufacturing, however, is hampered by its low manufacturing efficiency (print speed) and insufficient product quality (mechanical properties). Recent progresses in ultra-fast 3D printing of photo-polymers1-5 have alleviated the issue of manufacturing efficiency, but the mechanical performance of typical printed polymers still falls far behind what is achievable with conventional processing techniques. This is because of the printing requirements that restrict the molecular design towards achieving high mechanical performance. Here we report a 3D photo-printable resin chemistry that yields an elastomer with tensile strength of 94.6 MPa and toughness of 310.4 MJ m-3, both of which far exceed that of any 3D printed elastomer6-10. Mechanistically, this is achieved by the dynamic covalent bonds in the printed polymer that allow network topological reconfiguration. This facilitates the formation of hierarchical hydrogen bonds (in particular, amide hydrogen bonds), micro-phase separation and interpenetration architecture, which contribute synergistically to superior mechanical performance. Our work suggests a brighter future for mass manufacturing using 3D printing. Three-dimensional photo-printable resin chemistry yields an elastomer with tensile strength of 94.6 MPa and toughness of 310.4 MJ m-3, both of which far exceed that of any three-dimensional printed elastomer.