Traditional fiber-type artificial muscles primarily convert the volumetric expansion of materials into axial motion through a twisting process. However, they face challenges such as complex fabrication procedures, low energy density, and slow response speed. To overcome these limitations, developing new fiber materials that can achieve high-performance actuation without twisting has become a key challenge in the field of flexible actuators. Based on this, our research group, together with others in the field, has systematically investigated the structural design, fabrication methods, and actuation mechanisms of MXene/cellulose nanofibers composite fiber artificial muscles (MFAMs) with radially oriented titanium carbide (MXene) nanosheets. This work achieves a critical transition of MXene nanosheets from axial to radial orientation, thereby establishing a hydrogen-bonding network reconstruction-driven mechanism and overcoming the limitations of traditional thermal expansion-based actuation. This feature article mainly introduces the research progress of MFAMs from several aspects, including the development background of artificial muscle fabrication methods, as well as the structural design, interfacial regulation, and applications of MFAMs. It also provides a brief summary and outlook on future research directions for artificial muscles.

Owing to the tissue-like mechanical properties and environmental responsiveness, hydrogels exhibit great potential in diverse fields, including aerospace, biomedicine, and flexible electronics. Their surfaces are the regions interacted with other objects during utilizations, which are essential to the realization of functions. However, conventional homogeneous hydrogels are hard to meet precise requirements of surface characteristics in complex scenarios, limiting the expansion of their applications. To address this, recent studies have focused on patterning the surface properties of hydrogels, such as wettability, adhesion, and optical properties. Many strategies are developed enabled by different chemical or physical procedures, thus meeting the differential demands of scenarios. This review focuses on patterning of hydrogel surface properties, summarizing recent achievements in this field. Furthermore, it provides a perspective about the latest opportunities and challenges according to our research. Especially, we emphasize the approach and merits of patterning hydrogel surfaces via photochemistry to give valuable references for future works.

Natural surfaces provide compact strategies for multispectral energy regulation and offer transferable design rules for dynamic thermal management materials. This review summarizes bioinspired spectral-regulation materials following the logic of biological prototypes, spectral mechanisms, polymer/composite translation, and thermal-management functions. We first clarify the distinction between static radiative cooling and dynamic thermal management, emphasizing spectral modulation amplitude, triggering mode, cycling stability, and cross-band compatibility. Representative examples are then discussed in four spectral windows: visible-near-infrared modulation, mid-infrared emissivity regulation, solar-infrared dual-mode switching, and multispectral coordination. Particular attention is paid to the role of elastomers, flexible films, textiles, polymer matrices, and composite interfaces in translating natural photonic structures into processable and integrable devices. Finally, the review highlights future challenges in mechanism abstraction, standardized spectral evaluation, outdoor durability, and multifunctional trade-offs under complex service conditions.

Nanofluidic devices for ions transport possess the ability to bridge the bio-abiotic interface. However, current nanofluidic devices fail to realize the adaptive protection and nonlinear regulation functions similar to electronic current limiters. To address this issue, we reported a nanofluidic ionic current limiter based on composite fibers of graphene oxide (GO) and nanocellulose (NCF). The fibers fabricated by wet-spinning were charactered by ordered confined nanochannels with an interlayer spacing of approximately 1 nm, enabling controllable ion transport. Under strong electrical field stimulation, rapid ion accumulation at the channel entrance triggered a Coulomb blockade effect, leading to a decrease in ion concentration at the entrance and the establishment of an ion concentration gradient opposite to the direction of the electric field, which induced a reverse ion flow. Consequently, the response current exhibited a decrease beyond a voltage threshold, demonstrating a self-adaptive current-limiting behavior analogous to that in electronic circuits. Furthermore, a stimulus-response system built with this material successfully mimiced the transmarginal inhibition mechanisms of neural signals, with the signal carrier can be extended to neurotransmitter (dopamine). This work provides a new device prototype and theoretical foundation for developing adaptive bio‑inspired ionic logic circuits and neuromorphic computing systems.

Inspired by the self-repairing process and the branched structure of the loose connective tissue in the human body, we designed and synthesized molecular brush-based films with typical branched structures, which can achieve intelligent and effective self-repairing processes at room temperature without relying on dynamic covalent/noncovalent bonds. First, a macro-initiator (P(MA-Br)) was synthesized by reversible addition-fragmentation chain transfer homopolymerization based on the functional monomer containing an active bromine group (MA-Br). Subsequently, two types of molecular brushes were constructed by atom transfer radical polymerization: in each, a methyl group was installed at one side of the backbone, while poly(ethyl acrylate) or poly(butyl acrylate) side chains were densely grafted from the opposite side, labeling as PMA-g-PEA and PMA-g-PBA, respectively. The self-repairing behaviors of the molecular brush-based films at room temperature, as well as under acidic, neutral, and alkaline conditions, were studied. It was proved that the molecular brush-based films have good self-repairing functions, stability against acids and alkalis, and elastic characteristics. Compared with the PMA-g-PEA film, the PMA-g-PBA film showed a higher repair efficiency, which was attributted to better flexibility and stronger mobility of butyl chians at room temperature. It made PMA-g-PBA more likely to achieve self-repair after being damaged, driven by the stronger van der Waals force. Finally, the biomimetic self-healing mechanism of the molecular brushes was explored through computer simulation. The main reason lied in the van der Waals interactions between the side chains and the chain interlocking effect. This work overcomes the conventional reliance of self-healing materials on specific covalent or dynamic noncovalent interactions, achieving efficient room-temperature self-repair solely through the synergistic effect of polymer topology—specifically, the densely grafted brush architecture—and intrinsic, ubiquitous van der Waals interactions among side chains. Our strategy establishes a paradigm for designing structurally simple yet functionally robust self-healing polymeric materials.

Inspired from nature, developing actuator that can walk on water is attractive, but it still remains challenging to realize controllable motion on the water surface with tunable velocity and direction. Herein, a controllable water-surface walking robot was developed by using a hydrophobic liquid-crystal thin-film phase as the main body, integrating responsive liquid crystal elastomers (LCEs) as actuator arms, incorporating Disperse Red dye into the LCE as a photothermal conversion agent, and adsorbing camphor on the surface as the solute for Marangoni propulsion. In this design, the foldable LCE actuator arm served as the driving unit. Under 520 nm light irradiation, the LCE unfolded, enabling the controlled release of camphor. The resulting Marangoni effect propelled the robot to move unidirectionally on the water surface. By tuning the light intensity, the evaporation rate of camphor could be regulated, thereby allowing control over the Marangoni-driven locomotion speed. When the light was switched off, the LCE returned to its folded state and the motion stops. Furthermore, by arranging multiple foldable LCE actuator arms in different directions on a single robot and precisely controlling their folding/unfolding states with light, both the speed and direction of locomotion could be modulated. This study therefore provides a new strategy for untethered soft robots capable of precise spatiotemporal actuation and adaptation to complex aquatic environments.

Biodegradable stents are widely used in the treatment of vascular stenosis. However, post-implantation complications such as in-stent restenosis often lead to an increase in local blood pressure, significantly impacting patient prognosis. Therefore, continuous in situ monitoring of intravascular pressure holds significant early-warning potential. However, existing pressure sensors face challenges in terms of structural compatibility, service lifetime, and degradation behavior, limiting their clinical application. To address these challenges, this study proposed a design strategy that synergistically integrates pressure monitoring with degradable performance. A coaxial multilayer biodegradable capacitive pressure-sensing fiber was developed to match and integrate with the biodegradable stent. It was constructed using collagen surgical sutures as a flexible substrate, with conductive gold electrodes formed via thermal deposition, a poly(citrate) dielectric layer, and a polycaprolactone encapsulation layer. By regulating the composition and structure of the polymers, synergistic optimization of sensing performance and degradation rate was successfully achieved. The fabricated sensing fiber demonstrated a sensitivity of 0.051 kPa^-1 within 0~25 kPa (covering the physiological intravascular pressure range) and exhibited good biocompatibility. When integrated with a biodegradable stent, it provides short-term monitoring capabilities and long-term degradability, offering a novel approach for the development of biodegradable smart vascular stents and the functionalization of other implantable medical devices.

Dielectric elastomers (DEs) have broad application prospects in fields such as soft robots, flexible actuators, and artificial muscles due to their characteristics of large deformability, fast response speed, and good flexibility. The electromechanical coupling performance of DE is sensitive to environmental factors, among which humidity can change the dielectric properties, shear modulus, and viscous damping characteristics of the material, thereby affecting its deformation response and stability process. For this purpose, this study established a viscoelastic dielectric elastic force electric coupling analysis model considering the influence of humidity. This model was based on the Kelvin-Voigt-Maxwell (KVM) rheological model to describe the creep and relaxation behavior of materials, and combined with the Gent model to characterize the strain-stiffening behavior at large strains of dielectric elastomers. Through numerical simulation, the system analyzed the effects of humidity, pre tension ratio, DC voltage, and cyclic loading time scale on the dynamic response of viscoelastic dielectric elastomers. The results indicated that an increase in humidity would increase the total tensile and inelastic tensile strength of the dielectric elastomer, and prolong the time for the system to reach a steady state; The increase in pre stretching ratio and DC voltage would further enhance the electro deformation response. The spring branches exhibited obvious viscoelastic relaxation characteristics, while the dashpot response is significantly affected by the cyclic time scale. This study can provide theoretical reference for the structural design and performance optimization of dielectric elastomer actuators in humid environments.

Conventional hydrogels usually suffer from poor mechanical properties due to insufficient energy dissipation, which limits their applications in bioengineering and flexible electronics. In this work, a series of physically crosslinked double-network hydrogels were constructed by utilizing the synergistic effect of hydrophobic association (between poly(acrylamide-co-lauryl methacrylate) and sodium dodecyl sulfate micelles) and ionic crosslinking (between κ-carrageenan and potassium ions). The influence of the mass ratio of the two crosslinked networks on the microstructure, mechanical properties, dynamic rheological behavior, and pressure-sensitive response of the hydrogels was systematically investigated. The results showed that the hydrogel containing 1.6 wt% κ-carrageenan and 16 wt% acrylamide (designated as 16H1.6E) exhibited the best overall performance, with a compressive strength of 4.7 MPa at 90% compressive strain, an energy dissipation density of 281.2 kJ/m³, and complete recovery to its original height after 10 cyclic compressions. Under a constant voltage of 1 V, this hydrogel demonstrated a sensitive and stable piezoresistive response (with a relative resistance change ΔR/R₀ up to -0.8), enabling real-time conversion of compressive strain into electrical signals. This work provides a new strategy for developing fully physically crosslinked double-network hydrogels combining high mechanical strength, excellent recoverability, and sensitive piezoresistive response.

Dynamic mechanical changes in the extracellular matrix play a crucial role in regulating macrophage polarization and immune responses. However, the mechanical properties of conventional peptide hydrogels are generally fixed, and most systems can only achieve transitions between two modulus states ("soft-stiff"), making it difficult to mimic the dynamic mechanical characteristics of the extracellular matrix. To address this limitation, a multi-wavelength responsive peptide hydrogel with tunable modulus was constructed by introducing azobenzene and biocompatible coumarin as orthogonal photoresponsive units into an amphiphilic peptide sequence. Light-induced changes in peptide amphiphilicity enabled reversible and stepwise regulation of the hydrogel secondary structure and mechanical properties under irradiation with different wavelengths. Rheological measurements demonstrated that the hydrogel could reversibly switch among three modulus states ("stiff-soft-stiff") under 450, 365, and 405 nm light irradiation while maintaining good cycling stability. Moreover, different modulus states significantly influenced macrophage polarization behavior: stiffer hydrogels promoted polarization toward the M1 pro-inflammatory phenotype, whereas softer hydrogels favored the M2 anti-inflammatory/reparative phenotype. This study provides a new strategy for designing dynamic biomaterials for tissue engineering and regenerative medicine.

Light-driven actuators based on stimuli-responsive materials have great potential for applications in fields such as soft robotics and intelligent-responsive systems. However, most current light-driven actuators are constrained by slow response speeds and single-motion modes. Developing a light-driven actuation system that simultaneously features a rapid response, diverse motion modes, and high-performance output remains challenging. Herein, a light-driven multimodal actuator based on PPy/PEG/PVA composites was fabricated. Upon light irradiation, the actuator can execute three distinct motion modes—jumping, rolling, and flipping—while demonstrating a rapid response at the millisecond level and outstanding locomotion performance. Specifically, in the jumping mode, the actuator exhibited a minimum response time of only 8.4 ms, a maximum jumping height of 9.1 cm (57 body lengths, 57 BL), and a take-off velocity of approximately 1.36 m/s (850 BL/s). In the rolling mode, it achieved an average rolling velocity of up to 53 mm/s (33 BL/s). In the flipping mode, the maximum average angular velocity was 8.4 (°)/ms. These multimodal locomotion behaviors originate from the propulsive force generated by water vaporization, bubble generation, and bursting at the irradiated site, which are driven by the photothermal effect of PPy. Featuring controllable motion modes and directions, this light-driven PPy/PEG/PVA composite actuator offers promising applications for highly maneuverable soft robots in complex environments and light-driven intelligent-responsive systems.

The theoretical maximum reflectivity of cholesteric liquid crystals (CLCs) for unpolarized light is only 50%. Most existing hyper-reflective devices are designed for static performance and lack the capability of dynamic and reversible modulation. In this work, photoresponsive molecular motors were incorporated into polymer-stabilized cholesteric liquid crystals (PSCLCs) to construct a dual-chirality composite structure consisting of a static right-handed helical polymer network and dynamically tunable left-handed photoresponsive CLCs, which successfully achieved dynamically controllable hyper-reflection. A photoresponsive hyper-reflective device was fabricated via a "wash-out and refill" strategy, enabling reversible switching between a hyper-reflective state with nearly 100% reflectivity for unpolarized light and a conventional single-reflection state with 50% reflectivity. Key process parameters such as drying time were systematically optimized. The device maintained stable optical responses after 200 cycles of ultraviolet irradiation and thermal recovery. Meanwhile, the inversion mechanism of CLC helical structure and bidirectional regulation of photonic band gaps driven by molecular motors were clarified, and the core principle of hyper-reflection induced by the synergistic effect of dual opposite chiral structures was revealed. Taking advantage of the unique polarization selectivity and dynamic photoresponse of the device, patterned anti-counterfeiting devices were developed, and a four-level closed-loop anti-counterfeiting verification system was established. This study provides a new design strategy and experimental basis for high-security dynamic optical anti-counterfeiting technologies.

To enable spatially controlled and graded visual readout of structural color information, a programmable patterned structural color/liquid crystal elastomer actuator was fabricated by surface integration. Polystyrene photonic crystal templates were used as structural color units, and preset structural color patterns were obtained by transparent tape-assisted transfer and cutting to form an information storage layer. Carbon black-doped liquid crystal elastomer served as the photothermally responsive and programmable deformation matrix. The resulting composite actuator integrated the reversible large deformation of liquid crystal elastomer with the vivid and stable structural colors of photonic crystals, allowing programmable control of information display in a single system. In the folded initial state, the structural color patterns were concealed. Local near-infrared irradiation induced selective photothermal deformation in the irradiated region, revealing only the corresponding pattern area, whereas overall heating enabled one-step readout of the complete pattern. This surface-integration strategy provides a simple route for constructing liquid crystal elastomer actuators with programmable structural color patterns, with potential use in flexible encrypted displays and multifunctional soft actuators.

Using scorpion exuviae as the raw material, scorpion fluorescence extract (SFE) was obtained through alkali/acid/alkali pretreatment combined with NaOH/urea low-temperature freeze-thaw treatment. SFE was then introduced into an in situ free-radical copolymerization system of butyl acrylate (BA) and N-isopropylacrylamide (NIPAM) to prepare a series of transparent and flexible scorpion-fluorescent-substance-doped poly(butyl acrylate-co-N-isopropylacrylamide) (PBN-SFE) films. Structural characterization showed that the incorporation of SFE altered the local chemical environment of the ester carbonyl and amide-related groups in PBN, suggesting possible non-covalent interactions between SFE and PBN chain segments. Under 365 nm excitation, the SFE-doped films exhibited a blue-green visible fluorescence response, accompanied by significantly enhanced UV-shielding performance. In particular, the PBN-15 film showed an obvious blue-green fluorescence response under UV irradiation, while its average transmittance in the UV-B and UV-A regions decreased to 1.31% and 2.64%, respectively, reaching a high protection level of UPF 50+. The PBN-15 film also exhibited thermally induced partial recovery of damaged morphology, ethanol-assisted dissolution-recasting processability, and certain inhibitory effects against E. coli, S. aureus, and C. albicans. This work provides a new strategy for the utilization of scorpion-derived fluorescent substances and the design of naturally derived fluorescent/UV-shielding multifunctional flexible films.

Inspired by the dynamic lubrication mechanism of human joints, varieties of biomimetic responsive lubricating hydrogels have been developed for applications in artificial joint cartilage and moving mechanical components. Nevertheless, their mechanical and tribological properties degrade markedly after wear or accidental damage in practical service, which severely affects the operational safety and service life. Developing hydrogels with excellent shear-triggered self-healing lubricating capabilities is critical for the fabrication of biomimetic joints and related moving parts. In this work, a FT/OSA-PAM semi-convertible hydrogel was fabricated by integrating the shear-responsive supramolecular π-π noncovalent network of N-Fmoc-L-tryptophan (FT) with the dynamic covalent network of oxidized sodium alginate/polyacrylamide (OSA-PAM) cross-linked via Schiff base bonds. The aldehyde groups in OSA react with the amino groups on PAM chains to form reversible Schiff base bonds, endowing the hydrogel with interfacial reconstruction ability. Under shear, disassembly of the FT supramolecular network induces partial gel-sol transition of the hydrogel, and a sol lubricating layer forms on the surface to achieve shear-responsive lubrication. After the hydrogel is damaged, the shear stress inside the cracks is greatly reduced, enabling the FT sol to reassemble via π-π stacking. Meanwhile, the reversible Schiff base bonds between OSA and PAM work synergistically, allowing the hydrogel to accomplish self-healing under shear, which the self-healing efficiency of the hydrogel reaches (89.51±9.21)%, and its responsive lubricating performance can be fully healed. The results demonstrate that the synergistic combination of supramolecular π-π interactions and dynamic Schiff base bonds offers a viable strategy for designing and preparing shear-responsive lubricating hydrogels with high-efficiency self-healing performance.

Polymer mechanochemistry utilizes mechanical force to trigger chemical reactions. Among these, the mechanochromic effect, which converts mechanical stimuli into visual optical signals, serves as a pivotal tool for characterizing internal stress distributions within materials. The activation behavior of mechanophores is not only dependent on their intrinsic activation stress thresholds but is also intricately linked to the chemical environment of the matrix and the topological structure of the network. Furthermore, while single mechanophores typically release only a singular response signal, the synergistic or stepwise activation of tandem mechanophores can yield richer mechanochemical behaviors, thus holding unique research value. In this study, a biphenyl-bridged bis-spiropyran mechanophore (BDSP) was designed and synthesized to elucidate the mechanisms by which matrix polarity and network structure regulate BDSP activation behavior. UV spectroscopy was employed to identify the characteristic spectra of the mono-open-ring state (BDSPo-c, 590-610 nm) and the bis-open-ring state (BDSPo-o, 665-683 nm). Subsequently, BDSP was covalently incorporated into cross-linked polyurethane and multiple-network elastomers, and in situ UV spectroscopy was utilized to track its structural evolution during tensile deformation. This work reveals the regulatory patterns of matrix polarity and network topology on the activation behavior of bis-spiropyran mechanophores, offering novel insights for the construction of more sensitive and efficient mechanoresponsive functional polymer materials.

Mechanochromic polymers that convert mechanical force into visual optical signals hold significant potential for stress sensing and damage warning. However, conventional rhodamine-based mechanophores often undergo secondary color changes during stress relaxation, which interferes with the direct correlation between force and optical signals. Inspired by the selective ring-opening behavior of a rhodamine-fluorescein fused bis-spirolactone small molecule in solution, we designed and synthesized a novel fused mechanophore (Rh-Flu) and covalently incorporated it as a crosslinker into multi-network elastomers. Systematic investigation of the mechanoresponsive behaviors of the Rh-Flu crosslinked multiple poly(methyl acrylate) networks showed that Rh-Flu preferentially underwent ring-opening to form a stable mono-rhodamine ring-opened product under mechanical stimulation, with no secondary optical change after stress relaxation. The triple-network elastomer exhibited continuous and stable color changed (light yellow to orange) and fluorescence changed (blue to orange) under both tension and compression, showing a good linear relationship with stress and enabling stress field visualization. This work reveals the force-induced ring-opening selectivity of the fused bis-spirolactone structure in Rh-Flu, providing a new strategy for developing force-responsive polymers with direct and stable optical signals releasing.

Polydopamine (PDA) coatings have attracted considerable attention owing to their substrate-independent surface modification capability. However, conventional dopamine chemistry suffers from several limitations, including slow polymerization kinetics, poor process controllability, and high monomer cost, which severely hinder its industrial-scale application. In this study, a low-cost biomimetic polymerization system was developed using catechol (CA) and m-phenylenediamine (MPD), with ozone (O₃) introduced as an efficient oxidant. The rapid and controllable oxidative polymerization and coating deposition behavior of the CA&MPD system were systematically investigated. The results showed that ozone can generate reactive oxygen species, such as hydroxyl radicals, in situ in aqueous solution, thereby rapidly oxidizing CA to o-benzoquinone and driving its subsequent Michael addition and Schiff base condensation reactions with MPD. As a result, the polymerization time scale was shortened from hours to minutes. Compared with air oxidation, the ozone-assisted strategy significantly enhanced the coating deposition rate and surface uniformity. Moreover, real-time and precise control over the polymerization process was achieved by simply switching the ozone generator on and off. The resulting P(CA&MPD) coatings exhibited excellent hydrophilicity, chemical stability, and thermal stability. This strategy also showed good generality for biomimetic systems composed of CA and various diamines, including o-, m-, and p-phenylenediamine, hexamethylenediamine, and cyclohexanediamine. This work provides a green and general strategy for the rapid and controllable polymerization of low-cost dopamine-mimetic systems and the efficient construction of interfacial coatings, offering new opportunities for advancing polydopamine-like coating technologies toward practical applications.