Explore the vast range of titles available.

Inspired by the sophisticated design of biological systems, interest in soft intelligent actuators has increased significantly in recent years, providing attractive strategies for the design of elaborate soft mechanical systems. For the construction of those soft actuators, carbon nanomaterials were extensively and successfully explored for the properties of highly conductive, electrothermal, and photothermal conversion. This review aims to trace the recent achievements for the material and structural design as well as the general mechanisms of the soft actuators, paying particular attention to the contribution of carbon nanomaterials resulted from their diversified interplaying properties, which realized the flexible and dexterous deformation responding to various environmental stimuli, including light, electricity and humidity. The properties and mechanisms of soft actuators are summarized and the potential for future applications and research are presented. This Review article traces the nascent research area of soft actuators based on carbon nanomaterials. According to the driving modes of actuators, this paper is divided into light‐driven, electricity‐driven, humidity‐driven, and multi‐response‐driven, and comprehensively summarizes the material structure design and their mechanism. Finally, the future potential and possible applications of soft actuators based on carbon nanomaterials are proposed.

Rock dissolution induced by acidic groundwater poses a significant threat to the stability of geotechnical engineering. Therefore, it is crucial to develop a robust spectral prediction model to accurately evaluate the degree of rock acidification. Initially, red sandstone samples were immersed in hydrochloric acid solutions of different concentration for 1 h, 3 h, 5 h, 24 h, and 72 h, respectively. Fourier variation mid-infrared spectroscopy was employed to analyze the spectral characteristics of samples, assessing the acidification degrees. To mitigate environmental interference and eliminate redundant information, Savitzky-Golay (S-G) smoothing, normalization, and Principal Component Analysis (PCA) were applied to preprocess the spectral data of differently acidified rock samples. Subsequently, K-Nearest Neighbor (KNN), Support Vector Machine (SVM), and Random Forest (RF) algorithms were compared, and a fusion model of mid-infrared spectral prediction models for red sandstone samples with varying degrees of acidification was established. The fusion model was proposed to integrate the strengths of multiple models, enabling precise characterization of the acidification degrees of red sandstone. The results indicate that as concentration of hydrochloric acid solutions increases and soaking time extends, the reflectance spectral intensity of red sandstone samples decreases, confirming the sensitivity of spectral characteristics to acidification. The proposed fusion model achieves an accuracy of 95% in detecting the acidification degree of red sandstone, surpassing independent RF, KNN, and SVM models. This provides a valuable reference for non-destructive and real-time monitoring of rock engineering stability affected by acidic groundwater intrusion.

Smart actuators that can convert external energy stimuli into mechanical energy output have great potential in industrial, biomedical, and military applications. However, the existed disadvantage such as complex fabrication process, single stimulus source, and the requirement of artificial energy restrict their further development. Herein, a MXene/polyethylene (PE)‐based soft actuator with multistimulus response and the ability to be driven by natural sunlight and human humidity is proposed through a simple method. Owing to the excellent electrical conductivity, high photothermal conversion capability, and surface hydrophilicity of MXene, the MXene/PE actuator exhibits rapid and large bending deformation in response to external multistimuli such as light, electricity, heat, and humidity. Owing to the simple preparation, and anisotropic, tailorable and programmable properties of the MXene/PE actuator, a soft robot that can crawl directionally under light conditions is constructed. In addition, based on the high sensitivity response of the actuator to light and humidity, smart clothing that can generate reversible bending deformation under natural sunlight as well as sweat conditions is developed. These results provide a new inspiration for the design of high‐performance soft actuators with multistimulus response, and demonstrate the potential applications of the MXene/PE actuators in smart devices, bionic robots, and wearable clothing.

The PBA construction method is suitable for urban subway construction in situations with dense traffic and many surrounding buildings and can effectively reduce surface disturbance and control surface subsidence. Based on field-measured data, this study creates numerical finite element models of 3D stratum-structure, studies the influence of each process conversion on the subsidence of the ground surface and the force of the station supporting structure during the construction of the PBA station, and clarifies the optimal construction parameters. The research results show that the consistency between the field monitoring data and the simulation data is more than 80%, which verifies the correctness of the model. It is concluded that the formation of the pile-beam-arch is the main part of the supporting structure and that digging the pilot tunnel and the formation of the beam arch are the control factors of surface settlement. Based on this, the best sequence of pilot tunnel excavation and arch buckle of the two-story two-span station is obtained, and the optimal pilot tunnel excavation scheme of first the middle and then the side, first the upper and then the lower, and the best arch buckle scheme of the synchronous arch buckle on both sides is determined. The results of the research can serve as a guideline when selection the construction parameters for similar PBA stations.

Moisture responsive soft actuators are receiving increasing attention due to their unique potential in reducing external energy dependence and carbon footprint. For the conventional moisture responsive soft actuators, their bending deformation under moisture stimulation is usually bidirectional, and the orientation of the bending axis is random. Achieving a moisture responsive monolithic actuator with controllable unidirectional deformation remains a challenge. Here, a Ti3C2Tx MXene/carboxymethyl chitosan composite film actuator with thickness gradient along length direction is fabricated via a vacuum‐assisted “tilt‐filtration” approach. The actuator exhibits a “diode‐like” controllable unidirectional deformation behavior under moisture gradient, and its deformation direction is strictly correlated to its thickness gradient direction and moisture source direction. Based on this highly correlated actuation behavior with internal structural asymmetry, a self‐sustained oscillator under a constant moisture gradient is achieved. Besides, various multifunctional applications based on this actuator driven by human metabolism are also demonstrated, including non‐contact switch with unidirectional conductivity, intelligent keyboard for non‐contact character input, biomimetic crawling robot, wearable intelligent thermal management clothing, and a self‐powered respiratory sensor. This work paves the way for the realization of moisture responsive soft actuators with unidirectional controllable deformation, and further promotes the development of sustainable intelligent materials in soft robotics and electronics. A MXene‐based actuator with gradient thickness is fabricated by a novel and simple vacuum‐assisted “tilt‐filtration” approach. The actuator exhibits a “diode‐like” controllable unidirectional deformation behavior under moisture gradient, and its deformation direction is strictly correlated to its thickness gradient direction and moisture source direction. Based on this actuator, a series of versatile applications driven by human metabolism are demonstrated.

Excavation gap filling is an important means to control the strata movement in tunneling. In practice, synchronous grouting or secondary replenishment of the gap is usually used to control the settlement, instead of filling the excavation clearance. In fact, the diameter of the cutterhead is usually slightly larger than that of the shield, and the front shield is also larger than its back. As a result, there will be an annular gap (i.e., an excavation clearance) between the tunnel soil layer and the shield. Thus, effectively filling the gap contributes to controlling the formation displacement. In this paper, the Wei Lai Da Dao to Feng Tai Nan Lu section of Zhengzhou Metro Line 3 is selected as the study object. Based on the three-dimensional finite element method, the influence of an under-crossing shield tunnel sewage pipes on strata movement under complicated conditions is analyzed. Field tests also show that the movement and development trend are similar to the simulated results, which further indicates that, under similar geological conditions, numerical simulation results can be used to guide the filling of excavation clearance in EPB. It is found that the excavation gap filling can effectively reduce the surface settlement rate and make the surface settlement stabilize faster and the curve shape of “settlement trough” changes from “narrow and deep” to “shallow and wide.” However, the grout used in this method should be with the properties of short hardening time, large elastic modulus, and low shear strength. Besides, the excavation gap filling can also reduce the extrusion deformation of sewage pipe and inhibit the horizontal and vertical displacement of sewage pipes. Therefore, it is considered that excavation clearance filling is an effective method to reduce stratum movement and tunnel deformation, which is of great significance for future research and practical engineering.

Developing a multiresponsive and multifunctional soft actuator that can output mechanical deformation is crucial to the fields of soft robotics and wearable devices. Herein, a 2D metallic molybdenum disulfide (MoS2)‐based soft actuator with dual‐response and self‐sensing function is designed and fabricated. By using the outstanding photothermal property of 1T phase MoS2, good electrical property and network structure of carbon nanotubes (CNTs), hygroscopic expansion of paper, and thermal expansion of polyimide (PI), the MoS2‐based actuator can respond to external voltage and light stimulation and produce rapid and large bending deformation. In addition, the actuator can be used as a flexible strain sensor to realize real‐time sensing of bending deformation by using piezoresistive property of the MoS2–CNT composite film. Based on this soft actuator, a flexible mechanical gripper that can manipulate soft objects with irregular shape and intelligent wearable gloves that can automatically close to block the light irradiation are made. Furthermore, combined with the sensing feature of this MoS2‐based actuator, the gripper with integrated sensing function is also developed. These results indicate the great prospect of the MoS2‐based actuator in intelligent soft mechanical devices, robots, and wearable systems. A dual‐responsive MoS2‐based soft actuator is fabricated, which not only shows good electrical/optical‐induced actuation with large deformation, but also exhibits strain sensing function. Based on these actuators, a flexible mechanical gripper for manipulation of the objects is constructed. Meanwhile, the mechanical gripper can also realize the integrated sensing of its own light‐induced grasping process, revealing its great application potential.

Cephalopod skin is capable of fast color changing enabled by tunable skin transparency as well as structure color. Under this inspiration, herein, a flexible surface with unique hierarchical structure that integrates both transparency change in chemical color (optical scattering) and structure coloration (optical interfering) is developed by harnessing wrinkling instability, thanks to the interfacial Au catalysis in soft lithography. As a result, a hierarchical structure in terms of wrinkled film overlaid by nano‐dome array is obtained in the flexile surface. Experiments find that subject to biaxial strains from 0% to 60%, the hierarchical surface first experiences a transition from nontransparent to transparent owing to the flattening of the wrinkles and then exhibits iridescence structure color shifting from blue to red. The switchable and dynamical tunable mechanochromic characteristics are demonstrated in a smart window, offering potentials for developing flexible devices with optical multiple functionality. A flexible surface with hierarchical structure that integrates both chemical color (scattering in micro‐scale) and structure color change (interfering in nanoscale) is fabricated, by a one‐step soft lithography to harness wrinkling instability. Subject to biaxial strain, the hierarchical surface first experiences a transition from blurring to transparent and then exhibits iridescence in structure color redshift, offering a dynamic and switchable optical performance.

Current ionic polymer-metal composite (IPMC) always proves inadequate in terms of large attenuation and short working time in air due to water leakage. To address this problem, a feasible and effective solution was proposed in this study to enhance IPMC performance operating in air by doping polyethylene oxide (PEO) with superior water retention capacity into Nafion membrane. The investigation of physical characteristics of membranes blended with varying PEO contents revealed that PEO/Nafion membrane with 20 wt% PEO exhibited a homogeneous internal structure and a high water uptake ratio. At the same time, influences of PEO contents on electromechanical properties of IPMCs were studied, showing that the IPMCs with 20 wt% PEO presented the largest peak-to-peak displacement, the highest volumetric work density, and prolonged stable working time. It was demonstrated that doping PEO reinforced electromechanical performances and restrained displacement attenuation of the resultant IPMC.

Lost acceleration response reconstruction is crucial for assessing structural conditions in structural health monitoring (SHM). However, traditional methods struggle to address the reconstruction of acceleration responses with complex features, resulting in a lower reconstruction accuracy. This paper addresses this challenge by leveraging the advanced feature extraction and learning capabilities of fully convolutional networks (FCN) to achieve precise reconstruction of acceleration responses. In the designed network architecture, the incorporation of skip connections preserves low-level details of the network, greatly facilitating the flow of information and improving training efficiency and accuracy. Dropout techniques are employed to reduce computational load and enhance feature extraction. The proposed FCN model automatically extracts high-level features from the input data and establishes a nonlinear mapping relationship between the input and output responses. Finally, the accuracy of the FCN for structural response reconstruction was evaluated using acceleration data from an experimental arch rib and compared with several traditional methods. Additionally, this approach was applied to reconstruct actual acceleration responses measured by an SHM system on a long-span bridge. Through parameter analysis, the feasibility and accuracy of aspects such as available response positions, the number of available channels, and multi-channel response reconstruction were explored. The results indicate that this method exhibits high-precision response reconstruction capability in both time and frequency domains., with performance surpassing that of other networks, confirming its effectiveness in reconstructing responses under various sensor data loss scenarios.