Space-based gravitational wave (GW) detection offers a powerful platform for observing millihertz GW signals and probing extreme astrophysical phenomena. As an important part for GW detection, monitoring key state during test-mass (TM) capture, positioning, and release is essential. Here, we designed a capture, positioning, and release mechanism (CPRM) for TianQin project, and further constructed a monitoring system based on triboelectric nanogenerator (TENG) to achieve state recognition of TM during the three-stage process. Three nano-TENG sensors generate characteristic pulse signals (>0.5 V, >0.8 V, >2.5 V, respectively). Varied timing sequences and peak magnitudes of the signals characterize the mechanical motions of the CPRM, allowing effective feedback and state recognition throughout the multistage capture, positioning and release (CPR) process. This work provides a promising strategy for monitoring the TM states during the CPR process and broadens the application of TENGs in high-precision aerospace systems.
4D-printed mechanical metamaterials combine stimuli-responsive materials with architected mechanical designs, enabling printed structures to change shape, stiffness, deformation mode, or function after fabrication. This review discusses these systems as responsive architectures in which material response and geometry-driven mechanics are jointly designed. We summarize representative material platforms, external stimuli, and additive manufacturing routes, including shape-memory polymers, hydrogels, liquid crystal elastomers, conductive composites, field-responsive systems, and multimaterial hybrids. We then discuss structural design based on geometry, stiffness contrast, gradients, multistability, and topological transformation, along with the modeling and inverse-design methods used to support these designs. Representative applications are reviewed in programmable reconfiguration, wave and vibration control, recoverable energy absorption, sensing-integrated systems, intelligent regulation, and biomedical devices. Finally, remaining challenges are discussed, including slow actuation, fatigue resistance, multimaterial interface stability, quantitative programming, scalable fabrication, and standardized evaluation. These issues will shape the development of reliable adaptive mechanical systems.
This study presents a data-driven framework for the design, prediction, and optimization of electrothermally actuated composite structures based on continuous carbon-fiber reinforced shape memory polymers (CCF-SMPs). A Multiphysics model was developed and calibrated against experimental thermal-field, unfolding-trajectory, and recovery-force measurements. The resulting simulation–experiment dataset was then used to train and evaluate a surrogate model. Continuous fibers contributed to improved thermal uniformity, reduced activation gradients, and increased recovery force relative to pure SMP through a coupled electro-thermo-mechanical effect, rather than through thermal conductivity alone. A surrogate model trained on hybrid experimental-simulation datasets was developed to predict key outputs, including temperature evolution, unfolding angle, recovery force, and energy consumption, and was evaluated against independent experimental measurements. The framework was further validated on architected composite actuator units with varied fiber orientations and hinge geometries. AI-predicted force-displacement responses showed less than 7% stiffness error and less than 5% peak-force error relative to experiments. Finally, the optimizer was applied to variable-thickness morphing structures, achieving a 35% reduction in actuation time, a 28% improvement in geometric accuracy, and a 22% reduction in energy consumption. These results demonstrate the potential of AI-guided design for next-generation high-performance morphing composite systems.
The increasing clinical demands for temporary colonic interventions – such as bridge-to-surgery decompression and benign stricture management – require stents that balance compact delivery, stable support, and atraumatic retrieval. To address these conflicting needs, we propose a novel thermal-fluidic-driven, retrievable, variable-stiffness shape memory polymer (SMP) stent. The helical device features an integrated closed-loop fluid lumen, utilizing circulated water for rapid deployment, instantaneous structural fixation via active cooling, and subsequent softening for safe extraction. To explore the underlying design rules and navigate the inherent geometric trade-offs, we established a systematic multi-objective optimization framework. A Design of Experiments (DoE) strategy was employed to guide the finite element (FE) simulations, which assessed four functional objectives: minimizing intestinal stress, maximizing anti-migration force, maximizing radial support, and minimizing retrieval force. Using a high-fidelity surrogate model combining response surface methodology (RSM) and Gaussian process regression (GPR), we conducted NSGA-II optimization to identify a Pareto-optimal front. These non-dominated designs were clustered into seven families, providing tailored geometric solutions for distinct clinical needs. Experimental validation confirmed the framework’s accuracy, offering a robust design paradigm for next-generation, transient intraluminal devices.
Pumpable nanoencapsulated phase change slurries (NPCS) with thermal energy storage (TES) capacities exceeding that of water are attracting increasing interest due to their potential to reduce heat exchanger equipment size, thermal fluid flow rate or the temperature gap. The influence of shell composition and initiator type on core content and encapsulation efficiency cannot be predicted a priori. In this work, the shell monomer ratio (styrene/divinylbenzene, S/DVB), the initiator type, and the solids content were systematically investigated to maximize the TES capacity of the NPCS. NPCS with solids content ranging from 27.4 to 45.0 wt% were produced, achieving TES capacities in the operating range 288.15-304.65 K of 0.024/0.024 to 0.029/0.027 kWh kg(-1), respectively, for heating/cooling processes. Those values surpass those reported in literature. An S/DVB ratio of 75/25 combined with AIBN as initiator were identified as the optimal operating parameters. These conditions allowed to increase the solid content while keeping pumpability, yielding the s-S-75 similar to DVB25@RT27(45). This formulation exhibited a TES capacity 1.5 times higher than that of water for the same temperature change and a viscosity of 193.0 +/- 2.8 mPa & centerdot;s (680 s(-1), 298 K).
A vibration analysis of single-walled carbon nanotube (SWCNT) reinforced nanocomposite plates is investigated based on Mori-Tanaka (MT) micromechanical homogenization approach to determine equivalent elastic properties. The MT scheme used Eshelby's tensor formulation, to account the CNT geometry, orientation, and volume fraction. The homogenized properties are implemented into the first-order shear deformation theory (FSDT) plate formulation, and the equations governing the dynamics are solved via a suitable numerical method. A parametric investigation explores the influence of aspect ratio, CNT reinforced/ unreinforced, volume fraction on the frequencies of plates under simply supported boundary conditions. Results show that the inclusion of SWCNTs significantly enhances the stiffness, resulting in frequency increases for the same aspect ratio. Comparisons with unreinforced plates confirm that the MT-based model reliability, predicts frequency enhancement trends, with good agreement to reference solutions in the literature.
The rapid expansion of nuclear and radioactive technologies across medical diagnostics and therapy, industrial applications, and nuclear energy sectors has intensified the need for advanced radiation shielding materials. Conventional shielding solutions, such as lead-based materials and concrete, while effective, suffer from significant drawbacks, including toxicity, rigidity, and high density, that hinder their suitability for flexible or wearable protective applications. In response, elastomer-based composites have emerged as a promising class of next-generation shielding materials, offering advantages such as low toxicity, high flexibility, and lightweight structure. When compounded with appropriate elemental or hybrid fillers, elastomers can be designed to reduce various types of ionizing and neutron radiation effectively. This review presents a foundational overview of radiation-matter interactions, followed by a critical analysis of recent developments in elastomeric radiation shielding composites. Key focus areas include material formulations, shielding performance across different radiation types and energy levels, and the influence of filler selection. The review also discusses current challenges in material processing and scalability while outlining prospects in designing multifunctional, high-performance radiation shielding systems. With continued innovation in elastomer matrices and filler technologies, the development of versatile, efficient, and application-specific radiation shielding composites is now more feasible than ever, especially in healthcare and research.
Powering the rapidly increasing number of Internet of Things (IoT) devices has become a critical challenge in recent years. Magnetostrictive energy harvesting has attracted considerable attention as a potential solution; however, the output of existing technologies remains insufficient for practical applications. In this study, a performance enhancement strategy based on geometric structural design is proposed. Fe - Co magnetostrictive alloys with multiple cubic-based lattice architectures were fabricated using laser powder bed fusion, and their energy harvesting performances were systematically compared. Under both impact and repetitive compressive loading conditions, the power generation performance consistently followed the order: Cubic-auxetic > Cubic > Bulk. Notably, the cubic-auxetic lattice achieved an output energy approximately 116 times higher than that of the bulk structure under an impact load of 500 N, demonstrating a viable pathway toward self-powered IoT devices and wireless sensors. This enhanced performance is attributed to a strengthened inverse magnetostrictive effect arising from local stress concentration and increased strain energy density induced by the lattice geometry. Moreover, the auxetic lattice reflects a bioinspired design principle observed in natural hierarchical structures. These results highlight geometric structural design as an effective and universal strategy for advancing magnetostrictive energy harvesting technologies to support the expanding IoT ecosystem. [GRAPHICS]
IPMCs' low voltage requirement, large deformation, fast response, and biocompatibility make them promising for soft robotics, artificial muscles, and miniaturized medical devices. However, traditional sheet/rod-shaped IPMCs cannot adapt to catheter structures, and existing tubular actuators have low performance, which greatly limits the application of IPMCs in the field of interventional surgery. This study developed high-performance tubular ionic polymer-metal composite actuators with gold electrodes (Au-TIPMC; 0.6 and 0.8 mm outer diameter). An optimized electroless gold plating process was employed to create a dense and uniform gold electrode layer on the tube surface, significantly enhancing the electrochemical performance. The Au-TIPMC actuators can generate a large tip displacement (up to 18.21 mm) at low voltages (4 similar to 7 V). A steerable interventional catheter integrated with the TIPMC actuator successfully achieved active navigation and branch selection in a human aortic model without guidewire assistance, demonstrating its potential for application in interventional medical devices. [GRAPHICS]
Clear aligners have become a preferred orthodontic solution due to their aesthetics, comfort, and convenience. However, current aligners still suffer from poor fit caused by thermoforming-induced dimensional inaccuracies and force mismatch due to stress relaxation in thermoplastic materials. Here we address these limitations by developing a biocompatible, highly transparent polyurethane-based material (PUP) tailored for high-precision DLP printing. The PUP ink enables rapid, spatially resolved curing within 30 s and supports high-fidelity printing with feature sizes down to similar to 10 mu m. Moreover, 4D-printed PUP aligners combine accurate fit with programmable, long-term force delivery and can be reshaped for multiple treatment stages. Notably, the representative formulation meets clear-aligner-relevant yield thresholds (yield strength > 25 MPa and yield strain > 4%), supporting stable elastic force output within a clinically meaningful deformation window. This work demonstrates a smart aligner strategy that integrates precision manufacturing with active force control through shape memory, offering a practical route toward next-generation personalized orthodontic devices. [GRAPHICS]
All-solid-state thin-film lithium battery (ASSTFLB) is a new type of energy device that is suitable for miniaturized intelligent terminals, while its application is largely limited by the extremely high interface impedance between the electrodes and the solid-state electrolyte. Herein, we report a full magnetron sputtering (FMS) method to significantly decrease the interface impedance. By systematically optimizing the parameters of FMS, LiCoO2 (LCO) cathode, fluorine-doped Li0.33La0.557TiO3 (F-LLTO) electrolyte, and Ti3O anode are prepared. As a result, LCO cathode shows an initial capacity of 47.1 mu Ah cm(-2) mu m(-1) and a capacity retention rate of 82% after 100 cycles. Meanwhile, the internal resistance of F-LLTO electrolyte is as low as 728 Omega and the capacity retention of Ti3O anode reaches up to 100% after 200 cycles. Benefiting from the nano-compact interface and pore-free multilayer structure enabled by FMS, Ti3O|F-LLTO|LCO delivers a competitively low internal resistance of similar to 2600 Omega. This work provides a feasible nano-fabrication approach for high-performance solid-state micro-batteries and enriches the development of smart nano-materials for miniature electrochemical energy storage. [GRAPHICS] .
Graphene derivatives, particularly graphene oxide (GO) and graphene nanoplatelets (GNP), have emerged as promising nanoscale additives for enhancing mechanical properties and durability of concretes based on ordinary Portland cement (OPC) and alkali-activated binders (AAB). Due to their high specific surface area, high aspect ratio, and strong interfacial reactivity, these materials modify cementitious matrices at the nanoscale, leading to refined microstructures and improved load transfer when incorporated at appropriate dosages. This review critically examines the influence of GO and GNP on conventional OPC-based and AAB-based concretes, with emphasis on graphene concentration, dispersion techniques, surfactant selection, and ultrasonication parameters, as well as the underlying reinforcement mechanisms. Microstructural observations synthesized in this review indicate that GO and GNP enhance composite performance through interfacial bonding with hydration or geopolymer gels, nucleation-induced pore refinement, and crack bridging and pinning mechanisms. Studies reported improvements in compressive, splitting tensile, and flexural strengths when an optimum graphene content is added to the mix. Graphene dosages exceeding the system-specific optimum, or inadequate dispersion led to agglomeration of graphene derivatives and reduced performance of cementitious composites. This review addresses the optimal dosages of GO and GNP for enhancing the performance of OPC- and AAB-based concretes.
Mechanical metamaterials with tunable multistability and vibration isolation are highly desirable for impact protection and vibration suppression in complex service environments. However, in most existing systems, geometric parameters are fixed during fabrication, resulting in predetermined mechanical responses that cannot be reconfigured without remanufacturing. This study propose a modular metamaterial design enabled by thermally programmed shape memory polymers. Thermal-triggered geometric programming reconstructs unit cell end constraints, allowing programmable regulation of stability type and nonlinear force - displacement behavior while preserving structural topology. A programmable stability window is established through parametric analysis, enabling controllable stability transition and load-level tuning. At the metamaterial level, interlayer differentiated programming achieves layered steady-state configurations and designed collapse propagation paths, producing hierarchical peak-sequence responses. Vibration experiments further verify that the isolation onset frequency can be tuned to match different applied masses, with programming shifting the isolation region toward lower frequencies. This work extends thermal shape memory programming from a material response to a structural regulation strategy, providing a post-fabrication route for reconfigurable mechanical performance in multistable metamaterials.
We study thin viscoelastic layers with different constraints in steady-state adhesive sliding contact against wavy indenters. This is crucial for many applications involving compliant films and coatings, where adhesion, friction, and confinement may strongly interact, leading to distinct results compared to half-space geometries. Both a confined layer bonded to a rigid substrate and a free layer subjected to uniform pressure are considered. The problem is formulated within a rigorous energy- based framework for non-conservative viscoelastic materials. The results show that varying the thickness induces distinct responses on the two configurations for pull-off force, friction, and contact stability, with specific dependence on sliding speed due to different scale-dependent dissipation mechanisms. At low sliding speeds, small-scale dissipation localized at contact edges enhances effective adhesion. For thinner layers, this effect is suppressed by confinement and strongly amplified in free layers. Conversely, pull-off forces increase (decrease) in confined (free) layers. The friction coefficient under load control is independent of layer thickness and boundary conditions. At higher speeds, bulk viscoelasticity dominates, and friction decreases (increases) for confined (free) layers due to different bulk deformation mechanisms. A full-contact instability at intermediate velocities leads to discontinuous friction - velocity curves, a distinctive feature of adhesive viscoelastic contacts.
Smart adhesives, as a novel class of materials combining controllable adhesion and facile detachment, show great potential for applications in wearable devices and flexible electronics. However, existing adhesive systems exhibiting directional or adaptive adhesion often rely on globally coupled deformation or interface states, which limits independent and predictable regulation of adhesion along different directions. In this study, we propose a multi-directionally programmable adhesive based on a lambda (lambda)-patterned kirigami structure, which leverages the pattern's geometric asymmetry to facilitate directional adhesion, enabling independent regulation of adhesion performance in different directions without external stimuli. Using a precisely designed kirigami cutting strategy, we achieve decoupled mechanical responses along two orthogonal in-plane directions, yielding pronounced directional contrast and high adhesion enhancement ratios. Experimental results reveal that the structure attains a maximum of 20-fold directional contrast and 35-fold adhesion enhancement, while maintaining conformability to surfaces with varying Gaussian curvatures. To demonstrate practical utility, the kirigami design is implemented as a medical adhesive tape, providing reliable adhesion, resistance to disturbances, and directionally programmable, low-trauma detachment with a simple direction-dependent patterning demonstration. This kirigami-guided strategy offers a structurally tunable platform for anisotropic adhesion, laying a foundation for smart adhesive interfaces in complex environments.
Janus Transition metal dichalcogenides (TMDs) are a representative class of two-dimensional materials and are regarded as promising candidates for electronic and optical applications. As one of the key physical properties of two-dimensional materials, their thermal transport properties have been extensively investigated. However, a recent study suggests that Janus TMDs may stabilize a previously overlooked ground state with a distinct atomic arrangement (npj Computational Materials, 10 (2024) 232). Consequently, thermal conductivity reported by earlier works may lead to potential inaccuracies. Therefore, clarifying whether atomic arrangement affects their thermal transport properties and revealing the role of atomic arrangement on the thermal transport properties is essential for their practical applications. In this work, we take WSSe as a representative system and systematically investigate the thermal transport properties of the newly identified S-III Janus structure and perform a direct comparison with the conventional S-I phase. We found that the thermal conductivity is mainly contributed by acoustic phonon branches in both S-I and S-III structures. The atomic arrangement can weaken scattering rate of both longitudinal and transverse acoustic branch and leads to a longer phonon lifetime and thermal conductivity.
5G communication technology has spurred piezoelectric film bulk acoustic resonators (FBARs) to higher frequencies and thinner structures, highlighting the surface effect’s significance for their dynamic performance. This study systematically investigates the influence of surface effect on the Lamb wave propagation characteristics in ZnO-based FBARs. The state-space formalism and a Taylor series expansion are employed to formulate the surface piezoelectricity theory, which provides effective boundary conditions to characterize the role of surface effect in FBARs. Based on the displacement method, the dispersion equation is derived by combining the governing equations with the effective boundary conditions. Numerical results show that surface effects play a significant role in the propagation of Lamb waves in FBARs, and that the dispersion characteristics depend strongly on the film thickness and surface material parameters of FBARs. Although the FBAR’s thickness is on the order of micrometers, surface effects introduce a deviation of approximately 50 ppm in the cutoff frequency of the thickness-extensional (TE) mode. Furthermore, as the thickness of the ZnO-based FBAR approaches the nanoscale, the TE mode and the second thickness-shear (TSh2) mode exhibit a mode flip. Therefore, the Lamb wave propagation characteristics in FBARs can be effectively modulated through surface engineering.
This study presents a 4D-printed metamaterial with thermally programmable negative stiffness, addressing the critical need for adaptive materials in dynamic environments. Conventional mechanical metamaterials suffer from fixed functionalities and limited adaptability, restricting their use in applications requiring responsive behavior. By leveraging the thermomechanical properties of shape memory polylactic acid, we developed a distributed thermal control system capable of tuning the nonlinear force - displacement response. Through systematic material modeling and structural optimization, the metamaterial achieves controlled buckling and sequential collapse under compressive loads, significantly enhancing adaptability. In the vibration tests of the metamaterial base, different programming states markedly modify the vibration-isolation response and enable a tunable isolation region, while under impact loading the structure exhibits effective energy dissipation and impact-mitigation capability. Experimental validation demonstrates its potential in aerospace applications, where it attenuates shocks, suppresses vibrations, and dissipates energy across the spacecraft's lifecycle. This work pioneers a systematic framework for programmable metamaterial development, offering a versatile solution for advanced engineering challenges.
Considering the broad range of applications of hydrogen peroxide (H2O2), the present study focuses on the preparation and investigation of the hydrogen peroxide vapor (HPV) sensor. The flexible sensor based on an iron oxide/multi-walled carbon nanotubes nanocomposite (Fe2O3/MWCNTs) was fabricated using the radio frequency (RF) magnetron sputtering technique. To characterize the properties of the sensor, the nanocomposite material was comprehensively analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). The gas-sensing parameters of the sensor were examined under ultraviolet (UV) irradiation at various temperatures and concentrations of HPV. The Fe2O3/MWCNTs sensor exhibited the best sensing performance at an operating temperature of 100 degrees C, with a detection limit of 1 ppm of HPV (S = 1.52 response). The prepared sensor demonstrated excellent selectivity, showing no response to any other tested gases at the operating temperature.
Early-age behavior of the concrete strongly influences structural properties, yet most conventional methods are destructive and discontinuous. This study presents a real-time monitoring of setting time, hydration, strength development, and stiffness evolution in concrete incorporating Ordinary Portland Cement (OPC), Portland Pozzolana Cement (PPC), and Fiber-Reinforced Concrete using an embedded smart piezoelectric (PZT) patch sensor. The work provides an application-based comparison of electromechanical interference EMI-PZT performance and evaluates the correlation between the compressive strength and real-time stiffness evolution throughout 28 days. Experimental results revealed that OPC exhibited the highest peak temperature (38 degrees C) and heat liberation (137J), followed by PPC (33 degrees C; 122 J) and FRC (31 degrees C; 115 J), reflecting variations in hydration kinetics. At 28 days, OPC achieved a stiffness of 112 kNs/m which was 21% higher than PPC (88 kNs/m) and 12% higher than FRC (98 kNs/m). OPC also attained the highest compressive strength of 41 MPa, exceeding PPC and FRC concretes by 21% and 12%, respectively. A 30% increase in stiffness relates to a 65% increase in compressive strength, confirming a direct relationship between stiffness and the strength development of concrete. Overall, the study validates EMI-PZT sensing as an effective, real-time, nondestructive technique for evaluating concrete hydration.
