Flexible strain sensors have emerged as fundamental components in intelligent sensing systems, attributed to their lightweight, wearability, stretchability and responsiveness to strain. Traditional flexible strain sensors are plagued by inadequate interface bonding strength and dispersed distribution of stress fields. These factors result in the diminished electromechanical conversion efficiency, thereby significantly hindering the sensitivity of micro strain monitoring in intricate configurations. In response to this challenge, this review proposes theoretical framework for the collaborative regulation of interface and structures, with the objective of facilitating efficient electromechanical conversion. The interface strengthening mechanism and regulation methods of localized and gradient stress fields have been systematically elucidated, thereby uncovering the mechanism by which stress transfer induces electrical signal mutation in polymer composite materials. Simultaneously, it is essential to elucidate the trajectory of technological advancement from single modal responses to multimodal perception, ultimately to the integration of functional systems at the comprehensive level. Finally, this study will explore the critical scientific challenges related to micro strain sensing limitation and programmable sensitivity regulation. The objective of this investigation is to promote the advancement of sophisticated intelligent sensing systems that are marked by deep integration of interactions among humans, machines and objects.

With the ever-deepening understanding of nano-electromagnetic interactions and the advancements of fabrication methodologies of nanomaterials, diverse electromagnetic platforms utilizing nanomaterials have been developed for next-generation electromagnetic safeguarding applications. This study presents the design and fabrication of bioinspired porous Ti₂CT_X/Si₃N₄ composites featuring an aligned lamellar structure, aimed at facilitating the effective absorption and dissipation of electromagnetic radiation. The layered configuration of Ti₂CT_X/Si₃N₄ composites facilitates the repeated reflection of electromagnetic waves between neighboring Ti₂CT_X layers, hence enhancing the energy dissipation of these waves. At a Ti₂CT_X concentration of merely 0.21 wt.%, the effective absorption bandwidth of Ti₂CT_X/Si₃N₄ composites encompasses the whole X-band (8.2-12.4 GHz), with a minimum reflection loss of -53 dB achievable at a sample thickness of 5 mm. Simultaneously, the fabricated Ti₂CT_X/Si₃N₄ composites demonstrate advantages in lightweight characteristics and robust mechanical properties, offering significant insights for the application of Ti₂CT_X in nano-electromagnetic engineering, particularly in the realm of electromagnetic pollution mitigation.

Dental disease treatment has achieved significant progress, yet challenges remain due to limitations of conventional dental materials, including suboptimal biocompatibility and biodegradability. Functional hydrogels, as one kind of versatile biomaterial, have gained widespread attention in biomedical applications, offering notable advantages and promising potential for dental therapies. This paper summarizes the basic properties of functional hydrogels and recent advancements in treating various dental diseases. It emphasizes the working mechanisms and therapeutic effects. Lastly, the challenges and issues encountered by hydrogels in dental treatments are discussed, along with future development prospects. With ongoing advances in hydrogel design and fabrication, their performance is expected to improve further, expanding their role and potential in managing dental diseases, oral health, and related medical conditions.

Fracture energy is the property that characterizes how a material resists crack growth. In a standard measurement of fracture energy, an incision is typically introduced into the specimen. It is known that the measured fracture energy may depend on the incision curvature. However, the underlying mechanism of such dependence remains unclear. In this paper, we prepared polyacrylamide/Ca-alginate hydrogel specimens featuring incisions with circular tips of varying diameters. The fracture energy was subsequently measured through a pure shear test. We observed that the fracture energy is proportional to the incision diameter, with a slope comparable to the work of fracture for larger tip diameters. Conversely, for smaller tip diameters, the fracture energy remains independent of the incision diameter and aligns with the intrinsic fracture energy. This transition occurs at an incision diameter comparable to a material-specific scale known as the fractocohesive length. Notably, the fractocohesive length, rather than the inelastic zone scale, successfully explains the dependence of fracture energy measurement on incision curvature. The difference between these two length scales of the material here spans three orders of magnitude. These results will be helpful for establishing standards for measuring fracture energy of soft materials.

In response to the increasing demand for the prevention and control of chronic noncommunicable diseases, people are paying growing attention to the application of flexible optical waveguides in health assistance, and the specific functions of flexible optical waveguides are gradually enriched in the process. This review systematically explains the research progress of flexible optical waveguides in human health assistance. An analysis of the sensing principles used in flexible optical waveguides for signal sensing is provided. The specific applications of flexible optical waveguides in human health assistance are categorized into three main areas: invasive biomedical diagnosis and therapy, contact physiological information monitoring, and interactive soft robots. From the perspective of materials science, a comprehensive analysis is conducted on commonly used materials and their properties for flexible optical waveguides in human health assistance. Furthermore, the sensing principles and specific applications of flexible optical waveguides are provided, aiming to provide theoretical support and technological innovation direction for the construction of a new generation of intelligent health monitoring systems. The unique advantages of flexible optical waveguides in sensing, especially in human physiological signal sensing, are demonstrated through detailed theoretical analyses. Their specific applications in human health assistance are summarized under each category. Finally, this review proposes evolution paths for flexible optical waveguides by addressing current bottlenecks through material innovation (e.g., hybrids, metasurfaces), functional enhancement (e.g., self-powered sensing), and system integration (e.g., miniaturization, Internet of Things platforms).

Continuous and precise monitoring of pulse waveforms is essential for the prevention and early diagnosis of cardiovascular diseases. However, current pulse sensors suffer from significant motion artifacts caused by inadequate skin-device adhesion and poor interfacial conformability during physical activity. In this work, we develop a highly sensitive and conformal pressure sensor featuring an innovative island-bridge configuration capable of accurately measuring arterial pulse waveforms across multiple body artery sites, even under motion artifacts. Through finite element analysis and systematic experimental validation, the unique island-bridge design is demonstrated in achieving both superior signal fidelity and motion artifact suppression. The developed sensor shows a high-pressure sensitivity of 4.75 V/kPa, a rapid response time of less than 30 ms, and excellent durability over 6,000 cyclic loads. Furthermore, it has demonstrated exceptional performance in capturing pulse waveforms across multiple body sites, allowing the extraction of crucial cardiovascular parameters, even in the presence of motion artifacts. Given the remarkable advantages, our study presents a unique triboelectric sensor design that not only improves the sensitivity but also effectively eliminates motion artifacts, providing a promising solution for creating wearable pressure sensors for continuous cardiovascular monitoring.

Poly(lactic acid) (PLA) has critical limitations in food packaging applications because of its inherent brittleness and lack of active functionality. To address these limitations, we developed flexible PLA films with sustained-release antimicrobial activity via mesoporous Santa Barbara Amorphous-15 (SBA-15) encapsulation of cinnamon oil (MAO). SBA-15 (Brunauer–Emmett–Teller surface area: 568.9 m²/g; pore diameter: 7.5 nm) demonstrated exceptional MAO loading capacity (801.5 mg/g). MAO@SBA-15 was incorporated into the polyethylene glycol-plasticized PLA via solution casting. The 3 wt% MAO@SBA-15 composite exhibited the highest tensile strength (16.0 MPa) and crystallinity (32.4%) owing to the uniform filler dispersion and nucleation effects. At 7 wt% loading, films achieved superior barrier properties [water vapor permeability: 2.6 × 10^-13 g·cm/(cm²·s·Pa); oxygen transmission rate: 4.5 × 10^-13 cm³·cm/(cm²·s·Pa)], antioxidant activity (1,1-diphenyl-2-trinitrophenylhydrazine scavenging: 34.4%), and preservation efficacy for mulberries (weight loss rate: 3.6%; hardness: 0.82 N) over seven days. The MAO release followed Higuchi model (R² = 0.9738), confirming controlled diffusion. This study established a potentially scalable strategy for fabricating multifunctional PLA packaging with enhanced flexibility, barrier performance, and sustained bioactive delivery.

Soft microfluidic sensing platforms have emerged as a transformative technology for real-time, noninvasive, and continuous health monitoring. This paper reviews recent advancements in soft microfluidic systems, focusing on the biomedical sensing platforms such as colorimetric, electrochemical, optical, etc., sensing modalities. Additionally, the integration of multimodal sensing approaches is discussed as a strategy to enhance sensitivity, specificity, and robustness under dynamic physiological conditions. Key material and fabrication strategies enabling flexibility, stretchability, and biocompatibility are highlighted, along with their interfacing challenges in wearable formats. The review also explores the role of artificial intelligence in sensor design, data processing, and predictive diagnostics. By identifying current limitations and emerging trends, this work provides future directions toward developing next-generation soft microfluidic systems for personalized, decentralized healthcare.

Low-melting-point liquid metals (LMs), characterized by exceptional electrical conductivity, mechanical compliance, and eco-friendly, cost-effective processability, hold great promise as flexible conductors in human-machine interfaces, wearable bioelectronics, and emerging technologies. However, their intrinsic fluidity compromises device stability, while high surface tension and low viscosity present significant challenges for high-resolution patterning and scalable manufacturability. In this study, we develop a eutectic gallium indium-silver nanoparticles (EGaIn-AgNPs) biphasic conductive ink and employ electrohydrodynamic printing to achieve precise, high-resolution patterning of the EGaIn-AgNPs biphasic structure (~5 μm). This approach strategically embeds a solid phase within the LM matrix, effectively suppressing its inherent fluidity and substantially augmenting its mechanical stability and structural robustness. By leveraging the versatility and precision of electrohydrodynamic printing, we successfully fabricate lightweight, highly resolved conductive patterns that can conform seamlessly to complex and dynamic surfaces, such as human skin and plant leaves. This advancement addresses key challenges in LM-based flexible electronics, unlocking transformative opportunities in wearable electronics, implantable devices, next-generation consumer electronics, and smart agricultural systems.

Gastrointestinal (GI) robots overcome the limitations of conventional endoscopy, offering a noninvasive and precise approach for diagnosing and treating major GI diseases including colorectal cancer, gastric cancer, inflammatory bowel disease, and peptic ulcers. However, due to the dynamic, tortuous, mucus-rich, and pH-variable environment of GI tract, GI robots face serious challenges in achieving precise localization, stable operation, and reliable sensing. Leveraging the properties of tissue-matched modulus, adaptive deformation, and bioinspired design, soft robots can conform to the intestinal wall, minimizing mechanical damage and thereby offering new strategies for efficient sensing and treatment of GI diseases. Hereinto, this review presents a comprehensive GI soft robot system by integrating materials, structural designs, actuation modes, and physiological adaptability to achieve multifunctional performance and clinical reliability. Specifically, materials are classified into biocompatible elastomers, smart responsive polymers, and functionalized conductive materials to guide material selection and structural optimization. Subsequently, structural engineering methods including continuous encapsulation designs, modular-reconfigurable architectures, and biomimetic frameworks are introduced, alongside diverse actuation strategies of field-driven, fluid-driven, and chemically driven autonomous mechanisms. Following that, preclinical applications are highlighted as navigation and localization, drug delivery and controlled release, in vivo sensing, as well as minimally invasive manipulation and therapy. In the future, this integrated GI soft robotics technology will fundamentally reshape precision medicine, enabling a more intelligent and personalized therapeutic platform, and driving the evaluation of next-generation GI soft robotics.

Transfer printing, a foundational manufacturing route for integrating heterogeneous materials onto diverse substrates, holds great promise for applications in flexible electronics, emerging displays, and soft robotics. As applications grow more complex, the quality of ultrathin films integrated onto applicable substrates, initially fabricated on rigid substrates by spin-coating, physical vapor deposition, or chemical vapor deposition [e.g., photoresists, metals, two-dimensional (2D) materials] with thicknesses below 10 μm, becomes critical to the performance of advanced devices, including flexible/curved electronics and 2D films-based electronics. However, achieving damage-free transfer printing of ultrathin films requires resolving the trade-off in traditional methods between interfacial fracture and in-plane film damage. Herein, this review elucidates the principles underlying damage-free transfer printing of ultrathin films, highlights recent innovations that enable on-demand control of interfacial adhesion during the process, and summarizes typical applications based on transferred damage-free films. Finally, we provide perspectives on the remaining challenges and future developments needed to enable industrial-scale manufacturing and inspire continued innovation.

The smart wearable system composed of stretchable electronics and bodysuits is a focus in healthcare and human-machine interaction. Despite advances in stretchable electronics, a stretchability mismatch persists between zippers and stretchable fabrics, which are key components of bodysuits, affecting the system’s function, comfort, and aesthetics. The key challenge lies in the contradiction between the requirement for closely arranged teeth in traditional zippers and the demand for stretchability in stretchable zippers. Here, we report a bio-inspired stretchable zipper, which achieves interlocking through interlaced spatulate teeth, suppresses separation perpendicular to interlocking surfaces via a suture joint, and prevents excessive inter-tooth distance by a hook-furrow structure. The novel slider provides teeth rotation space during interlocking through the reciprocation of movable blocks. The stretchable zipper can maintain interlocking and effortless zipping/unzipping over a wide range of strain and strain differences (0%-25%, respectively). In applications for hemiplegia rehabilitation wearable systems and wound closure, stretchable zippers show advantages in enhancing conformability, paving the way for smart wearable systems.

The Internet of Things (IoT) holds significant potential for advancing smart home development. However, the challenge of maintaining a sustained power supply from batteries limits the widespread deployment of IoT systems. To address the critical issue of frequent battery replacement or recharging in IoT nodes, this work proposes a self-powered wireless sensing system (SWSS) that integrates graphene sharp-tip electrodes with a triboelectric nanogenerator. The non-metallic graphene electrodes, fabricated using laser-induced graphene technology, enable the system’s signal strength to match or even surpass that of similar self-powered systems employing metal electrodes. This facilitates efficient conversion and transmission of mechanical energy into electrical energy and wireless signals. The electrode distance, which affects signal quality, is optimized through COMSOL simulations; reducing the tip distance enhances signal generation up to a critical threshold. Experimental results demonstrate reliable signal transmission over distances exceeding five meters. A capacitance modulation method is developed to stabilize multi-frequency signal generation by making the modulation capacitance inversely proportional to signal frequency. Furthermore, the system operates stably for over 20,000 cycles, equivalent to a lifespan of more than 5.5 years. By integrating Braille into the sliding modules of four SWSS units, blind individuals can successfully control multiple devices in smart homes, highlighting the system’s potential for smart home and related applications.

Humidity monitoring is vital for respiratory health assessment, yet conventional sensors lack flexibility, back-end power supply, and environmental friendliness, demanding flexible, self-powered, and biodegradable devices. Here, we developed a flexible, fully biodegradable self-powered electronic skin (E-skin) that seamlessly integrates micro-supercapacitors (MSCs) and a humidity sensor. Highly hygroscopic agarose (AG) was selected as both the substrate and gel electrolyte, with Ti₃C₂T_x MXene nanosheet-based interdigital electrode arrays patterned on its surface via in-situ fabrication. No metal interconnects or polymer binders were introduced during the whole fabrication process. The MSCs based on AG/sweat gel electrolyte exhibited high area capacitance (15.6 mF·cm^-2), long-term cycling stability (up to 10,000 cycles), and desired biodegradable properties. Due to the strong interaction between AG and MXene with water molecules by abundant hydrophilic groups such as hydroxyl, the humidity sensor has high sensitivity and a good linear relationship within the range of 11%-97% relative humidity. The integrated E-skin system enables real-time monitoring of human breathing patterns (including the mouth and nose), as well as the humidity levels of non-contact finger touch and skin. This work paves the way for sustainable, self-sufficient wearable electronics in personalized respiratory monitoring.

Driven by the rising demand for mechanical adaptability, structural reconfigurability, and multifunctional integration, flexible circuits are gaining increasing importance in advanced electronic systems. They serve as key enablers for next-generation devices owing to their intrinsic mechanical compliance and stable electrical performance. In extreme environments, flexible circuits face severe reliability issues such as dielectric drift, interfacial delamination, crack propagation, and metal electromigration. Nevertheless, their deployment remains indispensable in aerospace systems operating under high temperature and pressure, in biomedical implants exposed to corrosive environments and dynamic loading, and in energy infrastructures subjected to strong acids, alkalis, and severe thermal gradients, since rigid alternatives cannot satisfy the stringent demands for mechanical adaptability and lightweight integration. This duality underscores both the challenges and the necessity of advancing flexible circuit technologies, where material innovations and cross-process strategies are crucial to ensure functionality under harsh conditions. This review provides a comprehensive account of the technological evolution of flexible circuit fabrication. On the materials front, the engineering of multiscale composite conductive networks has proven to significantly enhance interfacial bonding strength and environmental robustness. In terms of fabrication, subtractive manufacturing exhibits mature performance in patterning resolution, thermal effect suppression, and substrate compatibility. Additive manufacturing extends the frontier toward heterogeneous material integration and three-dimensional functional architectures. Meanwhile, conformal manufacturing provides novel paradigms for configurational control and interface modulation. By analyzing the characteristics and strengths of these fabrication strategies, this article further maps the application potential of flexible circuits in sensor arrays, communication modules, bioelectronic systems, and integrated photonics. It emphasizes the need to align process design with performance requirements. Key challenges remain, including reliability under extreme environments, delays in adopting sustainable manufacturing, and limited cross-process integration. Ultimately, the study argues that the future development of flexible circuits hinges on the innovation of functionalized materials, the establishment of sustainable fabrication platforms, and the convergence of hybrid manufacturing pathways. Together, these advances will drive a paradigm shift from passive structural flexibility to active system reconfiguration. Meanwhile, they will expand the scope of flexible electronics toward extreme, green, and reconfigurable application scenarios.

The programmable properties of polylactic acids and shape memory polymers in 4D printing enable time-dependent shape transformations, allowing the fabrication of 3D shells with zero material waste. However, achieving target geometries requires inverse design, often constrained by slow evolutionary algorithms or complex analytical models. Herein, we present a 2D curve matrix, tuned by material ratios and arc angles, to enable contraction or elongation and thereby reproduce protruding features such as noses. A fully convolutional network (FCN) directly generates design patterns with high accuracy from depth images in a single step, with multi-task learning predicting rib composition and curvature. In parallel, we refine the inverse design of the line matrix and utilize transfer learning to accurately reconstruct human facial geometries, while the FCN also performs well in forward prediction to bypass computational costs. Furthermore, the fabricated 3D shells closely match target facial features in both scale and geometry, with minimal deviation between simulations and experiments, demonstrating the method’s potential for scalable, customizable 4D-printed applications.

This study presents the design and implementation of a fully flexible, high-resolution magnetic tactile sensor that integrates a vertically periodic magnetized film with a 3 × 3 flexible Hall sensor array. To achieve optimal mechanical flexibility and electrical performance, graphene was employed as the active sensing material, and polyethylene terephthalate was chosen as the substrate, based on a comprehensive evaluation of carrier mobility, material thickness, mechanical compliance, and fabrication compatibility. The incorporation of a vertically periodic magnetization strategy in the magnetic film effectively suppressed lateral magnetic field interference and improved surface magnetic flux concentration. This architectural approach enabled spatial position recognition to be enhanced from 3 × 3 to 6 × 6 sensing units. The fabricated sensor exhibited robust performance, achieving an average sensitivity of 0.13 mV/N, a linearity coefficient of 0.97, and a hysteresis rate of 11.4%, demonstrating its potential for high-performance tactile sensing in flexible electronic systems.

Titanium carbide (MXene) has garnered much attention in the development of high-permittivity (ε) flexible polymeric dielectrics because of its exceptionally high electrical conductivity; nevertheless, large dielectric loss at the percolating filler loading severely restricts their engineering applications. In this work, the exfoliated MXene was first surface-oxidized (O-MXene) and then encapsulated with a polydopamine (PDA) layer, and the dielectric properties of the O-MXene@PDA/polyvinylidene fluoride (PVDF) nanocomposites were investigated. The findings reveal that compared with both pristine MXene and MXene@PDA, the double-shell O-MXene@PDA imparts PVDF with evidently enhanced ε and breakdown strength (E_b) along with significantly lower dielectric loss. The elevated ε is ascribed to the O-MXene@PDA inducing multiple intra-particle and inter-particle polarizations. The presence of double shells not only induces deep charge traps capturing mobile charges but also raises the energy barrier for trapped charge de-trapping, subsequently leading to remarkably restrained loss and leakage current in the nanocomposites. Moreover, the second PDA interlayer enhances interfacial interactions between MXene and PVDF, and notably mitigates the strong dielectric mismatch between the two components, therefore lessening the formation of electric trees and promoting the E_b. The theoretical fitting and simulations provide deep insights into the underlying multiple polarization mechanisms and the impact of the double shells on charge migration. This core@double-shell approach offers new insights into the fabrication and design of percolating nanocomposites at low filler loading with concurrently high ε and E_b but low loss, presenting potential applications in power electronic devices and power systems.

Current human-robot interaction (HRI) systems for training embodied intelligent robots often suffer from limited motion dimensionality and unintuitive control. This work presents the Touch-Code Glove, a multimodal HRI interface integrating functional materials, structural intelligence, and deep-learning decoding. A triboelectric digital interface is embedded into the Wrist-pad via a mosaic-patterned array of polyamide/polytetrafluoroethylene-doped silicone rubber films, generating polarity-dependent digital signal pairs upon contact. A co-electrode layout enables 16 touch points with minimal wiring, allowing multiplexed, programmable tactile input via sliding or multi-point gestures. Coupled triboelectric signals are accurately decoded using a convolutional neural network and long short-term memory model, achieving over 98% recognition accuracy. Complementarily, a double-network conductive hydrogel composed of sodium alginate, polyacrylamide, and sodium chloride is integrated into the Finger-fibers and the Wrist-pad to provide strain-sensing capabilities with excellent stretchability, high linearity, low hysteresis, and long-term stability. The system incorporates three concurrent sub-mapping strategies: gesture-driven control, wrist posture-based movement, and touch path-guided input, which together enable real-time control of robotic hands and arms without requiring professional training. This triboelectric-hydrogel hybrid interface offers a materials-centric solution for intelligent, wearable, and accessible HRI, paving the way for next-generation multimodal robotic control systems in assistive and industrial applications.