Researchers worldwide have shown increasing interest in hydrogels, recognizing their vast potential for integration in industrial domains like medical technology and robotic systems. Despite considerable progress, the design of hydrogels with balanced mechanical robustness, low energy loss during deformation, quick shape restoration, and extended strain detection capability remains an active area of research. This investigation has been conducted to develop hydrophobically associated acrylamide (Amm) and lauryl methacrylate (LM) hydrogel reinforced with hydroxyethyl cellulose (HEC). A robust mechanical performance is observed with a fracture strain of 705 % and a tensile stress of 407 kPa. Additionally, it demonstrates excellent anti-fatigue resistance and conductivity of 0.37 Sm-1 and responds to strains ranging from 100 % to 700 %, while the cyclic durability of the hydrogel was assessed by performing repeated stretching and releasing at 300 % strain for 560 s, exceeding 720 cycles. A gauge factor of 17 was achieved at 600 % strain, with response and recovery times of 130 ms and 110 ms, respectively. The hydrogel is capable of detecting a variety of human movements, including the extension of the knee, the movement of the elbow, and the position of the finger at a single angle and at various angles, as well as the writing and speaking of various words. This suggests that the developed hydrogels are capable of monitoring the motion of the human body and will be used as a substitute for conductive materials utilized for strain sensors.

Dual-mode anti-counterfeiting is effective to improve information security and information storage capacity. However, it remains challenging to achieve dual-mode reversible information encryption and decryption. Here, a hydrogel-based erasable and reprogrammable dual-mode encryption system is fabricated by copolymerizing a photo-responsive spiropyrane derivate (SPA) into poly(2-hydroxyethyl methacrylate) network in the presence of fluorescent 6-((2-aminoethyl)amino)-2-butyl-naphthalimide (ABN). The SPA moieties experience reversible ring opening/closing reaction and color change under UV or visible light, which is employed to encrypt information into the hydrogels by UV, and to erase the information by white light. On the other hand, ABN in the hydrogel provides fluorescence under UV, which can be quenched by picric acid (PA) through it-it stacking and then recovered by using Na2CO3 to remove PA. The reversible responsiveness of SPA and ABN to external stimuli is independent to each other, and is used to establish a dual-mode information encryption/decryption that is operated separately. Complementary authentication is demonstrated to combine two independently encrypted/ decrypted information to make complete content. The erasable and reprogrammable hydrogel-based information encryption system shows outstanding advantages including good dual-channel reversibility, ultrafast writing in 10 s, rapid erasure in 50 s, and favorable reusability and durability. It shows significant potential for complementary information verification and patient privacy protection.

Ultraviolet radiation (UVR) could significantly accelerate skin aging, a complex and inevitable biological process involving intrinsic and extrinsic mechanisms with the characteristics of dehydration, reduction in collagen synthesis, decrease in vascularity and elasticity, thinning of epidermal and dermal layers, greying and loss of hair, changes in cellular metabolism, increased susceptibility to cancer, as well as appearance of brown pots and wrinkle on skin surface. Collagen peptides have great potentials in amelioration of UVR-induced photoaging through excellent moisture retention activity, hygroscopicity, tyrosinase inhibitory activity, and antioxidant activity. Research on anti-aging applications of collagen purified from animal by-products is increasingly prevalent nowadays. In this review, collagen peptides possessing anti-aging potentials towards skin exposed to UVR-induced oxidative stress have been discussed with special emphasis on molecular mechanisms. Moreover, issues and safety of collagen supplementation on aging skin were also discussed, aiming to provide important theoretical basis of collagen protein in alleviating skin aging induced by UVR.

We used a binary solvent strategy to construct a multi-crosslinking network of eutectogel, which exhibits exceptional mechanical behavior, self-healing, and adhesion to multiple substrates due to diverse interactions and accessible functional groups.

Interactive stretchable sensors with dual electrical and optical signals have gained prominence due to their high detection accuracy, robust signal synergy stability in electromagnetic/optical interference environments, and visualization of mechanical stimuli. However, it remains a challenge to fabricate an observation angle-insensitive optical/electrical dual-modal sensor capable of quantifying strain degree through optical signal intensity. Inspired by cuttlefish skin and spider legs, an observation angle-independent optical/electrical dual-modal sensor with microcrack structure based on fluorescent hydrogel is developed that can quantify the magnitude of applied strain through fluorescent signals. A pH-responsive fluorescent rhodamine-derived monomer (Rho) is copolymerized into poly(acrylamide-co-2-hydroxyethyl methacrylate) network, yielding a fluorescent hydrogel that serves as the dual-modal sensor coated with a carbon nanotube (CNT) film. In the relaxed state, the intact CNT film shields the hydrogel's fluorescence emission. Upon stretching, the mechanical mismatch between the flexible hydrogel and rigid CNT film induces microcracks in the latter, allowing fluorescence to penetrate and thus generating a detectable fluorescence signal. Herein, the fluorescence signal is insensitive to observation angles and exhibits a linear correlation with applied strain (R2 = 0.9853). Meanwhile, the strain-induced microcracks disrupt the conductive paths of the CNT film, leading to a progressive increase in resistance. In this way, the sensor achieves simultaneous optical/electrical dual-modal outputs through the evolution of strain-induced microcracks in the CNT film. The sensors are mounted on the dorsal surfaces of robotic fingers for detection of finger movements and gesture recognition. Besides, the sensor can be applied to dark-environment exploration and serve as a potential encryption device, demonstrating its versatility. This research advances the development of flexible strain sensors and expands their application fields.

ABSTRACT Organisms rely on seamlessly integrated sensing and action feedback loops to dynamically adjust their behavior for adaptation, learning, and survival. Biomimetic self‐sensing hydrogel soft robots are an emerging class of intelligent systems that integrate actuation and sensing functions within a single compliant structure. They are characterized by tissue‐like softness, high adaptability, and the ability to monitor deformation and environmental interactions in real time. Such intelligent systems have great potentials in soft robotics, biomedical devices, and human–machine interaction. This review comprehensively summarizes recent advances in biomimetic self‐sensing hydrogel soft robots. It covers biomimetic microstructured hydrogel actuators responsive to diverse external stimuli, as well as biomimetic microstructured hydrogel sensors for detecting pressure, strain, and multidimensional signals. Endowing hydrogel sensors with stimulus‐responsive actuation or imparting hydrogel actuators with sensing capabilities allows for the integration of both sensing and actuation functions into a single hydrogel device, thereby resulting in a self‐sensing hydrogel actuator. The biomimetic self‐sensing with microstructured hydrogel actuators driven by thermal, optical, magnetic, and tactile stimuli is described in detail. Some in‐depth analysis of current challenges and future perspectives is provided at the end of the review. This review offers valuable insights into the development of autonomous, intelligent soft robotic systems.

High-refractive-index polymers (HRIPs) are of increasing interest due to their ability to combine optical functionality with polymer processability. Sulfone-containing polymers are particularly promising owing to the strongly polarizable -SO2-- group and rigid aromatic backbones. However, most reported sulfone-based HRIPs rely on step-growth polycondensation, which is often limited by harsh reaction conditions and poor structural tunability. In this work, we demonstrate an effective radical polymerization strategy for synthesizing highrefractive-index polymers containing diphenyl sulfone moieties. The synthetic route begins with stepwise functionalization of substituted aromatic precursors to yield 4-methyl diphenyl sulfone derivatives, which are subsequently brominated using N-bromosuccinimide (NBS) to form 4-bromomethyl diphenyl sulfone intermediates. These intermediates are then reacted with acrylates to produce polymerizable monomers, followed by radical polymerization to afford polymers. This approach allows efficient incorporation of sulfone and aromatic units into the polymer, offering flexible control of substituents on the aromatic rings. The resulting polymers exhibit refractive index in the range of 1.590-1.622 at 486.1 nm, accompanied by high Abbe numbers, excellent optical transparency, and robust thermal stability. Compared with conventional step-growth methods, the radical polymerization route provides milder conditions, broad functional group tolerance, and more precise control over chemical structures, enabling systematic tuning of refractive index and Abbe number.

Nature is full of fascinating examples where physical strategies help achieve adhesion, self-healing, climbing, and attachment. For instance, reptiles climb walls without falling to the ground, and DNA double helix reannealing, as well as protein folding and refolding, occur due to noncovalent interactions. Similarly, in the self-healing of human skin and the formation of water clusters, noncovalent interactions play a critical role. Hydrogels having noncovalent supramolecular interactions are renowned for their intricate structure and excellent mechano-responsive properties, establishing them as key materials for human-machine interactions, drug delivery, biosensors, strain sensors, energy storage, and energy harvesting systems. This review explains the mechanism of supramolecular interactions in conductive hydrogels (CHs), details comparative studies between conductive supramolecular polymer hydrogels (CSuPHs) and traditional hydrogels, and recent strategies for improving the mechanical strength of CSuPHs. Additionally, it discusses different types of flexible sensors based on supramolecular interactions and explains the emerging applications of CSuPHs in wearable electronics (human motion monitoring, strain and pressure sensing, wearable smart gloves, and sweat analysis), energy storage and harvesting systems (triboelectric nano-generator (TENG), piezo-electric nanogenerators (PENG)). It highlights the challenges exist and future prospects of CSuPHs.

ABSTRACT The rising burden of chronic diseases and aging populations has raised an urgent demand for real‐time, personalized, and continuous health monitoring. However, the rigidity and bulkiness of traditional medical devices often impair wearability and hinder practical deployment. In contrast, ultra‐thin wearable flexible electronic devices have emerged as promising alternatives, due to excellent inherent flexibility, minimal thickness, superior tissue conformability, and long‐term reliability. This Review presents a comprehensive overview of recent advances in this field by critically analyzing three core pillars: material engineering, device–tissue interface engineering, and application‐specific system integration. First, we summarize various functional materials from elastomers and textiles to hydrogels and metal nanomeshes, with emphasis on their chemical modification, structural design, and functional integration. Second, we examine strategies for constructing adhesive, seamless, and low‐impedance device–tissue interfaces via optimized molecular interactions, interfacial architectures, and mechanical conformality. Finally, we highlight representative applications in electrocardiogram (ECG) monitoring, stomatology, and ophthalmotology. By bridging materials, interfaces, and systems, this Review summarizes progress and challenges in wearable thin‐film electronics and proposes key future directions: automated patterning, standardized interface testing, and improved in vivo validation, which will help inspire future research across materials science and biomedical engineering.

Metal-organic frameworks (MOFs) have numerous applications, such as energy storage, medical delivery, and wastewater remediation. Nevertheless, their applications to conductive hydrogels are restricted due to their limited dispersion, and aggregation within the network leading to limited stretchability, susceptibility to damage during cyclic activities, and reduction in the lifetime of the sensor. To overcome these issues, the selection of a suitable solvent medium, surfactant, and surface chemistry of the polymer chain in the hydrogel network are the primary factors. Herein, we created a flexible and tough, poly(lauryl methacrylate-acrylamide)@cobalt-manganese metal organic framework supramolecular composite hydrogel. Cetyltrimethylammonium bromide (CTAB), a cationic surfactant, and polymer chains facilitated the uniform distribution of the Co-Mn-MOFs. Hydrophobic interaction along with the other supramolecular interactions leads to synergistic reinforcement of the MOFs leading to uniform dispersion of the MOFs. The subsequently produced Co-Mn-MOF-based supramolecular hydrogels display remarkable anti-fatigue resistance, ultra-stretchability (1655%), toughness (447 kJ m-3), high conductivity of 0.33 S m-1, and a strain detection range from minute to large (0.5-700%) with a gauge factor of 9.47, and can be sculpted in diverse 3d-like designs. A sensor was developed and utilized to detect various human actions, and varied levels of strain and pressure, and was applied as an artificial epidermis. We believe that this approach has potential for creating wearable strain sensors, artificial skin, and MOF-based smart electronics.

Conductive hydrogels have shown great promise in wearable electronics due to their inherent advantages of flexibility, biocompatibility and conductivity. However, current research efforts on hydrogel-based wearable sensors primarily focus on terrestrial applications, adapting conductive hydrogels for underwater sensing remains a significant challenge. Herein, a robust, durable, anti-swelling and highly conductive hydrogel composed of poly (N-acryloyl glycinamide) and silver nanoparticles (PNAGA/Ag NPs) is prepared by a straightforward one- pot polymerization and reduction technique for underwater sensing and communication purposes. The effective incorporation of Ag NPs, facilitated by the high solubility of silver nitrate (Ag NO3) in the pre-gelation solution, imparts the hydrogel with impressive mechanical toughness (3.32 MJ/m3), fatigue resistance, and a high electrical conductivity of 4.1 mS/cm. The PNAGA/Ag NPs hydrogel demonstrates excellent performance as a temperature, pressure and strain sensor. The strong dual hydrogen bonding interactions among the bisamide groups on the polymer chains endow the hydrogel with good anti-swelling properties, making the Ag NPs remain stably within the network without expansion or diffusion for over 30 days. Resultantly, the hydrogel sensor is developed to transmit information using Morse code for underwater communication. Through collaboration with machine learning algorithms, the hydrogel sensor achieves real-time language recognition with a high identification accuracy of 100 %. This work successfully integrates anti-swelling characteristics, mechanical robustness, and electrical conductivity within a hydrogel system, offering a viable solution for utilizing hydrogel-based sensors in underwater environments.

In this work, a supertough, self-healable, and extreme-environment-tolerable liquid metal (LM) composite organohydrogel was fabricated by dispersing LM particles (LMPs) with water-soluble starch (WS) and leveraging multilevel hydrogen-bonding interactions. Attributed to the cooperation of the strong dual-hydrogen bonds and weak monohydrogen bonds, the organohydrogel obtained an outstanding tensile strength of 2.0 ± 0.13 MPa and toughness of 16.0 ± 1.0 MJ m-3, as well as desirable self-healing ability. The organohydrogel strain sensor has a high gauge factor (GF) of 15.08 along with a large detection range (0-1159%), demonstrating its outstanding sensitivity. It was successfully applied for manipulator gesture detection in harsh environments, showing excellent detection resolution and sensing stability in a wide temperature range (-20 to 50 °C). This work provides a new avenue for preparing multifunctional LM composite gels, showing great promise for next-generation wearable electronics.

Conductive hydrogels are one of the most abundant materials used for non-audible speech interfaces (NASI) and motion monitoring because hydrogels are intrinsically flexible and have the ability of smart sensing. However, developing hydrogels for dual applications faces many challenges, such as NASI demand exceptional precision and responsiveness to accurately capture subtle facial or vocal movements, ensuring seamless communication in environments where traditional speech is impractical. On the other hand, human motion monitoring requires robust adhesion and adaptability to detect dynamic and complex bodily motions with high sensitivity. In this system, we have developed dual functionality iontronic hydrogels that can adhere to human skin without any stimulus, precisely measure the mechano responses of human skin. The hydrogels were developed from acrylamide (AAm), 2-(Dimethylamino) ethyl acrylate methyl chloride (DMAEAMC), and albumin (ABM). ABM improved both mechanical and adhesive performance of hydrogels, making an ideal candidate for NASI and motion monitoring. The presence of NaCl ions makes hydrogels intrinsically conductive, due to which hydrogels have high sensitivity and fast response recovery time. Thanks to the large working range and self-adhesion to human skin, the hydrogel electrode worked as an epidermal transducer to monitor different tiny and large physiological activities which include audible and non-audible words, large human joints movements, writing, etc. This approach can open new windows for developing advanced materials for skin-like sensors and transducers in the field of health monitoring soft robotics, tissue engineering, electronic, and ionic skins.

The development of self-powered, flexible, and multi-function sensors is highly anticipated in wearable electronics, however, it remains a daunting challenge to identify different signals based on a single device with singular sensing material without algorithmic support. Here, a smart adaptable hydrogel is developed by co-introducing two ions with vastly different hydrophilicity for the construction of an electrochemically self-powered, flexible, and reversibly switchable difunctional chemosensor with a metal-air battery structure. The prepared hydrogel can readily switch between water-rich and water-deficient states for crosstalk-free detection of oxygen and humidity respectively, since O2 gas and water molecules can directly participate in the oxygen reduction reaction in the device and act alone as limiting reactants and catalysts to affect the reaction rate under different hydrogel states. The resulting sensor demonstrates breakthrough O2 and humidity sensing performance with sensitivities as high as 4170.5%/% and 380.2%/% RH in water-rich and water-deficient states, respectively, and ultrawide detection ranges. Thanks to these, the devices can be applied for real-time and remote monitoring of ambient oxygen, transcutaneous oxygen pressure changes, respiration, and skin moisture by combining with wireless communication technology, and therefore have important application prospects in the fields of safety, health management, and non-contact human-machine interaction.

With the advancement of skin bioelectronics, hydrogel-based wearable devices have broadened their applications in health monitoring and strain sensing. However, their use is hampered by inadequate mechanical properties, a limited sensing range, and restricted environmental sensitivity. In this study, we draw inspiration from the hierarchical structure and unique interaction mechanism of ovalbumin (OVA) to report the synthesis of a multifunctional dual-network ionic conductive hydrogel (ICH). This hydrogel is reinforced thermally by self-assembled OVA, a globular protein. The polyacrylamide/gellan gum@OVA (PAM/GG@OVA) hydrogel has modulated framework that shows impressive mechanical properties: a fracture stress of 1.12 MPa, toughness of 582.77 kJm-3, stretchability of 1087 %, and adhesiveness of 8.22 kPa. Additionally, they maintain a high electrical conductivity of 0.43 S/m, making them suitable for real-time strain sensing applications. These characteristics allow the hydrogel to function as a multifunctional, durable wearable device, boasting excellent sensitivity with a gauge factor of 13.67 and a quick response time of 150 ms. When utilized as a flexible strain sensor, the hydrogel effectively detects a wide range of human movements, from subtle vocal cord vibrations to large joint motions, while ensuring stable adhesion to the skin. Furthermore, the hydrogel is capable of accurately recognizing and replicating hand written text. By investigating the reinforcing properties of ovalbumin, these findings lay the groundwork for the sustainable development of hydrogel-based wearable electronic devices that are durable, environmentally adaptable, and capable of multi-sensory responsiveness.

In many areas, advances in soft robotics, human-machine interfaces, and healthcare technology are revolutionising the way humans engage with machines (inspection, etc.). Strain-sensitive conductive hydrogels have attracted considerable scientific interest due to their potential applications in various fields. Traditional hydrogels often face limitations such as significant hysteresis energy, low electrical conductivity, limited elasticity, slow response rates, and inadequate shape recovery. This research aims to design a conductive hydrogel with excellent strain-sensing properties to address these challenges. The hydrogel is strengthened with Agar (Ag), butyl acrylate (BA), and acrylamide (Amm), which function as hydrophobic and hydrophilic monomers, respectively. Ag-enhanced mechanical properties are significantly affected by their insertion into the polymeric system. The developed hydrogel demonstrated a fracture stress of 338 kPa and a remarkable fracture strain of 1224 % (for 0.04 % of Ag). The frequency sweep and strain amplitude tests of the rheological analysis confirmed the elastic properties of the hydrogel. Moreover, the developed hydrogel exhibits excellent electrical conductivity of 354 mSm-1 and demonstrates remarkable sensitivity to mechanical deformation. It responds effectively to both low (50 %) and high (700 %) strain levels and maintains exceptional anti-fatigue performance with continuous standing stretching at 400 % strain for 500 s. Additionally, it features a rapid response time of 110 ms, a recovery time of 120 ms, and a gauge factor of 11 at 700 % strain. The Ag4 hydrogel also demonstrates potential for use as electronic skin, effectively functioning when attached to different joints, such as the neck, elbows, and fingers. The hydrogel can function as an electronic pen when it comes into contact with a plastic pen cover.

Conductive hydrogels are among the most promising materials for flexible iontronic transducers due to their inherent flexibility and smart sensing capabilities, which are essential for wearable technologies. However, creating iontronic transducers from hydrogels presents challenges such as limited stretchability, poor adhesion, short working ranges, and slow response recovery times. To overcome these obstacles, we have developed a multifunctional hydrogel by incorporating bovine serum albumin protein (BSA) with chemically crosslinked acrylamide (AAm) and guar gum (GG). The addition of BSA significantly enhances the mechanical properties of the AAm-GG hydrogel, particularly improving its adhesiveness to various substrates, including human skin. This improvement allows the iontronic transducer to accurately monitor a range of human activities without delay. Moreover, the transducer’s high conductivity and robust mechanical performance enable it to operate over long ranges with rapid response recovery times, high sensitivity, and stability, ensuring no signal loss. Consequently, our iontronic transducer is capable of monitoring both large and small human activities, such as wrist, elbow, and knee movements, as well as actions like speaking and drinking. Notably, this transducer also excels in language tracing, both in speech and writing, having been successfully tested in five different languages, making it superior to other transducers of its kind. This approach could pave the way for the development of next-generation, skin-like iontronic transducers for applications in wearable electronics, health monitoring, artificial intelligence, and ionic skins.

The development of hydrogel-based sensors is frequently hindered by low electrical conductivity and excessive swelling in aqueous environments. Herein, we present a novel strategy for fabricating high-performance poly (vinyl alcohol) (PVA)-polypyrrole (PPy) hydrogels via an in-situ chemical vapor deposition (CVD) process. This method drives the uniform growth of a continuous, interpenetrating PPy network within the PVA matrix through hydrogen-bond-directed templating, resulting in a composite hydrogel with integrated superior properties. The optimized PVA-PPyCVD hydrogel achieves a high electrical conductivity (3.69 S/m) and exceptional water stability, with a minimal mass change of <7 % after 15 days of immersion. A high doping level of similar to 28 %, as verified by XPS, and a reduced energy gap (4.95 eV) revealed by DFT calculations, underpin the enhanced charge transport. The hydrogel demonstrates versatile sensing capabilities, including strain, water level, and ammonia gas detection, showcasing its potential for reliable use in wearable electronics and environmental monitoring. This work establishes CVD as a novel and scalable route to high-performance conductive hydrogels.

Continuous real-time monitoring of non-cognitive markers is essential for the preliminary detection, control, and regulation of long-standing health conditions. Existing diagnostic techniques are frequently invasive and often not well suited for at-home monitoring, limiting their use in early detection of disorders. In this study, a flexible organohydrogel-based wearable sensor has been developed offering high accuracy and durability for real-time human health assessment. Employing a solvent co-cross linking strategy, a wrinkle texture organohydrogel is synthesized by combining polyacrylamide (PAm), and polymethylmethacrylate (PMMA) grafted onto the surface of cellulose nanocrystals (CNCs) through the free radical graft copolymerization technique. This innovative approach combines both physical and chemical interaction to eliminate mechano-chemical conflict and provide the organohydrogel with a balanced mechanical performance (2100% stretchability), toughness (519 kJ m-3), flexibility, conductivity ( 0.29 S m-1), remarkable adhesion, wide working range (-60 °C to 60 °C), and fast self-healing properties. In contrast to conventional hydrogels, this one-pot synthesis eliminates the need for metallic nanofillers, lowering cytotoxicity. In addition, PAm in combination with CNCs also provides biocompatibility, whereas sodium chloride makes the organohydrogel ionically conductive and sensitive. The engineered sensor exhibits enhanced efficiency, durability, and sensitivity and can be employed in haptic sensing technology.