Anisotropically Conductive Hydrogels with Directionally Aligned PEDOT:PSS in a PVA Matrix

Design Strategies of PEDOT:PSS-Based Conductive Hydrogels and Their Applications in Health Monitoring

Conductive hydrogels, particularly those incorporating poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), have revolutionized wearable health monitoring by merging tissue-like softness with robust electronic functionality. This review systematically explores design strategies for PEDOT:PSS-based hydrogels, focusing on advanced gelation methods, including polymer crosslinking, ionic interactions, and light-induced polymerization, to engineer hierarchical networks that balance conductivity and mechanical adaptability. Cutting-edge fabrication techniques such as electrochemical patterning, additive manufacturing, and laser-assisted processing further enable precise microstructural control, enhancing interfacial compatibility with biological systems. The applications of these hydrogels in wearable sensors are highlighted through their capabilities in real-time mechanical deformation tracking, dynamic tissue microenvironment analysis, and high-resolution electrophysiological signal acquisition. Environmental stability and long-term durability are critical for ensuring reliable operation under physiological conditions and mitigating performance degradation caused by fatigue, oxidation, or biofouling. By addressing critical challenges in environmental stability and long-term durability, PEDOT:PSS hydrogels demonstrate transformative potential for personalized healthcare, where their unique combination of softness, biocompatibility, and tunable electro-mechanical properties enables seamless integration with human tissues for continuous, patient-specific physiological monitoring. These systems offer scalable solutions for multi-modal diagnostics, empowering tailored therapeutic interventions and chronic disease management. The review concludes with insights into future directions, emphasizing the integration of intelligent responsiveness and energy autonomy to advance next-generation bioelectronic interfaces.

Design Strategies and Emerging Applications of Conductive Hydrogels in Wearable Sensing

Conductive hydrogels, integrating high conductivity, mechanical flexibility, and biocompatibility, have emerged as crucial materials driving the evolution of next-generation wearable sensors. Their unique ability to establish seamless interfaces with biological tissues enables real-time acquisition of physiological signals, external stimuli, and even therapeutic feedback, paving the way for intelligent health monitoring and personalized medical interventions. To fully harness their potential, significant efforts have been dedicated to tailoring the conductive networks, mechanical properties, and environmental stability of these hydrogels through rational design and systematic optimization. This review comprehensively summarizes the design strategies of conductive hydrogels, categorized into metal-based, carbon-based, conductive polymer-based, ionic, and hybrid conductive systems. For each type, the review highlights structural design principles, strategies for conductivity enhancement, and approaches to simultaneously enhance mechanical robustness and long-term stability under complex environments. Furthermore, the emerging applications of conductive hydrogels in wearable sensing systems are thoroughly discussed, covering physiological signal monitoring, mechano-responsive sensing platforms, and emerging closed-loop diagnostic-therapeutic systems. Finally, this review identifies key challenges and offers future perspectives to guide the development of multifunctional, intelligent, and scalable conductive hydrogel sensors, accelerating their translation into advanced flexible electronics and smart healthcare technologies.

Boron-Stabilized Anisotropic Water-in-Polymer Salt Electrolyte with an Exceptionally Low Salt Concentration by Hofmeister Effect for Aqueous Lithium-Ion Batteries

Water-based electrolytes provide safe, reliable, and cost-effective energy storage solutions; however, their application in aqueous lithium-ion batteries is hindered by low energy density and short cycling life due to the limited electrochemical stability window. While high lithium salt concentrations can mitigate some of these issues, they often lead to increased solvent viscosity and higher costs, limiting commercialization. In this study, a boron-stabilized anisotropic polyvinyl alcohol (PVA) hydrogel electrolyte, referred to as BaP, is proposed to address the challenges related to high lithium salt (LiTFSI) concentrations. Due to the Hofmeister effect, the BaP water-in-polymer electrolyte can retain a high concentration of lithium salt even when low concentrations of lithium salt are used. Briefly, the BaP promotes the salting-in phenomenon of Li ions, while the TFSI ions induce salting-out, allowing BaP to synergistically achieve high lithium salt concentrations. Due to these unique characteristics, the BaP hydrogel exhibits a wide electrochemical stability window similar to that of highly concentrated electrolytes, enabling stable operation in a LiMn2O4||Li4Ti5O12 full cell by suppressing hydrogen evolution. Moreover, the biodegradability of BaP contributes to the development of a more environmentally friendly battery system.

Bioinspired Super-Robust Conductive Hydrogels for Machine Learning-Assisted Tactile Perception System

Conductive hydrogels have attracted significant attention due to exceptional flexibility, electrochemical property, and biocompatibility. However, the low mechanical strength can compromise their stability under high stress, making the material susceptible to fracture in complex or harsh environments. Achieving a balance between conductivity and mechanical robustness remains a critical challenge. In this study, super-robust conductive hydrogels were designed and developed with highly oriented structures and densified networks, by employing techniques such as stretch-drying-induced directional assembly, salting-out, and ionic crosslinking. The hydrogels showed remarkable mechanical property (tensile strength: 17.13-142.1 MPa; toughness: 50 MJ m- 3), high conductivity (30.1 S m-1), and reliable strain sensing performance. Additionally, it applied this hydrogel material to fabricate biomimetic electronic skin device, significantly improving signal quality and device stability. By integrating the device with 1D convolutional neural network algorithm, it further developed a real-time material recognition system based on triboelectric and piezoresistive signal collection, achieving a classification accuracy of up to 99.79% across eight materials. This study predicted the potential of the high-performance conductive hydrogels for various applications in flexible smart wearables, the Internet of Things, bioelectronics, and bionic robotics.

PEDOTs-Based Conductive Hydrogels: Design, Fabrications, and Applications

Conductive hydrogels combine the benefits of soft hydrogels with electrical conductivity and have gained significant attention over the past decade. These innovative materials, including poly(3,4-ethylenedioxythiophene) (PEDOTs)-based conductive hydrogels (P-CHs), are promising for flexible electronics and biological applications due to their tunable flexibility, biocompatibility, and hydrophilicity. Despite the recent advances, the intrinsic correlation between the design, fabrications, and applications of P-CHs has been mostly based on trial-and-error-based Edisonian approaches, significantly limiting their further development. This review comprehensively examines the design strategies, fabrication technologies, and diverse applications of P-CHs. By summarizing design strategies, such as molecular, network, phase, and structural engineering, and exploring both 2D and 3D fabrication techniques, this review offers a comprehensive overview of P-CHs applications in diverse fields including bioelectronics, soft actuators, energy devices, and solar evaporators. Establishing this critical internal connection between design, fabrication, and application aims to guide future research and stimulate innovation in the field of functional P-CHs, offering broad benefits to multidisciplinary researchers.

High-Strength, Antiswelling Directional Layered PVA/MXene Hydrogel for Wearable Devices and Underwater Sensing

Hydrogel sensors are widely utilized in soft robotics and tissue engineering due to their excellent mechanical properties and biocompatibility. However, in high-water environments, traditional hydrogels can experience significant swelling, leading to decreased mechanical and electrical performance, potentially losing shape, and sensing capabilities. This study addresses these challenges by leveraging the Hofmeister effect, coupled with directional freezing and salting-out techniques, to develop a layered, high-strength, tough, and antiswelling PVA/MXene hydrogel. In particular, the salting-out process enhances the self-entanglement of PVA, resulting in an S-PM hydrogel with a tensile strength of up to 2.87 MPa. Furthermore, the S-PM hydrogel retains its structure and strength after 7 d of swelling, with only a 6% change in resistance. Importantly, its sensing performance is improved postswelling, a capability rarely achievable in traditional hydrogels. Moreover, the S-PM hydrogel demonstrates faster response times and more stable resistance change rates in underwater tests, making it crucial for long-term continuous monitoring in challenging aquatic environments, ensuring sustained operation and monitoring.

Progress of Research on Conductive Hydrogels in Flexible Wearable Sensors

Conductive hydrogels, characterized by their excellent conductivity and flexibility, have attracted widespread attention and research in the field of flexible wearable sensors. This paper reviews the application progress, related challenges, and future prospects of conductive hydrogels in flexible wearable sensors. Initially, the basic properties and classifications of conductive hydrogels are introduced. Subsequently, this paper discusses in detail the specific applications of conductive hydrogels in different sensor applications, such as motion detection, medical diagnostics, electronic skin, and human-computer interactions. Finally, the application prospects and challenges are summarized. Overall, the exceptional performance and multifunctionality of conductive hydrogels make them one of the most important materials for future wearable technologies. However, further research and innovation are needed to overcome the challenges faced and to realize the wider application of conductive hydrogels in flexible sensors.