Flexible display technology is actively explored as a cornerstone of the next generation of wearables and soft electronics, set to revolutionize devices with its potential for lightweight, thin, and mechanically flexible features. Flexible thin-film transistors (TFTs) utilizing promising materials such as amorphous silicon (a-Si), low-temperature polysilicon (LTPS), metal oxides (MOs), and organic semiconductors are essential to enable flexible platforms. Among these, MO semiconductors stand out for flexible displays due to their high carrier mobility, low processing temperature requirements, excellent electrical uniformity, transparency to visible light, and cost-effectiveness. Furthermore, the maturity of MO TFT technology in the existing display industry and its compatibility with complementary-metal-oxide-semiconductor (CMOS) processes are driving active research toward integrated circuits for wearable electronics beyond display applications. Specifically, achieving both high mechanical flexibility and electrical performance in MO TFTs is crucial for implementing complex integrated circuits such as microprocessors and backplanes for ultra-high resolution augmented reality (AR)/virtual reality (VR) displays. Therefore, this review provides recent advances in high-mobility flexible MO TFTs, focusing on materials, fabrication processes, and device architecture engineering methods for implementing MO TFTs on flexible substrates, as well as strategies to reduce the impact of mechanical stress on MO TFTs. Next, MO TFT-based display and integrated circuit applications for next-generation flexible and stretchable electronics are introduced and discussed. Finally, the review concludes with an outlook on the potential achievements and prospects of MO TFTs in the development of next-generation flexible display technologies.

Highly sensitive strain sensors are crucial for monitoring subtle plant growth changes and show diverse applications in plant sensing. However, the prevailing integrated fabrication methods for such sensors tend to be costly and complex, impeding their fundamental design and practical usage. Herein, we develop a simple and effective multimaterial all-3D printing technique to manufacture integrated strain sensors with a multilayered structure. Such an all-3D-printed strain sensor exhibits excellent sensing performance enabling precise detection of minor strains in plant growth, including high stretchability (> 300%), high sensitivity (~12.78) with good linearity (0.98), and good long-term stability over 3,000 loading/unloading cycles. We further validate the potential applications of our 3D-printed integrated strain sensor for accurate and continuous monitoring of bamboo growth in both horizontal and vertical directions over 14 days. Our all-3D-printed strain sensor offers a promising avenue for integrated strain sensing systems toward plant growth monitoring.

Soft robots have become increasingly popular due to their compliance, deformability, and adaptability. Soft sensors, particularly bending sensors, play a crucial role in providing essential posture and position information for these robots. However, current soft bending sensors encounter difficulties in accurately measuring joint bending angles and directions under different curvatures. To address these challenges, we propose a novel dual-colored layer structured (DCLS) bending sensor based on the optical soft waveguide. The DCLS sensor is constructed using polydimethylsiloxane (PDMS) as the clear core, with red and blue layers on each side. The sensor’s performance is evaluated through experiments involving bending, compression, and impact conditions. The DCLS bending sensor exhibits excellent calibration-free properties, allowing it to effectively monitor bending angles and directions of joints of varying sizes without requiring any additional calibration. The sensor is successfully integrated into various soft robots, including a fruit sorting robot, a fish-inspired robot, and a hand orthotic exoskeleton robot, showcasing its versatility and potential for different applications.

The real-time assessment and personalized monitoring of human bladder status is important for individuals with involuntary voiding, overactive bladder and bladder disorders such as urinary incontinence. To address the shortcomings of traditional urodynamic methods where the equipment is bulky, complex, invasive, expensive and unable to continuously monitor bladder status, and to meet the needs of healthcare professionals and family members to know the patient’s bladder capacity, this paper designs the biocompatible integrated bladder electronics for wireless capacity monitoring assessment. The device employs chitosan, which exhibits favorable biocompatibility, to fabricate patch electrodes, and optimizes their performance through the plasticizing effect of glycerol, with a polarization resistance of 4.8983 kΩ, a maximum tensile force of up to 107.5 kPa, and remains chemically stable for long-term wear. The principle of bioelectrical impedance analysis is employed to integrate a hardware system comprising multiple modules, including a microcontroller, information processing, communication, display and power supply. After the integrated system design is completed with electrodes connected and encapsulated, data on bladder electrical impedance changes is gathered and transmitted wirelessly to the user interface for non-invasive real-time monitoring and intelligent assessment of bladder capacity. The experimental results demonstrate a high correlation between human bladder electrical impedance and bladder volume, with a systematic measurement correlation coefficient reaching 96.7%. The research equipment is portable, simple to operate, and radiation-free to the human body. It has significant potential for real-time monitoring and intelligent alarm of bladder capacity.

Biohybrid robots (bio-bots), made of biocompatible skeletons with living drives (e.g., biological living tissues or cells), represent a new direction of robotics technology due to their attractive advantages of softness, flexibility, adaptability and biocompatibility, accompanied by the remarkable capabilities of self-assembly, self-healing, and self-replication. This paper provides a brief review of recent advances of bio-bots from a functional view, including walking, swimming and non-locomotion bio-bots, by exploring their structure designs along with their operational principles. The performances of these bio-bots are summarized and compared followed by the discussions of challenges and perspectives, which provide valuable insight and guidance for future developments of bio-bots.

Tri-axial tactile sensors that provide real-time information on both normal and shear forces are enabling technologies for tactile perception, which open up new possibilities in robotics, human-machine interfaces, environmental sensing, and health monitoring. Among tri-axial tactile sensors based on different mechanisms, inductive sensors possess good robustness against environmental contamination. Their low sensitivity to normal and shear loads, however, is a critical barrier. This work presents the rational design of soft inductive tri-axial tactile sensors that are capable of distinguishing static or dynamic normal and shear loads, with exceptional tactile sensitivity. Dual mechanisms of Biot-Savart law and Eddy current effect are explored to overcome the long-standing sensitivity issue. In addition, a hybrid coil with non-uniform spacing is designed to generate uniform magnetic fields, addressing the limitations of traditional uniform coils and significantly improving the sensor’s tactile sensitivity. The picosecond pulsed laser scribing technique makes it possible to pattern silver nanowires into inductive coils with high fidelity. A porous compressible layer is adopted to enable adjustable sensitivity and sensing range to meet diverse application demands. Finally, the sensor is integrated between the user’s leg and the orthosis, showcasing the sensor’s capability for real-time monitoring of tri-axial forces and its robustness against environmental objects.

Heterointerface engineering has drawn considerable interest in tuning interfacial polarization and promoting impedance matching. Therefore, it has become a key strategy for optimizing electromagnetic wave (EMW) absorption. This comprehensive review primarily focused on the EMW absorbing strategies of polymer-based materials, emphasizing the critical developments of heterointerface engineering. A possible EMW absorbing mechanism of polymer-based materials was proposed, emphasizing the synergism of multi-components, microstructure design, and heterointerface engineering. Key innovations in structural design such as porous structure, multilayered structure, and segregated structure are explored, highlighting their contributions to enhancing EMW absorption. Also, the review highlights the latest research progress of advanced conductive polymer-based and insulating polymer-based materials with desirable EMW absorption performance; their fabrication methods, structures, properties, and EMW absorption mechanisms were elucidated in detail. Key challenges on polymer-based EMW absorbing materials are presented followed by some future perspectives.

With the continuous development of small and medium-sized electronic devices, which bring convenience to people’s lives, electromagnetic wave (EMW) pollution has emerged as a significant issue. The development of materials with electromagnetic interference (EMI) shielding capabilities for protection against harmful radiation plays a vital role. Currently, a wide range of multifunctional, lightweight EMI shielding materials have been created to address various environmental requirements. However, a single EMI shielding material has been difficult to meet the requirements of high-speed transmission of electromagnetic radiation of electronic equipment because when such devices operate at high speeds, they typically generate elevated temperatures, and excessive electromagnetic radiation further exacerbates heat accumulation, reducing both efficiency and lifespan. Therefore, thermal management is essential to lower operating temperatures and ensure optimal performance. Phase change materials (PCMs) are known for storing a large amount of energy, and have significant potential in thermal management, so flexible EMI phase change composites (PCCs) have emerged. This review provides a detailed examination of flexible EMI shielding materials based on various fillers, the potential of flexible PCMs in thermal management, and the latest advancements in developing new lightweight EMI PCCs. Finally, we suggest some potential research directions for flexible EMI shielding PCCs, hoping to contribute to the rapid advancement of next-generation flexible electronics, human thermal management, and artificial intelligence.

Although polyvinyl alcohol (PVA) hydrogels display huge potential in tissue engineering, flexible and wearable electronic devices and soft robotics, their low intrinsic thermal conductivity and weak mechanical properties severely limit their wider applications in these areas. Herein, a Hofmeister effect-assisted “directional freezing-stretching” tactic is employed for simultaneously enhancing the intrinsic thermal conduction and mechanical properties of PVA hydrogels. The hydrogels are obtained through directional freezing followed by salting-out treatment and subsequent mechanical stretching and salting-out (DFS). The DFS PVA hydrogel with 15 wt% of PVA and a stretching ratio of 4 (DFS4) exhibits the highest thermal conductivity of 1.25 W/(m·K), which is 2.4 and 2.8 times that of PVA hydrogel prepared through frozen-thawed (FT) [0.52 W/(m·K)] and frozen-salted out (FS) [0.45 W/(m·K)] methods, respectively. The DFS4 PVA hydrogel also possesses greatly improved mechanical performances, exhibiting an elongation at break of 163.1%. In addition, the tensile strength, toughness, and elastic modulus of DFS4 PVA hydrogel significantly increase to 27.1 MPa, 25.3 MJ·m^-3, and 21.5 MPa from 0.4 MPa, 0.32 MJ·m^-3, and 0.07 MPa for FT PVA hydrogels, respectively. It is elucidated that the salting-out effect generates hydrophobic and crystalline regions, while directional freezing and stretching enhance the chain orientation in the DFS strategy. These effects synergistically contribute to the improvement of thermal conductivity and mechanical properties of PVA hydrogels.

Wearable strain sensors hold immense promise in monitoring human motion activities due to their low cost, lightweight design, and excellent biocompatibility. For example, continuous real-time monitoring of neck activity can effectively prevent the onset of acute torticollis. However, current approaches to monitoring sleep neck posture primarily depend on technologies such as computer vision, which are characterized by limited wearability and portability issues. Herein, this work introduces a cost-effective, highly sensitive carbon-based strain sensor fabricated on a fabric substrate with a printing technique, which is eco-friendly and biocompatible. The proposed sensor displays a broad sensing range of 112%, high sensitivity (gauge factor > 210), low sensing limit (~ 0.1 ‰), and outstanding long-term stability over 3,000 cycles. The sensor’s utilization in monitoring joint motion, vocal cord activity, pulse, and electrocardiogram (ECG) is illustrated. Moreover, a portable system for monitoring neck activity and ECG signals while sleeping has been engineered, capable of detecting neck movements and ECG signals during sleeping hours. The composite materials design strategy combined with printing techniques provides a potential route for high-performance and low-cost wearable strain sensors in health monitoring.

Thermoelectric (TE) materials and sensors have emerged as a frontier in health and environmental monitoring, offering a silent, simple, and reliable alternative to traditional power generation methods by harnessing waste heat into usable electrical energy. They also offer superior stability and longevity, making them ideal for long-term monitoring applications. Furthermore, when compared to other self-powered biosensors, TE sensors excel in their ability to operate in a wide range of temperatures and environmental conditions, providing a more reliable and consistent power source for sensor operation. This review delves into the recent advancements in TE-based sensors, highlighting their multifunctional capabilities in real-time health monitoring and environmental sensing. We explore the fundamental principles of TE conversion, including the Seebeck effect, and assess the performance metric, specifically the figure-of-merit (ZT). The integration of TE materials with flexible and wearable electronics is discussed, emphasizing flexible materials for their high efficiency and mechanical robustness. Applications in self-powered wearable devices and internet of things (IoT)-integrated environmental monitoring systems are underscored, particularly in fire detection and personal health monitoring. Challenges in material limitations, miniaturization, and scalability are addressed, with a focus on future research directions to enhance the sustainability and longevity of TE sensors. This review provides a comprehensive overview of the development of TE sensor technology and its future trajectory, emphasizing the importance of ongoing research to address current challenges and realize the capabilities of these innovative devices.

Soft material robots are uniquely suited to address engineering challenges in extreme environments in new ways that traditional rigid robot embodiments cannot. Soft robot material flexibility, resistance to brittle fracture, low thermal conductivity, biostability, and self-healing capabilities present new solutions advantageous to specific environmental conditions. In this review, we examine the requirements for building and operating soft robots in various extreme environments, including within the human body, underwater, outer space, search and rescue sites, and confined spaces. We analyze the implementations of soft robotic devices, including actuators and sensors, which meet these requirements. Besides the structure of these devices, we explore ways to expand the use of soft robots in extreme environments with design optimization, control systems, and their future applications in educational and commercial products. We further discuss the current limitations of soft robots recognizing challenges to compliance, strength, and control. With this in mind, we present arguments for the future of robotics in which hybrid (rigid and soft) structures meet complex environmental needs.