Recently, various piezoresistive composites with good flexibility have been developed as sensing materials for flexible strain sensors (FSSs). External forces will be applied to strain sensors when they are used in some circumstances such as wrist bending, etc. However, conventional flexible composites may fail upon being subjected to external forces since they have low strength and are unable to protect the inner vulnerable structure of flexible sensors. In this work, the reduced graphene oxide-coated glass fabric (RGO@GF)/silicone composite is fabricated and used to make high-performance structural flexible strain sensors. The composite is not only flexible and sensitive to strain, but also exhibits the high tensile strength needed to maintain the structural integrity of the flexible strain sensor. Silicone resin and GF are employed to provide flexibility and high strength, respectively. By coating RGO on the surface of GF, the nonconductive GF becomes conductive, which renders the piezoresistive behavior and strain-sensing ability to the RGO@GF/silicone composite. The as-prepared structural flexible sensor not only possesses a good strain sensitivity with a gauge factor of around 113, which is much higher than that of typical strain sensors based on metals, but can also maintain its structural integrity until the applied external force is over 800 N, while the conventional flexible strain sensor fails upon being subjected to an external force of only 5 N. Moreover, the as-prepared structural FSS is applied to monitor wrist movement and breathing to demonstrate its applicability. Overall, the RGO@GF/silicone composite exhibits great potential as a sensing material for structural FSSs for wrist movement, etc.

The development of highly sensitive wearable and foldable pressure sensors is one of the central topics in artificial intelligence, human motion monitoring, and health care monitors. However, current pressure sensors with high sensitivity and good durability in low, medium, and high applied strains are rather limited. Herein, a flexible pressure sensor based on hierarchical three-dimensional and porous reduced graphene oxide (rGO) fiber fabrics as the key sensing element is presented. The internal conductive structural network is formed by the rGO fibers which are mutually contacted by interfused or noninterfused fiber-to-fiber interfaces. Thanks to the unique structures, the sensor can show an excellent sensitivity from low to high applied strains (0.24−70.0%), a high gauge factor (1668.48) at an applied compression of 66.0%, a good durability in a wide range of frequencies, a low detection limit (1.17 Pa), and anultrafast response time (30 ms). The dominated mechanism is that under compression, the slide of the graphene fibers through the polydimethylsiloxane matrix reduces the connection points between the fibers, causing a surge in electrical resistance. In addition, because graphene fibers are porous and defective, the change in geometry of the fibers also causes a change in the electrical resistance of the composite under compression. Furthermore, the interfused fiber-to-fiber interfaces can strengthen the mechanical stability under 0.01−1.0 Hz loadings and high applied strains, and the wrinkles on the surface of the rGO fibers increased the sensitivity under tiny loadings. In addition, the noninterfused fiber-to-fiber interfaces can produce a highly sensitive contact resistance, leading to a higher sensitivity at low applied strains.

Inspired by biological cilia, a highly flexible dual-mode electronic cilia (EC) sensor is fabricated from graphene-coated magnetic cilia arrays, which possesses excellent pressure and magnetic field sensing capabilities.

Sensitivity is one of the most important parameters for strain sensors. Appropriate evaluation of the sensitivity is of great significance in developing new strain sensors since, otherwise, misleading conclusions may be made. The estimation of the sensitivity coefficient of piezoresistive strain sensors based on the previously used expressions is highly dependent on the initial resistance R 0 and the sensor type (namely positive or negative). Here, it is clearly displayed that this will result in large inaccuracies in the sensitivity coefficient evaluation. Based on the modified expression by replacing R 0 with the instantaneous resistance R, the data for the sensitivity coefficient reported in literature are re‐estimated. The results reveal that most of the so‐called records reported in literature of the sensitivity coefficient are overestimated. The highest gauge factor reported so far is corrected from 1 000 000 to only 3313. On the other hand, the sensitivity coefficient for negative piezoresistive sensors is shown to be somewhat underestimated.

Recent advances in the material and structural design of skin-like electronics have enhanced the interactions between the virtual and physical worlds and between people and objects. Herein, the existing flexible sensing materials and microstructures, including flexible stimuli-responsive materials and response-and stretchability-enhanced microstructures, are reviewed. Five typical skin-like electronics with sensitivities analogous to the human senses (olfactory, visual, auditory, tactile, and gustatory senses) and their corresponding applications (gas, light, chemical composition, sound, and mechanical signal monitoring) are introduced. Finally, it is concluded with some perspectives on challenges and opportunities for future research in flexible hybrid electronics.