Meanwhile, they also could dramatically improve the electrical conductivity of the hydrogel, thus significantly enhancing the sensitivity of strain sensor. For example, carbon nanomaterials could greatly increase the elongation of the hydrogel due to strong interaction between their rich surface groups and polymer skeleton. Recently, conductive materials, such as conductive polymers, carbon nanomaterials, and metal nanoparticles, have been incorporated into a polymer matrix to improve the electromechanical performances of hydrogel-based strain sensors. Nevertheless, it is still challenging to combine good mechanical property with high sensing performance to design a highly stretchable and sensitive strain sensing hydrogel for wearable electronics. This problem can be effectively alleviated by introducing effective energy dissipation domains or constructing a double-network hydrogel. However, with limited degree of crosslinking and high viscosity, single-network hydrogels exhibit poor mechanical property and stability. Hydrogel, a three-dimensional (3D) networked structure containing a large amount of water or ionic liquid, has been widely explored for flexible strain sensors for its excellent stretchability, surface compliance, and biocompatibility. However, the limited tensile properties and low sensitivity severely impede their practical applications in flexible strain sensors. Elastic polymer substrates are widely utilized for the fabrication of stretchable electronics, such as polydimethylsiloxane, polyurethane, and poly(ethylene terephthalate), which manifest high transparency, a certain degree of elasticity, and good stability. Among them, flexible strain sensors convert physiological activity signals into visible electrical signals in the form of signal transmission, exhibiting great potential in flexible touch screens, health clinical monitoring, industrial robots, and so on. In recent years, electronic skins (E-skins) have attracted extensive interests due to their similar functions to the human skin, including stretchability, multifunctional sensing capabilities, and wide sensing range. Moreover, the hydrogel-based flexible sensors, with high sensitivity and durability, could be employed to monitor full-range human motions and assembled into some aligned devices for subtle pressure detection, providing enormous potential in facial expression and phonation recognition, handwriting verification, healthy diagnosis, and wearable electronics. Particularly, the as-prepared flexible pressure sensor revealed ultrahigh sensitivity (10.75 kPa -1) with a wide response range (0-61.5 kPa), fast response (33.5 ms), and low limit of detection (0.87 Pa). The resulting nanocomposited hydrogels featured great tensile performance (2400%), toughness, and resilience. The strong interaction between the double-network hydrogel matrix and MXene greatly improved the mechanical properties of the hydrogels. The uniformly distributed hydrophilic MXene nanosheets formed a three-dimensional conductive network throughout the hydrogel, endowing the flexible sensor with high sensitivity. Herein, highly stretchable, sensitive, and multifunctional flexible strain sensors based on MXene- (Ti 3C 2T -) composited poly(vinyl alcohol)/polyvinyl pyrrolidone double-network hydrogels were prepared. However, it remains a challenge to fulfill the requirements on detecting full-range human activities with existing flexible strain sensors.
#Acid elastic reality skin
Electronic skin is driving the next generation of cutting-edge wearable electronic products due to its good wearability and high accuracy of information acquisition.