In recent years, due to the broad application prospects of flexible wearable sensors in personal health monitoring, human motion detection, artificial skin, and soft robots, people's growing interest in them has attracted attention. Among various types of wearable sensors, resistance strain sensors are competitive due to their simple manufacturing and high sensing performance. Usually, strain sensors integrate soft elastomers as supporting materials and conductive components as sensing elements to achieve mechanical electrical conversion. Although there are countless sensors based on conductive networks aimed at improving sensor performance, current designs mainly focus on detecting uniaxial stimuli, limiting their applicability in identifying complex multidimensional strains related to multi degree of freedom motion.

In order to overcome the limitations of uniaxial strain sensing, various methods have been explored to manufacture strain sensors with anisotropic electromechanical properties. The most commonly used strategy is to construct a directional conductive network in an elastic matrix. Therefore, when designing anisotropic strain sensors, various conductive fillers with anisotropic properties are commonly used, such as two-dimensional fillers like graphene and MXene, as well as one-dimensional fillers like carbon nanotubes (CNTs), carbon fibers, and silver nanowires. These strain sensors exhibit different responses to strains perpendicular and parallel to the packing direction. However, a major challenge remains achieving a balance to ensure that strain sensors have anisotropy, high sensitivity, and a wide monitoring range simultaneously.

Source: Sensor Expert Network