Flexible strain sensors have experienced growing demand due to their several potential applications, such as personalized health monitoring, human motion detection, structural health monitoring, smart garments, and robots. Recently, several academic results have been reported concerning flexible and stretchable strain sensors. These reports indicate that the materials and design methods have an important influence on the performance of strain sensors. Carbon-based nanomaterials including carbon-based nanofibers, carbon nanotubes, graphene, and carbon black nanoparticles play a key role in the fabrication of flexible strain sensors with excellent properties. In terms of design, carbon-based nanomaterials are generally combined with polymers to maintain the flexibility and stability of a strain sensor. Various combined methods were successfully developed using different assembly structures of carbon-based nanomaterials in polymers, such as uniform mixing and ordered structures, including films, fibers, nanofiber membranes, yarns, foams, and fabrics. The working mechanisms of the flexible strain sensors, including changing the conductive network between overlapped nanomaterials, tunneling effect, and crack propagation, are also different compared with that of traditional semiconductor and metal sensors. The effects of the carbon-based nanomaterial structures in polymers on the strain sensing performance have been comprehensively studied and analyzed. The potential applications of flexible strain sensors and current challenges have been summarized and evaluated. This review provides some suggestions for further development of flexible and stretchable strain sensors with outstanding performance.

柔性应变传感器由于其多种潜在应用而经历了不断增长的需求，例如个性化健康监控，人体运动检测，结构健康监控，智能服装和机器人。最近，已经报道了有关柔性和可拉伸应变传感器的一些学术成果。这些报告表明，材料和设计方法对应变传感器的性能具有重要影响。碳基纳米材料，包括碳基纳米纤维，碳纳米管，石墨烯和炭黑纳米颗粒，在制造具有优异性能的柔性应变传感器中起着关键作用。在设计方面，碳基纳米材料通常与聚合物结合以保持应变传感器的柔韧性和稳定性。使用碳基纳米材料在聚合物中的不同组装结构（例如均匀混合和有序结构，包括薄膜，纤维，纳米纤维膜，纱线，泡沫和织物）成功开发了各种组合方法。与传统的半导体和金属传感器相比，柔性应变传感器的工作机制也有所不同，包括改变重叠的纳米材料之间的导电网络，隧穿效应和裂纹扩展。聚合物中的碳基纳米材料结构对应变传感性能的影响已得到了全面的研究和分析。柔性应变传感器的潜在应用和当前的挑战已经得到了总结和评估。