现代传感技术逐渐面向智能化、多功能化、小型化、柔性化、人性化等方向发展，使传感器的适用范围大大拓宽。石墨烯，作为一种新型碳纳米材料，因其独特的二维结构特点、受缺陷调控的电学特性及多维度空间适应性，已成为高灵敏传感的首选材料之一，并有望在柔性传感器件中获得应用。本论文以开发小尺度变形高灵敏柔性应变传感器为目标，构建了一种编织结构石墨烯应变敏感材料，将其与柔性衬底结合组装为应变传感器。通过宏观编织结构和微观多晶形貌的合理设计优化其应变传感响应，实现了超高灵敏（2%应变范围内灵敏系数达到500）。研究了应变传感性能、工作机制、影响因素及潜在应用。系统探究了编织结构石墨烯作为应变敏感材料信号获取和转换机制：不是通过晶格变形改变其本征导电性能，也不是通过变形控制石墨烯与互连电极之间的接触状态来调控接触电阻，而是通过变形调整石墨烯晶片之间的接触状态以改变晶片间的接触电阻。通过设计石墨烯微米条带、平面网格结构石墨烯等对照样，结合Voronoi建模分析，推导出编织结构石墨烯在小变形下的高灵敏传感特性，源于其特殊的宏微观结构—即微观上多晶堆叠裂化、宏观上横纵条带相互弱搭接。研究了编织结构石墨烯柔性应变传感器性能的三个影响因素：石墨烯材料本身、衬底和封装。结果表明，减少石墨烯厚度、提高石墨烯长宽比、降低衬底刚度、采用氧等离子体处理衬底有助于提升传感器灵敏度。而增加石墨烯厚度、减少石墨烯长宽比、采用45度角拉伸、提高衬底刚度、预拉伸衬底、封装等方案有助于提升量程。灵敏度与量程是相互制约的一对参数，实际应用中可以根据具体场合需要采用合理的工艺策略，以获得满意的折中方案。探索了编织结构石墨烯柔性应变传感器在实际应用中的性能，对多种微信号（包括应变、振动、压力等）进行收集、识别和传输，及监测生命体的生理状态（如脉搏、手势识别、微笑、发声等），在人机交互、智能机器人、移动医疗等领域具有应用前景。进一步将应变传感器与可拉伸的电致变色模块一体化集成，实现了受拉伸程度调控的可视化应变传感，赋予了该器件更多的功能性。
The development direction of modern sensor technology is to achieve intelligence, multifunction, miniaturization, flexibility and humanization, greatly broadening the range of sensor applications. Graphene, as one of the newly emerging carbon nano-materials with unique sturture feature, defect-affected electrical property and multidimensional spatial adaptability, has become one promising candidate for highly sensitive sensing material and it is expected to be used in flexible sensors.In this thesis, to develop a highly sensitive and flexible strain sensor to detect small deformation, graphene woven fabrics (GWFs) was synthesized and then transferred onto a flexbile substrate to assemble the strain sensor. Through rational design of its macro woven structure and micro polycrystalline morphology, the strain sensing response of graphene was improved, leading to a high sensitivity with gauge factor (GF) of 500 under 2% strain. The related strain sensing properties, working mechanism, performance optimization strategies as well as potential applications were investigated.The mechanism of signal acquisition and conversion for GWFs as strain sensing element was systematically investigated. The resistance variation of GWFs under deformation was not caused by either the intrinsic conductivity change due to graphene lattice deformation or the contact state change between the graphene and the electrodes, but caused by the the contact resistance variation between adjacent graphene sheets. According to the comparison of the strain response results among graphene micro strip, flat graphene grid and GWFs, it was inferred that the ultrahigh sensitivity of GWFs was attributed to its unique macro and micro structures, i.e., the polycrystalline stacking cracking on the microscopic level and a weak overlap between the interlaced graphene ribbons on the macroscopic level.Three factors affecting the performance of the GWFs based flexible strain sensor were studied: graphene itself, substrate and encapsulation. The results indicated that the thickness reduction, aspect ratio increasement of GWFs, and the stiffness reduction, oxygen plasma treatment of substrate would improve the sensor sensitivity. While the thickness increasement, aspect ratio reduction of GWFs, stretching at an angle of 45 degree, larger substrate stiffness, prestretching substrate as well as encapsulation would improve the working range. Generally, sensitivity and range are a pair of mutual restricted parameters, thus reasonable process strategies would be required to get a satisfactory compromise according to the specific occasion in practical applications.The performance of the GWFs based flexible strain sensor in practical appplications was explored. The sensor could collect, identify and transmit a variety of micro signals including strain, vibration and pressure, etc. In addition, the sensor could monitor the physiological state of the body (such as pulse, gesture recognition, smile, voice, etc.), demonstrating its application prospects in the fields of electronic skin, intelligent robots and human-computer interaction. Furthermore, the strain sensor was integrated with a stretchable electrochromic module to realize the visualization of the strain sensing, which would enhance the versatility of the sensor.
