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中文核心期刊

面内随机堆叠石墨烯复合材料压阻传感机理与压阻性能

PIEZORESISTIVE SENSING MECHANISM AND PIEZORESISTIVE PERFORMANCE OF IN-PLANE RANDOM STACKED GRAPHENE COMPOSITES

  • 摘要: 面内随机堆叠石墨烯复合材料(graphene composites, GC)是可穿戴柔性传感器的基础材料之一, 但是其压阻传感机理与压阻性能仍然有待深入研究. 本文基于GC的微观结构特征, 利用0 \sim 1间均匀分布随机数获得石墨烯在复合材料中的位置和方向, 建立了二维GC压阻传感器模型. 根据GC均匀变形的特点和有限单元法发展了GC压阻性能的计算方法, 计算得到了相对电阻、灵敏度系数、石墨烯片的微观形态与电流密度云图. 研究结果表明, GC中的压阻效应是由于在变形过程中石墨烯形态的改变, 包括GC中石墨烯片的密度随应变变化、石墨烯片滑移、分离导致电子迁移路径和无效片数量的改变, 而GC中石墨烯片密度随应变的变化是影响压阻效应的主要因素. 石墨烯片间的相对滑移产生线性传感特征, 分离反之. 高面分比GC与大尺寸石墨烯的GC拥有较大的感知范围, 低面分比GC和小尺寸石墨烯的GC具有更高的灵敏度系数. 最后将接触面的面内电阻率设为应变的函数, 研究了石墨烯片的接触效应对GC压阻性能影响, 解释了GC压阻性能的接触效应和影响机理. 研究结论可为GC生产方法的改进与创新、以及GC压阻传感器件的制备提供理论依据和技术参考.

     

    Abstract: Many experimental researches on the in-plane random stacked graphene composites (GC) for wearable sensors have been carried out. Due to the limitation of experimental technology, its piezoresistive sensing mechanism and piezoresistive performance are still an open problem. Based on the microstructure characteristics of GC, the position and direction of graphene flakes in GC are determined by the uniformly distributed random numbers between 0 and 1, and a novel two-dimensional GC model is established. According to the uniform deformation characteristics of GC, the finite element method for piezoresistive performance of GC is developed. The relative resistance, gauge factor, morphology of graphene flakes and current density contour of GC are obtained. By connecting them, it is revealed that the substantial cause of piezoresistive effect is the change of graphene flakes density and the specific reason is the variation of the electron migration pathway and the invalid flakes number. The increase of the length of electron migration pathway caused by the relative sliding of overlapped graphene flakes leads to the linear sensing characteristics, while the cut of the number of electron migration pathway and the increase in the number of invalid flakes induced by the separation of graphene flakes bring about the non-linear sensing effect. In addition, the results show that GC with high area fraction and GC with large-scale graphene flakes have a large sensing range, while GC with low area fraction and GC with small-scale graphene flakes have a higher gauge factor. Finally, the in-plane resistivity of contact surface of overlapped graphene flakes is assumed as a function of strain and the influence of contact resistance on piezoresistive effect of the GC is investigated, to understand the mechanism of the GC piezoresistive performance. These results can contribute to the improvement or innovation of GC fabrication method and the production of the GC piezoresistive sensing devices for expected sensing performance.

     

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