基于半导电复合材料的内因型差动压阻传感器研究

To increase the sensitivity of flexible piezoresistive sensor based on semi-conductive composite under low compressive pressure, an intrinsic-factor-induced differential structure, which is composed of positive coefficient unit (PPCU) and negative piezoresistivity coefficient unit (NPCU), is designed. The conductive phase conent of the composite in PPCU is lower than the critical content, and the piezoresistivity is monotonically increasing. The conductive phase conent of the composite in NPCU is higher than the critical content, and the piezoresistivity is monotonically decreasing. PPCU and NPCU are used as as the neighboring arms of an electrical bridge to realize the conversion from the compressive pressure to the voltage. In this project, the effects of the conductive phase content on the pieozresistivity will be researched, the piezoresistive model based on effective condcutive path thoery will be established, and the intrinsic-factor-induced differential piezoresistive sensor will be developed. The necessity and novelty of the intrinsic-factor-induced diffrential structure are listed as follows. The traditional “extrinic-factor-induced” differential structure, which is to exert the opposite sub-excitaitons on the sub-units with idential properties, cannot be used in the application where the opposite sub-excitations cannot be achieved. The “intrinsic-factor-induced” differential structure, which is to use the sub-units with opposite properties to bear the identical sub-excitations, can solve the limitations that the “extrinic-factor-induced” differential structure cannot be used to measure the small interlayer pressure measurement. The conclusions drawn in this project can not only offer the theoretical and experimental bases for the research on the piezoresistive effect of semi-conductive composites, but also provide the technique foundation for the development of the inerlayer pressure measurement system of the industrial equipment. Therefore, this project has important theoretical meaning and applying value.

为提高基于半导电复合材料的压阻传感器在低压力下的灵敏度，本项目拟设计由正、负压阻系数子单元构成的“内因型”差动结构。正压阻系数子单元的导电相含量低于临界含量，其压阻特性单调递增。负压阻系数子单元的导电相含量高于临界含量，其压阻特性单调递减。正、负压阻系数子单元作为电桥相邻桥臂以实现压力-电压转换。本项目拟研究导电相含量等因素对压阻特性的影响，建立基于有效导电通道理论的压阻模型，研制内因型差动压阻传感器。内因型差动的必要性和创新性在于：传统差动通过“将相反的子激励施于特性相同的子单元上”来实现差动，故不能用于“无法实现相反子激励”的场合；而内因型差动是通过“用特性相反的子单元承受相同的子激励”来实现差动，故可解决传统差动结构“不能用于狭小层间压力测量”的局限。本项目的成果可为半导电复合材料压阻效应研究提供理论和实验依据，还可为工业设备层间压力测量提供技术基础，具有重要的理论意义和应用价值。

基于半导电复合材料的柔性压阻传感器可用于实现现代工业大型设备狭小曲面层间压力测量，为提高这种压阻传感器在低压力下的灵敏度，本项目研究了导电相含量和压缩循环等因素对压阻特性的影响规律与机理，设计了由正压阻系数子单元（PPCU）和负压阻系数子单元（NPCU）构成的“内因型”差动结构。实验结果表明：当半导电复合材料的导电相含量低于临界含量下限值时，压阻特性单调递增；当半导电复合材料的导电相含量高于临界含量上限值时，压阻特性单调递减；当半导电复合材料的导电相含量介于临界含量下限值与上限值之间时，压阻特性非单调（复合材料电阻随压力的增大先减小后增大）；随着载荷循环的增加，压阻特性重复性逐渐提高。将正压阻系数子单元的导电相含量设计为低于临界含量下限值，以使其压阻特性单调递增；将负压阻系数子单元的导电相含量设计为高于临界含量上限值，以使其压阻特性单调递减。将正压阻系数子单元和负压阻系数子单元作为电桥相邻桥臂并设计了信号处理系统以实现压力测量。系统测试表明：本项目所研制的由正、负压阻系数子单元构成的内因型差动传感器在0-0.1MPa量程内，测量偏差小于5%FS，灵敏度高于2mV/kPa。本项目设计的内因型差动结构是通过“用特性相反的子单元承受相同的子激励”来实现差动，故而解决了传统差动结构“不能用于狭小层间压力测量”的局限。本项目的成果可为半导电复合材料压阻效应研究提供理论和实验依据，还可为工业设备狭小曲面层间压力测量提供技术基础。