边缘效应对电容式叉指状微纳力测量装置的影响与分析

Analysis of fringe effect on finger structure capacitive micro/nano force measurement device

针对电容式微纳力测量装置中普遍存在边缘效应影响的问题,利用有限元模拟与理论计算相结合的方法,比较分析了不同参数条件下边缘效应对微纳力输出值的影响,同时根据有限元模拟所得电势分布云图与等势线分布图,分析了不同极板相对位置、加载电压下,电容边缘效应影响不同所产生的原因。结果表明:叉指电容具有良好的输出稳定性,在处于相交状态70%区域范围内,输出波动幅度在5.2%以内,电容边缘效应影响可忽略;当相交长度大于叉指长度90%时,边缘效应对微纳力输出值的影响超过22.1%,理论计算公式已无法准确计算实际微纳力输出值;且该区域内加载电压升高到1200V时,边缘效应对微纳力输出值的影响可达50.1%。在微纳力测量装置设计与应用过程中应使叉指电容相交长度小于叉指长度的90%,且保持较低加载电压以减小边缘效应影响。

The fringe effect was existed in capacitive micro/nano force measurement device.The finite element simulation and theoretical calculation method were used to analyze fringe effects on the output value of micro/nano force under different parameters.Based on the potential distribution cloud map and isopotential distribution map obtained by the finite element simulation,the causes of capacitor fringe effects under different relative positions of the plates and different loading voltages were analyzed.Results showed that the finger structure capacitive micro/nano force output value was stable.Within 70%of the intersecting region,the micro/nano force fluctuation was within 5.2%,and the capacitor edge effect could be ignored.When the intersection length was greater than 90%of the finger structure capacitor length,the fringe effect on the output value of the micro/nano force exceeded 22.1%.The output micro/nano force value couldn’t be predicted by the theoretical calculation formula.In this region,when the load voltage increased to 1200 V,the fringe effect on the output value of micro/nano force could reach 50.1%.During the design and application of the micro/nano force measurement device,the interdigitated length should be less than 90%of finger structure capacitor length,and the load voltage should be kept low to reduce the edge effect.