Capacitive strain gauges on flexible polymer substrates for wireless, intelligent systems
Capacitive strain gauges on flexible polymer substrates for wireless, intelligent systems
复制标题
用于无线智能系统的柔性聚合物基板上的电容式应变计
DOI：
10.5194/jsss-3-77-2014
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发表时间：
2014
影响因子：
1
通讯作者：
J. Wilde
中科院分区：
文献类型：
--
作者：
R. Zeiser;T. Fellner;J. Wilde
抽象的。本文介绍了一种新型的叉指式电容应变计，它是在聚酰亚胺和液晶聚合物（LCP）箔基板上制作的。采用薄膜技术沉积和图案化金属化层，结构尺寸可达15 μm。我们确定了传感器配置的线性应变灵敏度，并通过分析方法确定了对输出信号影响最大的参数。应变片的有限元法（FEM）模拟表明敏感结构内的机械应变的复杂相互作用及其对电容的影响。研究了几何参数和材料参数对应变灵敏度的影响，并进行了优化。我们在50 μm厚的标准聚合物箔上实现了薄膜，这是通过将箔临时键合到载体晶片上来实现的。制造后的应变传感器的表征揭示了应变系数以及温度高达100 °C和相对湿度高达100%的交叉灵敏度。电极宽度为45 μm、间隙为15 μm的传感器在电容为48 pF时的应变系数为−1.38。此外，当使用LCP代替聚酰亚胺作为传感器基板和封装时，我们实现了对湿度的交叉灵敏度从1435 ppm %−1 RH大幅降低到55 ppm %−1 RH。由两个正交电容组成的传感器半桥的应变系数为2.3，温度交叉灵敏度降低到240 ppm K−1。最后，提出了一种传感器系统，利用一个特殊的仪器集成电路（IC）。对于这个系统，性能数据，包括交叉灵敏度和功耗。
Abstract. This paper presents a novel capacitive strain gauge with interdigital electrodes, which was processed on polyimide and LCP (liquid crystal polymer) foil substrates. The metallization is deposited and patterned using thin-film technology with structure sizes down to 15 μm. We determined linear strain sensitivities for our sensor configuration and identified the most influencing parameters on the output signal by means of an analytical approach. Finite-element method (FEM) simulations of the strain gauge indicated the complex interaction of mechanical strains within the sensitive structure and their effect on the capacitance. The influence of geometry and material parameters on the strain sensitivity was investigated and optimized. We implemented thin films on 50 μm thick standard polymer foils by means of a temporary bonding process of the foils on carrier wafers. The characterization of the strain sensors after fabrication revealed the gauge factor as well as the cross sensitivities on temperatures up to 100 °C and relative humidity up to 100%. The gauge factor of a sensor with an electrode width of 45 μm and a clearance of 15 μm was −1.38 at a capacitance of 48 pF. Furthermore, we achieved a substantial reduction of the cross sensitivity against humidity from 1435 to 55 ppm %−1 RH when LCP was used for the sensor substrate and the encapsulation instead of polyimide. The gauge factor of a sensor half-bridge consisting of two orthogonal capacitors was 2.3 and the cross sensitivity on temperature was reduced to 240 ppm K−1. Finally, a sensor system was presented that utilizes a special instrumentation Integrated Circuit (IC). For this system, performance data comprising cross sensitivities and power consumption are given.