de Rijk Tim Mike, Schewzow Sascha, Schander Andreas, Lang Walter
Institute for Microsensors, Actuators and Systems, University Bremen, 28359 Bremen, Germany.
Sensors (Basel). 2023 Oct 20;23(20):8606. doi: 10.3390/s23208606.
High-aspect-ratio carbon nanotubes can be directly mixed into polymers to create piezoresistive polymers. Reducing the cross-sensitivity and creating unidirectional sensitive sensors can be achieved by aligning the nanotubes before they are cured in the polymer layer. This research presents and characterises this alignment of carbon nanotubes inside polydimethylsiloxane and gives the corresponding strain sensor results. The influence on the alignment method, as well as the field strength, frequency and time is shown. An analytical model is created to investigate the sensor's behaviour and determine the effect of electron-tunnelling in the sensor. A numerical model gives insight into the necessary applied field strength, frequency and time to facilitate alignment in viscous liquids. The experimental data show a two-phase piezoresistive response; first, a linear strain response, after which the more dominant electron-tunnelling piezoresistive phase starts with high gauge factors up to k ≈ 4500 in the preferential direction, depending on the carbon nanotube concentration. Gauge factors in the orthogonal direction remain low (k ≈ 22). Finally, the dynamic stability of the sensors is proven by exposing the sensors to a cyclic strain. Small initial drifts are observed but appear to stabilise after several cycles.
高长径比的碳纳米管可以直接混入聚合物中以制造压阻聚合物。在纳米管于聚合物层中固化之前使其排列，可以降低交叉敏感性并制造单向敏感传感器。本研究展示并表征了聚二甲基硅氧烷内部碳纳米管的这种排列情况，并给出了相应的应变传感器结果。展示了对排列方法以及场强、频率和时间的影响。创建了一个分析模型来研究传感器的行为，并确定传感器中电子隧穿的影响。一个数值模型深入了解了在粘性液体中促进排列所需的外加场强、频率和时间。实验数据显示出两相压阻响应；首先是线性应变响应，之后更占主导的电子隧穿压阻相开始，在优先方向上具有高达k≈4500的高应变系数，这取决于碳纳米管的浓度。正交方向上的应变系数保持较低（k≈22）。最后，通过将传感器暴露于循环应变来证明传感器的动态稳定性。观察到有小的初始漂移，但在几个循环后似乎会稳定下来。
