Smiths Interconnect , 8851 SW Old Kansas Ave. , Stuart , Florida 34997 , United States.
ACS Appl Mater Interfaces. 2019 Oct 30;11(43):39560-39573. doi: 10.1021/acsami.9b13684. Epub 2019 Oct 15.
Recent interest in the fields of human motion monitoring, electronic skin, and human-machine interface technology demands strain sensors with high stretchability/compressibility (ε > 50%), high sensitivity (or gauge factor (GF > 100)), and long-lasting electromechanical compliance. However, current metal- and semiconductor-based strain sensors have very low (ε < 5%) stretchability or low sensitivity (GF < 2), typically sacrificing the stretchability for high sensitivity. Composite elastomer sensors are a solution where the challenge is to improve the sensitivity to GF > 100. We propose a simple, low-cost fabrication of mechanically compliant, physically robust metallic carbon nanotube (CNT)-polydimethylsiloxane (PDMS) strain sensors. The process allows the alignment of CNTs within the PDMS elastomer, permitting directional sensing. Aligning CNTs horizontally (HA-CNTs) on the substrate before embedding in the PDMS reduces the number of CNT junctions and introduces scale-like features on the CNT film perpendicular to the tensile strain direction, resulting in improved sensitivity compared to vertically-aligned CNT-(VA-CNT)-PDMS strain sensors under tension. The CNT alignment and the scale-like features modulate the electron conduction pathway, affecting the electrical sensitivity. Resulting GF values are 594 at 15% and 65 at 50% strains for HA-CNT-PDMS and 326 at 25% and 52 at 50% strains for VA-CNT-PDMS sensors. Under compression, VA-CNT-PDMS sensors show more sensitivity to small-scale deformation than HA-CNT-PDMS sensors due to the CNT orientation and the continuous morphology of the film, demonstrating that the sensing ability can be improved by aligning the CNTs in certain directions. Furthermore, mechanical robustness and electromechanical durability are tested for over 6000 cycles up to 50% tensile and compressive strains, with good frequency responses with negligible hysteresis. Finally, both types of sensors are shown to detect small-scale human motions, successfully distinguishing various human motions with reaction and recovery times of as low as 130 ms and 0.5 s, respectively.
最近，人们对人体运动监测、电子皮肤和人机接口技术领域产生了浓厚的兴趣，这使得人们对具有高拉伸/压缩性（ε＞50%）、高灵敏度（或应变系数（GF＞100））和持久机电顺应性的应变传感器产生了需求。然而，目前基于金属和半导体的应变传感器的拉伸性非常低（ε＜5%）或灵敏度低（GF＜2），通常是牺牲拉伸性来提高灵敏度。复合弹性体传感器是一种解决方案，其挑战在于提高灵敏度以达到 GF＞100。我们提出了一种简单、低成本的机械顺应性、物理坚固性的金属碳纳米管（CNT）-聚二甲基硅氧烷（PDMS）应变传感器的制造方法。该工艺允许 CNT 在 PDMS 弹性体中进行定向排列，从而实现定向传感。在将 CNT 嵌入 PDMS 之前，将 CNT 水平（HA-CNTs）排列在衬底上可以减少 CNT 结的数量，并在垂直于拉伸应变方向上引入 CNT 薄膜的鳞片状特征，从而与拉伸时的垂直排列 CNT-（VA-CNT）-PDMS 应变传感器相比，提高了灵敏度。CNT 排列和鳞片状特征调节电子传导途径，从而影响电灵敏度。HA-CNT-PDMS 的 GF 值在 15%和 50%应变下分别为 594 和 65，VA-CNT-PDMS 的 GF 值在 25%和 50%应变下分别为 326 和 52。在压缩时，由于 CNT 取向和薄膜的连续形态，VA-CNT-PDMS 传感器对小变形的灵敏度高于 HA-CNT-PDMS 传感器，这表明通过沿某些方向对齐 CNT 可以提高传感器的检测能力。此外，对超过 6000 个循环进行了机械鲁棒性和机电耐久性测试，在高达 50%的拉伸和压缩应变下，具有良好的频率响应，几乎没有滞后。最后，两种类型的传感器都被证明可以检测到人体的微小运动，成功地区分了各种人体运动，反应和恢复时间分别低至 130ms 和 0.5s。
