Department of Civil, Construction, and Environmental Engineering, Iowa State University, Ames, IA 50011, USA.
Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011, USA.
Sensors (Basel). 2023 Jul 4;23(13):6146. doi: 10.3390/s23136146.
Recent advances in soft polymer materials have enabled the design of soft machines and devices at multiple scales. Their intrinsic compliance and robust mechanical properties and the potential for a rapid scaling of the production process make them ideal candidates for flexible and stretchable electronics and sensors. Large-area electronics (LAE) made from soft polymer materials that are capable of sustaining large deformations and covering large surfaces and are applicable to complex and irregular surfaces and transducing deformations into readable signals have been explored for structural health monitoring (SHM) applications. The authors have previously proposed and developed an LAE consisting of a corrugated soft elastomeric capacitor (cSEC). The corrugation is used to engineer the directional strain sensitivity by using a thermoplastic styrene-ethylene-butadiene-styrene (SEBS). A key limitation of the SEBS-cSEC technology is the need of an epoxy for reliable bonding of the sensor onto the monitored surface, mainly attributable to the sensor's fabrication process that comprises a solvent that limits its direct deployment through a painting process. Here, with the objective to produce a paintable cSEC, we study an improved solvent-free fabrication method by using a commercial room-temperature-vulcanizing silicone as the host matrix. The matrix is filled with titania particles to form the dielectric layer, yielding a permittivity of 4.05. Carbon black powder is brushed onto the dielectric and encapsulated with the same silicone to form the conductive stretchable electrodes. The sensor is deployed by directly painting a layer of the silicone onto the monitored surface and then depositing the parallel plate capacitor. The electromechanical behavior of the painted silicone-cSEC was characterized and exhibited good linearity, with an R2 value of 0.9901, a gauge factor of 1.58, and a resolution of 70 με. This resolution compared well with that of the epoxied SEBS-cSEC reported in previous work (25 με). Its performance was compared against that of its more mature version, the SEBS-cSEC, in a network configuration on a cantilever plate subjected to a step-deformation and to free vibrations. Results showed that the performance of the painted silicone-sCEC compared well with that of the SEBS-cSEC, but that the use of a silicone paint instead of an epoxy could be responsible for larger noise and the under-estimation of the dominating frequency by 6.7%, likely attributable to slippage.
软聚合物材料的最新进展使得在多个尺度上设计软机器和设备成为可能。它们的固有顺应性和稳健的机械性能以及生产过程快速扩展的潜力使它们成为柔性和可拉伸电子产品和传感器的理想候选材料。由能够承受大变形并覆盖大表面的软聚合物材料制成的大面积电子产品（LAE），适用于复杂和不规则的表面，并将变形转换为可读信号，已被探索用于结构健康监测（SHM）应用。作者之前提出并开发了一种由波纹软弹性体电容器（cSEC）组成的 LAE。通过使用热塑性苯乙烯-乙烯-丁二烯-苯乙烯（SEBS），波纹结构用于通过工程设计来实现定向应变灵敏度。SEBS-cSEC 技术的一个关键限制是需要使用环氧树脂将传感器可靠地粘合到被监测表面上，这主要归因于传感器的制造工艺，其中包括一种限制其通过涂漆工艺直接部署的溶剂。在这里，我们的目标是生产一种可涂漆的 cSEC，因此研究了一种改进的无溶剂制造方法，该方法使用商业室温硫化硅酮作为主体基质。该基质中填充有二氧化钛颗粒以形成介电层，介电常数为 4.05。将碳黑粉末刷到介电层上，并使用相同的硅酮将其封装，形成可拉伸的导电电极。通过直接将一层硅酮涂覆到被监测的表面上，然后沉积平行板电容器来部署传感器。对涂漆硅酮-cSEC 的机电行为进行了表征，表现出良好的线性，R2 值为 0.9901，应变系数为 1.58，分辨率为 70 με。与之前工作中报道的环氧 SEBS-cSEC 的分辨率（25 με）相比，该分辨率相当。在悬臂板上的阶跃变形和自由振动的网络配置中，将其性能与更成熟的 SEBS-cSEC 版本进行了比较。结果表明，涂漆硅酮-sCEC 的性能与 SEBS-cSEC 相当，但使用硅酮漆而不是环氧树脂可能会导致更大的噪声和主导频率的低估，这可能归因于滑动。
