Hossain Md Alamgir, Plautz-Ratkovski Gabriela, DeGraff Joshua, Dickens Tarik J, Liang Zhiyong, Hill Curtis, Jones Jennifer, Ramakrishnan Subramanian
Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, Florida 32310, United States.
High Performance Materials Institute, Department of Industrial and Manufacturing Engineering, Florida State University, Tallahassee, Florida 32310, United States.
ACS Omega. 2025 Jan 3;10(1):1429-1439. doi: 10.1021/acsomega.4c09042. eCollection 2025 Jan 14.
Structural health monitoring (SHM) systems are critical in ensuring the safety of space exploration, as spacecraft and structures can experience detrimental stresses and strains. By deploying conventional strain gauges, SHM systems can promptly detect and assess localized strain behaviors in structures; however, these strain gauges are limited by low sensitivity (gauge factor, GF ∼ 2). This study introduces an approach to printing strain gauges with high sensitivity, while also considering stretchability and long-term durability. Through direct ink writing (DIW), these devices can be produced by the extrusion of a wide range of viscoelastic inks. The viscoelastic properties of the ink can be tuned with the help of additives to aid in the processing for a desired application. In this work, a series of inks were prepared from commercially available CB028 (silver ink used in screen printing) by adding a combination of ethyl cellulose (EC) and polyolefin (PO) (additives). With the goal of optimizing the long-term sensing response of the printed strain gauges, a systematic study of the rheological properties (frequency sweep analyses, yield stress, viscoelastic recovery, viscosity measurements, and tack tests) was conducted. A viscoelastic window approach was used to predict the optimal properties of the formulated inks. Using this approach, it was determined that 90% CB028, 5% EC, and 5% PO provided enhanced elastic properties, adhesion, and peel strength compared to commercial CB028. The formulated ink has enhanced tack (129 mN/mm) and peel strength (23.3 kJ/mm), which led to a viscoelastic window ideal for direct ink writing of the strain gauges. Printed structures were tested in a three-point bending configuration to record the piezoresistive responses that were correlated to the formulated rheological properties and underlying microstructure. The results revealed gauge factors as high as 106 with stable sensing responses for more than 300 cycles of strain. Scanning electron microscopy analysis also revealed minimal crack formation, which resulted in a stable response. The research demonstrated the feasibility of developing high-performance inks for potential printed strain gauge applications.
结构健康监测（SHM）系统对于确保太空探索的安全至关重要，因为航天器和结构可能会承受有害的应力和应变。通过部署传统应变片，SHM系统可以迅速检测和评估结构中的局部应变行为；然而，这些应变片受到低灵敏度（应变片系数，GF ∼ 2）的限制。本研究介绍了一种打印高灵敏度应变片的方法，同时还考虑了拉伸性和长期耐久性。通过直接墨水书写（DIW），这些器件可以通过挤出各种粘弹性墨水来生产。墨水的粘弹性特性可以借助添加剂进行调整，以有助于针对所需应用进行加工。在这项工作中，通过添加乙基纤维素（EC）和聚烯烃（PO）（添加剂）的组合，由市售的CB028（用于丝网印刷的银墨水）制备了一系列墨水。为了优化打印应变片的长期传感响应，对其流变特性（频率扫描分析、屈服应力、粘弹性恢复、粘度测量和粘性测试）进行了系统研究。采用粘弹性窗口方法来预测配制墨水的最佳性能。使用这种方法，确定90%的CB028、5%的EC和5%的PO与市售CB028相比，具有增强的弹性性能、附着力和剥离强度。配制的墨水具有增强的粘性（129 mN/mm）和剥离强度（23.3 kJ/mm），这导致了一个适合直接墨水书写应变片的粘弹性窗口。在三点弯曲配置中对打印结构进行测试，以记录与配制的流变特性和底层微观结构相关的压阻响应。结果显示应变片系数高达106，在超过300个应变循环中具有稳定的传感响应。扫描电子显微镜分析还显示裂纹形成极少，这导致了稳定的响应。该研究证明了开发用于潜在打印应变片应用的高性能墨水的可行性。
