Wireless Printed Large-Area Sensors for Continuous Structural Health Monitoring

Structural health monitoring (SHM) is critical to the continuous safety assessment of infrastructure components, particularly for those with concerns over aging and structural deterioration. Traditional strain sensors in SHM often face limitations in sensitivity, durability, and scalability, particularly for large-area monitoring. In this work, these challenges are addressed by introducing a digitally fabricated strain sensor using additive 3D direct writing technology. The sensor uses a hybrid structure of stretchable carbon and silver materials to improve sensitivity and durability. It achieves dual-axis strain sensing by positioning carbon elements in both horizontal and vertical directions, enabling 2D strain mapping. A temperature sensor with nickel oxide nanoparticles provides temperature compensation, ensuring accurate strain measurements. To optimize performance, design parameters are fine-tuned, and comprehensive tests—including static, dynamic, and tensile strength evaluations are performed. The sensor, measuring 5 cm in length and 0.8 mm in width, reaches a maximum gauge factor of 2.45 at room temperature and shows minimal resistance change (0.01%) after 1000 bending cycles with a 5 mm radius. It detects small deformations with a resolution of 0.05%, and dynamic tests, such as earthquake simulations, verify its stability. Tensile testing, using a dynamic servohydraulic Material Testing System (MTS) frame for tension/compression, validates the accuracy of the sensor. This research advances SHM technology by offering a novel digital manufacturing approach for dual-axis strain sensing, demonstrating the potential of the sensor for continuous, low-cost, large-area monitoring.