In a recent article published in the journal Scientific Reports, researchers from the US have developed a 5G-enabled, battery-less smart skin for self-monitoring megastructures and digital twin applications. These smart skins utilize millimeter wave (mmWave) reflect-array-based sensors to enable wide interrogation angles for local strain monitoring in composite materials. This technology aims to revolutionize structural health monitoring by providing continuous and accurate data without the need for batteries.
(a) Backside view of mounted ‘smart’ skin DUT with two glued wired strain gauges displayed. (b) Backside view of embedded ‘smart’ skin DUT with two glued wired strain gauges displayed. (c) Experimental setup of the cyclic loading of the embedded ‘smart’ skin sensor with the angle of incidence of 20∘ and at a distance of 1 m. Image Credit: https://www.nature.com/articles/s41598-024-58257-7
Background
The field of structural health monitoring (SHM) faces significant challenges related to the implementation of traditional wired sensing systems in large-scale infrastructures. Wired sensors, while reliable in providing data, present practical limitations in terms of installation complexity and operational constraints, especially in dynamic structures like helicopter blades or wind turbine blades.
The intricate electrical routing of sensors throughout composite structures and the need for power sources for data acquisition circuits hinder the scalability and flexibility of SHM systems. These challenges highlight the need for innovative, wireless sensing solutions that can overcome the limitations of wired systems and enable seamless integration into various structures.
Research on 5G-enabled, battery-less smart skins is crucial for several reasons. Firstly, these sensors offer a practical alternative to wired systems, eliminating the complexities associated with electrical routing and power supply requirements. Moreover, the scalability and adaptability of these wireless sensors make them ideal for deployment in self-monitoring megastructures, where continuous surveillance of structural integrity is essential for ensuring safety and performance.
The Current Study
The development of these battery-less smart skins involved a series of technical steps to design and validate the mmWave reflect-array-based sensors. The fabrication process of the smart skin sensors included the following key components:
Sensor Design: The sensor design was based on a Van-Atta array concept, enabling wide interrogation angles for local strain monitoring in composite materials. The design aimed to achieve high sensitivity and resolution for detecting structural deformations.
Prototype Fabrication: Proof-of-concept prototypes of the smart skin sensors were fabricated using advanced manufacturing techniques. The sensors were designed to be compact, flexible, and fully passive, requiring no external power source for operation.
Experimental Setup: The experiments involved mounting and embedding the sensors in commonly used materials for wind turbine blades to simulate real-world applications. The sensors were subjected to cyclic mechanical loading to evaluate their performance under varying strain conditions.
Measurement and Analysis: The sensors were interrogated off-axis with a proof-of-concept reader to measure their response to different levels of strain. The data collected from the experiments were analyzed to assess the sensitivity, resolution, and repeatability of the sensors.
Performance Evaluation: The performance of the smart skin sensors was evaluated based on their ability to detect and monitor local strains in composite materials. The sensors demonstrated a sensitivity of 7.55 kHz/μ-strain and 7.92 kHz/μ-strain for mounted and embedded sensors, respectively, at 1 meter from the interrogator.
Interrogation Angle Testing: The sensors were tested for their ability to support highly oblique interrogation angles, overcoming structural interference observed during boresight interrogation. The experiments confirmed that the sensors could maintain high detectability even at off-axis angles of ±40°.
Results and Discussion
The experimental findings of the 5G-enabled, battery-less smart skins for self-monitoring megastructures showcased significant progress in structural health monitoring technology. The sensors, utilizing mmWave reflect-array design, demonstrated excellent detectability and sensitivity in identifying local strains in composite materials.
The proof-of-concept prototypes of the smart skin sensors displayed a strong ability to detect strains, with impressive results for both mounted and embedded sensors. These outcomes highlighted the sensors' capacity to provide precise and dependable data even under varying mechanical conditions.
A notable discovery was the sensors' ability to handle interrogation from different angles, allowing for effective monitoring of structural changes at various positions. This feature addressed limitations associated with traditional interrogation methods, enhancing the sensors' versatility.
The sensitivity of the sensors was measured accurately, showcasing their ability to detect subtle strain changes with high accuracy. This characteristic makes them suitable for real-time monitoring of structural health, ensuring timely detection of any potential issues.
The experiments also indicated the potential for long-range sensor interrogation by utilizing the 5G/mmWave infrastructure. With further enhancements to the reader system and optimization of the interrogation process, the sensors could be deployed over extended distances, facilitating widespread use in megastructures.
Conclusion
In conclusion, the development of 5G-enabled, battery-less smart skins represents a significant advancement in structural health monitoring technology. The researchers emphasized the transformative impact of these skins on structural health monitoring, offering a cost-effective, energy-autonomous solution for continuous monitoring of megastructures.
The sensors exhibited a wide interrogation angle, allowing for comprehensive monitoring of structural deformations in megastructures. The proof-of-concept prototypes showed promising results in terms of sensitivity and reliability, highlighting the potential of this technology for real-world applications.
Journal Reference
Lynch, C., Adeyeye, A., Abbara, E.M. et al. (2024). 5G-enabled, battery-less smart skins for self-monitoring megastructures and digital twin applications. Scientific Reports 14, 10002. https://doi.org/10.1038/s41598-024-58257-7, https://www.nature.com/articles/s41598-024-58257-7