Conformal Space-Filling Electromagnetic Skins for the Wireless Monitoring of 3D Object Integrity

The widespread use of polymer-based objects such as pipes, cables, tiles, gaskets in a wide range of applications demands for large scale a regular monitoring of their health status in order to prevent potential failures during service. Indeed, the exposure of these objects to mechanical or chemical stressing agents may accelerate their aging process thus decreasing their natural lifetime. A non-invasive and early monitoring of these aging signs (such as surface defects) may enable a predictive maintenance in order to avoid, or at least to minimize, unexpected failures. This paper describes a wireless crack detection method based on space-filling curves working like an electromagnetic second-skin enveloping the object. The conformal sensor permits to remotely transmit the presence of small defects over the object by using Radio Frequency Identification antennas and microchip transponders provided with anti-tampering features. The proposed idea is corroborated by numerical modeling and by some experimentations with a plastic pipe joint coated by a three-cells sensing skin made by silver conductive paint that is suitable to enable a wireless robust crack detection system up to 1.5m distance.