Abstract
We propose and demonstrate a wireless, passive, metamaterial-based sensor that allows for remotely monitoring submicron displacements over millimeter ranges. The sensor comprises a probe made of multiple nested split ring resonators (NSRRs) in a double-comb architecture coupled to an external antenna in its near-field. In operation, the sensor detects displacement of a structure onto which the NSRR probe is attached by telemetrically tracking the shift in its local frequency peaks. Owing to the NSRR's near-field excitation response, which is highly sensitive to the displaced comb-teeth over a wide separation, the wireless sensing system exhibits a relatively high resolution (<1 μm) and a large dynamic range (over 7 mm), along with high levels of linearity (R2 > 0.99 over 5 mm) and sensitivity (>12.7 MHz/mm in the 1–3 mm range). The sensor is also shown to be working in the linear region in a scenario where it is attached to a standard structural reinforcing bar. Because of its wireless and passive nature, together with its low cost, the proposed system enabled by the metamaterial probes holds a great promise for applications in remote structural health monitoring.
Highlights
Structural health monitoring (SHM) is essential to ensuring the reliability of structures and protection of human life using the structures
The fact that the nested split ring resonators (NSRRs) probe operates in the near field of the antenna provides important advantages in terms of sensitivity
To predict this behavior and develop a better insight for its operation, numerical studies were systematically carried out using the transient solver of the commercial CAD software CST Microwave Studio®. These simulations were used to compare the localization of fields on the NSRR when the NSRR is excited within the near field of the antenna for four different scenarios, where the monitoring distance (Dm, which is the separating distance between the antenna and the NSRR) is 5 cm for all cases
Summary
Structural health monitoring (SHM) is essential to ensuring the reliability of structures and protection of human life using the structures. A large number of displacement and strain measurement technologies have been reported in the literature, and it has been identified that sensors that leverage remote measurement via wireless monitoring are of higher importance [1,2,3,4,5,6,7]. This is due to their capability to deliver temporal information about structural elements in a completely nondestructive manner. Previous works that incorporate passive wireless sensors for the purpose of SHM are summarized by Deivasigamani et al in [8]
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