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A transformative hierarchical sensing ecosystem integrating the Annamdas & Soh Pioneering Metamaterial (3–8 GHz) framework with deep-penetrating L/S-Band (1–3 GHz) civil waves, Ka/V-Band (26.5–75 GHz) composite surface waves, and Sub-THz G-Band (110–300 GHz) photoelastic radiation—inverted in real-time via Parameterized Quantum Neural Networks (QNN / VQE) to reconstruct full 2D stress tensors and micro-cracks.
Prior to the seminal research conducted by Annamdas and Soh at Nanyang Technological University, electromagnetic metamaterials and split-ring resonators (SRRs) were confined strictly to electromagnetic cloaking, telecommunication filter circuits, and radar cross-section absorbers.
In their landmark IWSHM 2015 (10th International Workshop on Structural Health Monitoring, Stanford University) presentation, Annamdas and Soh proved for the first time in global scientific history that a passive microwave circular metamaterial could track structural deflection, strain, and load severity across the 3 to 8 GHz band through localized surface plasmon (LSP) resonance shifts near 6.035 GHz in both bonded contact and non-contact near-field configurations.
Demonstrated passive circular metamaterials tracking load and deflection in contact and near-field regimes via 6.035 GHz LSP resonance dip and RMSD metric.
Combines deep civil concrete waves (1–3 GHz), Annamdas-Soh LSP (3–8 GHz), guided composite surface waves (26.5–75 GHz), and Sub-THz photoelastic radiation (110–300 GHz).
Inverts high-dimensional multi-spectral dispersion tensors in Hilbert space using parameter-shift gradients, reconstructing the 2D stress tensor $[\sigma_{xx}, \sigma_{yy}, \tau_{xy}]$.
Bridging classical electromagnetic metamaterial theory with quantum neural network inversion.
The circular passive metamaterial behaves as an effective $L_{\text{eff}} - C_{\text{eff}}$ resonator whose resonant frequency $f_0$ shifts as mechanical strain perturbs the substrate dielectric permittivity $\varepsilon_{\text{eff}}$:
Evanescent near-field coupling decays exponentially with standoff: $\Delta\varepsilon_{\text{eff}} \propto \exp(-d_{\text{gap}}/\delta_p)$, where $\delta_p$ is the reactive penetration depth.
Damage severity is quantified across the transmission band using the Root Mean Square Deviation between the pristine baseline spectrum and the in-situ spectrum:
Allows instant classification: $\text{RMSD} \le 2\%$ Pristine, $2-10\%$ Incipient Damage, and $>15\%$ Severe Fracture.
Sub-millimeter G-band waves experience stress-induced optical anisotropy, enabling direct reconstruction of principal stress differences via phase delay:
Rayleigh scattering cross-section follows $\sigma_{\text{RCS}} \propto a^6 / \lambda_0^4$, giving high sensitivity to micro-cracks ($a < 150\,\mu\text{m}$).
Planar metamaterial elements couple into Lamb and Rayleigh surface modes across 26.5–75 GHz. Delaminations and adhesive bondline defects scatter the forward wave:
Enables high-resolution composite skin and adhesive bondline integrity scanning in aerospace components.
Lower microwave frequencies (1–3 GHz) penetrate deeply into heterogeneous lossy materials like reinforced concrete without severe attenuation:
Allows detection of internal voids, deep rebar corrosion, and moisture ingress behind concrete covers.
Parameterized Quantum Circuits evaluate exact analytical gradients directly on quantum hardware without finite-difference errors:
Eliminates non-uniqueness and local traps when inverting multi-frequency scattering data to reconstruct $[\sigma_{xx}, \sigma_{yy}, \tau_{xy}]$.